https://news.mcmedia.cam/feed/Astro MCMedia News RSS Feed - Astro specific feed https://news.mcmedia.cam/rss-info.html MCMedia RSS Generator v1.0 Thu, 11 Jun 2026 19:50:34 +0000 https://arxiv.org/abs/2605.02826 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2605.02826v4 Announce Type: replace-cross Abstract: The structure of the ground $(2^+)$ and excited $(1^+)$ bound states of the $^8$B and $^8$Li nuclei is studied within the framework of the $\alpha+^3$He($^3$H)+$p(n)$ three-body potential cluster model based on the hyperspherical Lagrange-mesh method. The two-body realistic potentials have been applied from the literature. Convergent theoretical estimates for the three-body binding energy and matter radius have been obtained with the maximal hypermomentum $K_{max}=22$ and 28 for the ground and excited $1^+$ states, respectively. The ANC value of the virtual transition of the $^8$B nucleus is estimated self-consistently by matching the overlap integral of the $^8$B three-body and the $^7$Be two-body wave functions with it's asymptotics. The obtained values are $0.211$~fm$^{-1/2}$ and $0.739$~fm$^{-1/2}$ in the spin 1 and spin 2 channels, respectively. For the ANC values of the $^8$Li nucleus the estimates $0.220$~fm$^{-1/2}$ and $0.774$~fm$^{-1/2}$ are extracted. The ratio $C^2(^8 {\rm B})/C^2(^8 {\rm Li})=0.912$ implies a breaking of the mirror symmetry of the strong nuclear forces of order 27\% due to the Coulomb interaction and the dynamical three-body effects. For the $S_{17}(0)$ -factor an estimate $22.492\pm0.014$ eV b was obtained based on the asymptotic theory developed by D. Baye [Phys. Rev. C {\bf 62},065803 (2000)]. The spin 2 channel contributes with $S^{(2)}_{17}(0)=20.838 \pm 0.014$ eV b, while the spin 1 channel yields $S^{(1)}_{17}(0)=1.654 \pm 0.003$ eV b. These results for $S_{17}(0)$ are in a good agreement with the estimate $20.8\pm0.7{\rm(th)}\pm1.4{\rm(exp)}$ eV b of the SF II, but larger than the recommended value $20.5\pm0.70$ eV b of the SF III. At the same time, our estimate is very close to the value 22.4 eV b used in the most successful Solar Model BAR2M [W.~Yang and Z.~Tian, AJ {\bf 970} (2024), 38]. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2509.25070 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2509.25070v3 Announce Type: replace-cross Abstract: Molecular hydrogen (H$_2$) is one of the key chemical species that controls and shapes a wide spectrum of astrophysical processes from galaxy evolution to planet formation. Although catalyzation on dust grain surfaces is the dominant formation channel of H$_2$ in the interstellar medium, its efficiency across $20-200~\rm K$ has remained not fully understood. Here, using multiscale simulations combining ab-initio-level machine learning force fields, constrained path-integral Monte Carlo, and kinetic Monte Carlo, we perform a systematic, quantum-mechanical study of the full H$_2$ formation sequence, including hydrogen adsorption, diffusion, association and desorption. We explicitly consider the decoupling of gas and dust temperatures, making our results applicable to photon-dominated regions (PDRs) and dense cold clouds. Our results show that on the bare, crystalline surfaces studied here (graphitic and silicate grains), physisorbed hydrogen is negligible, and nuclear quantum effects (NQEs) in chemisorbed hydrogen atoms are essential for efficient formation at low temperatures, overcoming the classical Boltzmann suppression. This work presents a quantitative NQEs-inclusive study on silicate surfaces (exemplified by enstatite) and graphitic grains, revealing surface-specific adsorption behavior. These findings provide a first-principles quantum foundation for interstellar H$_2$ formation, complementing empirical multipliers, and enable new observational constraints on dust composition and molecular cloud evolution. The framework also extends to other astrochemical reactions on dust grains under full NQEs. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2603.20429 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2603.20429v2 Announce Type: replace Abstract: RR Lyrae stars (RRLs) are classical tracers of old stellar populations, yet growing evidence suggests the presence of a metal-rich ([Fe/H]>-0.5), intermediate-age (2-7 Gyr) sub-population in the Milky Way disc. Binary evolution, particularly stable mass transfer, has been proposed as a viable formation channel, predicting that most metal-rich, intermediate-age (<9 Gyr) RRLs should reside in binaries with orbital periods of ~900-2000 days. However, no genuine RRL binaries have been robustly identified, including in the Gaia DR3 astrometric binary catalogues, despite Gaia being sensitive to the predicted orbital-period range. We investigate whether the lack of detections in Gaia DR3 reflects an intrinsically low binary fraction or instead arises from observational biases. We analyse a carefully selected sample of 100 Gaia DR3 RRLs designed to trace the metal-rich population with thin-disc kinematics and compare them with predictions from binary evolution models. We generate realistic Gaia observation mocks, including variability-induced astrometric biases, and assess the detectability of binaries and the posterior constraints on the hidden binary fraction using astrometric quality indicators, such as RUWE, and a robust Bayesian inference. While current uncertainties prevent a definitive rejection of a high fraction of hidden binaries, our results reveal tensions between existing binary evolution predictions and the Gaia DR3 non-detections. This suggests either the presence of unaccounted systematics in the modelling of Gaia observations or the need to revise assumptions in binary evolution models. We predict that Gaia DR4 will significantly improve the binary detectability and provide powerful new constraints on the post-interaction binary populations. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2511.19196 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2511.19196v2 Announce Type: replace Abstract: We present the scientific case for exploiting the capabilities of the PLATO mission to study bright pulsating white dwarfs across a wide spectral range, including hydrogen-deficient types (GW Vir and DBV stars) and hydrogen-rich classes (classical DAVs, pulsating extremely low-mass DA white dwarfs, and ultra-massive DA white dwarfs). PLATOs exceptional photometric precision, long-duration continuous monitoring, and extensive sky coverage promise transformative advances in white dwarf asteroseismology. Our key objectives include probing the internal structure and chemical stratification of white dwarfs, detecting secular changes in pulsation modes over extended timescales, and discovering rare or previously unknown classes of pulsators. To assess feasibility, we constructed a sample of 650 white dwarf candidates identified within PLATOs Southern LOPS2 field using the PLATO complementary science catalogue combined with Gaia DR3, and derived atmospheric parameters through photometric modeling. This sample comprises 118 DA white dwarfs (including 23 ZZ Ceti candidates), and 41 non-DAs (including 35 DBV candidates). Simulated observations using PlatoSim demonstrate that PLATO will be capable of detecting white dwarf pulsation modes with amplitudes as low as 0.1 mma depending on stellar magnitude, observation duration, pixel location, and the number of contributing cameras. We provide detailed detection limits and visibility forecasts for known pulsators across a representative range of these parameters. Furthermore, we emphasize strong synergies with Gaia astrometry, TESS photometry, and targeted spectroscopic campaigns, which together will enable robust mode identification and detailed stellar modeling. Collectively, these efforts will unlock unprecedented insights into white dwarf origins, evolution and internal physics, and the fate of their planetary systems. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2508.21805 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2508.21805v2 Announce Type: replace Abstract: With its third data release (DR3), Gaia begins unveiling dormant candidate compact object (CO) binaries with luminous companions (LC) as predicted by several past theoretical studies. To date, 3 black hole (BH), 21 neutron star (NS), and 3200 white dwarf (WD) candidates have been identified with LCs in detached orbits using astrometry. We adopt an observationally motivated sampling scheme for the star formation history of the Milky Way, and initial zero-age main-sequence binary properties, incorporate all relevant binary interaction processes during evolution to obtain a realistic present-day intrinsic population of CO--LC binaries. We apply Gaia's selection criteria to identify the \colc\ binaries detectable using the observational cuts applicable for DR3 as well as its end-of-mission (EOM). We find that under the DR3 selection cuts, our detectable population includes no BH--LCs, approximately 10-40 NS--LCs, and around ~4300 WD--LCs. Our predicted NS--LC population is in good agreement with the current DR3 census, both in its predicted yield and in the orbital and stellar properties, and we recover a close analogue of the Gaia NS1 candidate together with its detailed formation pathway. For WD--LCs, we find that a moderate natal kick of 5-15 km/s imparted at WD formation is required to match the observed orbital properties of WD-LC candidates in DR3. We further show that Gaia BH3-like binaries can form through standard isolated binary evolution without invoking any additional modelling assumptions, whereas reproducing Gaia BH1 and BH2 remains challenging within this framework. Looking ahead to the EOM, we predict detection of ~30-300 BH--LCs, ~1500-5000 NS-LCs, and ~10^5-10^6 WD-LC binaries, primarily due to the significantly longer observational baseline. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2507.10038 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2507.10038v3 Announce Type: replace Abstract: Parametric instability of Alfv\'en wave packets with monochromatic carrier wave in low-$\beta$ plasma is studied using one-dimensional magnetohydrodynamic simulations. The results show spatial growth of incoming perturbations as they propagate through the mother wave. For sufficiently short packets, the perturbations emerge downstream of the packet as small-amplitude reverse Alfv\'en waves and forward slow magnetosonic waves. For larger packets the perturbations reach non-linear amplitude while still inside the mother wave. In this case, a downstream section of the mother wave collapses but the remaining upstream section stays largely intact and enters the phase of very slow evolution. The length scale separating the linear and non-linear regimes, as well as determining the size of the surviving section in the non-linear regime, is set by the Alfv\'en crossing time of the packet, the growth rate of the parametric instability for the unmodulated carrier wave, and the amplitude of incoming perturbations. The results are discussed in connection with the physics of solar wind. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11848 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11848v1 Announce Type: cross Abstract: The second solar spectrum is the spectrum of the Stokes parameter Q (linear polarization) close to the solar limb. It is made of a few polarized lines with Q/I of about 1% (such as CaI, SrI, or BaII), but most lines exhibit weaker polarization. This paper presents processing of unpublished observations made in 2008 with the Meudon solar tower spectropolarimeter, which are of interest for weak and turbulent unresolved magnetic field measurements in the quiet Sun, through the Hanle effect. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11587 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11587v1 Announce Type: cross Abstract: Accurate photometric zero-points are essential for translating observed magnitudes into physical fluxes, from comparing with models to ensuring consistency across surveys. We determine the zero-points needed to place the Sloan Digital Sky Survey (SDSS) $ugriz$ system on its nominal AB definition, by exploiting the sensitivity of the Infrared Flux Method (IRFM) to broadband flux calibration. Using benchmark effective temperatures for over 6,000 FGK-type stars, we invert the method to identify the zero-point corrections required for SDSS photometry to reproduce the adopted temperature scale. The $r$ band is found to be very well standardized, while the $i$ and $z$ bands show offsets of a few hundredths of a magnitude, consistent with previous studies. We also find a small offset in the $g$ band. The largest discrepancy occurs in the $u$ band, where the derived offset depends strongly on the adopted filter transmission curves, in particular whether one uses the original definition commonly adopted in the literature or the updated measurements that account for the presence of a red leak. This effect introduces a colour-dependent zero-point offset that becomes apparent when using a sample of late-type stars. Independent comparisons with CALSPEC spectrophotometric standards and Gaia XP spectra broadly support the offsets derived from the IRFM analysis. Our results provide a revised set of SDSS zero-points anchored to the IRFM temperature scale and demonstrate that large stellar samples can be used to constrain photometric calibration. The methodology presented here offers a complementary approach to traditional spectrophotometric calibration and may prove useful for future large-scale surveys. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11367 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11367v1 Announce Type: cross Abstract: Hot evolved stars are key objects to reconstruct the various evolutionary pathways of Sun-like stars, to probe binary interactions and the physics of supernovae. They serve as powerful observational constraints to test diffusion, mixing, and mass loss in hot stellar atmospheres. Furthermore, hot stars serve as laboratories to test and derive atomic data for highly ionised trans-iron group elements and to investigate different nucleosynthesis models. Hot evolved stars emit most of their flux in the ultraviolet (UV) and a lot of progress has been made in characterizing their UV-spectra both on the observational and on the modelling side. The unique capabilities of HST to obtain high- and medium-resolution UV-spectra played a crucial role and are needed to further advance this field also in preparation for HWO. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12361 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12361v1 Announce Type: new Abstract: Coronal mass ejections (CMEs) undergo significant geometric evolution as they propagate from the Sun to 1 AU, influencing their radial size, expansion, and space weather impact. We investigate the evolution of CME aspect ratio and expansion dynamics for four fast and four slow Earth-directed CMEs. Using multipoint coronagraphic observations with the Graduated Cylindrical Shell (GCS) model and corrected in situ measurements of associated magnetic clouds (MCs) at 1 AU, we track the evolution of aspect ratio from the low-middle corona to interplanetary space. We find that aspect ratio does not remain constant but exhibits a systematic three-phase evolution: a rise phase in the low-middle corona ($\lesssim10$-$15\,R_{\odot}$), a saturation phase at intermediate heights, and then a decline phase in the interplanetary space. The ratio of radial expansion speed to leading-edge speed ($V_{\rm exp}/V_{\rm LE}$) decreases substantially from the corona to 1 AU, indicating a reduction in radial expansion efficiency during interplanetary propagation. The consistent evolution of aspect ratio and $V_{\rm exp}/V_{\rm LE}$ suggests a transition from magnetically dominated expansion in the corona to a regime increasingly controlled by the heliospheric environment. We note that fast CMEs show stronger early expansion and evolve into larger, more radially extended structures, whereas slow CMEs exhibit a more gradual rise and a steeper decline. These results demonstrate that CME geometry evolves significantly during propagation and highlight the need to incorporate aspect ratio evolution in models to improve predictions of CME size, arrival time, and geoeffectiveness. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12242 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12242v1 Announce Type: new Abstract: The location of a star along the horizontal branch (HB) during core-helium burning is primarily determined by the amount of mass lost by its progenitor. We investigate the formation and properties of stripped core-helium-burning stars, focusing on how the residual hydrogen-envelope mass ($M_{\mathrm{env}}$) and the timing of envelope removal shape their properties. We used the MESA stellar evolution code to model stars that lose their hydrogen envelopes on the first giant branch. We explored two limiting cases for the timing of stripping, corresponding to the minimum and maximum core masses for helium ignition, for progenitors with initial masses below $\sim$6 $M_{\odot}$ at two metallicities ($Z=0.02$ and $Z=0.004$), while systematically varying $M_{\mathrm{env}}$. As expected, the effective temperature along the HB decreases as $M_{\mathrm{env}}$ increases. We determined the maximum $M_{\mathrm{env}}$ required to avoid subsequent evolution through the thermally pulsing asymptotic giant branch, which ranges from $\sim0.05$ $M_{\odot}$, for low-mass progenitors to $\sim0.30$ $M_{\odot}$ for intermediate-mass progenitors. In low-mass progenitors, early envelope removal triggers a late hot flash, naturally explaining the hottest blue hook stars. In intermediate-mass systems, partial envelope stripping can produce extended pre-HB configurations consistent with puffed-up stripped stars observed in binaries with Be companions. Our post-stripping evolutionary tracks are publicly available for use in binary evolution and population synthesis studies. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12148 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12148v1 Announce Type: new Abstract: In this work, we derive upper limits for the strength of the near-core magnetic field in intermediate-mass stars, since high-order g-modes can be fully suppressed by a critical magnetic field. Both poloidal and toroidal components of the magnetic field are included. We examine how the upper limits on magnetic field strengths are affected by the degree and azimuthal order of the oscillations, as well as the magnetic field configuration. We consider two gamma-Doradus stars hosting high-order g-modes and an evolved delta-Scuti star with mixed modes, all with prior mode identification from observations. We determine the best structural model from their stellar parameters through grid-based modeling with MESA. Frequencies for the best models are extracted using GYRE and matched to the observed modes. The critical magnetic fields for all calculated frequencies in our models are obtained from the Dedalus code, from which we can infer an upper limit on the near-core field strength. We find an upper limit on the near-core radial field strength of Br ~ 130 kG and Br ~ 13 kG, assuming a dipole field configuration, for the two gamma-Doradus stars KIC 3127996 and KIC 5876187, respectively. For 44 Tau, analysis of mixed modes yields a field strength of Br ~ 1771 kG. Different magnetic field configurations and mode degrees lead to different estimates. The results for the radial component of the magnetic field in the main sequence gamma-Doradus stars are consistent with estimates of magnetic field strengths in red giant stars that assume an internal field generated by a core dynamo, although the stronger of the two inferred magnetic fields may require some enhancement by a fossil field. The toroidal component does not affect g-modes significantly and is required to be more than 200 times stronger than the radial component to suppress g-modes. (abridged for arXiv) Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12034 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12034v1 Announce Type: new Abstract: Mode visibilities can be estimated from observed power spectra or from theory by making assumptions about the damping processes occurring in the star. However, a quantitative comparison between the two approaches was so far not feasible due to observational biases. The biases arise from the fact that in observations, the power spectrum is divided into frequency segments in which modes of a certain spherical degree are expected to dominate. In this work, we used synthetic power spectra to calculate the visibility as it has been done in observations and compare it with published observed visibilities to quantify the influence of the biases. We find that, taking the biases into account, the observed spatial response of the dipole modes is 1.47, which is closer to the theoretical value than previous estimates. In particular, we predict that the normalized dipole mode visibility of late red-giant branch (RGB) stars might be overestimated by up to 20% in published observations. For stars with depressed dipole modes, we find that the normalized dipole mode visibilities estimated in observational studies might be overestimated by 20% throughout their entire evolution on the RGB. The quadrupole mode visibility, on the other hand, appears to be largely unaffected by the biases, expect on the late RGB. In addition, we investigated the evolution of the visibility and detectability of the mixed mode signature while testing different prescriptions for the energy loss caused by a strong internal magnetic field in the stellar core. We argue that taking into account the inner turning point of the g-mode cavity could allow a portion of the mode energy to be preserved when interacting with a strong magnetic field. We further show that such partial dissipation allows the mixed mode signature to be both present or absent in the observable power spectra, which is consistent with observations. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11927 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11927v1 Announce Type: new Abstract: We build a three-dimensional (3D) red supergiant (RSG) stellar model for common envelope evolution (CEE) simulations by transporting a 1D stellar model to a 3D numerical grid, mimicking core nuclear power by depositing energy to an inner shell, and mimicking stellar emission by cooling grid cells with densities below the photospheric density. We do not relax the model; rather, we let it perform its natural pulsation. We find that when we mimic photospheric emission by cooling low-density grid cells, the oscillations slowly decay on a time scale much longer than in the absence of photospheric cooling. When we mimic both nuclear energy production, by depositing the stellar luminosity in an inner shell above the inert core of the stellar model, and the photospheric cooling, the oscillations do not decay and their amplitude slowly increases with time. The main pulsational period is about 1 year, comparable to the stellar dynamical time, suggesting a fundamental radial pulsation mode. The non-spherical structure of the stellar model and rapid low-amplitude temporal variations in the average stellar radius testify to the presence of non-radial oscillation modes on top of the fundamental radial mode. We also obtain vigorous convection, as RSG stars have. We conclude that the best way of preparing a giant star to simulate CEE and grazing-envelope evolution is to deposit energy with the stellar luminosity in an inner shell, and to cool the outer low-density numerical shell. There is no need to relax the model. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11908 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11908v1 Announce Type: new Abstract: We investigate two massive young stellar objects (YSOs), IRAS21078+5211 and G035.02+0.35, where evidence for magnetohydrodynamic (MHD) disk winds (DWs) has been obtained at scales of 10-100 au through measurements of the 22GHz water maser velocity distribution within the Protostellar Outflows at the EarliesT Stages (POETS) survey. We employ IRAM Northern Extended Millimeter Array and archival Atacama Large Millimeter Array observations of IRAS21078+5211 and G035.02+0.35, respectively, to study kinematics and physical conditions of the corresponding protostellar winds on scales of 100-1000 au using the same molecular tracers. In IRAS21078+5211, the emissions of several molecules, particularly SO, SO2, CH3CN and CH3OH, are distributed along the axis of the radio jet, and present a LSR velocity (Vlsr) gradient transversal to the jet axis. Position-velocity (PV) plots of the SO lines show patterns consistent with Keplerian rotation. The SO2 emission comes from high velocity gas flowing close to the jet axis, while CH3CN and CH3OH present larger radial extension than the S-bearing species. In G035.02+0.35, the same molecules are instead distributed along the major axis of the rotating disk, and their Vlsr gradients consistently trace the disk rotation. The corresponding PV plots present Keplerian profiles. SO is the only molecular species whose emission extends well outside the disk. In both YSOs, the spatial and velocity distributions of SO are consistent with a rotating wind magneto-centrifugally launched from the YSO disk. The comparison with models of molecule formation and excitation in shocks indicates that the different radial extension of the molecular species observed in the protostellar wind of IRAS21078+5211, as well as the lack of molecules, except SO, in the G035.02+0.35's wind, can be explained in terms of a radially extended MHD DW, rather than a compact X-wind. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11594 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11594v1 Announce Type: new Abstract: Reliable estimates of stellar effective temperature ($T_{\mathrm {eff}}$) are fundamental to stellar population studies and Galactic astrophysics. However, the majority of stars observed in modern large-scale photometric surveys lack spectroscopic measurements, making empirical colour--$T_{\mathrm {eff}}$ relations essential tools. In this work, we present updated empirical colour--$T_{\mathrm {eff}}$ calibrations based on Sloan Digital Sky Survey (SDSS) $ugriz$ photometry combined with 2MASS $JHK_{\mathrm s}$ data. Effective temperatures are determined on a homogeneous InfraRed Flux Method (IRFM) scale using a combined sample of 3902 GALAH and 2535 APOGEE stars with high-quality photometry and well-characterised atmospheric parameters. Using this dataset, we establish empirical relations between $T_{\mathrm {eff}}$ and colour indices constructed from SDSS and 2MASS combinations. We provide both colour--metallicity--$T_{\mathrm {eff}}$ and colour--$T_{\mathrm {eff}}$ relations for dwarfs and giants. The calibrations are derived using low-order polynomial models with iterative $3\sigma$ clipping. Their performance depends on the adopted colour index, with long-baseline colours such as $(g-K_{\mathrm s})_0$ and $(g-z)_0$ achieving internal precisions of $\sim$30--50~K. Comparisons with previous calibrations show general agreement, with differences attributable to sample selection, photometric zero-points, and functional form. The resulting relations provide a homogeneous and internally consistent framework for estimating $T_{\mathrm {eff}}$ from SDSS and 2MASS photometry alone, and are well suited for application to large photometric surveys lacking spectroscopic information. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11492 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11492v1 Announce Type: new Abstract: The Space Weather Around Young Suns (SWAYS) program was introduced in \citet{Davis2025} as a multi-wavelength monitoring program for studying the activity and particle environments of nearby, young, solar-type stars. The SWAYS program currently includes the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) operating between 13--87\,MHz to search for stellar equivalents of solar type~II and III bursts, which are associated with bulk plasma motion in the corona and interplanetary medium. These observations are accompanied by simultaneous photometric data from the high-precision, optical instrument Flarescope to identify associated flare events. These two instruments have collectively acquired nearly 900\,hr of data with $\approx70\%$ overlap between November 2023--June 2024, dedicated to six stars. Here, we present the results of this first season of the SWAYS observing campaign, which include a superflare from the star EK~Draconis with no accompanying low-frequency particle-flux signal. The novelty of the coordination at these specific parts of the spectrum allow us to uniquely evaluate the conditions that may have inhibited a radio detection. We find that the exceptionally hot, dense coronae of incredibly active stars may not be conducive to the development of the instabilities required for type~II and III bursts, or else inspire new expectations for when we should expect to observe a signal relative to the time of the flare. This may represent the plasma-density complement to the magnetospheric limitations to observing space-weather signatures at low frequencies. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12390 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12390v1 Announce Type: new Abstract: Overview: Wind-driven bubbles are dynamic systems that can accelerate cosmic rays, depending on their physical properties, up to very high energies. We investigate how a time-dependent description of the particle transport may impact the escaping cosmic-ray flux. Model: The wind bubble system is modeled as spherically symmetric. Cosmic rays are continuously injected at the position of the termination shock and propagate through advection and diffusion until the escape at the time-dependent position of the forward shock, which is treated as a free escape boundary. Methods: The one-dimensional spherical time-dependent transport equation is solved by transforming it into the corresponding set of stochastic differential equations, and integrated with a modified version of the open source cosmic-ray propagation framework CRPropa. Results: We find that, during the wind driven phase, the downstream escaping spectra from wind bubbles can be harder than $\sim E^{-2}$, the conventional expectation from diffusive shock acceleration. Depending on the turbulence model the initial energy spectrum can be significantly suppressed at lowest energies, which could be an observable feature to distinguish between different turbulence realizations. This effect could lead to an efficient confinement of low energy particles, potentially leading to observable implication in terms of multi-messenger radiation and cosmic-ray accumulated grammage within the bubble. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12356 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12356v1 Announce Type: new Abstract: Recent Very Long Baseline Interferometry (VLBI) and Gaia astrometry reveal systematic milliarcsecond-scale offsets between the radio and optical centroids of active galactic nuclei (AGN). These "radio-optical offsets" do not alter the standard opacity-driven interpretation of radio core shifts. Instead, they indicate that the optical emission centroid is frequently displaced downstream of the radio synchrotron optical depth $\tau = 1$ surface, implying that additional dissipation and particle reacceleration occur beyond the opacity radio core within relativistic jets. We perform steady-state, axisymmetric relativistic magnetohydrodynamic (RMHD) simulations of AGN jets, including baryonic mass-load from stellar winds, varying jet kinetic power, and stellar core radius. Synthetic synchrotron emission maps in radio and optical bands are generated via a radiative transfer code, and centroid offsets are extracted for comparison with observations. Parsec-scale radio-optical offsets arise only for jet powers $L_{\rm j} \sim 10^{42.5} - 10^{44}\,\rm{erg}\,\rm{s}^{-1}$. In this regime, stellar winds trigger jet deceleration at intrinsic distances of a few $10^2-10^3\,\rm{pc}$, shifting the optical centroid downstream and producing offsets of $\sim 0.1 - 4\,\rm{mas}$ (a few tens of parsecs at $z=1$). Offsets depend on stellar distribution, viewing angle, and optical jet dominance, and vanish outside this power range. We reproduce the observed redshift evolution of offset incidence, linking it to the cosmic evolution of thermally pulsing asymptotic giant branch (TP-AGB) mass loss. Although stellar mass loading is unlikely to be the sole dissipation mechanism, its unavoidable presence in galactic nuclei makes it a natural baseline for energy dissipation. Radio-optical offsets therefore offer a constraint on AGN jet power and jet-host coupling, independent of traditional lobe-based methods. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12205 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12205v1 Announce Type: new Abstract: The distribution of the effective inspiral spin ($\chi_\mathrm{eff}$) of the binary black holes detected by LIGO-Virgo-KAGRA can shed light on their formation pathways. We analyze the GWTC-5.0 dataset with two models-one flexible, one fully parametric-that jointly describe $\chi_\mathrm{eff}$ and primary mass. We clarify that the previously-reported skewness in the $\chi_\mathrm{eff}$ distribution is better understood as additional structure beyond a non-skewed Gaussian bulk centered at small $\chi_\mathrm{eff}$. This additional structure extends to larger $|\chi_\mathrm{eff}|$, a result previously reported using GWTC-4.0 data. We measure the asymmetry of the distribution of $\chi_\mathrm{eff}$ outside the Gaussian bulk from the data. With both the parametric and the flexible analyses, we find tentative evidence for a mass-dependent excess of positive $\chi_\mathrm{eff}$ over negative ones outside the Gaussian bulk. Only at $m_1 \in [46,65]\,M_\odot$ do the data require a negative $\chi_\mathrm{eff}$ component outside the Gaussian bulk, with $23\text{:}1$ odds. If $\chi_\mathrm{eff}$ outside the Gaussian bulk are produced by hierarchical mergers-as it has been suggested-then a fraction of those mergers may be produced in environments that can generate a surplus of binaries with positive $\chi_\mathrm{eff}$, such as the disks of active galactic nuclei. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12111 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12111v1 Announce Type: new Abstract: SN 1006 is a historical Type Ia supernova remnant that exhibits non-thermal emission ranging from radio to multi-TeV $\gamma$-rays. Most of this emission (particularly X-rays and $\gamma$-rays) is concentrated in polar caps aligned with the ambient magnetic field, which makes it an ideal laboratory for studying cosmic ray (CR) acceleration at different shock obliquities and the hadronic/leptonic nature of the $\gamma$-ray emission. We model SN 1006's morphology, multi-wavelength spectrum, and radial profile using a self-consistent multi-zone kinetic model of particle acceleration that accounts for: CR-driven shock modification, magnetic field amplification, drift in magnetic fluctuations, and temporal dynamics including adiabatic and synchrotron losses. Our model can reproduce both the observed spectral and spatial properties, with the exception of the radio profile that we argue requires 3D hydrodynamic effects to replicate. We find that quasi-parallel regions (where the shock normal aligns with the ambient magnetic field) exhibit very prominent CR acceleration ($\sim$20% efficiency), while quasi-perpendicular regions exhibit efficiencies below 1%, consistent with the results of kinetic simulations. We also find that electrons are responsible for the majority of the $\gamma$-ray emission from SN 1006 (i.e., it is a leptonic source), with the exception of the northwest region due to an encounter with a dense cloud. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12092 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12092v1 Announce Type: new Abstract: In this work, we systematically study the gravitational lensing properties and observational signatures of compact boson stars. Unlike black holes, the photon effective potential of a compact boson star develops a nearly flat region, whose width increases with the compactness of the star. This flat structure significantly broadens the range of impact parameters that can produce large-angle deflections, leading to noticeably wider lensing rings of all orders. Photons constituting these rings traverse more complex paths, rendering the resulting images more sensitive to the spatial distribution of the accretion flow. Ray tracing results show that, compared to black hole models, the image topology and visibility amplitudes of compact boson stars exhibit a stronger dependence on the accretion flow structure. These results highlight qualitative differences in the observational properties of compact boson stars and black holes. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12049 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12049v1 Announce Type: new Abstract: Our study focuses on the strong tidal disruption of a cold helium white dwarf passing a black hole. We model the white dwarf as a Bose-Fermi droplet and use quantum hydrodynamic equations to simulate the binary system's evolution. As the white dwarf passes through periastron, it loses a significant amount of mass. This mass falls onto the black hole and forms an accretion disc. Quantized vortices appear in the accretion disc, manifesting as strong electromagnetic radiation signals that exhibit characteristic flickering patterns changing on a timescale of a few seconds. Meanwhile, the white dwarf moves away from the black hole. As the white dwarf moves through space, vortices run along its surface. This elongates its geometry, causing it to rotate and emit gravitational waves. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11964 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11964v1 Announce Type: new Abstract: Spherically symmetric, general relativistic Bondi accretion is known as the Michel flow. The stationary integral transonic solutions for the Michel flow has been constructed for multi-component accretion described by an equation of state where the adiabatic index varies with the radial distance along which the streamlines are studied, and the corresponding phase portrait spanned by such radial distance and the flow Mach number has been obtained. Borrowing the techniques used in the dynamical systems theory, the nature of the transonic points of the aforementioned flow has been classified. The steady state flow has been perturbed to study the stability of the stationary solutions, and it has been found that such flows are stable under the (linear) radial perturbation. As a consequence of the stability analysis, the corresponding acoustic space time embedded within the accreting matter has been obtained, and the horizon of the metric of such sonic space time has been identified by constructing the causal structure with the help of the Carter-Penrose diagrams. In this way, the accreting black hole systems in the general relativistic set up has been investigated from various different perspectives - from its astrophysical aspects, from the dynamical systems point of view, as well as within the realm of the classical analogue gravity phenomena. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11959 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11959v1 Announce Type: new Abstract: $g$ mode resonances in eccentric binary neutron star systems are potential probes of internal stratification, superfluidity, composition gradients, and the equation of state. Although such weak dynamical tidal signatures are unlikely to be resolved with current detector sensitivities, third generation observations may make them accessible, in which case identifying the weak resonant phase shift would provide information beyond the bulk adiabatic tidal deformability. We build a four class dataset in an eccentric harmonic framework, containing point particle, adiabatic tide, resonant $g$ mode, and pure noise samples, and use Einstein Telescope (ET) and Cosmic Explorer (CE) detector data to test whether this weak resonant phase signature can be identified from noisy time domain strain. The ET, CE, and ET+CE deep learning models reach accuracies of $0.655$, $0.815$, and $0.897$, respectively. On the same simulated samples, the matched filtering method reaches lower accuracies of $0.514$, $0.677$, and $0.689$. This result arises from the fact that the resonant correction manifests as a weak phase morphology difference superimposed on the adiabatic tidal background, whereas matched filtering is sensitive only to the overall similarity. Hence, in the presence of weak phase differences, the neural classifier employed in deep learning is better able to learn these local phase and morphology features from the complete time domain strain segment. The results indicate that joint third generation observations improve the identifiability of weak internal mode phase information. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11939 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11939v1 Announce Type: new Abstract: Dwarf galaxies, characterized by their low luminosities and masses, are excellent candidates for searches for intermediate-mass black holes (IMBHs), particularly when they show strong accretion and ejection activity. The dwarf galaxy SDSS J101747.09+393207.7 has recently been found to display a very high X-ray luminosity and an X-shaped optical structure, possibly caused by a dwarf--dwarf merger. To explore its potential IMBH ejection activity, we performed very long baseline interferometry (VLBI) observations at 4.9 GHz. In this work, we present the detection of a milliarcsecond-scale, compact, sub-microjansky radio component near the optical centroid. According to some existing radio sky survey data, the radio component was not detected until 2015; it displayed an optically thin steep radio spectrum and declining flux densities across 0.8--5 GHz from 2019 to 2025. Therefore, we identify it as a short-lived and rarely seen ejecta that was produced by unstable accretion onto a massive black hole and likely faded away in a few decades. These results indicate that short-lived, episodic jet activity from accreting IMBHs in dwarf galaxies might exist. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11921 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11921v1 Announce Type: new Abstract: With the aim to study the spectral properties of some X-ray sources from recently observed {\it Chandra} data, 9 galaxies which have been observed by {\it Chandra} ACIS-S during the year 2018 to 2022 have been considered for the present work. 27 sources with net source counts $ \ge$ 100 have been considered. The spectra of all the sources were fitted using two empirical models -- an absorbed powerlaw and an absorbed disk blackbody. From their estimated bolometric luminosities, the 27 X-ray sources are categorized as 6 X-ray binaries (XRBs) and 21 Ultraluminous X-ray sources (ULXs). All the six XRBs are found to be in the spectrally hard state ($\Gamma \sim$ 1.52-2.29) which indeed may be due to thermal comptonization. Only one ULX, CXOUJ032251.2-370950 (X-5), was found to be spectrally soft while the remaining 20 ULXs were spectrally hard. The spectral parameters of X-5 with an inner disk temperature (kT$_{in}$) $\sim $ 0.5 keV and an estimated bolometric luminosity, L$_X \sim$ 3.26 $\times$ 10$^{39}$ erg s$^{-1} $ requires a black hole of mass, M$_{BH} \sim$ 137.86$^{+66.62}_{-47.41}$ M$_\odot $ accreting at $ \sim$ 0.19 times its Eddington limit. 8 ULXs, X-4, X-8, X-9, X-10, X-11, X-12, X-20 and X-21, were found to be in the Extremely luminous X-ray sources (ELXs) regime with even their lower limit of luminosity $>$ 10$^{40}$ erg s$^{-1}$. Softening/Hardening of spectra with or without changes in the luminosity were also observed in some ULXs/ELXs. In the hard ELX, X-8, spectral softening with almost consistent luminosity was observed. While in the ULXs X-20 and X-25 spectral softening with increasing luminosity was observed. However spectral hardening with increase in luminosity were observed in the ULXs X-21 and X-26. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11900 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11900v1 Announce Type: new Abstract: Most galaxies host supermassive black holes (SMBHs) that remain weakly accreting or dormant for much of their lifetimes. At the lowest accretion rates, these systems may represent the transition between active nuclei and dormant black holes, but whether they can still launch collimated jets remains unclear. The nuclei in our Galaxy (\sgra) and M31 are key examples of this regime, although no clear jet structure has yet been detected in either source. Here we report multi-frequency very long baseline interferometric observations of \Msixty\ (NGC~4649), a nearby elliptical galaxy hosting a nearly dormant SMBH with an Eddington ratio of $\sim10^{-8}$. We detect a compact two-sided jet with an unusually steep synchrotron spectrum, demonstrating that collimated outflows can persist even under nearly dormant accretion conditions. The apparent radio core exhibits an unprecedentedly steep frequency-dependent position shift toward the SMBH, locating the central engine only $\sim57\,\mu$as, corresponding to a projected distance of $\sim10$ Schwarzschild radii, upstream of the 8.37-GHz core. The observed jet morphology and steep core-shift behaviour are reproduced by general relativistic magnetohydrodynamic and radiative-transfer simulations, indicating a magnetically dominated, non-equipartition jet-launching region that departs from the standard conical equipartition picture. These results provide direct observational evidence that jet production can survive near the dormant SMBHs and establish \Msixty\ as a unique laboratory for probing jet formation on event-horizon scales in the lowest-accretion SMBH regime. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11788 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11788v1 Announce Type: new Abstract: A recent analysis of the centrifugal instability in the case of pressure-supported compressible relativistic rotation, with application to astrophysical jets, yielded a generalisation of the famous Rayleigh criterion for Newtonian flows. According to this criterion, the centrifugal instability is strongly affected by the flow Mach number, and not only in the relativistic fluid dynamics but also in its Newtonian limit. To validate the Newtonian version of this criterion, we performed axisymmetric numerical simulations of non-relativistic transonic rotating flows which are stable according to the original Rayleigh criterion but can be either stable or unstable according to the new one. The results of computer simulations are found to be in perfect agreement with the theory. The hydrodynamic stability of accretion disks is often explained by referring to the original Rayleigh criterion, even if their rotation is highly supersonic. To clarify the matter, we analysed the hydrodynamic stability of flows rotating about central compact object and derived an instability criterion that retains the explicit dependence on the flow Mach number. This criterion turns out to be equivalent to the standard Solberg-H{\o}iland criterion, which does not involve the Mach number. The same applies to the case of pressure-supported rotation, where the role of gravity is played by the centrifugal force. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11748 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11748v1 Announce Type: new Abstract: Dielectronic recombination (DR) is expected to be the dominant recombination process during the non-local thermodynamic equilibrium (non-LTE) phase of kilonovae, yet reliable DR data remain unavailable for most heavy ions. Current spectral models therefore rely on simplified recombination prescriptions, introducing significant uncertainties into predicted spectra. We present an optimization strategy for open f-shell ions using \texttt{AUTOSTRUCTURE}, targeting uranium ions U II--U IV relevant to kilonova ejecta. As a benchmark case, calculations are performed for Nd III to validate the treatment of the f-shell structure and its impact on DR. The resulting DR rate coefficients are of order $10^{-10}$--$10^{-12}$ cm$^{3}$s$^{-1}$ over temperatures relevant to kilonova plasmas. The optimized rates are intended for implementation in radiative-transfer calculations with \texttt{SUMO} to assess the sensitivity of kilonova spectra to improved recombination physics. The Nd III benchmark demonstrates that refinements to the atomic structure can produce measurable changes in spectral features, motivating similar calculations for actinide ions. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11544 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11544v1 Announce Type: new Abstract: We report on NICER and MAXI observations of a long-duration thermonuclear X-ray burst and a subsequent outburst-like X-ray flare from the neutron star low-mass X-ray binary MAXI J0911--655. Prior to the burst, the source was in a persistent low/hard state with a power-law-dominated spectrum ($\Gamma \sim 1.7$) and a mass accretion rate of $\sim 1\%$ of the Eddington limit. The long burst, detected by MAXI on 2020 May 22 (MJD 58991.7101), was rapidly followed up by NICER. From time-resolved spectroscopy of the cooling tail, we estimate an exponential decay time of $\approx43$ minutes, the ignition column depth of $\approx0.1\times 10^{12}~{\rm g ~cm^{-2}}$, the burst fluence of $\approx 1.1\times 10^{-4}~{\rm erg~cm^{-2}}$, and the total energy release of $\approx1.2\times10^{42}$ erg. Approximately one day after the burst onset, the 0.5-10 keV light curve unexpectedly re-brightened, initiating an outburst-like flare. During the peak of this flare, the persistent power-law flux increased from its pre-burst level of $\sim0.27\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$ to $1.4\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$. This flux enhancement was accompanied by significant spectral softening, with the photon index increasing to $\Gamma \sim 2.2$. Subsequently, the flux decayed and the source returned to its baseline low/hard state. The observed timescales and energetics suggest that intense irradiation from the long burst amplified the ongoing thermal-viscous accretion process. This heating drove an inside-out heating front that temporarily enhanced the mass accretion rate, providing compelling observational evidence of a thermonuclear burst directly modulating the accretion dynamics of its surrounding disk. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11322 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11322v1 Announce Type: new Abstract: Event Horizon Telescope (EHT) images of black holes appear as rings with a brightness asymmetry. Here, we expand on our previous study of the asymmetry magnitude $a_1$ to study the position angle of the peak brightness asymmetry $\mathrm{PA}_1$ in general relativistic magnetohydrodynamic (GRMHD) models. For larger spin magnitudes ($a_{*}>0$ and $a_{*}\lesssim-0.5$), the mean $\mathrm{PA}_1$ falls within $1\sigma$ of the approaching limb of the black hole, regardless of viewing inclination, disk magnetization, or source. By comparing the $(a_1, \mathrm{PA}_1)$ distribution in M87* observations with models, we demonstrate that we can mildly disfavor low-magnitude spins and strongly disfavor all spin vectors that point toward Earth. The alignment of $\mathrm{PA}_1$ relative to the large-scale jet axis may suggest that M87*'s disk does not have a large tilt. By combining $\mathrm{PA}_1$ with the pattern speed measured in optimistic 2026 M87* video conditions, the EHT can constrain whether M87* is prograde or retrograde with $\sim 84\%$ accuracy. In Sgr A*, we show that a detection of $(a_1, \mathrm{PA}_1)$ could constrain the magnitude and direction of the galactic center spin vector. Finally, if future EHT expansions increase the sample of horizon-scale sources, a simple set of observables (ring diameter, asymmetry magnitude, and asymmetry angle) could enable robust constraints on black hole mass, spin, and inclination. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11307 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11307v1 Announce Type: new Abstract: Synchrotron self absorption (SSA) is seen across a variety of astrophysical sources, and observation of an SSA peak in the spectrum is a powerful tool for estimating the physical conditions and the minimum energy of the emitting region. We begin with the (re)derivation of the usual SSA parameter estimates, carefully considering dependencies and assumptions, obtaining the most accurate traditional SSA minimum energy equations currently available. Traditional methods rely on the assumption that the emitting region is quasi-spherical and homogeneous. However, many observations of SSA show that the spectral index at frequencies below the peak is less than the expected $+2.5$ (non-thermal) or $+2$ (thermal). We argue that an inhomogeneous emitting region is the most likely explanation in many cases. Power law inhomogeneous cylindrical slab and broken power law inhomogeneous sphere models are used to investigate how the presence of inhomogeneity affects parameter estimates using traditional SSA methods. We find that in some cases inhomogeneity can lead to traditional SSA methods underestimating the minimum energy and the size of the emitting region by over an order of magnitude. Quantitative correction factors are found which can be applied to traditional estimates to correct for inhomogeneity, depending on the value of the observed flattened spectral index and the range in frequency over which this value is observed. Furthermore, we derive simple correction factors for non-spherical homogeneous emitting regions. Finally, we explore the effects of inhomogeneity on measurements of polarisation around the spectral peak, and on lightcurves for expanding emitting regions. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11299 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11299v1 Announce Type: new Abstract: We conduct a global general relativistic neutrino-radiation-transfer magnetohydrodynamics simulation of a $1.35$-$1.35M_\odot$ binary neutron star with the unprecedented spatial resolution of $6.25$\,m on the Japanese supercomputer FUGAKU. The total consumed CPU time is $\approx 530$ million core hours. We initialize the binary neutron star's magnetic field to be $3.16\times 10^{12}$~G at maximum, which is compatible with the upper end of the observed binary pulsars. We demonstrate that the Kelvin-Helmholtz instability that emerges when the two neutron stars touch amplifies the magnetic field to an expected electromagnetic saturation energy of $\sim 10^{50}$~erg within $3$~ms after the merger. The spectral analysis indicates that the Kazantsev and Kolmogorov spectra are reproduced in the magnetic and kinetic power spectral densities, respectively. We also find that it induces stellar-scale magnetic field amplification by at least a factor of $316$. We conclude that a magnetar may form at least temporarily following neutron star mergers in a few ms. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11294 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11294v1 Announce Type: new Abstract: Three-body interactions exhibit phases of strong chaotic evolution as well as hierarchical motion where one body separates from a binary and follows a hyperbolic or elliptic trajectory around it. The binaries produced during phases of hierarchical motion may lead to gravitational wave (GW) inspirals, but this depends on the outcomes of the chaotic states. In this paper we re-derive the elliptic outcome distribution using equilibrium statistical mechanics and explore it together with the hyperbolic distribution. When comparing to N-body simulations, we find that we can reduce the elliptic outcome model to one free parameter instead of the previously used two and that the predicted disintegration probabilities agree except for very low angular momentum triples. We then use both outcome distributions along with a star cluster model to design a Monte Carlo algorithm for repeated binary-single scatterings within dense star systems. We explore star cluster masses of $[10^5 - 10^7] M_{\odot}$, with the goal of quantifying observably eccentric merger (OEM) GWs, visible to instruments such as LIGO and Virgo. Assuming an OEM detection sensitivity of $f_{\rm min}=10 {\rm Hz}, e_{\rm min} = 0.1$, we find the elliptic OEMs are about $\sim (32 - 63)\%$ of the total elliptic mergers and that the total cluster mass greatly impacts the fraction of ejected binaries. The OEM to total merger fraction (OEM fraction) is found to be $(2.6 - 4.4)\%$. Considering the detection sensitivity that GW interferometers have today $(f_{\rm min} \simeq 34.4 {\rm Hz})$ we obtain the OEM fraction in the $(1.6 - 3.1)\%$ range. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11291 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11291v1 Announce Type: new Abstract: Based on its predominantly thermal X-ray emission and long spin period, the isolated neutron star eRASSU J131716.9-402647 is one of the most promising candidates for membership in the still small class of X-ray dim isolated neutron stars (XDINSs). Confirmation of this classification, however, requires a more detailed characterisation of the source's timing and spectral properties. In this work, we present new NICER observations which, together with previous X-ray follow-up, allow us to constrain the timing properties and long-term evolution of eRASSU J131716.9-402647. We obtain a coherent timing solution with a spin period of $P\sim12.8$ s and a period derivative of $\dot{P}\sim9\times 10^{-14}$ s s$^{-1}$, which best-describes the spin evolution of the source. These parameters imply a dipolar magnetic field strength of $3\times10^{13}$ G and a spin-down luminosity of order $10^{30}$ erg s$^{-1}$. Spectral modelling reveals no significant change in the spectral state over the 15 months of observational monitoring and indicates a thermal luminosity that likely exceeds the rotational energy loss. This suggests a thermal evolution that has been significantly influenced by past reheating. The energy dependence of the double-humped pulse profile closely resembles that observed in the XDINS RX J1308.6+2127, with the pulsed fraction increasing towards higher energies. Taken together, these results unambiguously confirm the XDINS nature of eRASSU J131716.9-402647, making it the first newly confirmed XDINS in more than two decades. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11234 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11234v1 Announce Type: new Abstract: In recent years, the Large Area Telescope (LAT) onboard the \emph{Fermi} satellite has detected more than 300 pulsars in the high energy range. The population studies of high energy pulsars show that the gamma ray luminosity of a pulsar ($L_\gamma$) can be expressed in terms of the spin down luminosity ($\dot{E}$) as $L_\gamma \propto \dot {E}^s$ having exponent $s\sim 0.68$. This high energy emission, assumed to originate far from the stellar surface and near the light cylinder, is usually studied in either purely curvature or purely synchrotron regime. In this work, we adopt a synchro-curvature radiation framework to understand the origin of gamma ray emission from the pulsar and its implications at the population-level. By comparing the observed cutoff energies of the differential gamma-ray spectra with the theoretical synchro-curvature predictions and enforcing radiation reaction approximation, we determine the equilibrium Lorentz factor and pitch angle of the emitting charged particles. This approach allows to quantify the relative roles of curvature and synchrotron radiation to the radiative losses, thereby providing a physically grounded interpretation of the luminosity trend across the pulsar population. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11506 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11506v1 Announce Type: cross Abstract: Ultraviolet spectroscopy with the Hubble Space Telescope (HST) provides the most direct and sensitive probe of the disk-circumgalactic medium (CGM) interface at radii of 20 kpc, where galaxies exchange gas, metals, and energy with their surroundings. Many of the key diagnostics of the multiphase circumgalactic medium -- including H I, O VI, C II-IV, Si II-IV, N V, Ne VIII, and other metal transitions -- lie in the ultraviolet and are inaccessible from the ground, making HST the only observatory capable of making the required observations. By measuring the physical (column density, density), chemical (metallicity, ionization structure), and kinematical properties of the gas at the disk-CGM interface, UV absorption-line spectroscopy reveals how galaxies acquire fresh fuel, recycle enriched material, and drive feedback into their halos. When combined with spectroscopic characterization of the host galaxy's stellar populations and the feedback they generate (outflow velocity, mass loading), we will establish a direct understanding of how stellar populations enable circulation of gas and metals through the galactic ecosystem. HST's ultraviolet (UV) spectroscopic capability provides the only comprehensive observational pathways for uncovering the physical drivers that regulate galaxy growth and evolution in the low-redshift Universe. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11404 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11404v1 Announce Type: cross Abstract: In the outer Solar System, for example in the Saturnian system, a planet's strong gravity attracts micrometeoroids and generates hypervelocity impacts on bodies such as rings and satellites. Micrometeoroids are seemingly non-icy, whereas the targets are typically icy, and both the impactor and the target may span a wide range of porosities. In this study, we perform three-dimensional iSALE simulations of hypervelocity impacts of rocky impactors onto icy targets, varying the impact angle and the porosities of the impactor and target ($\phi_{\rm imp}$ and $\phi_{\rm tar}$). We consider two end-member porosities (0% and 90%) for oblique ($45^\circ$) impacts. At an impact velocity of 30 km/s, characteristic of Saturn's rings, we find that the morphology of early-stage crater formation varies significantly with porosity, transitioning from deep-penetration, narrow-channel cavities ($\phi_{\rm imp}=0$, $\phi_{\rm tar}=90%$) to very shallow craters driven by near-surface vapor blowoff ($\phi_{\rm imp}=90%$, $\phi_{\rm tar}=0%$), with intermediate, more hemispherical cavity shapes when the porosities are comparable. Here, we focus on the thermodynamic fate of the impactor, which represents the exogenic material responsible for modifying the target surface. The impactor material is strongly heated and is efficiently vaporized regardless of the porosities of the impactor and target. However, the peak pressure and peak temperature experienced by the impactor vary by nearly an order of magnitude. These results imply that hypervelocity impacts occurring, for example, in Saturn's rings efficiently vaporize exogenic non-icy impactors upon impact, while the subsequent thermodynamic pathways $-$ such as condensation and chemical evolution $-$ may differ depending on the thermodynamic conditions. Our results are expected to be applicable to a variety of planetary systems. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11378 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11378v1 Announce Type: cross Abstract: The source of the optical/UV emission in tidal disruption events (TDEs) remains an enduring question in the field. Connecting the observed emission to the source is critical for both our understanding of these transients and for using TDEs to study the efficiency of super-Eddington accretion and black hole growth. To explore this connection, we ran time-dependent 1D radiation hydrodynamic simulations of TDE emission with the Sedona monte carlo radiative transfer code, focusing on the reprocessing paradigm. Our simulations follow a compact, evolving X-ray and EUV bright source and surrounding reprocessing outflow over multiple months, using luminosities and mass flow rates consistent with hydro simulations of tidal disruptions. We determine the efficiency of reprocessing as a function of time in this dramatically changing environment and reproduce key observables including timescales, luminosities, and color evolution. Notably, we see a strong wavelength-dependence in the emission timescale due to reprocessing effects. Early on there is an X-ray flare which quickly fades as material builds up and obscures the hot source. At the same time, the optical/UV luminosity begins to rise. Though the optical/UV light curve has a similar shape to the bolometric light curve, the optical peak is offset by $\sim$3 weeks from the bolometric peak due to the time required to build up the reprocessing layer. This implies that early time, high energy emission may be missed for TDEs discovered in optical surveys, and the initial disruption and mass return time to the black hole may occur earlier than optical light curves suggest. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12355 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12355v1 Announce Type: new Abstract: Little Red Dots (LRDs) are a heterogeneous class of objects, with several proposed scenarios for their physical nature and evolution. While these theories have been tested on individual LRDs using limited spectral features, a systematic Bayesian analysis of the LRD population incorporating the different models across a broad wavelength range is still lacking. In this study, we conduct a consistent ultraviolet (UV)-to-optical continuum fitting analysis of 66 LRDs at 2<z<6 using JWST/NIRSpec PRISM spectroscopy. Employing a modified version of Bagpipes--including blackbody (BB) emission affected by Balmer absorption, stellar and nebular emission attenuated by dust, and an active galactic nucleus (AGN) component--we assess the performance of the black hole star (BH*) model in describing the LRD population. We adopt broad priors and therefore do not impose any specific physical scenario. Our results show that only ~6% of LRDs with statistically robust solutions (52 objects in total) are best-fit by a BH* in the optical and a host galaxy in the UV. ~8% of LRDs show BB-dominated optical continua but lack a stellar component or exhibit AGN UV leakage. Most LRDs are dominated by stellar and/or AGN emission in the optical, with minor BB contribution. When we adopt a prior that disfavors a strong AGN continuum to enforce BH*-like solutions, the percentage of BH$^*$ systems increases to ~40%, highlighting the strong degeneracy between a BH* solution and alternative scenarios. Even when BH*-like solutions are enforced, many LRDs still require a stellar-dominated optical continuum. This may reveal limitations of the BH* model or point to an evolutionary sequence in which the BB contribution decreases as the host grows, leading to lower BB temperatures and higher stellar masses at lower z. In this scenario, more pronounced ''V'' shapes would correspond to later stages in LRD evolution. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12254 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12254v1 Announce Type: new Abstract: Studying young stellar populations within galaxies can help refine our understanding of recent star formation in galaxies and their evolution. With this motivation, we present a catalog of ~25,000 recently formed (within 400 Myr) star-forming clumps (SFCs) in 17 morphologically diverse nearby galaxies, including 8 massive, classic spirals, 6 intermediate-mass, flocculent spirals, and 3 dwarf irregulars. We used far- and near-UV observations from the UltraViolet Imaging Telescope (UVIT), whose ~1.5" angular resolution and 28' field-of-view allow us to probe SFCs at a mean physical scale of ~54 parsec, within the full extent of our galaxies. We adopted a homogeneous SFC detection criterion, corrected for spatially varying dust attenuation (using 6" resolution A_V maps, made by combining FUV with archival infrared observations), and estimated the SFC ages by comparing the observed UV color-magnitude diagrams with Starburst99 simple stellar population models. Using our SFC catalog, we studied the age demographic of the recently formed stellar populations across different galaxy morphologies and observed age trends consistent with several well-known phenomena, such as the inside-out formation of disc galaxies, local gravitational instabilities leading to flocculent spiral arms, and the stochastic nature of star formation in dwarf galaxies. Leveraging full galaxy coverage and FUV data, our catalog complements existing optically-identified star cluster catalogs in the literature towards improving our understanding of star formation across a wide range of galaxy morphologies, masses, and environments. We make the SFC catalog and A_V maps of our 17 galaxies publicly available with this paper. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12249 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12249v1 Announce Type: new Abstract: An accurate determination of the dust attenuation within galaxies is essential to derive key physical properties such as the star formation rate (SFR). We present an analysis using the JWST/NIRISS data from the GLASS-JWST ERS programme to investigate and characterise the stellar and nebular reddening of galaxies at $1.0<z<2.4$, down to the sub-kpc scale. We use a multiregion fitting method to extract high-quality H$\alpha$ and H$\beta$ emission line maps for 99 individual galaxies across a stellar mass range $7.0<\log_{10}(M_*/\mathrm{M}_{\odot})<10.5$. We find no evidence for ratios of the Balmer decrement (H$\alpha$/H$\beta$) below the intrinsic limit for Case B recombination, beyond the expected variation from observational uncertainties. We reproduce the local correlation between the Balmer decrement and total stellar mass, and find no measurable difference when splitting the sample by redshift, with negligible attenuation below $\log_{10}(M_*/\mathrm{M}_{\odot})\lesssim8.5$. Similarly, the best-fit relation between the nebular and continuum reddening follows the same relation as in local starburst galaxies, $E(B-V)_{\mathrm{SED}} = (0.46\pm0.02)E(B-V)_{\mathrm{neb}}$, together indicating no significant evolution in the dust geometry within galaxies out to $z\lesssim2.4$. We derive best-fit linear relations between the differential nebular-stellar reddening and the SED-derived star formation rate (SFR) and stellar mass, finding statistically significant relations for both quantities. We use our spatially-resolved measurements to derive an empirical calibration between the resolved differential reddening, and the SFR surface density. These will enable crucial dust attenuation corrections for spatially-resolved science at higher redshifts where the Balmer lines are inaccessible, such as with future Roman grism observations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12156 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12156v1 Announce Type: new Abstract: The shutdown of star formation - quenching - marks a pivotal transition in the lives of massive galaxies, which dominate the present-day stellar mass density. This review synthesizes our current understanding of the mechanisms that trigger and maintain quiescence. We discuss the nuances of how quiescent systems are identified across cosmic time and summarize the evolving physical properties of the growing massive population, including their stellar populations, chemical enrichment histories, and gas and dust reservoirs, highlighting several key results: (1) Quiescent galaxies can be identified with empirical color selections, but evolving specific star formation rate thresholds offer a more robust physical distinction from star-forming systems. (2) The earliest massive quiescent stellar populations show rapid formation histories and high metallicities, with enhanced $\alpha$-elemental abundances often distinct from local analogs. (3) Nascent studies of gas and dust in quiescent galaxies reveal diverse multiphase reservoirs and outflows, pointing to fast ejective and slow regulatory modes of galaxy quenching. (4) In situ processes establish galaxy central density, while assembly continues via (minor) mergers post-quenching, reshaping all massive galaxies and disrupting rotation in most cases. We distill observations into two broad modes by which massive galaxies form and quench: one involves a rapid, early shutdown driven by supermassive black hole outflows on short timescales; the other proceeds gradually through gas exhaustion, virial heating, or preventative feedback, each leaving distinct observational signatures. Together, these pathways offer a testable framework for modeling the formation and evolution of massive galaxies, which will be informed by future studies of their stars, gas, dust, and dynamics. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12076 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12076v1 Announce Type: new Abstract: The population of Compton-thick (CTK) AGN represents a critical yet elusive phase in the growth of supermassive black holes. Constraining their abundance and evolution at high z is essential for understanding both SMBH growth and the origin of the cosmic X-ray background. We investigate the X-ray luminosity function (XLF) of CTK AGN at z > 3 using one of the largest available samples of X-ray-selected AGN at high z, containing 811 sources from XMM-Newton XXL-N and Chandra CCLS and CDF-S/N surveys. We first selected a subsample of ten high-probability CTK candidates, identified through x-ray spectral fitting. Their multiwavelength properties are examined through SED modelling to assess the robustness of their CTK classification. For most sources, the inferred X-ray luminosities appear overestimated when compared with their IR luminosities. After updating the NH posteriors with IR-informed priors, only three sources remain consistent with the CTK regime. To compute the XLF for the entire CTK AGN population, we used 24 microns photometry to estimate IR luminosities and update the X-ray posteriors for all the remaining sources. Incorporating IR priors systematically reduces the inferred CTK number densities, yielding a more conservative and physically consistent estimate of the XLF. We find that CTK AGN constitute 17 per cent of the total AGN population at 3 1e23 cm-2) increases toward higher redshifts, the stable CTK fraction supports the interpretation that, at these epochs, the interstellar medium in typical host galaxies cannot produce CTK levels of obscuration. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11872 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11872v1 Announce Type: new Abstract: The rotational velocity of interstellar gas in the Milky Way, and other galaxies, has been taken to represent the circular velocity of a test particle in the Galaxy gravitational field, and hence an indicator of the Galaxy mass. The derived circular velocity is found to be too high for the gas to be gravitationally bound to the galaxy given the observed Galaxy mass in stars and gas, and consequently an extra component of mass in the Milky Way and other galaxies, namely dark matter, has been postulated. However recently the observational satellite Gaia, has been carrying out ground-breaking astrometric observations to accurately measure, inter alia, the three dimensional velocities of stars in the vicinity of the Sun and beyond. This has revealed that the circular velocity derived from the stellar population is much less than that of the gas, and the rotation curve, circular velocity versus radius, is distinctly declining with radius, whereas the gas rotation curve is not declining. By combining results from multiple observations of the gas velocity, averaging the velocities in radial bins, we establish that there is a grand average rotation curve. This can be compared directly with a grand average of the published Gaia rotation curves, and the confidence level in the difference between the two estimated by statistical analysis. The difference is shown to have a high degree of confidence, and increases with galactocentric radius. The lower circular rotation curve from the stellar velocities has resulted in significantly reduced estimates of the dark matter mass fraction of the Milky Way. The higher rotation of the gas lacks an explanation, but it is unlikely to be an accurate indicator of the kinematic mass of the Galaxy. This also has significant consequences for the mass of external galaxies based on gas rotation curves. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11733 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11733v1 Announce Type: new Abstract: We analyze the geometry and kinematics of substructures within molecular clouds identified in an unbiased catalog from the MWISP survey. These substructures are defined as spatially connected regions enclosed by the 20% peak-integrated-intensity contour of each cloud. After applying selection criteria on voxel size and excluding structures truncated by map boundaries, we construct a sample and quantify their projected morphology using the projected scale ratio $R=\Delta b/(\Delta l\cdot\cos b)$. This ratio essentially measures $\tan\theta$ where $\theta$ is the plane-of-sky angle of an elongated filament relative to the Galactic plane. The resulting sample exhibits a median $R=0.96$, indicating a slight but systematic preference for elongation along Galactic longitude. This tendency becomes more pronounced at larger spatial scales. We further investigate the relative orientations among the structural major axes, velocity-gradient directions, and plane-of-sky magnetic-field orientations derived from Planck data for a subsample of well-defined structures. We find that, for cloud structures within our sample, with physical scale $\sim 0.3$ to $\sim 30$ pc, velocity gradients tend to be perpendicular to the major axes, while magnetic-field are generally aligned parallel to them. This scale range differs from those typically probed in studies of dense cores ($\sim 0.05$ pc) and GMC-scale structures ($\gtrsim$ 10 to 100 pc), which have reported scale-dependent variations in relative orientations. In addition, the alignment between velocity gradients and magnetic fields shows a gradual weakening with increasing physical scale. These results suggest that the observed anisotropy of molecular cloud substructures may arise from a combination of large-scale Galactic dynamics, anisotropic gas motions, and magnetic fields, with the relative importance of these effects varying with scale. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11444 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11444v1 Announce Type: new Abstract: We present ALMA high-resolution ($\sim$0.25$^{\prime\prime}$/2 kpc) CO(5-4) and CO(4-3) observations of three $z\sim 3$ submillimetre-selected dusty galaxies from the ALESS survey. These data complement existing [sub]-kpc scale ALMA 870$\mu$m continuum imaging and JWST NIRCam and MIRI imaging from the ALESS-JWST program, allowing us to trace the molecular gas, dust-obscured star formation, and stellar populations on similar spatial scales. We spectroscopically confirm that two of the sources lie at the same redshift and are likely interacting. We find that the molecular-gas distribution broadly follows the dusty star-forming structures seen in the 870$\mu$m dust continuum imaging, but that the gas reservoirs are significantly more extended than the dust emission with a spatial extent comparable to the rest-frame near-infrared stellar emission. By modeling the kinematics for the two highest signal-to-noise sources, we find that the galaxies are well-fit by rotating disc models with high ratios of ordered to random motion ($V_{\rm{max}}/\overline{\sigma}=5\pm1$ and $6\pm1$), although smaller-scale kinematic deviations cannot be ruled out at the current sensitivity and spatial resolution. Finally, utilizing the high-resolution 870$\mu$m dust continuum and CO data, we investigate star-formation scaling relations on kpc-scales in these high-redshift galaxies. Assuming a constant CO-to-H$_{2}$ conversion factor and excitation ratio, we find that the data are offset from theoretical star-formation relation predictions that do not take turbulence into account, but consistent with gravo-turbulent models, thereby suggesting that turbulence plays a central role in regulating star formation at high redshift. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11394 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11394v1 Announce Type: new Abstract: We present the first spatially contiguous study of the physical and chemical structure of the Helix Nebula (NGC~7293, PNG 036.1-57.1) based on integral-field spectroscopy from the SDSS-V Local Volume Mapper (LVM). The wide-field observations provide nearly complete spectroscopic coverage of the nebula, enabling a spaxel-by-spaxel analysis of extinction, electron density and temperature, ionisation structure, and chemical abundances. We reconstruct calibrated datacubes from the LVM row-stacked spectra and measure 41 optical emission lines, including hydrogen, helium, and collisionally excited metal lines. The resulting maps reveal a strongly stratified nebula, with highly ionised gas traced by \heii~concentrated toward the central cavity, low-ionisation material dominating the bright shell, and neutral or transition-zone gas enhanced in the outer regions. The Helix is a low-density object, with typical electron densities of $\sim10^{2}\mathrm{cm^{-3}}$, and exhibits a non-uniform temperature structure, with variations of several thousand Kelvin across different ionisation zones. We derive a near-solar oxygen abundance, $12+\log(\mathrm{O/H})\simeq8.7$, consistent with spatially complete sampling. The central abundance pattern indicates a significant contribution from unobserved O$^{3+}$, suggesting that apparent abundance variations are primarily driven by ionisation effects rather than true chemical inhomogeneities. We also find evidence for a sulfur deficit of $\sim$1 dex, consistent with the planetary-nebula sulfur anomaly. The helium and nitrogen abundances place the Helix near the classical boundary of Type~I planetary nebulae, suggesting moderate chemical enrichment by its progenitor star. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11374 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11374v1 Announce Type: new Abstract: The quasar Eigenvector-1/Main Sequence (E1/MS) provides a physically motivated empirical framework to organize the spectroscopic diversity of type~1 active galactic nuclei (AGN). In its optical plane, the full width at half maximum of H$\beta$ and the Fe\,II strength ratio $R_{\mathrm{FeII}}$ define a sequence that is primarily driven by Eddington ratio, with important secondary roles played by black-hole mass, orientation, spectral energy distribution, and chemical enrichment. The E1/MS framework is therefore well suited to identify highly accreting and possibly super-Eddington (SE) sources, usually associated with the extreme Population~A (xA) spectral types. We discuss why E1/MS is a useful tool to search for SE accretors among jetted AGN and, conversely, to place $\gamma$-ray-detected AGN in the broader context of quasar phenomenology. We summarize two complementary results: (1) some candidate SE accretors show radio properties such as high brightness temperature non-thermal cores or radio lobes} consistent with jet activity; and (2) a subset of low-redshift $\gamma$-ray narrow-line Seyfert~1 galaxies exhibit optical spectra consistent with xA or borderline-xA classification. We also expand the discussion of recent developments in E1/MS studies, including metallicity trends, the spectral energy distribution of xA quasars, and the role of highly accreting quasars as discovery tools for extreme accretion states, as probes of quasars at the reionization epoch, and as possible cosmological probes. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11359 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11359v1 Announce Type: new Abstract: The interstellar medium (ISM) is a complex, multiphase medium, where disentangling the distribution of gas and magnetic field structure across different phases remains a considerable challenge. Recently, Faraday tomography enabled by broadband polarized radio observations has emerged as a promising probe of 3D ISM gas and magnetic field structures. However, the interpretation of these observations is obscured by our limited understanding of the different ISM components probed by the distinct Faraday depth features. In this work, we present a comprehensive multi-frequency ($\sim$300 MHz - 23 GHz) analysis comparing features in the Faraday-rotated, polarized synchrotron emission and HI structures over the full high-latitude (|b|>30 degrees) diffuse sky. Using measures of HI structure complexity along the line of sight (LOS), we observe enhanced depolarization across synchrotron radio frequencies in regions with high HI complexity characterized by multiple HI velocity components. We also find that the first and second moments of the Faraday depth spectra are linked to the underlying neutral gas structure. These results indicate that regions of the ISM that are dominated by neutral gas could directly contribute a significant portion of the diffuse synchrotron emission and Faraday rotation. These findings establish new observational constraints for Galactic magnetic field models that synthesize multiphase tracers into a single coherent picture. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11345 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11345v1 Announce Type: new Abstract: We present gas-phase metallicities of star-forming galaxies at $z=1$-10 with deep JWST/NIRSpec spectra from the JADES full data release, Dark Horse, and OASIS programmes. We stack $\sim$1500 medium-resolution spectra, yielding detections of the [OIII]$\lambda$4363 auroral line down to $12+\log(\mathrm{O/H})=7.0$ to derive stack-based strong-line calibrations over the metallicity range $12+\log(\mathrm{O/H})=7.0$-8.7. At a fixed metallicity, our stacks exhibit [OIII]$\lambda$5007/H$\beta$ and [OIII]$\lambda$5007/[OII]$\lambda\lambda$3726,3729 values generally lower than calibrations based on high-$z$ individual auroral-line emitters, suggesting an observational bias towards higher excitation introduced when requiring auroral line detections in individual spectra. Based on our new calibrations, we obtain canonical mass-metallicity relations (MZRs) at z$=$1-10, identifying a decrease in metallicities from $z\sim0$ to z$\sim$4-10, without significant change in slope. Moreover, we identify 50 promising candidates of extremely metal-poor galaxies (EMPGs) with $12+\log(\mathrm{O/H})=6.7$-7.3 (1-4\% solar metallicity) at $z=1.2$-9.1. The MZRs of EMPGs are characterised by a large scatter, with those having lower metallicities generally exhibiting lower sSFRs, opposite of what expected from the local Fundamental Metallicity Relation. These results support a stochastic star-formation history involving gas consumption/ejection and metal-poor inflow, strongly affecting metallicities of low-mass galaxies. Furthermore, we identify two Little Red Dots in our EMPG candidates, both exhibiting broad H$\alpha$ and prominent Ly$\alpha$, offering insights into the early black-hole growth in extremely metal-poor environments. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11329 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11329v1 Announce Type: new Abstract: In this paper we present the chemical screening of the complex stellar population discovered in the Bulge Fossil Fragment Liller 1. This study is part of the Bulge Cluster Origin (BulCO) survey based on a Large Program at the ESO-VLT with the high resolution spectrograph CRIRES+. The survey is aimed at performing an unprecedented chemical screening of 17 stellar systems orbiting the Milky Way bulge, with the ultimate goal of unveiling their origin and true nature. We measured precise chemical abundances of iron, CNO, iron-peak, $\alpha$- other light-elements, and neutron-capture elements for a sample of 30 red giant branch stars, kinematic members of Liller 1. The presented analysis provides the high-resolution spectroscopic proof of the complex chemistry of this massive stellar system, with multi-metallicity sub-populations of different ages that nicely fits into a self-enrichment scenario. We find no evidence for the Na-O anticorrelation associated with genuine globular clusters; rather the overall abundance trends are similar to those seen in the bulge field and in Terzan 5, providing definitive evidence of an in-situ formation of Liller 1 within the Galactic bulge. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11328 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11328v1 Announce Type: new Abstract: After quenching galaxies keep growing in size across time, as established in the literature up to cosmic noon. In this work, we assemble one of the largest and most comprehensive multi-wavelength photometric sample of massive quenched galaxies at z > 3, counting 137 quiescent candidates within 825 sq.arcmin and redshift 3 3, albeit with a large scatter. This suggests that the commonly used parameters of a Sersic distribution cannot explain the large intrinsic scatter around the stellar mass-size relation, suggesting that other physical quantities need to be taken into account to break the degeneracy between evolution paths across the galaxy population. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11323 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11323v1 Announce Type: new Abstract: Magnetic fields permeate the multiphase interstellar medium (ISM), yet their phase-dependent structure remains poorly constrained by observations. Dust polarization and \ion{H}{1} emission together offer complementary probes of the plane-of-sky magnetic field and cold neutral medium (CNM) gas structure, respectively. Recent observational work has shown that in the diffuse ISM, the dust polarization fraction correlates positively with the CNM mass fraction ($f_{\rm CNM}$) but not with total \ion{H}{1} column density, suggesting a phase-dependent magnetic field geometry. Here, we use extremely high-resolution ($2048^3$) simulations of the turbulent, magnetized, multiphase ISM to investigate the physical origin of this trend. By constructing synthetic \ion{H}{1} and dust polarization maps, we directly compare our simulations to the observational results of \citet{Lei:2024}. We recover a positive $f_{\rm CNM}$-polarization correlation most clearly for sightlines intersecting fewer than $\sim$20 discrete CNM clouds, while the trend becomes weak or intermittent for larger cloud counts, consistent with the expectation that high-Galactic-latitude sightlines contain relatively few independent cold structures. We show that this correlation reflects genuine phase-dependent magnetic structure: CNM clouds tend to be elongated along the local magnetic field and, when normalized by column density, exhibit lower magnetic disorder than the warm neutral medium (WNM). We further demonstrate that apparent discrepancies between simulation- and observation-based measures of magnetic disorder arise from whether disorder is quantified per unit path length or per unit mass. Our results support a picture in which CNM structures host relatively ordered magnetic fields, producing higher polarization fractions along CNM-dominated sightlines in the diffuse ISM. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11315 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11315v1 Announce Type: new Abstract: The properties of spiral galaxies in the early universe remain poorly studied and, as such, little is known about their nature and evolution. We use JWST data to measure the pitch angles of spiral galaxies across cosmic time. Our sample consists of 593 spiral galaxies with stellar masses ($M_*$) greater than $10^{10} M_\odot$ up to $z \sim 3.5$, drawn from the CEERS and JADES surveys. Spiral galaxies are identified by fine-tuning a Zoobot deep-learning model. We use SpArcFiRe to identify spiral arms and measure their pitch angles. We find no significant redshift evolution in the average pitch angle across the full sample. However, in the most massive systems (log$(M_*/M_\odot)=11-12$), spiral arms slightly wind up with time. We show that at $z>1.25$, pitch angle does not correlate with some key internal galaxy properties (stellar mass, bulge mass, disk mass, specific star formation rate [sSFR]). In contrast, at $z<1.25$, pitch angle shows a weak but statistically significant negative correlation with stellar mass, bulge mass, and disk mass, and a positive correlation with sSFR at $z<0.75$. We also find no dependence of pitch angle on the tidal strength applied by nearby companions. These results indicate a transition epoch at $z\sim1$: above this redshift, spiral structures appear to be primarily locally driven and not correlated with global galaxy properties; and below this redshift, spiral arms are regulated by global gravitational potential, consistent with the predictions of the density wave theory. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11313 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11313v1 Announce Type: new Abstract: Low surface brightness tidal debris around galaxies, such as tails, streams, and shells, together with other interaction-driven morphological disturbances, serve as valuable indicators of past or ongoing galaxy mergers. With the growing data volume from surveys like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), automated detection methods are essential. This paper evaluates the performance of two automated methods, a Self-Supervised Learning (SSL) model and the Concentration-Asymmetry-Smoothness (CAS) parameter method, in tracing interaction-driven disturbances and merger signatures, with visual classification used as the benchmark. Visual classification yields a high-confidence disturbance fraction of 25.1 +/- 1.5% in our sample and serves as the reference standard for assessing the completeness and precision of the automated approaches. Visual classification is affected by galaxy distance and image resolution, which limit the detectability of faint low surface brightness structures. The SSL model achieves high recall (0.86 +/- 0.04) and low contamination (0.2) by retraining only its linear classifier on a small labelled dataset, making it suitable for identifying a broad set of disturbed systems, including faint tidal debris and other interaction-driven morphological disturbances, thereby providing a more complete census of merger-related features. The CAS method, using the traditional threshold A > 0.35, shows higher precision (0.77) but lower recall (0.20), indicating a conservative approach that captures cleaner but less complete samples. Visual classification and the SSL model show a significant positive correlation between stellar mass and disturbance fraction, while the CAS method exhibits a much weaker trend. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2510.08699 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2510.08699v2 Announce Type: replace Abstract: The number of observed gravitational wave (GW) events is growing fast thanks to rapidly improving detector sensitivities. GWs from compact binary coalescences like Black Holes or Neutron Stars behave like standard sirens and can be used as cosmological probes. To this aim, generally, the observation of an electromagnetic counterpart and the measurement of the redshift are needed. However, even when those are not available, it is still possible to exploit these "dark sirens" via statistical methods. In this work, we explore a method that exploits the information contained in the cross-correlation of samples of GW events with matter over-density tracers like galaxy catalogues. Contrary to other currently employed dark-sirens methods, this approach does not suffer from systematic errors related to the incompleteness of the galaxy catalogue. To further enhance the technique, we implement tomography in redshift space for the galaxy catalogue and luminosity distance space for the GWs. We simulate future data collected by the array of currently existing detectors, namely LIGO, Virgo, and Kagra, as well as planned third-generation ones such as the Einstein Telescope and Cosmic Explorers. We cross-correlate these data with those from upcoming photometric galaxy surveys such as Euclid. We perform a sensitivity forecast employing a full-likelihood approach and explore the parameter space with Monte Carlo Markov Chains. We find that with this method, third-generation detectors will be able to determine the Hubble constant $H_0$ with an error of only 0.7%, which is enough to provide decisive information to shed light on the Hubble tension. Furthermore, for the other cosmological parameters, we find that the GWs and galaxy surveys information are highly complementary, and the use of both significantly improves the ability to constrain the underlying cosmology. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2510.04179 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2510.04179v4 Announce Type: replace Abstract: We perform a consistency check of DESI DR2 BAO constraints ($D_M/r_d, D_H/r_d)$ by reconstructing the same quantities from DES supernovae (SNe) in bins with the same effective redshift $z_{\textrm{eff}} \in \{ 0.510, 0.706, 0.934 \}$ and a Planck $r_d$ prior. Through mock analysis we show that $D_M(z_{\rm eff})$ and $D_{H}(z_{\rm eff})$ can be locally reconstructed model agnostically from $\Lambda$CDM and extended models, but only if one employs frequentist methods; purely Bayesian reconstructions from Markov Chain Monte Carlo (MCMC) exhibit bias. We find that the ratio of the three $D_M/r_d$ values at different $z_{\textrm{eff}}$ are consistent with a horizontal, thus confirming that the distance duality relation holds up to calibration. However, the $D_H/r_d$ ratio shows a decreasing trend driven by the $z_{\textrm{eff}} = 0.934$ bin, the significance of which varies from $2.5 \sigma$ with Bayesian methods down to $1.4 \sigma$ with frequentist methods. We show that replacing DES with DES-Dovekie SNe reduces the significance to $1.7 \sigma$ and $1.2 \sigma$ in Bayesian and frequentist approaches, respectively. We conclude that distances reconstructed from SNe show good agreement with DESI BAO distances across the redshifts studied. We also note that $D_M(z_{\rm eff} = 0.510)/r_d$ reconstructed from SNe favours DESI BAO over transversal BAO against a backdrop of a $3.7 \sigma$ disagreement. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2509.09665 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2509.09665v3 Announce Type: replace Abstract: One of the most pressing problems in current cosmology is the cause of the Hubble tension. We revisit a two-rung distance ladder, composed only of Cepheid periods and magnitudes, anchor distances in the Milky Way, Large Magellanic Cloud, NGC 4258, and host galaxy redshifts. We adopt the SH0ES data for the most up-to-date and carefully vetted measurements, where the Cepheid hosts were selected to harbour also Type Ia supernovae. We introduce two important improvements: a rigorous selection modelling and a state-of-the-art density and peculiar velocity model using Manticore-Local, based on the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. We infer $H_0 = 71.1 \pm 1.4~\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$, assuming the Cepheid host sample was selected by supernova magnitudes. However, the actual selection criteria are not clear, and other assumptions can increase $H_0$ by up to one statistical standard deviation. The posterior has a lower central value and a 41 per cent smaller uncertainty than a previous study using the same distance-ladder data. This result is lower than the supernova-based SH0ES inferred value of $H_0 = 73.2 \pm 0.9~\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$ at about $1.3\sigma$, and is in $2.8\sigma$ tension with the latest cosmic microwave background results in the standard cosmological model. These results demonstrate that a measurement of $H_0$ of sufficient precision to weigh in on the Hubble tension is achievable using second-rung data alone, underscoring the importance of robust and accurate statistical and velocity-field modelling. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12408 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12408v1 Announce Type: cross Abstract: Recent results from the DAMIC-M and PandaX collaborations have excluded the standard freeze-in production of dark matter for masses in the range $3~\mathrm{MeV} \lesssim m_\chi \lesssim 1~\mathrm{GeV}$ in the context of extensions of the Standard Model featuring an additional ultra-light $U(1)_{\rm X}$ gauge boson. In this work, we analyze the constraints induced by DAMIC-M and PandaX results on the reheating temperature in freeze-in models at stronger coupling, or when a non-thermal source (such as inflaton decay) comes into play. We identify viable scenarios in which the DM relic abundance is correctly reproduced while evading current experimental bounds on the electron-scattering cross section, $\overline{\sigma}_\mathrm{e}$. In particular, we show that for reheating temperatures below the electroweak scale, Boltzmann suppressed production can be compensated by stronger couplings, bringing freeze-in scenarios within present experimental reach. Finally, we study a hybrid scenario in which a small branching ratio of inflaton decay seeds a nonzero initial dark-matter abundance. We show that such contributions can significantly modify freeze-in predictions across broad regions of parameter space, offering an additional pathway for probing extremely feeble interactions. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12297 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12297v1 Announce Type: cross Abstract: The origin of cosmic acceleration remains a central problem in cosmology, commonly attributed to a cosmological constant within the $\Lambda$CDM model or to dynamical dark energy. Here, we develop an alternative approach in which acceleration emerges from quantum post-selection, a standard feature of quantum theory that is not usually incorporated into cosmological modelling. While quantum theory admits both pre-selected and post-selected ensembles, quantum cosmological models are almost exclusively formulated in terms of initial conditions. Building on previous work on post-selected quasiclassical dynamics, we construct a minimal predictive cosmological model in which post-selection and coarse-graining generate effective late-time acceleration without introducing a cosmological constant, dark energy, or modifications of general relativity. The resulting expansion history is highly constrained theoretically and depends on at most two parameters beyond standard Friedmann evolution. Confrontation with type Ia supernova and cosmic chronometer data yields statistically competitive fits while naturally avoiding the coincidence problem. The model also reproduces the standard radiation- and matter-dominated behaviour at early times and predicts a present-day jerk parameter significantly different from the $\Lambda$CDM value. These results suggest that cosmic acceleration may arise as a macroscopic quantum cosmological effect rather than from additional cosmological fluids or modified gravitational dynamics. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11923 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11923v1 Announce Type: cross Abstract: The propagation of very-high-energy (VHE; $E_{\gamma} \geq 100$ GeV) gamma rays from extragalactic sources is affected by interactions with photons of the extragalactic background light (EBL), resulting in pair production that attenuates the intrinsic gamma-ray flux. This interaction renders the Universe increasingly opaque to VHE photons at high energies and redshifts. New physics scenarios involving axion-like particles (ALPs) could modify this expected optical depth. In particular, ALPs with masses $m_a \sim 10$ eV can decay into two photons over cosmological timescales, thereby contributing to the diffuse EBL. If such ALPs constitute a significant fraction of the dark matter density, their decay would enhance the EBL intensity and consequently increase the gamma-ray optical depth. In this study, we investigate this scenario using a large sample of gamma-ray spectra observed with the High Energy Stereoscopic System (H.E.S.S.) and the Fermi Large Area Telescope. We model the contribution of decaying ALPs to the EBL and assess their impact on the spectra of blazars across redshifts. By comparing these observations with standard EBL models, we place constraints on the properties of heavy ALPs, specifically their mass and photon coupling, and evaluate their viability as a dark matter candidate capable of modifying the gamma-ray transparency of the Universe. From the combined analysis, and under the assumption that ALPs constitute the entire dark matter density, we derive 95% confidence exclusion limits on the photon-ALP coupling down to $g_{a\gamma} \sim 7 \times 10^{-12}$ GeV$^{-1}$ for masses $m_a\sim 15$ eV. These constraints are competitive with existing astrophysical bounds and provide complementary sensitivity to other techniques, closing a previously unconstrained region of parameter space in the $m_a \sim 2.5$-$20$ eV range. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11305 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11305v1 Announce Type: cross Abstract: For broadband imaging surveys, filter-substrate refraction causes light at different wavelengths to follow slightly different paths through the filter substrate before reaching the detector. This effect produces two chromatic perturbations to the point spread function (PSF): a shift in the effective focal position along the optical axis (longitudinal shift), which manifests as a defocus-like perturbation, and a wavelength-dependent displacement of the image position in the focal plane (lateral shift), which manifests as image decentering. Using image simulations, we provide the first study of these two effects independently across all eight Roman imaging bands and over the full focal plane. We compute the resulting PSF and photometric errors from images with and without the effect included, and compare the magnitude of the effect to the Roman science requirements. We find that the lateral shift is the dominant contribution, producing PSF size and ellipticity residuals in most bands of order ~0.3-0.4%. These exceed the Roman science requirements for weak lensing by roughly an order of magnitude. The effect is also strongly field dependent, increasing toward the edges of the focal plane. By contrast, flux residuals remain below one third of the 1% requirement for most bands, except in R062 and W146. We find the longitudinal shift to be subdominant and negligible in most bands, including the weak lensing bands. Finally, we implement the dominant lateral-shift effect in a framework suitable for large-scale image simulations and validate that the resulting PSF size and shape changes are accurately reproduced. Overall, we find that filter-substrate refraction is a relevant chromatic effect for Roman PSF modeling, and we provide tools to model and incorporate it in large-scale image simulations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12405 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12405v1 Announce Type: new Abstract: Small-scale galaxy clustering is expected to contain substantial cosmological information, but the extent to which this information constrains halo-based cosmologies independent of an assumed galaxy--halo connection remains unclear. We quantify this dependence using LRG-like mock galaxy catalogs built from 81 cosmologies in the {\tt \textsc{AbacusSummit}} suite. We analyze two-point correlation function multipoles on scales ranging from $5$--$80$ Mpc/$h$ and compare two limiting treatments, the \enquote{floor} and \enquote{ceiling}, of the standard five-parameter HOD model. In the conservative floor case, we impose only broad initial HOD bounds and profile over HOD parameters to determine the minimum constraining power available; we accomplish this with {\tt HODmin}, a two-stage global optimization algorithm written for minimizing $\chi^2$ in HOD space. In the optimistic ceiling case, we assume the HOD parameters are known exactly. We find a significant difference between the floor and ceiling when comparing against the same Planck $\Lambda$CDM mock data vector with identical modeling assumptions: for the floor, $25\%$ of the discrete {\tt \textsc{AbacusSummit}} cosmologies tested are excluded at $3\sigma$, whereas for the ceiling, $\sim81\%$ are excluded. Many cosmologies agree well with data in the floor, and yet in the ceiling are excluded by multiple orders of magnitude in $\chi^2$. We therefore observe the strength of small-scale clustering constraints depends heavily on the amount of prior HOD information assumed. We compare the sensitivity of this effect to various choices like scale cut, angle cut, multipole inclusion, mock phase, and mock HOD model. Our wide floor--ceiling bracket indicates that informative galaxy--halo priors are necessary for extracting strong small-scale clustering constraints. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12389 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12389v1 Announce Type: new Abstract: Weak lensing by large-scale structure is a powerful cosmological probe. While most analyses rely on second-order correlations, these are primarily sensitive to the parameter combination $S_8 = \sigma_8 (\Omega_m/0.3)^{0.5}$, limiting their ability to constrain $\Omega_m$ and other cosmological parameters independently. Higher-order statistics capture non-Gaussian features of the density field and can therefore break parameter degeneracies and extract more cosmological information from weak lensing surveys. We present a joint analysis of second- and third-order cosmic shear in the final data release of the Kilo-Degree Survey (KiDS-Legacy). We combine COSEBIs (Complete Orthogonal Sets of E-/B-mode Integrals) at scales between 2' and 300' with third-order aperture mass moments at scales between 4' and 32' to perform a joint analysis of second- and third-order statistics. Compared to previous KiDS analyses, we implement several methodological advances: an intrinsic alignment model with redshift and mass dependence, a baryon correction model validated on multiple hydrodynamical simulations, and corrections for reduced shear and source clustering. Combining COSEBIs with third-order aperture mass statistics in KiDS-Legacy yields $\Omega_m = 0.297^{+0.056}_{-0.040}$ and $S_8 = 0.806^{+0.025}_{-0.023}$, significantly tightening the $\Omega_m$ constraints and more than doubling the figure of merit in the $\Omega_m$--$S_8$ plane compared to the two-point analysis alone. The third-order measurements pass stringent internal consistency tests, are fully compatible with the KiDS-Legacy 2-point constraints, other 2+3-point lensing results and with Planck CMB measurements within $1\sigma$, providing no evidence for an $S_8$ tension and demonstrating the maturity of 3-point cosmic shear as a key probe for forthcoming surveys. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12265 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12265v1 Announce Type: new Abstract: Quasars can serve as standard candles through an empirical scaling relation between their ultraviolet (UV) and X-ray luminosities. As high-redshift probes, it is critical to test whether this relation evolves with redshift. In this work, we reconstruct the Hubble diagram of the Pantheon+ sample using the deep learning--based LADDER algorithm and use it as a reference to investigate the quasar scaling relation. Our results, which are consistent with those from Gaussian process regression and narrow-bin analyses, show that the potentially contaminated sample at $z 0.7$ sample; thus, it should be further screened or excluded when quasars are used as cosmological probes. We find that the scaling relation exhibits a non-linear redshift dependence that cannot be accounted for by a simple linear correction, and that this behavior is a feature of the current data sample rather than a consequence of cosmological model misspecification. To use quasars as standardizable candles, further modeling of the scaling relation and intrinsic dispersion, or more advanced data processing techniques, is required. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12255 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12255v1 Announce Type: new Abstract: Nonlinear structure growth generates higher-order correlations and morphological features in the cosmic density field that cannot be fully characterized by two-point statistics. Upcoming surveys will measure these features with greater precision, making it essential to develop methods capable of extracting as much cosmological information as possible from them. Field-level inference (FLI) is one such approach, in which cosmological parameters are constrained by comparing observed maps to forward-modeled maps, either directly or through learned summaries that retain map-level information. In this work, we compare FLI with power-spectrum-based inference using the same forward-modeling pipeline for generating weak lensing maps, with the goal of quantifying the gain from map-level analysis relative to two-point statistics. We perform this comparison with both implicit and explicit inference methods, using 8-million-parameter forward models based on Lagrangian perturbation theory and particle-mesh (PM) N-body evolution. The two FLI approaches yield closely consistent posteriors; this agreement, together with coverage tests confirming the calibration of the implicit analyses, gives us confidence in the recovered field-level constraints. Relative to the power-spectrum-based analyses, these results show significant gains in cosmological information, especially when small scales are included in the PM-based forward model. We then discuss the remaining challenges that must be addressed before PM-based explicit FLI can be applied to observational datasets. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12170 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12170v1 Announce Type: new Abstract: We develop a stochastic framework for the stationary spherical Jeans equation, motivated by the field-dependent nature of the gravitational coupling in scalar--tensor theories. We model unresolved spatial fluctuations of the scalar sector as an effective stochastic contribution to the gravitational coupling, $\Geff(r,\omega)=\Gbar(r)+\Gamma_G(r)\xi(r,\omega)$. This approach induces a linear It\^o stochastic differential equation for the radial velocity dispersion $y(r)=\sigma_r^2(r)$, defining a nonautonomous radial random flow rather than a time-evolution problem. We derive the associated Fokker--Planck equation and obtain integral expressions for the mean, variance, and covariance of the radial velocity dispersion. Because the noise is additive, the deterministic Jeans solution is recovered as the mean profile, while the stochastic sector produces a probability band around it. We specialize the construction to Navarro--Frenk--White, Hernquist, and Einasto halo models and propagate the radial covariance to the projected line-of-sight velocity dispersion. This provides a semi-analytical framework for assessing how effective gravitational fluctuations can affect halo kinematic observables in the stationary Jeans regime. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12137 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12137v1 Announce Type: new Abstract: We measure the dark matter halo mass function, with backsplash halos removed, from a wide range of cosmological-box and zoom-in simulations. These include the MultiDark Planck boxes, along with a suite of zoom-in simulations of Group, Milky Way, and LMC-mass halos. The Milky Way simulations include both CDM and non-CDM initial conditions. Using these measurements, we calibrate the parameters of flexible fitting functions for the halo mass function and the window function, along with parameterized models for various systematics, including finite box size effects, halo isolation criteria, halo detection efficiency, and contamination by artificial halos (objects forming from particle noise in the initial conditions). We show that this model shows remarkable consistency with N-body simulations over a broad range of redshifts, and ten orders of magnitude in halo mass ($10^6\mathrm{M}_\odot$ to $10^{16}\mathrm{M}_\odot$). Our model typically maintains a high precision of 12% and captures complex behaviors, including small-scale cut-offs, oscillations, and enhancements. In specific mass intervals for certain power spectra, we see larger deviations of 40-50%. Furthermore, when integrated with a simple model for environmental dependence, this fitting function provides a robust description of how environmental density influences the halo mass function. This precision model captures a wide variety of dark matter paradigms (including thermal relics, axions, and models with dark-sector interactions), is accurate for halo masses down to $10^7\mathrm{M}_\odot$, and is a critical ingredient for model-independent dark-matter inference from forthcoming data. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11929 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11929v1 Announce Type: new Abstract: We study the effects of dimension-four and dimension-six nonminimal Higgs couplings to the Ricci scalar $R$ in the $R^2$-Higgs inflation model in light of the recent ACT and SPT observations. We show that the dimension-six operators $|\Phi|^2 R^2$ and $|\Phi|^4 R$ can accommodate the enhanced scalar spectral index $n_s$ preferred by the combined CMB+BAO analyses. Using a doubly covariant formalism, we find that the same region of parameter space that explains the observed value of $n_s$ can also induce rapid preheating through the production of the Goldstone modes. If thermalization proceeds efficiently through this preheating mechanism, it may help match the inflationary scale with the CMB reference scale. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11725 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11725v1 Announce Type: new Abstract: We perform a Bayesian inference analysis of an inflationary model based on an inverse-tangent potential, incorporating reheating dynamics in both constant and dynamical equation-of-state (DEOS) frameworks. Using Planck and ACT constraints on the scalar spectral index, we find preferred values $\kappa\simeq0.5-0.6$ and $N_k\simeq40-60$, leading to reheating temperatures $T_{RH}\sim10^{10}-10^{14}$ GeV and reheating durations $N_{RH}\sim3-36$ e-folds. Reheating weighted $H_0$ posteriors shift the Planck inference towards the ACT preferred region through the intrinsic $n_s-H_0$ degeneracy of the CMB likelihood. In the DEOS framework, reheating with a constant decay rate yields $N_{RH}\simeq4-8$ e-folds and $T_{RH}\simeq10^{13}$ GeV, while a dynamical decay rate produces a strong dependence on the Yukawa coupling $y$, with $N_{RH}$ varying from $\mathcal{O}(30)$ to $\mathcal{O}(1)$ e-folds and the reheating temperature spanning $\sim10^{-2}-10^{14}$ GeV. Imposing inflation-reheating consistency significantly restricts the viable parameter space to a narrow region around $n_s\simeq0.9720-0.9725$ and $r\simeq0.026-0.060$, demonstrating that reheating dynamics provide a nontrivial bridge between early-universe inflation and late-time cosmological parameter inference. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11545 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11545v1 Announce Type: new Abstract: We investigate stationary halo-like solutions of the Gross-Pitaevskii-Poisson (GPP) system, which describes self-gravitating Bose-Einstein condensates with repulsive self-interactions, as a dark matter model. The boson mass $m_\phi$, scattering length $a_s$, and total particle number $N$ are kept explicit, with $N$ treated as an independent macroscopic control parameter. Solving the stationary GPP equations over a broad parameter space, we identify ground-state, excited-state, and unbound solution branches according to their binding properties and nodal structure. The ground-state branch occupies a well-defined region of the $(m_\phi,N)$ plane whose location depends strongly on the self-interaction strength, whereas the excited-state and unbound regions are largely insensitive to the initial ansatz. From the converged solutions, we derive empirical scaling relations connecting the characteristic halo radius $R_{99}$ to $m_\phi$, $a_s$, and $N$. In the weakly interacting regime, the results reproduce the standard Schrodinger-Poisson mass-radius relation, while finite self-interactions reveal an intermediate regime in which gravity, quantum pressure, and repulsive interactions jointly determine the equilibrium structure. As an astrophysical application, we show that ground-state solutions can reproduce representative dwarf-galaxy rotation curves using only the solitonic component. We also examine the implications of current Lyman-$\alpha$ forest constraints and find that, although increasing $a_s$ shifts equilibrium solutions toward larger boson masses compatible with existing bounds, the resulting configurations do not reproduce the observed dwarf-galaxy kinematics. These results provide a systematic characterization of stationary GPP halos and establish a direct connection between microscopic particle properties and observable galactic quantities. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11368 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11368v1 Announce Type: new Abstract: Following our previous work constraining interacting dark energy (IDE) models, which showed their potential to alleviate the Hubble tension, in this work we investigate the non-linear effects of the IDE scenario favoured by CMB and DESI observations. The implications of IDE for the $S_8$ tension remain unclear, since current weak-lensing and large-scale-structure analyses either exclude highly non-linear scales or model the non-linear regime using prescriptions calibrated within $\Lambda$CDM. We address this issue by implementing a fully self-consistent IDE pipeline. We perform N-body simulations of the IDE model with a transfer rate $Q=\xi {\cal H}\rho_x$ using a modified implementation of RAMSES. Since the dark matter Euler equation remains unchanged with respect to $\Lambda$CDM, the interaction can be incorporated through the modified background evolution and an effective time-dependent dark matter particle mass. We find scale-dependent deviations in the quasi-linear and non-linear regimes of the matter power spectrum, together with modifications to the density-field morphology and halo abundance. Our results show that the impact of IDE on quasi-linear and non-linear structure formation cannot be captured by standard $\Lambda$CDM-calibrated prescriptions, highlighting the importance of model-consistent non-linear modelling for future weak-lensing and large-scale-structure constraints on interacting dark energy cosmologies. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11312 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11312v1 Announce Type: new Abstract: Although measurements of the Cosmic Microwave Background (CMB) are consistent with a nearly scale-invariant primordial spectrum of adiabatic perturbations, in which the energy densities of different components (radiation, baryons, and dark matter) fluctuate proportionally, there could also exist isocurvature perturbations, in which density fluctuations of the individual components differ from the adiabatic mode. Cold dark matter isocurvature (CDI) perturbations with a variety of spectral tilts generated in pre-inflationary axion models provide one such example. In this article, we present the most updated constraints on these axion CDI perturbations using the latest CMB anisotropy measurements from Planck, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT). We study both fixed spectral indices with values ranging from red- to blue-tilted spectra as well as the case with a free index. We find that the constraint on the spectral index gets moderately improved with the combined datasets compared to Planck alone, while the bounds on the isocurvature amplitudes for the fixed spectral indices we consider do not get tighter. We also discuss the theoretical implications of our constraints, in particular for models giving rise to blue-tilted spectra. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11309 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11309v1 Announce Type: new Abstract: We present cosmological constraints from the Dark Energy Survey Year 3 (DES Y3) weak lensing data using hierarchical hybrid statistics within a Bayesian simulation-based inference framework that is based on the Gower Street simulations. To maximize the precision of the inference, we have developed a new, information-theory based, data compression of the weak lensing maps to just seven highly informative summary statistics. The hybrid scheme exploits the high information content of the power spectrum, compressing both the power spectrum and neural-based summaries that are designed to extract further information. Our simulation-based approach enables principled forward modelling of all major sources of systematic uncertainty and survey properties into realistic mock observations, including the survey mask, photometric redshift uncertainties, intrinsic galaxy alignments, multiplicative shear calibration bias, source galaxy clustering, non-Gaussian shape noise, and non-linear structure formation. The summary statistics are then used in a Bayesian simulation-based inference pipeline. The inference is validated through coverage tests and checks for robustness against baryonic feedback. Assuming a $w$CDM cosmology, our analysis yields $S_8 = 0.808 \pm 0.017$, $\Omega_{\rm m} = 0.325 \pm 0.024$, and $w < -0.766$ (marginalized posterior 68 per cent credible intervals). This rigorous combination of information theory, physics- and neural network-based extreme data compression, and principled Bayesian analysis improves the figure of merit for $(\Omega_{\rm m}, S_8, w)$ by 60 per cent over the previous state-of-the-art, and by almost a factor of 3 over two-point analyses of the same data. They are the most precise joint constraints on $(\Omega_{\rm m}, S_8, w)$ from weak gravitational lensing data alone of any survey to date. We intend to apply this analysis to the more recent DES Y6 data. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11300 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11300v1 Announce Type: new Abstract: Parity-violating physics in the Universe can generate correlations between the Cosmic Microwave Background (CMB) $E$- and $B$-modes, but detecting such signals requires extremely accurate calibration of instruments. We describe a data-driven method to calibrate the relative polarisation angle between CMB experiments using cross-correlations of observations over a common sky region. Unlike standard self-calibration approaches, this method does not assume vanishing isotropic cosmic birefringence or primordial $EB$ correlations when estimating the relative misalignment angle, and therefore preserves sensitivity to parity-violating physics. As a proof of concept, we forecast the performance of this method using the Simons Observatory (SO) Small Aperture Telescopes (SATs) as a calibrated reference. If they can be calibrated to an uncertainty of $0.08^\circ$, as anticipated from the SO wire grid calibration system, we show that the SO Large Aperture Telescope and Planck could be calibrated to uncertainties of $0.10^\circ$ and $0.17^\circ$, respectively, at $\sim 145$ GHz. This approach relies on the availability of at least one well-calibrated instrument, and provides a complementary path to improving polarisation calibration across experiments, enabling more robust searches for parity-violating physics in the CMB, such as cosmic birefringence. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2605.02826 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2605.02826v4 Announce Type: replace-cross Abstract: The structure of the ground $(2^+)$ and excited $(1^+)$ bound states of the $^8$B and $^8$Li nuclei is studied within the framework of the $\alpha+^3$He($^3$H)+$p(n)$ three-body potential cluster model based on the hyperspherical Lagrange-mesh method. The two-body realistic potentials have been applied from the literature. Convergent theoretical estimates for the three-body binding energy and matter radius have been obtained with the maximal hypermomentum $K_{max}=22$ and 28 for the ground and excited $1^+$ states, respectively. The ANC value of the virtual transition of the $^8$B nucleus is estimated self-consistently by matching the overlap integral of the $^8$B three-body and the $^7$Be two-body wave functions with it's asymptotics. The obtained values are $0.211$~fm$^{-1/2}$ and $0.739$~fm$^{-1/2}$ in the spin 1 and spin 2 channels, respectively. For the ANC values of the $^8$Li nucleus the estimates $0.220$~fm$^{-1/2}$ and $0.774$~fm$^{-1/2}$ are extracted. The ratio $C^2(^8 {\rm B})/C^2(^8 {\rm Li})=0.912$ implies a breaking of the mirror symmetry of the strong nuclear forces of order 27\% due to the Coulomb interaction and the dynamical three-body effects. For the $S_{17}(0)$ -factor an estimate $22.492\pm0.014$ eV b was obtained based on the asymptotic theory developed by D. Baye [Phys. Rev. C {\bf 62},065803 (2000)]. The spin 2 channel contributes with $S^{(2)}_{17}(0)=20.838 \pm 0.014$ eV b, while the spin 1 channel yields $S^{(1)}_{17}(0)=1.654 \pm 0.003$ eV b. These results for $S_{17}(0)$ are in a good agreement with the estimate $20.8\pm0.7{\rm(th)}\pm1.4{\rm(exp)}$ eV b of the SF II, but larger than the recommended value $20.5\pm0.70$ eV b of the SF III. At the same time, our estimate is very close to the value 22.4 eV b used in the most successful Solar Model BAR2M [W.~Yang and Z.~Tian, AJ {\bf 970} (2024), 38]. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2509.25070 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2509.25070v3 Announce Type: replace-cross Abstract: Molecular hydrogen (H$_2$) is one of the key chemical species that controls and shapes a wide spectrum of astrophysical processes from galaxy evolution to planet formation. Although catalyzation on dust grain surfaces is the dominant formation channel of H$_2$ in the interstellar medium, its efficiency across $20-200~\rm K$ has remained not fully understood. Here, using multiscale simulations combining ab-initio-level machine learning force fields, constrained path-integral Monte Carlo, and kinetic Monte Carlo, we perform a systematic, quantum-mechanical study of the full H$_2$ formation sequence, including hydrogen adsorption, diffusion, association and desorption. We explicitly consider the decoupling of gas and dust temperatures, making our results applicable to photon-dominated regions (PDRs) and dense cold clouds. Our results show that on the bare, crystalline surfaces studied here (graphitic and silicate grains), physisorbed hydrogen is negligible, and nuclear quantum effects (NQEs) in chemisorbed hydrogen atoms are essential for efficient formation at low temperatures, overcoming the classical Boltzmann suppression. This work presents a quantitative NQEs-inclusive study on silicate surfaces (exemplified by enstatite) and graphitic grains, revealing surface-specific adsorption behavior. These findings provide a first-principles quantum foundation for interstellar H$_2$ formation, complementing empirical multipliers, and enable new observational constraints on dust composition and molecular cloud evolution. The framework also extends to other astrochemical reactions on dust grains under full NQEs. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2603.20429 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2603.20429v2 Announce Type: replace Abstract: RR Lyrae stars (RRLs) are classical tracers of old stellar populations, yet growing evidence suggests the presence of a metal-rich ([Fe/H]>-0.5), intermediate-age (2-7 Gyr) sub-population in the Milky Way disc. Binary evolution, particularly stable mass transfer, has been proposed as a viable formation channel, predicting that most metal-rich, intermediate-age (<9 Gyr) RRLs should reside in binaries with orbital periods of ~900-2000 days. However, no genuine RRL binaries have been robustly identified, including in the Gaia DR3 astrometric binary catalogues, despite Gaia being sensitive to the predicted orbital-period range. We investigate whether the lack of detections in Gaia DR3 reflects an intrinsically low binary fraction or instead arises from observational biases. We analyse a carefully selected sample of 100 Gaia DR3 RRLs designed to trace the metal-rich population with thin-disc kinematics and compare them with predictions from binary evolution models. We generate realistic Gaia observation mocks, including variability-induced astrometric biases, and assess the detectability of binaries and the posterior constraints on the hidden binary fraction using astrometric quality indicators, such as RUWE, and a robust Bayesian inference. While current uncertainties prevent a definitive rejection of a high fraction of hidden binaries, our results reveal tensions between existing binary evolution predictions and the Gaia DR3 non-detections. This suggests either the presence of unaccounted systematics in the modelling of Gaia observations or the need to revise assumptions in binary evolution models. We predict that Gaia DR4 will significantly improve the binary detectability and provide powerful new constraints on the post-interaction binary populations. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2511.19196 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2511.19196v2 Announce Type: replace Abstract: We present the scientific case for exploiting the capabilities of the PLATO mission to study bright pulsating white dwarfs across a wide spectral range, including hydrogen-deficient types (GW Vir and DBV stars) and hydrogen-rich classes (classical DAVs, pulsating extremely low-mass DA white dwarfs, and ultra-massive DA white dwarfs). PLATOs exceptional photometric precision, long-duration continuous monitoring, and extensive sky coverage promise transformative advances in white dwarf asteroseismology. Our key objectives include probing the internal structure and chemical stratification of white dwarfs, detecting secular changes in pulsation modes over extended timescales, and discovering rare or previously unknown classes of pulsators. To assess feasibility, we constructed a sample of 650 white dwarf candidates identified within PLATOs Southern LOPS2 field using the PLATO complementary science catalogue combined with Gaia DR3, and derived atmospheric parameters through photometric modeling. This sample comprises 118 DA white dwarfs (including 23 ZZ Ceti candidates), and 41 non-DAs (including 35 DBV candidates). Simulated observations using PlatoSim demonstrate that PLATO will be capable of detecting white dwarf pulsation modes with amplitudes as low as 0.1 mma depending on stellar magnitude, observation duration, pixel location, and the number of contributing cameras. We provide detailed detection limits and visibility forecasts for known pulsators across a representative range of these parameters. Furthermore, we emphasize strong synergies with Gaia astrometry, TESS photometry, and targeted spectroscopic campaigns, which together will enable robust mode identification and detailed stellar modeling. Collectively, these efforts will unlock unprecedented insights into white dwarf origins, evolution and internal physics, and the fate of their planetary systems. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2508.21805 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2508.21805v2 Announce Type: replace Abstract: With its third data release (DR3), Gaia begins unveiling dormant candidate compact object (CO) binaries with luminous companions (LC) as predicted by several past theoretical studies. To date, 3 black hole (BH), 21 neutron star (NS), and 3200 white dwarf (WD) candidates have been identified with LCs in detached orbits using astrometry. We adopt an observationally motivated sampling scheme for the star formation history of the Milky Way, and initial zero-age main-sequence binary properties, incorporate all relevant binary interaction processes during evolution to obtain a realistic present-day intrinsic population of CO--LC binaries. We apply Gaia's selection criteria to identify the \colc\ binaries detectable using the observational cuts applicable for DR3 as well as its end-of-mission (EOM). We find that under the DR3 selection cuts, our detectable population includes no BH--LCs, approximately 10-40 NS--LCs, and around ~4300 WD--LCs. Our predicted NS--LC population is in good agreement with the current DR3 census, both in its predicted yield and in the orbital and stellar properties, and we recover a close analogue of the Gaia NS1 candidate together with its detailed formation pathway. For WD--LCs, we find that a moderate natal kick of 5-15 km/s imparted at WD formation is required to match the observed orbital properties of WD-LC candidates in DR3. We further show that Gaia BH3-like binaries can form through standard isolated binary evolution without invoking any additional modelling assumptions, whereas reproducing Gaia BH1 and BH2 remains challenging within this framework. Looking ahead to the EOM, we predict detection of ~30-300 BH--LCs, ~1500-5000 NS-LCs, and ~10^5-10^6 WD-LC binaries, primarily due to the significantly longer observational baseline. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2507.10038 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2507.10038v3 Announce Type: replace Abstract: Parametric instability of Alfv\'en wave packets with monochromatic carrier wave in low-$\beta$ plasma is studied using one-dimensional magnetohydrodynamic simulations. The results show spatial growth of incoming perturbations as they propagate through the mother wave. For sufficiently short packets, the perturbations emerge downstream of the packet as small-amplitude reverse Alfv\'en waves and forward slow magnetosonic waves. For larger packets the perturbations reach non-linear amplitude while still inside the mother wave. In this case, a downstream section of the mother wave collapses but the remaining upstream section stays largely intact and enters the phase of very slow evolution. The length scale separating the linear and non-linear regimes, as well as determining the size of the surviving section in the non-linear regime, is set by the Alfv\'en crossing time of the packet, the growth rate of the parametric instability for the unmodulated carrier wave, and the amplitude of incoming perturbations. The results are discussed in connection with the physics of solar wind. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11848 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11848v1 Announce Type: cross Abstract: The second solar spectrum is the spectrum of the Stokes parameter Q (linear polarization) close to the solar limb. It is made of a few polarized lines with Q/I of about 1% (such as CaI, SrI, or BaII), but most lines exhibit weaker polarization. This paper presents processing of unpublished observations made in 2008 with the Meudon solar tower spectropolarimeter, which are of interest for weak and turbulent unresolved magnetic field measurements in the quiet Sun, through the Hanle effect. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11587 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11587v1 Announce Type: cross Abstract: Accurate photometric zero-points are essential for translating observed magnitudes into physical fluxes, from comparing with models to ensuring consistency across surveys. We determine the zero-points needed to place the Sloan Digital Sky Survey (SDSS) $ugriz$ system on its nominal AB definition, by exploiting the sensitivity of the Infrared Flux Method (IRFM) to broadband flux calibration. Using benchmark effective temperatures for over 6,000 FGK-type stars, we invert the method to identify the zero-point corrections required for SDSS photometry to reproduce the adopted temperature scale. The $r$ band is found to be very well standardized, while the $i$ and $z$ bands show offsets of a few hundredths of a magnitude, consistent with previous studies. We also find a small offset in the $g$ band. The largest discrepancy occurs in the $u$ band, where the derived offset depends strongly on the adopted filter transmission curves, in particular whether one uses the original definition commonly adopted in the literature or the updated measurements that account for the presence of a red leak. This effect introduces a colour-dependent zero-point offset that becomes apparent when using a sample of late-type stars. Independent comparisons with CALSPEC spectrophotometric standards and Gaia XP spectra broadly support the offsets derived from the IRFM analysis. Our results provide a revised set of SDSS zero-points anchored to the IRFM temperature scale and demonstrate that large stellar samples can be used to constrain photometric calibration. The methodology presented here offers a complementary approach to traditional spectrophotometric calibration and may prove useful for future large-scale surveys. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11367 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11367v1 Announce Type: cross Abstract: Hot evolved stars are key objects to reconstruct the various evolutionary pathways of Sun-like stars, to probe binary interactions and the physics of supernovae. They serve as powerful observational constraints to test diffusion, mixing, and mass loss in hot stellar atmospheres. Furthermore, hot stars serve as laboratories to test and derive atomic data for highly ionised trans-iron group elements and to investigate different nucleosynthesis models. Hot evolved stars emit most of their flux in the ultraviolet (UV) and a lot of progress has been made in characterizing their UV-spectra both on the observational and on the modelling side. The unique capabilities of HST to obtain high- and medium-resolution UV-spectra played a crucial role and are needed to further advance this field also in preparation for HWO. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12361 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12361v1 Announce Type: new Abstract: Coronal mass ejections (CMEs) undergo significant geometric evolution as they propagate from the Sun to 1 AU, influencing their radial size, expansion, and space weather impact. We investigate the evolution of CME aspect ratio and expansion dynamics for four fast and four slow Earth-directed CMEs. Using multipoint coronagraphic observations with the Graduated Cylindrical Shell (GCS) model and corrected in situ measurements of associated magnetic clouds (MCs) at 1 AU, we track the evolution of aspect ratio from the low-middle corona to interplanetary space. We find that aspect ratio does not remain constant but exhibits a systematic three-phase evolution: a rise phase in the low-middle corona ($\lesssim10$-$15\,R_{\odot}$), a saturation phase at intermediate heights, and then a decline phase in the interplanetary space. The ratio of radial expansion speed to leading-edge speed ($V_{\rm exp}/V_{\rm LE}$) decreases substantially from the corona to 1 AU, indicating a reduction in radial expansion efficiency during interplanetary propagation. The consistent evolution of aspect ratio and $V_{\rm exp}/V_{\rm LE}$ suggests a transition from magnetically dominated expansion in the corona to a regime increasingly controlled by the heliospheric environment. We note that fast CMEs show stronger early expansion and evolve into larger, more radially extended structures, whereas slow CMEs exhibit a more gradual rise and a steeper decline. These results demonstrate that CME geometry evolves significantly during propagation and highlight the need to incorporate aspect ratio evolution in models to improve predictions of CME size, arrival time, and geoeffectiveness. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12242 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12242v1 Announce Type: new Abstract: The location of a star along the horizontal branch (HB) during core-helium burning is primarily determined by the amount of mass lost by its progenitor. We investigate the formation and properties of stripped core-helium-burning stars, focusing on how the residual hydrogen-envelope mass ($M_{\mathrm{env}}$) and the timing of envelope removal shape their properties. We used the MESA stellar evolution code to model stars that lose their hydrogen envelopes on the first giant branch. We explored two limiting cases for the timing of stripping, corresponding to the minimum and maximum core masses for helium ignition, for progenitors with initial masses below $\sim$6 $M_{\odot}$ at two metallicities ($Z=0.02$ and $Z=0.004$), while systematically varying $M_{\mathrm{env}}$. As expected, the effective temperature along the HB decreases as $M_{\mathrm{env}}$ increases. We determined the maximum $M_{\mathrm{env}}$ required to avoid subsequent evolution through the thermally pulsing asymptotic giant branch, which ranges from $\sim0.05$ $M_{\odot}$, for low-mass progenitors to $\sim0.30$ $M_{\odot}$ for intermediate-mass progenitors. In low-mass progenitors, early envelope removal triggers a late hot flash, naturally explaining the hottest blue hook stars. In intermediate-mass systems, partial envelope stripping can produce extended pre-HB configurations consistent with puffed-up stripped stars observed in binaries with Be companions. Our post-stripping evolutionary tracks are publicly available for use in binary evolution and population synthesis studies. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12148 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12148v1 Announce Type: new Abstract: In this work, we derive upper limits for the strength of the near-core magnetic field in intermediate-mass stars, since high-order g-modes can be fully suppressed by a critical magnetic field. Both poloidal and toroidal components of the magnetic field are included. We examine how the upper limits on magnetic field strengths are affected by the degree and azimuthal order of the oscillations, as well as the magnetic field configuration. We consider two gamma-Doradus stars hosting high-order g-modes and an evolved delta-Scuti star with mixed modes, all with prior mode identification from observations. We determine the best structural model from their stellar parameters through grid-based modeling with MESA. Frequencies for the best models are extracted using GYRE and matched to the observed modes. The critical magnetic fields for all calculated frequencies in our models are obtained from the Dedalus code, from which we can infer an upper limit on the near-core field strength. We find an upper limit on the near-core radial field strength of Br ~ 130 kG and Br ~ 13 kG, assuming a dipole field configuration, for the two gamma-Doradus stars KIC 3127996 and KIC 5876187, respectively. For 44 Tau, analysis of mixed modes yields a field strength of Br ~ 1771 kG. Different magnetic field configurations and mode degrees lead to different estimates. The results for the radial component of the magnetic field in the main sequence gamma-Doradus stars are consistent with estimates of magnetic field strengths in red giant stars that assume an internal field generated by a core dynamo, although the stronger of the two inferred magnetic fields may require some enhancement by a fossil field. The toroidal component does not affect g-modes significantly and is required to be more than 200 times stronger than the radial component to suppress g-modes. (abridged for arXiv) Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12034 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12034v1 Announce Type: new Abstract: Mode visibilities can be estimated from observed power spectra or from theory by making assumptions about the damping processes occurring in the star. However, a quantitative comparison between the two approaches was so far not feasible due to observational biases. The biases arise from the fact that in observations, the power spectrum is divided into frequency segments in which modes of a certain spherical degree are expected to dominate. In this work, we used synthetic power spectra to calculate the visibility as it has been done in observations and compare it with published observed visibilities to quantify the influence of the biases. We find that, taking the biases into account, the observed spatial response of the dipole modes is 1.47, which is closer to the theoretical value than previous estimates. In particular, we predict that the normalized dipole mode visibility of late red-giant branch (RGB) stars might be overestimated by up to 20% in published observations. For stars with depressed dipole modes, we find that the normalized dipole mode visibilities estimated in observational studies might be overestimated by 20% throughout their entire evolution on the RGB. The quadrupole mode visibility, on the other hand, appears to be largely unaffected by the biases, expect on the late RGB. In addition, we investigated the evolution of the visibility and detectability of the mixed mode signature while testing different prescriptions for the energy loss caused by a strong internal magnetic field in the stellar core. We argue that taking into account the inner turning point of the g-mode cavity could allow a portion of the mode energy to be preserved when interacting with a strong magnetic field. We further show that such partial dissipation allows the mixed mode signature to be both present or absent in the observable power spectra, which is consistent with observations. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11927 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11927v1 Announce Type: new Abstract: We build a three-dimensional (3D) red supergiant (RSG) stellar model for common envelope evolution (CEE) simulations by transporting a 1D stellar model to a 3D numerical grid, mimicking core nuclear power by depositing energy to an inner shell, and mimicking stellar emission by cooling grid cells with densities below the photospheric density. We do not relax the model; rather, we let it perform its natural pulsation. We find that when we mimic photospheric emission by cooling low-density grid cells, the oscillations slowly decay on a time scale much longer than in the absence of photospheric cooling. When we mimic both nuclear energy production, by depositing the stellar luminosity in an inner shell above the inert core of the stellar model, and the photospheric cooling, the oscillations do not decay and their amplitude slowly increases with time. The main pulsational period is about 1 year, comparable to the stellar dynamical time, suggesting a fundamental radial pulsation mode. The non-spherical structure of the stellar model and rapid low-amplitude temporal variations in the average stellar radius testify to the presence of non-radial oscillation modes on top of the fundamental radial mode. We also obtain vigorous convection, as RSG stars have. We conclude that the best way of preparing a giant star to simulate CEE and grazing-envelope evolution is to deposit energy with the stellar luminosity in an inner shell, and to cool the outer low-density numerical shell. There is no need to relax the model. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11908 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11908v1 Announce Type: new Abstract: We investigate two massive young stellar objects (YSOs), IRAS21078+5211 and G035.02+0.35, where evidence for magnetohydrodynamic (MHD) disk winds (DWs) has been obtained at scales of 10-100 au through measurements of the 22GHz water maser velocity distribution within the Protostellar Outflows at the EarliesT Stages (POETS) survey. We employ IRAM Northern Extended Millimeter Array and archival Atacama Large Millimeter Array observations of IRAS21078+5211 and G035.02+0.35, respectively, to study kinematics and physical conditions of the corresponding protostellar winds on scales of 100-1000 au using the same molecular tracers. In IRAS21078+5211, the emissions of several molecules, particularly SO, SO2, CH3CN and CH3OH, are distributed along the axis of the radio jet, and present a LSR velocity (Vlsr) gradient transversal to the jet axis. Position-velocity (PV) plots of the SO lines show patterns consistent with Keplerian rotation. The SO2 emission comes from high velocity gas flowing close to the jet axis, while CH3CN and CH3OH present larger radial extension than the S-bearing species. In G035.02+0.35, the same molecules are instead distributed along the major axis of the rotating disk, and their Vlsr gradients consistently trace the disk rotation. The corresponding PV plots present Keplerian profiles. SO is the only molecular species whose emission extends well outside the disk. In both YSOs, the spatial and velocity distributions of SO are consistent with a rotating wind magneto-centrifugally launched from the YSO disk. The comparison with models of molecule formation and excitation in shocks indicates that the different radial extension of the molecular species observed in the protostellar wind of IRAS21078+5211, as well as the lack of molecules, except SO, in the G035.02+0.35's wind, can be explained in terms of a radially extended MHD DW, rather than a compact X-wind. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11594 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11594v1 Announce Type: new Abstract: Reliable estimates of stellar effective temperature ($T_{\mathrm {eff}}$) are fundamental to stellar population studies and Galactic astrophysics. However, the majority of stars observed in modern large-scale photometric surveys lack spectroscopic measurements, making empirical colour--$T_{\mathrm {eff}}$ relations essential tools. In this work, we present updated empirical colour--$T_{\mathrm {eff}}$ calibrations based on Sloan Digital Sky Survey (SDSS) $ugriz$ photometry combined with 2MASS $JHK_{\mathrm s}$ data. Effective temperatures are determined on a homogeneous InfraRed Flux Method (IRFM) scale using a combined sample of 3902 GALAH and 2535 APOGEE stars with high-quality photometry and well-characterised atmospheric parameters. Using this dataset, we establish empirical relations between $T_{\mathrm {eff}}$ and colour indices constructed from SDSS and 2MASS combinations. We provide both colour--metallicity--$T_{\mathrm {eff}}$ and colour--$T_{\mathrm {eff}}$ relations for dwarfs and giants. The calibrations are derived using low-order polynomial models with iterative $3\sigma$ clipping. Their performance depends on the adopted colour index, with long-baseline colours such as $(g-K_{\mathrm s})_0$ and $(g-z)_0$ achieving internal precisions of $\sim$30--50~K. Comparisons with previous calibrations show general agreement, with differences attributable to sample selection, photometric zero-points, and functional form. The resulting relations provide a homogeneous and internally consistent framework for estimating $T_{\mathrm {eff}}$ from SDSS and 2MASS photometry alone, and are well suited for application to large photometric surveys lacking spectroscopic information. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11492 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11492v1 Announce Type: new Abstract: The Space Weather Around Young Suns (SWAYS) program was introduced in \citet{Davis2025} as a multi-wavelength monitoring program for studying the activity and particle environments of nearby, young, solar-type stars. The SWAYS program currently includes the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) operating between 13--87\,MHz to search for stellar equivalents of solar type~II and III bursts, which are associated with bulk plasma motion in the corona and interplanetary medium. These observations are accompanied by simultaneous photometric data from the high-precision, optical instrument Flarescope to identify associated flare events. These two instruments have collectively acquired nearly 900\,hr of data with $\approx70\%$ overlap between November 2023--June 2024, dedicated to six stars. Here, we present the results of this first season of the SWAYS observing campaign, which include a superflare from the star EK~Draconis with no accompanying low-frequency particle-flux signal. The novelty of the coordination at these specific parts of the spectrum allow us to uniquely evaluate the conditions that may have inhibited a radio detection. We find that the exceptionally hot, dense coronae of incredibly active stars may not be conducive to the development of the instabilities required for type~II and III bursts, or else inspire new expectations for when we should expect to observe a signal relative to the time of the flare. This may represent the plasma-density complement to the magnetospheric limitations to observing space-weather signatures at low frequencies. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.12390 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12390v1 Announce Type: new Abstract: Overview: Wind-driven bubbles are dynamic systems that can accelerate cosmic rays, depending on their physical properties, up to very high energies. We investigate how a time-dependent description of the particle transport may impact the escaping cosmic-ray flux. Model: The wind bubble system is modeled as spherically symmetric. Cosmic rays are continuously injected at the position of the termination shock and propagate through advection and diffusion until the escape at the time-dependent position of the forward shock, which is treated as a free escape boundary. Methods: The one-dimensional spherical time-dependent transport equation is solved by transforming it into the corresponding set of stochastic differential equations, and integrated with a modified version of the open source cosmic-ray propagation framework CRPropa. Results: We find that, during the wind driven phase, the downstream escaping spectra from wind bubbles can be harder than $\sim E^{-2}$, the conventional expectation from diffusive shock acceleration. Depending on the turbulence model the initial energy spectrum can be significantly suppressed at lowest energies, which could be an observable feature to distinguish between different turbulence realizations. This effect could lead to an efficient confinement of low energy particles, potentially leading to observable implication in terms of multi-messenger radiation and cosmic-ray accumulated grammage within the bubble. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12356 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12356v1 Announce Type: new Abstract: Recent Very Long Baseline Interferometry (VLBI) and Gaia astrometry reveal systematic milliarcsecond-scale offsets between the radio and optical centroids of active galactic nuclei (AGN). These "radio-optical offsets" do not alter the standard opacity-driven interpretation of radio core shifts. Instead, they indicate that the optical emission centroid is frequently displaced downstream of the radio synchrotron optical depth $\tau = 1$ surface, implying that additional dissipation and particle reacceleration occur beyond the opacity radio core within relativistic jets. We perform steady-state, axisymmetric relativistic magnetohydrodynamic (RMHD) simulations of AGN jets, including baryonic mass-load from stellar winds, varying jet kinetic power, and stellar core radius. Synthetic synchrotron emission maps in radio and optical bands are generated via a radiative transfer code, and centroid offsets are extracted for comparison with observations. Parsec-scale radio-optical offsets arise only for jet powers $L_{\rm j} \sim 10^{42.5} - 10^{44}\,\rm{erg}\,\rm{s}^{-1}$. In this regime, stellar winds trigger jet deceleration at intrinsic distances of a few $10^2-10^3\,\rm{pc}$, shifting the optical centroid downstream and producing offsets of $\sim 0.1 - 4\,\rm{mas}$ (a few tens of parsecs at $z=1$). Offsets depend on stellar distribution, viewing angle, and optical jet dominance, and vanish outside this power range. We reproduce the observed redshift evolution of offset incidence, linking it to the cosmic evolution of thermally pulsing asymptotic giant branch (TP-AGB) mass loss. Although stellar mass loading is unlikely to be the sole dissipation mechanism, its unavoidable presence in galactic nuclei makes it a natural baseline for energy dissipation. Radio-optical offsets therefore offer a constraint on AGN jet power and jet-host coupling, independent of traditional lobe-based methods. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12205 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12205v1 Announce Type: new Abstract: The distribution of the effective inspiral spin ($\chi_\mathrm{eff}$) of the binary black holes detected by LIGO-Virgo-KAGRA can shed light on their formation pathways. We analyze the GWTC-5.0 dataset with two models-one flexible, one fully parametric-that jointly describe $\chi_\mathrm{eff}$ and primary mass. We clarify that the previously-reported skewness in the $\chi_\mathrm{eff}$ distribution is better understood as additional structure beyond a non-skewed Gaussian bulk centered at small $\chi_\mathrm{eff}$. This additional structure extends to larger $|\chi_\mathrm{eff}|$, a result previously reported using GWTC-4.0 data. We measure the asymmetry of the distribution of $\chi_\mathrm{eff}$ outside the Gaussian bulk from the data. With both the parametric and the flexible analyses, we find tentative evidence for a mass-dependent excess of positive $\chi_\mathrm{eff}$ over negative ones outside the Gaussian bulk. Only at $m_1 \in [46,65]\,M_\odot$ do the data require a negative $\chi_\mathrm{eff}$ component outside the Gaussian bulk, with $23\text{:}1$ odds. If $\chi_\mathrm{eff}$ outside the Gaussian bulk are produced by hierarchical mergers-as it has been suggested-then a fraction of those mergers may be produced in environments that can generate a surplus of binaries with positive $\chi_\mathrm{eff}$, such as the disks of active galactic nuclei. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12111 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12111v1 Announce Type: new Abstract: SN 1006 is a historical Type Ia supernova remnant that exhibits non-thermal emission ranging from radio to multi-TeV $\gamma$-rays. Most of this emission (particularly X-rays and $\gamma$-rays) is concentrated in polar caps aligned with the ambient magnetic field, which makes it an ideal laboratory for studying cosmic ray (CR) acceleration at different shock obliquities and the hadronic/leptonic nature of the $\gamma$-ray emission. We model SN 1006's morphology, multi-wavelength spectrum, and radial profile using a self-consistent multi-zone kinetic model of particle acceleration that accounts for: CR-driven shock modification, magnetic field amplification, drift in magnetic fluctuations, and temporal dynamics including adiabatic and synchrotron losses. Our model can reproduce both the observed spectral and spatial properties, with the exception of the radio profile that we argue requires 3D hydrodynamic effects to replicate. We find that quasi-parallel regions (where the shock normal aligns with the ambient magnetic field) exhibit very prominent CR acceleration ($\sim$20% efficiency), while quasi-perpendicular regions exhibit efficiencies below 1%, consistent with the results of kinetic simulations. We also find that electrons are responsible for the majority of the $\gamma$-ray emission from SN 1006 (i.e., it is a leptonic source), with the exception of the northwest region due to an encounter with a dense cloud. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12092 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12092v1 Announce Type: new Abstract: In this work, we systematically study the gravitational lensing properties and observational signatures of compact boson stars. Unlike black holes, the photon effective potential of a compact boson star develops a nearly flat region, whose width increases with the compactness of the star. This flat structure significantly broadens the range of impact parameters that can produce large-angle deflections, leading to noticeably wider lensing rings of all orders. Photons constituting these rings traverse more complex paths, rendering the resulting images more sensitive to the spatial distribution of the accretion flow. Ray tracing results show that, compared to black hole models, the image topology and visibility amplitudes of compact boson stars exhibit a stronger dependence on the accretion flow structure. These results highlight qualitative differences in the observational properties of compact boson stars and black holes. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.12049 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12049v1 Announce Type: new Abstract: Our study focuses on the strong tidal disruption of a cold helium white dwarf passing a black hole. We model the white dwarf as a Bose-Fermi droplet and use quantum hydrodynamic equations to simulate the binary system's evolution. As the white dwarf passes through periastron, it loses a significant amount of mass. This mass falls onto the black hole and forms an accretion disc. Quantized vortices appear in the accretion disc, manifesting as strong electromagnetic radiation signals that exhibit characteristic flickering patterns changing on a timescale of a few seconds. Meanwhile, the white dwarf moves away from the black hole. As the white dwarf moves through space, vortices run along its surface. This elongates its geometry, causing it to rotate and emit gravitational waves. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11964 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11964v1 Announce Type: new Abstract: Spherically symmetric, general relativistic Bondi accretion is known as the Michel flow. The stationary integral transonic solutions for the Michel flow has been constructed for multi-component accretion described by an equation of state where the adiabatic index varies with the radial distance along which the streamlines are studied, and the corresponding phase portrait spanned by such radial distance and the flow Mach number has been obtained. Borrowing the techniques used in the dynamical systems theory, the nature of the transonic points of the aforementioned flow has been classified. The steady state flow has been perturbed to study the stability of the stationary solutions, and it has been found that such flows are stable under the (linear) radial perturbation. As a consequence of the stability analysis, the corresponding acoustic space time embedded within the accreting matter has been obtained, and the horizon of the metric of such sonic space time has been identified by constructing the causal structure with the help of the Carter-Penrose diagrams. In this way, the accreting black hole systems in the general relativistic set up has been investigated from various different perspectives - from its astrophysical aspects, from the dynamical systems point of view, as well as within the realm of the classical analogue gravity phenomena. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11959 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11959v1 Announce Type: new Abstract: $g$ mode resonances in eccentric binary neutron star systems are potential probes of internal stratification, superfluidity, composition gradients, and the equation of state. Although such weak dynamical tidal signatures are unlikely to be resolved with current detector sensitivities, third generation observations may make them accessible, in which case identifying the weak resonant phase shift would provide information beyond the bulk adiabatic tidal deformability. We build a four class dataset in an eccentric harmonic framework, containing point particle, adiabatic tide, resonant $g$ mode, and pure noise samples, and use Einstein Telescope (ET) and Cosmic Explorer (CE) detector data to test whether this weak resonant phase signature can be identified from noisy time domain strain. The ET, CE, and ET+CE deep learning models reach accuracies of $0.655$, $0.815$, and $0.897$, respectively. On the same simulated samples, the matched filtering method reaches lower accuracies of $0.514$, $0.677$, and $0.689$. This result arises from the fact that the resonant correction manifests as a weak phase morphology difference superimposed on the adiabatic tidal background, whereas matched filtering is sensitive only to the overall similarity. Hence, in the presence of weak phase differences, the neural classifier employed in deep learning is better able to learn these local phase and morphology features from the complete time domain strain segment. The results indicate that joint third generation observations improve the identifiability of weak internal mode phase information. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11939 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11939v1 Announce Type: new Abstract: Dwarf galaxies, characterized by their low luminosities and masses, are excellent candidates for searches for intermediate-mass black holes (IMBHs), particularly when they show strong accretion and ejection activity. The dwarf galaxy SDSS J101747.09+393207.7 has recently been found to display a very high X-ray luminosity and an X-shaped optical structure, possibly caused by a dwarf--dwarf merger. To explore its potential IMBH ejection activity, we performed very long baseline interferometry (VLBI) observations at 4.9 GHz. In this work, we present the detection of a milliarcsecond-scale, compact, sub-microjansky radio component near the optical centroid. According to some existing radio sky survey data, the radio component was not detected until 2015; it displayed an optically thin steep radio spectrum and declining flux densities across 0.8--5 GHz from 2019 to 2025. Therefore, we identify it as a short-lived and rarely seen ejecta that was produced by unstable accretion onto a massive black hole and likely faded away in a few decades. These results indicate that short-lived, episodic jet activity from accreting IMBHs in dwarf galaxies might exist. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11921 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11921v1 Announce Type: new Abstract: With the aim to study the spectral properties of some X-ray sources from recently observed {\it Chandra} data, 9 galaxies which have been observed by {\it Chandra} ACIS-S during the year 2018 to 2022 have been considered for the present work. 27 sources with net source counts $ \ge$ 100 have been considered. The spectra of all the sources were fitted using two empirical models -- an absorbed powerlaw and an absorbed disk blackbody. From their estimated bolometric luminosities, the 27 X-ray sources are categorized as 6 X-ray binaries (XRBs) and 21 Ultraluminous X-ray sources (ULXs). All the six XRBs are found to be in the spectrally hard state ($\Gamma \sim$ 1.52-2.29) which indeed may be due to thermal comptonization. Only one ULX, CXOUJ032251.2-370950 (X-5), was found to be spectrally soft while the remaining 20 ULXs were spectrally hard. The spectral parameters of X-5 with an inner disk temperature (kT$_{in}$) $\sim $ 0.5 keV and an estimated bolometric luminosity, L$_X \sim$ 3.26 $\times$ 10$^{39}$ erg s$^{-1} $ requires a black hole of mass, M$_{BH} \sim$ 137.86$^{+66.62}_{-47.41}$ M$_\odot $ accreting at $ \sim$ 0.19 times its Eddington limit. 8 ULXs, X-4, X-8, X-9, X-10, X-11, X-12, X-20 and X-21, were found to be in the Extremely luminous X-ray sources (ELXs) regime with even their lower limit of luminosity $>$ 10$^{40}$ erg s$^{-1}$. Softening/Hardening of spectra with or without changes in the luminosity were also observed in some ULXs/ELXs. In the hard ELX, X-8, spectral softening with almost consistent luminosity was observed. While in the ULXs X-20 and X-25 spectral softening with increasing luminosity was observed. However spectral hardening with increase in luminosity were observed in the ULXs X-21 and X-26. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11900 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11900v1 Announce Type: new Abstract: Most galaxies host supermassive black holes (SMBHs) that remain weakly accreting or dormant for much of their lifetimes. At the lowest accretion rates, these systems may represent the transition between active nuclei and dormant black holes, but whether they can still launch collimated jets remains unclear. The nuclei in our Galaxy (\sgra) and M31 are key examples of this regime, although no clear jet structure has yet been detected in either source. Here we report multi-frequency very long baseline interferometric observations of \Msixty\ (NGC~4649), a nearby elliptical galaxy hosting a nearly dormant SMBH with an Eddington ratio of $\sim10^{-8}$. We detect a compact two-sided jet with an unusually steep synchrotron spectrum, demonstrating that collimated outflows can persist even under nearly dormant accretion conditions. The apparent radio core exhibits an unprecedentedly steep frequency-dependent position shift toward the SMBH, locating the central engine only $\sim57\,\mu$as, corresponding to a projected distance of $\sim10$ Schwarzschild radii, upstream of the 8.37-GHz core. The observed jet morphology and steep core-shift behaviour are reproduced by general relativistic magnetohydrodynamic and radiative-transfer simulations, indicating a magnetically dominated, non-equipartition jet-launching region that departs from the standard conical equipartition picture. These results provide direct observational evidence that jet production can survive near the dormant SMBHs and establish \Msixty\ as a unique laboratory for probing jet formation on event-horizon scales in the lowest-accretion SMBH regime. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11788 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11788v1 Announce Type: new Abstract: A recent analysis of the centrifugal instability in the case of pressure-supported compressible relativistic rotation, with application to astrophysical jets, yielded a generalisation of the famous Rayleigh criterion for Newtonian flows. According to this criterion, the centrifugal instability is strongly affected by the flow Mach number, and not only in the relativistic fluid dynamics but also in its Newtonian limit. To validate the Newtonian version of this criterion, we performed axisymmetric numerical simulations of non-relativistic transonic rotating flows which are stable according to the original Rayleigh criterion but can be either stable or unstable according to the new one. The results of computer simulations are found to be in perfect agreement with the theory. The hydrodynamic stability of accretion disks is often explained by referring to the original Rayleigh criterion, even if their rotation is highly supersonic. To clarify the matter, we analysed the hydrodynamic stability of flows rotating about central compact object and derived an instability criterion that retains the explicit dependence on the flow Mach number. This criterion turns out to be equivalent to the standard Solberg-H{\o}iland criterion, which does not involve the Mach number. The same applies to the case of pressure-supported rotation, where the role of gravity is played by the centrifugal force. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11748 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11748v1 Announce Type: new Abstract: Dielectronic recombination (DR) is expected to be the dominant recombination process during the non-local thermodynamic equilibrium (non-LTE) phase of kilonovae, yet reliable DR data remain unavailable for most heavy ions. Current spectral models therefore rely on simplified recombination prescriptions, introducing significant uncertainties into predicted spectra. We present an optimization strategy for open f-shell ions using \texttt{AUTOSTRUCTURE}, targeting uranium ions U II--U IV relevant to kilonova ejecta. As a benchmark case, calculations are performed for Nd III to validate the treatment of the f-shell structure and its impact on DR. The resulting DR rate coefficients are of order $10^{-10}$--$10^{-12}$ cm$^{3}$s$^{-1}$ over temperatures relevant to kilonova plasmas. The optimized rates are intended for implementation in radiative-transfer calculations with \texttt{SUMO} to assess the sensitivity of kilonova spectra to improved recombination physics. The Nd III benchmark demonstrates that refinements to the atomic structure can produce measurable changes in spectral features, motivating similar calculations for actinide ions. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11544 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11544v1 Announce Type: new Abstract: We report on NICER and MAXI observations of a long-duration thermonuclear X-ray burst and a subsequent outburst-like X-ray flare from the neutron star low-mass X-ray binary MAXI J0911--655. Prior to the burst, the source was in a persistent low/hard state with a power-law-dominated spectrum ($\Gamma \sim 1.7$) and a mass accretion rate of $\sim 1\%$ of the Eddington limit. The long burst, detected by MAXI on 2020 May 22 (MJD 58991.7101), was rapidly followed up by NICER. From time-resolved spectroscopy of the cooling tail, we estimate an exponential decay time of $\approx43$ minutes, the ignition column depth of $\approx0.1\times 10^{12}~{\rm g ~cm^{-2}}$, the burst fluence of $\approx 1.1\times 10^{-4}~{\rm erg~cm^{-2}}$, and the total energy release of $\approx1.2\times10^{42}$ erg. Approximately one day after the burst onset, the 0.5-10 keV light curve unexpectedly re-brightened, initiating an outburst-like flare. During the peak of this flare, the persistent power-law flux increased from its pre-burst level of $\sim0.27\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$ to $1.4\times10^{-9}~{\rm erg~cm^{-2}~s^{-1}}$. This flux enhancement was accompanied by significant spectral softening, with the photon index increasing to $\Gamma \sim 2.2$. Subsequently, the flux decayed and the source returned to its baseline low/hard state. The observed timescales and energetics suggest that intense irradiation from the long burst amplified the ongoing thermal-viscous accretion process. This heating drove an inside-out heating front that temporarily enhanced the mass accretion rate, providing compelling observational evidence of a thermonuclear burst directly modulating the accretion dynamics of its surrounding disk. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11322 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11322v1 Announce Type: new Abstract: Event Horizon Telescope (EHT) images of black holes appear as rings with a brightness asymmetry. Here, we expand on our previous study of the asymmetry magnitude $a_1$ to study the position angle of the peak brightness asymmetry $\mathrm{PA}_1$ in general relativistic magnetohydrodynamic (GRMHD) models. For larger spin magnitudes ($a_{*}>0$ and $a_{*}\lesssim-0.5$), the mean $\mathrm{PA}_1$ falls within $1\sigma$ of the approaching limb of the black hole, regardless of viewing inclination, disk magnetization, or source. By comparing the $(a_1, \mathrm{PA}_1)$ distribution in M87* observations with models, we demonstrate that we can mildly disfavor low-magnitude spins and strongly disfavor all spin vectors that point toward Earth. The alignment of $\mathrm{PA}_1$ relative to the large-scale jet axis may suggest that M87*'s disk does not have a large tilt. By combining $\mathrm{PA}_1$ with the pattern speed measured in optimistic 2026 M87* video conditions, the EHT can constrain whether M87* is prograde or retrograde with $\sim 84\%$ accuracy. In Sgr A*, we show that a detection of $(a_1, \mathrm{PA}_1)$ could constrain the magnitude and direction of the galactic center spin vector. Finally, if future EHT expansions increase the sample of horizon-scale sources, a simple set of observables (ring diameter, asymmetry magnitude, and asymmetry angle) could enable robust constraints on black hole mass, spin, and inclination. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11307 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11307v1 Announce Type: new Abstract: Synchrotron self absorption (SSA) is seen across a variety of astrophysical sources, and observation of an SSA peak in the spectrum is a powerful tool for estimating the physical conditions and the minimum energy of the emitting region. We begin with the (re)derivation of the usual SSA parameter estimates, carefully considering dependencies and assumptions, obtaining the most accurate traditional SSA minimum energy equations currently available. Traditional methods rely on the assumption that the emitting region is quasi-spherical and homogeneous. However, many observations of SSA show that the spectral index at frequencies below the peak is less than the expected $+2.5$ (non-thermal) or $+2$ (thermal). We argue that an inhomogeneous emitting region is the most likely explanation in many cases. Power law inhomogeneous cylindrical slab and broken power law inhomogeneous sphere models are used to investigate how the presence of inhomogeneity affects parameter estimates using traditional SSA methods. We find that in some cases inhomogeneity can lead to traditional SSA methods underestimating the minimum energy and the size of the emitting region by over an order of magnitude. Quantitative correction factors are found which can be applied to traditional estimates to correct for inhomogeneity, depending on the value of the observed flattened spectral index and the range in frequency over which this value is observed. Furthermore, we derive simple correction factors for non-spherical homogeneous emitting regions. Finally, we explore the effects of inhomogeneity on measurements of polarisation around the spectral peak, and on lightcurves for expanding emitting regions. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11299 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11299v1 Announce Type: new Abstract: We conduct a global general relativistic neutrino-radiation-transfer magnetohydrodynamics simulation of a $1.35$-$1.35M_\odot$ binary neutron star with the unprecedented spatial resolution of $6.25$\,m on the Japanese supercomputer FUGAKU. The total consumed CPU time is $\approx 530$ million core hours. We initialize the binary neutron star's magnetic field to be $3.16\times 10^{12}$~G at maximum, which is compatible with the upper end of the observed binary pulsars. We demonstrate that the Kelvin-Helmholtz instability that emerges when the two neutron stars touch amplifies the magnetic field to an expected electromagnetic saturation energy of $\sim 10^{50}$~erg within $3$~ms after the merger. The spectral analysis indicates that the Kazantsev and Kolmogorov spectra are reproduced in the magnetic and kinetic power spectral densities, respectively. We also find that it induces stellar-scale magnetic field amplification by at least a factor of $316$. We conclude that a magnetar may form at least temporarily following neutron star mergers in a few ms. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11294 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11294v1 Announce Type: new Abstract: Three-body interactions exhibit phases of strong chaotic evolution as well as hierarchical motion where one body separates from a binary and follows a hyperbolic or elliptic trajectory around it. The binaries produced during phases of hierarchical motion may lead to gravitational wave (GW) inspirals, but this depends on the outcomes of the chaotic states. In this paper we re-derive the elliptic outcome distribution using equilibrium statistical mechanics and explore it together with the hyperbolic distribution. When comparing to N-body simulations, we find that we can reduce the elliptic outcome model to one free parameter instead of the previously used two and that the predicted disintegration probabilities agree except for very low angular momentum triples. We then use both outcome distributions along with a star cluster model to design a Monte Carlo algorithm for repeated binary-single scatterings within dense star systems. We explore star cluster masses of $[10^5 - 10^7] M_{\odot}$, with the goal of quantifying observably eccentric merger (OEM) GWs, visible to instruments such as LIGO and Virgo. Assuming an OEM detection sensitivity of $f_{\rm min}=10 {\rm Hz}, e_{\rm min} = 0.1$, we find the elliptic OEMs are about $\sim (32 - 63)\%$ of the total elliptic mergers and that the total cluster mass greatly impacts the fraction of ejected binaries. The OEM to total merger fraction (OEM fraction) is found to be $(2.6 - 4.4)\%$. Considering the detection sensitivity that GW interferometers have today $(f_{\rm min} \simeq 34.4 {\rm Hz})$ we obtain the OEM fraction in the $(1.6 - 3.1)\%$ range. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11291 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11291v1 Announce Type: new Abstract: Based on its predominantly thermal X-ray emission and long spin period, the isolated neutron star eRASSU J131716.9-402647 is one of the most promising candidates for membership in the still small class of X-ray dim isolated neutron stars (XDINSs). Confirmation of this classification, however, requires a more detailed characterisation of the source's timing and spectral properties. In this work, we present new NICER observations which, together with previous X-ray follow-up, allow us to constrain the timing properties and long-term evolution of eRASSU J131716.9-402647. We obtain a coherent timing solution with a spin period of $P\sim12.8$ s and a period derivative of $\dot{P}\sim9\times 10^{-14}$ s s$^{-1}$, which best-describes the spin evolution of the source. These parameters imply a dipolar magnetic field strength of $3\times10^{13}$ G and a spin-down luminosity of order $10^{30}$ erg s$^{-1}$. Spectral modelling reveals no significant change in the spectral state over the 15 months of observational monitoring and indicates a thermal luminosity that likely exceeds the rotational energy loss. This suggests a thermal evolution that has been significantly influenced by past reheating. The energy dependence of the double-humped pulse profile closely resembles that observed in the XDINS RX J1308.6+2127, with the pulsed fraction increasing towards higher energies. Taken together, these results unambiguously confirm the XDINS nature of eRASSU J131716.9-402647, making it the first newly confirmed XDINS in more than two decades. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11234 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11234v1 Announce Type: new Abstract: In recent years, the Large Area Telescope (LAT) onboard the \emph{Fermi} satellite has detected more than 300 pulsars in the high energy range. The population studies of high energy pulsars show that the gamma ray luminosity of a pulsar ($L_\gamma$) can be expressed in terms of the spin down luminosity ($\dot{E}$) as $L_\gamma \propto \dot {E}^s$ having exponent $s\sim 0.68$. This high energy emission, assumed to originate far from the stellar surface and near the light cylinder, is usually studied in either purely curvature or purely synchrotron regime. In this work, we adopt a synchro-curvature radiation framework to understand the origin of gamma ray emission from the pulsar and its implications at the population-level. By comparing the observed cutoff energies of the differential gamma-ray spectra with the theoretical synchro-curvature predictions and enforcing radiation reaction approximation, we determine the equilibrium Lorentz factor and pitch angle of the emitting charged particles. This approach allows to quantify the relative roles of curvature and synchrotron radiation to the radiative losses, thereby providing a physically grounded interpretation of the luminosity trend across the pulsar population. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.11506 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11506v1 Announce Type: cross Abstract: Ultraviolet spectroscopy with the Hubble Space Telescope (HST) provides the most direct and sensitive probe of the disk-circumgalactic medium (CGM) interface at radii of 20 kpc, where galaxies exchange gas, metals, and energy with their surroundings. Many of the key diagnostics of the multiphase circumgalactic medium -- including H I, O VI, C II-IV, Si II-IV, N V, Ne VIII, and other metal transitions -- lie in the ultraviolet and are inaccessible from the ground, making HST the only observatory capable of making the required observations. By measuring the physical (column density, density), chemical (metallicity, ionization structure), and kinematical properties of the gas at the disk-CGM interface, UV absorption-line spectroscopy reveals how galaxies acquire fresh fuel, recycle enriched material, and drive feedback into their halos. When combined with spectroscopic characterization of the host galaxy's stellar populations and the feedback they generate (outflow velocity, mass loading), we will establish a direct understanding of how stellar populations enable circulation of gas and metals through the galactic ecosystem. HST's ultraviolet (UV) spectroscopic capability provides the only comprehensive observational pathways for uncovering the physical drivers that regulate galaxy growth and evolution in the low-redshift Universe. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11404 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11404v1 Announce Type: cross Abstract: In the outer Solar System, for example in the Saturnian system, a planet's strong gravity attracts micrometeoroids and generates hypervelocity impacts on bodies such as rings and satellites. Micrometeoroids are seemingly non-icy, whereas the targets are typically icy, and both the impactor and the target may span a wide range of porosities. In this study, we perform three-dimensional iSALE simulations of hypervelocity impacts of rocky impactors onto icy targets, varying the impact angle and the porosities of the impactor and target ($\phi_{\rm imp}$ and $\phi_{\rm tar}$). We consider two end-member porosities (0% and 90%) for oblique ($45^\circ$) impacts. At an impact velocity of 30 km/s, characteristic of Saturn's rings, we find that the morphology of early-stage crater formation varies significantly with porosity, transitioning from deep-penetration, narrow-channel cavities ($\phi_{\rm imp}=0$, $\phi_{\rm tar}=90%$) to very shallow craters driven by near-surface vapor blowoff ($\phi_{\rm imp}=90%$, $\phi_{\rm tar}=0%$), with intermediate, more hemispherical cavity shapes when the porosities are comparable. Here, we focus on the thermodynamic fate of the impactor, which represents the exogenic material responsible for modifying the target surface. The impactor material is strongly heated and is efficiently vaporized regardless of the porosities of the impactor and target. However, the peak pressure and peak temperature experienced by the impactor vary by nearly an order of magnitude. These results imply that hypervelocity impacts occurring, for example, in Saturn's rings efficiently vaporize exogenic non-icy impactors upon impact, while the subsequent thermodynamic pathways $-$ such as condensation and chemical evolution $-$ may differ depending on the thermodynamic conditions. Our results are expected to be applicable to a variety of planetary systems. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11378 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11378v1 Announce Type: cross Abstract: The source of the optical/UV emission in tidal disruption events (TDEs) remains an enduring question in the field. Connecting the observed emission to the source is critical for both our understanding of these transients and for using TDEs to study the efficiency of super-Eddington accretion and black hole growth. To explore this connection, we ran time-dependent 1D radiation hydrodynamic simulations of TDE emission with the Sedona monte carlo radiative transfer code, focusing on the reprocessing paradigm. Our simulations follow a compact, evolving X-ray and EUV bright source and surrounding reprocessing outflow over multiple months, using luminosities and mass flow rates consistent with hydro simulations of tidal disruptions. We determine the efficiency of reprocessing as a function of time in this dramatically changing environment and reproduce key observables including timescales, luminosities, and color evolution. Notably, we see a strong wavelength-dependence in the emission timescale due to reprocessing effects. Early on there is an X-ray flare which quickly fades as material builds up and obscures the hot source. At the same time, the optical/UV luminosity begins to rise. Though the optical/UV light curve has a similar shape to the bolometric light curve, the optical peak is offset by $\sim$3 weeks from the bolometric peak due to the time required to build up the reprocessing layer. This implies that early time, high energy emission may be missed for TDEs discovered in optical surveys, and the initial disruption and mass return time to the black hole may occur earlier than optical light curves suggest. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12355 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12355v1 Announce Type: new Abstract: Little Red Dots (LRDs) are a heterogeneous class of objects, with several proposed scenarios for their physical nature and evolution. While these theories have been tested on individual LRDs using limited spectral features, a systematic Bayesian analysis of the LRD population incorporating the different models across a broad wavelength range is still lacking. In this study, we conduct a consistent ultraviolet (UV)-to-optical continuum fitting analysis of 66 LRDs at 2<z<6 using JWST/NIRSpec PRISM spectroscopy. Employing a modified version of Bagpipes--including blackbody (BB) emission affected by Balmer absorption, stellar and nebular emission attenuated by dust, and an active galactic nucleus (AGN) component--we assess the performance of the black hole star (BH*) model in describing the LRD population. We adopt broad priors and therefore do not impose any specific physical scenario. Our results show that only ~6% of LRDs with statistically robust solutions (52 objects in total) are best-fit by a BH* in the optical and a host galaxy in the UV. ~8% of LRDs show BB-dominated optical continua but lack a stellar component or exhibit AGN UV leakage. Most LRDs are dominated by stellar and/or AGN emission in the optical, with minor BB contribution. When we adopt a prior that disfavors a strong AGN continuum to enforce BH*-like solutions, the percentage of BH$^*$ systems increases to ~40%, highlighting the strong degeneracy between a BH* solution and alternative scenarios. Even when BH*-like solutions are enforced, many LRDs still require a stellar-dominated optical continuum. This may reveal limitations of the BH* model or point to an evolutionary sequence in which the BB contribution decreases as the host grows, leading to lower BB temperatures and higher stellar masses at lower z. In this scenario, more pronounced ''V'' shapes would correspond to later stages in LRD evolution. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12254 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12254v1 Announce Type: new Abstract: Studying young stellar populations within galaxies can help refine our understanding of recent star formation in galaxies and their evolution. With this motivation, we present a catalog of ~25,000 recently formed (within 400 Myr) star-forming clumps (SFCs) in 17 morphologically diverse nearby galaxies, including 8 massive, classic spirals, 6 intermediate-mass, flocculent spirals, and 3 dwarf irregulars. We used far- and near-UV observations from the UltraViolet Imaging Telescope (UVIT), whose ~1.5" angular resolution and 28' field-of-view allow us to probe SFCs at a mean physical scale of ~54 parsec, within the full extent of our galaxies. We adopted a homogeneous SFC detection criterion, corrected for spatially varying dust attenuation (using 6" resolution A_V maps, made by combining FUV with archival infrared observations), and estimated the SFC ages by comparing the observed UV color-magnitude diagrams with Starburst99 simple stellar population models. Using our SFC catalog, we studied the age demographic of the recently formed stellar populations across different galaxy morphologies and observed age trends consistent with several well-known phenomena, such as the inside-out formation of disc galaxies, local gravitational instabilities leading to flocculent spiral arms, and the stochastic nature of star formation in dwarf galaxies. Leveraging full galaxy coverage and FUV data, our catalog complements existing optically-identified star cluster catalogs in the literature towards improving our understanding of star formation across a wide range of galaxy morphologies, masses, and environments. We make the SFC catalog and A_V maps of our 17 galaxies publicly available with this paper. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12249 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12249v1 Announce Type: new Abstract: An accurate determination of the dust attenuation within galaxies is essential to derive key physical properties such as the star formation rate (SFR). We present an analysis using the JWST/NIRISS data from the GLASS-JWST ERS programme to investigate and characterise the stellar and nebular reddening of galaxies at $1.0<z<2.4$, down to the sub-kpc scale. We use a multiregion fitting method to extract high-quality H$\alpha$ and H$\beta$ emission line maps for 99 individual galaxies across a stellar mass range $7.0<\log_{10}(M_*/\mathrm{M}_{\odot})<10.5$. We find no evidence for ratios of the Balmer decrement (H$\alpha$/H$\beta$) below the intrinsic limit for Case B recombination, beyond the expected variation from observational uncertainties. We reproduce the local correlation between the Balmer decrement and total stellar mass, and find no measurable difference when splitting the sample by redshift, with negligible attenuation below $\log_{10}(M_*/\mathrm{M}_{\odot})\lesssim8.5$. Similarly, the best-fit relation between the nebular and continuum reddening follows the same relation as in local starburst galaxies, $E(B-V)_{\mathrm{SED}} = (0.46\pm0.02)E(B-V)_{\mathrm{neb}}$, together indicating no significant evolution in the dust geometry within galaxies out to $z\lesssim2.4$. We derive best-fit linear relations between the differential nebular-stellar reddening and the SED-derived star formation rate (SFR) and stellar mass, finding statistically significant relations for both quantities. We use our spatially-resolved measurements to derive an empirical calibration between the resolved differential reddening, and the SFR surface density. These will enable crucial dust attenuation corrections for spatially-resolved science at higher redshifts where the Balmer lines are inaccessible, such as with future Roman grism observations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12156 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12156v1 Announce Type: new Abstract: The shutdown of star formation - quenching - marks a pivotal transition in the lives of massive galaxies, which dominate the present-day stellar mass density. This review synthesizes our current understanding of the mechanisms that trigger and maintain quiescence. We discuss the nuances of how quiescent systems are identified across cosmic time and summarize the evolving physical properties of the growing massive population, including their stellar populations, chemical enrichment histories, and gas and dust reservoirs, highlighting several key results: (1) Quiescent galaxies can be identified with empirical color selections, but evolving specific star formation rate thresholds offer a more robust physical distinction from star-forming systems. (2) The earliest massive quiescent stellar populations show rapid formation histories and high metallicities, with enhanced $\alpha$-elemental abundances often distinct from local analogs. (3) Nascent studies of gas and dust in quiescent galaxies reveal diverse multiphase reservoirs and outflows, pointing to fast ejective and slow regulatory modes of galaxy quenching. (4) In situ processes establish galaxy central density, while assembly continues via (minor) mergers post-quenching, reshaping all massive galaxies and disrupting rotation in most cases. We distill observations into two broad modes by which massive galaxies form and quench: one involves a rapid, early shutdown driven by supermassive black hole outflows on short timescales; the other proceeds gradually through gas exhaustion, virial heating, or preventative feedback, each leaving distinct observational signatures. Together, these pathways offer a testable framework for modeling the formation and evolution of massive galaxies, which will be informed by future studies of their stars, gas, dust, and dynamics. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.12076 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12076v1 Announce Type: new Abstract: The population of Compton-thick (CTK) AGN represents a critical yet elusive phase in the growth of supermassive black holes. Constraining their abundance and evolution at high z is essential for understanding both SMBH growth and the origin of the cosmic X-ray background. We investigate the X-ray luminosity function (XLF) of CTK AGN at z > 3 using one of the largest available samples of X-ray-selected AGN at high z, containing 811 sources from XMM-Newton XXL-N and Chandra CCLS and CDF-S/N surveys. We first selected a subsample of ten high-probability CTK candidates, identified through x-ray spectral fitting. Their multiwavelength properties are examined through SED modelling to assess the robustness of their CTK classification. For most sources, the inferred X-ray luminosities appear overestimated when compared with their IR luminosities. After updating the NH posteriors with IR-informed priors, only three sources remain consistent with the CTK regime. To compute the XLF for the entire CTK AGN population, we used 24 microns photometry to estimate IR luminosities and update the X-ray posteriors for all the remaining sources. Incorporating IR priors systematically reduces the inferred CTK number densities, yielding a more conservative and physically consistent estimate of the XLF. We find that CTK AGN constitute 17 per cent of the total AGN population at 3 1e23 cm-2) increases toward higher redshifts, the stable CTK fraction supports the interpretation that, at these epochs, the interstellar medium in typical host galaxies cannot produce CTK levels of obscuration. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11872 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11872v1 Announce Type: new Abstract: The rotational velocity of interstellar gas in the Milky Way, and other galaxies, has been taken to represent the circular velocity of a test particle in the Galaxy gravitational field, and hence an indicator of the Galaxy mass. The derived circular velocity is found to be too high for the gas to be gravitationally bound to the galaxy given the observed Galaxy mass in stars and gas, and consequently an extra component of mass in the Milky Way and other galaxies, namely dark matter, has been postulated. However recently the observational satellite Gaia, has been carrying out ground-breaking astrometric observations to accurately measure, inter alia, the three dimensional velocities of stars in the vicinity of the Sun and beyond. This has revealed that the circular velocity derived from the stellar population is much less than that of the gas, and the rotation curve, circular velocity versus radius, is distinctly declining with radius, whereas the gas rotation curve is not declining. By combining results from multiple observations of the gas velocity, averaging the velocities in radial bins, we establish that there is a grand average rotation curve. This can be compared directly with a grand average of the published Gaia rotation curves, and the confidence level in the difference between the two estimated by statistical analysis. The difference is shown to have a high degree of confidence, and increases with galactocentric radius. The lower circular rotation curve from the stellar velocities has resulted in significantly reduced estimates of the dark matter mass fraction of the Milky Way. The higher rotation of the gas lacks an explanation, but it is unlikely to be an accurate indicator of the kinematic mass of the Galaxy. This also has significant consequences for the mass of external galaxies based on gas rotation curves. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11733 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11733v1 Announce Type: new Abstract: We analyze the geometry and kinematics of substructures within molecular clouds identified in an unbiased catalog from the MWISP survey. These substructures are defined as spatially connected regions enclosed by the 20% peak-integrated-intensity contour of each cloud. After applying selection criteria on voxel size and excluding structures truncated by map boundaries, we construct a sample and quantify their projected morphology using the projected scale ratio $R=\Delta b/(\Delta l\cdot\cos b)$. This ratio essentially measures $\tan\theta$ where $\theta$ is the plane-of-sky angle of an elongated filament relative to the Galactic plane. The resulting sample exhibits a median $R=0.96$, indicating a slight but systematic preference for elongation along Galactic longitude. This tendency becomes more pronounced at larger spatial scales. We further investigate the relative orientations among the structural major axes, velocity-gradient directions, and plane-of-sky magnetic-field orientations derived from Planck data for a subsample of well-defined structures. We find that, for cloud structures within our sample, with physical scale $\sim 0.3$ to $\sim 30$ pc, velocity gradients tend to be perpendicular to the major axes, while magnetic-field are generally aligned parallel to them. This scale range differs from those typically probed in studies of dense cores ($\sim 0.05$ pc) and GMC-scale structures ($\gtrsim$ 10 to 100 pc), which have reported scale-dependent variations in relative orientations. In addition, the alignment between velocity gradients and magnetic fields shows a gradual weakening with increasing physical scale. These results suggest that the observed anisotropy of molecular cloud substructures may arise from a combination of large-scale Galactic dynamics, anisotropic gas motions, and magnetic fields, with the relative importance of these effects varying with scale. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11444 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11444v1 Announce Type: new Abstract: We present ALMA high-resolution ($\sim$0.25$^{\prime\prime}$/2 kpc) CO(5-4) and CO(4-3) observations of three $z\sim 3$ submillimetre-selected dusty galaxies from the ALESS survey. These data complement existing [sub]-kpc scale ALMA 870$\mu$m continuum imaging and JWST NIRCam and MIRI imaging from the ALESS-JWST program, allowing us to trace the molecular gas, dust-obscured star formation, and stellar populations on similar spatial scales. We spectroscopically confirm that two of the sources lie at the same redshift and are likely interacting. We find that the molecular-gas distribution broadly follows the dusty star-forming structures seen in the 870$\mu$m dust continuum imaging, but that the gas reservoirs are significantly more extended than the dust emission with a spatial extent comparable to the rest-frame near-infrared stellar emission. By modeling the kinematics for the two highest signal-to-noise sources, we find that the galaxies are well-fit by rotating disc models with high ratios of ordered to random motion ($V_{\rm{max}}/\overline{\sigma}=5\pm1$ and $6\pm1$), although smaller-scale kinematic deviations cannot be ruled out at the current sensitivity and spatial resolution. Finally, utilizing the high-resolution 870$\mu$m dust continuum and CO data, we investigate star-formation scaling relations on kpc-scales in these high-redshift galaxies. Assuming a constant CO-to-H$_{2}$ conversion factor and excitation ratio, we find that the data are offset from theoretical star-formation relation predictions that do not take turbulence into account, but consistent with gravo-turbulent models, thereby suggesting that turbulence plays a central role in regulating star formation at high redshift. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11394 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11394v1 Announce Type: new Abstract: We present the first spatially contiguous study of the physical and chemical structure of the Helix Nebula (NGC~7293, PNG 036.1-57.1) based on integral-field spectroscopy from the SDSS-V Local Volume Mapper (LVM). The wide-field observations provide nearly complete spectroscopic coverage of the nebula, enabling a spaxel-by-spaxel analysis of extinction, electron density and temperature, ionisation structure, and chemical abundances. We reconstruct calibrated datacubes from the LVM row-stacked spectra and measure 41 optical emission lines, including hydrogen, helium, and collisionally excited metal lines. The resulting maps reveal a strongly stratified nebula, with highly ionised gas traced by \heii~concentrated toward the central cavity, low-ionisation material dominating the bright shell, and neutral or transition-zone gas enhanced in the outer regions. The Helix is a low-density object, with typical electron densities of $\sim10^{2}\mathrm{cm^{-3}}$, and exhibits a non-uniform temperature structure, with variations of several thousand Kelvin across different ionisation zones. We derive a near-solar oxygen abundance, $12+\log(\mathrm{O/H})\simeq8.7$, consistent with spatially complete sampling. The central abundance pattern indicates a significant contribution from unobserved O$^{3+}$, suggesting that apparent abundance variations are primarily driven by ionisation effects rather than true chemical inhomogeneities. We also find evidence for a sulfur deficit of $\sim$1 dex, consistent with the planetary-nebula sulfur anomaly. The helium and nitrogen abundances place the Helix near the classical boundary of Type~I planetary nebulae, suggesting moderate chemical enrichment by its progenitor star. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11374 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11374v1 Announce Type: new Abstract: The quasar Eigenvector-1/Main Sequence (E1/MS) provides a physically motivated empirical framework to organize the spectroscopic diversity of type~1 active galactic nuclei (AGN). In its optical plane, the full width at half maximum of H$\beta$ and the Fe\,II strength ratio $R_{\mathrm{FeII}}$ define a sequence that is primarily driven by Eddington ratio, with important secondary roles played by black-hole mass, orientation, spectral energy distribution, and chemical enrichment. The E1/MS framework is therefore well suited to identify highly accreting and possibly super-Eddington (SE) sources, usually associated with the extreme Population~A (xA) spectral types. We discuss why E1/MS is a useful tool to search for SE accretors among jetted AGN and, conversely, to place $\gamma$-ray-detected AGN in the broader context of quasar phenomenology. We summarize two complementary results: (1) some candidate SE accretors show radio properties such as high brightness temperature non-thermal cores or radio lobes} consistent with jet activity; and (2) a subset of low-redshift $\gamma$-ray narrow-line Seyfert~1 galaxies exhibit optical spectra consistent with xA or borderline-xA classification. We also expand the discussion of recent developments in E1/MS studies, including metallicity trends, the spectral energy distribution of xA quasars, and the role of highly accreting quasars as discovery tools for extreme accretion states, as probes of quasars at the reionization epoch, and as possible cosmological probes. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11359 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11359v1 Announce Type: new Abstract: The interstellar medium (ISM) is a complex, multiphase medium, where disentangling the distribution of gas and magnetic field structure across different phases remains a considerable challenge. Recently, Faraday tomography enabled by broadband polarized radio observations has emerged as a promising probe of 3D ISM gas and magnetic field structures. However, the interpretation of these observations is obscured by our limited understanding of the different ISM components probed by the distinct Faraday depth features. In this work, we present a comprehensive multi-frequency ($\sim$300 MHz - 23 GHz) analysis comparing features in the Faraday-rotated, polarized synchrotron emission and HI structures over the full high-latitude (|b|>30 degrees) diffuse sky. Using measures of HI structure complexity along the line of sight (LOS), we observe enhanced depolarization across synchrotron radio frequencies in regions with high HI complexity characterized by multiple HI velocity components. We also find that the first and second moments of the Faraday depth spectra are linked to the underlying neutral gas structure. These results indicate that regions of the ISM that are dominated by neutral gas could directly contribute a significant portion of the diffuse synchrotron emission and Faraday rotation. These findings establish new observational constraints for Galactic magnetic field models that synthesize multiphase tracers into a single coherent picture. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11345 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11345v1 Announce Type: new Abstract: We present gas-phase metallicities of star-forming galaxies at $z=1$-10 with deep JWST/NIRSpec spectra from the JADES full data release, Dark Horse, and OASIS programmes. We stack $\sim$1500 medium-resolution spectra, yielding detections of the [OIII]$\lambda$4363 auroral line down to $12+\log(\mathrm{O/H})=7.0$ to derive stack-based strong-line calibrations over the metallicity range $12+\log(\mathrm{O/H})=7.0$-8.7. At a fixed metallicity, our stacks exhibit [OIII]$\lambda$5007/H$\beta$ and [OIII]$\lambda$5007/[OII]$\lambda\lambda$3726,3729 values generally lower than calibrations based on high-$z$ individual auroral-line emitters, suggesting an observational bias towards higher excitation introduced when requiring auroral line detections in individual spectra. Based on our new calibrations, we obtain canonical mass-metallicity relations (MZRs) at z$=$1-10, identifying a decrease in metallicities from $z\sim0$ to z$\sim$4-10, without significant change in slope. Moreover, we identify 50 promising candidates of extremely metal-poor galaxies (EMPGs) with $12+\log(\mathrm{O/H})=6.7$-7.3 (1-4\% solar metallicity) at $z=1.2$-9.1. The MZRs of EMPGs are characterised by a large scatter, with those having lower metallicities generally exhibiting lower sSFRs, opposite of what expected from the local Fundamental Metallicity Relation. These results support a stochastic star-formation history involving gas consumption/ejection and metal-poor inflow, strongly affecting metallicities of low-mass galaxies. Furthermore, we identify two Little Red Dots in our EMPG candidates, both exhibiting broad H$\alpha$ and prominent Ly$\alpha$, offering insights into the early black-hole growth in extremely metal-poor environments. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11329 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11329v1 Announce Type: new Abstract: In this paper we present the chemical screening of the complex stellar population discovered in the Bulge Fossil Fragment Liller 1. This study is part of the Bulge Cluster Origin (BulCO) survey based on a Large Program at the ESO-VLT with the high resolution spectrograph CRIRES+. The survey is aimed at performing an unprecedented chemical screening of 17 stellar systems orbiting the Milky Way bulge, with the ultimate goal of unveiling their origin and true nature. We measured precise chemical abundances of iron, CNO, iron-peak, $\alpha$- other light-elements, and neutron-capture elements for a sample of 30 red giant branch stars, kinematic members of Liller 1. The presented analysis provides the high-resolution spectroscopic proof of the complex chemistry of this massive stellar system, with multi-metallicity sub-populations of different ages that nicely fits into a self-enrichment scenario. We find no evidence for the Na-O anticorrelation associated with genuine globular clusters; rather the overall abundance trends are similar to those seen in the bulge field and in Terzan 5, providing definitive evidence of an in-situ formation of Liller 1 within the Galactic bulge. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11328 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11328v1 Announce Type: new Abstract: After quenching galaxies keep growing in size across time, as established in the literature up to cosmic noon. In this work, we assemble one of the largest and most comprehensive multi-wavelength photometric sample of massive quenched galaxies at z > 3, counting 137 quiescent candidates within 825 sq.arcmin and redshift 3 3, albeit with a large scatter. This suggests that the commonly used parameters of a Sersic distribution cannot explain the large intrinsic scatter around the stellar mass-size relation, suggesting that other physical quantities need to be taken into account to break the degeneracy between evolution paths across the galaxy population. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11323 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11323v1 Announce Type: new Abstract: Magnetic fields permeate the multiphase interstellar medium (ISM), yet their phase-dependent structure remains poorly constrained by observations. Dust polarization and \ion{H}{1} emission together offer complementary probes of the plane-of-sky magnetic field and cold neutral medium (CNM) gas structure, respectively. Recent observational work has shown that in the diffuse ISM, the dust polarization fraction correlates positively with the CNM mass fraction ($f_{\rm CNM}$) but not with total \ion{H}{1} column density, suggesting a phase-dependent magnetic field geometry. Here, we use extremely high-resolution ($2048^3$) simulations of the turbulent, magnetized, multiphase ISM to investigate the physical origin of this trend. By constructing synthetic \ion{H}{1} and dust polarization maps, we directly compare our simulations to the observational results of \citet{Lei:2024}. We recover a positive $f_{\rm CNM}$-polarization correlation most clearly for sightlines intersecting fewer than $\sim$20 discrete CNM clouds, while the trend becomes weak or intermittent for larger cloud counts, consistent with the expectation that high-Galactic-latitude sightlines contain relatively few independent cold structures. We show that this correlation reflects genuine phase-dependent magnetic structure: CNM clouds tend to be elongated along the local magnetic field and, when normalized by column density, exhibit lower magnetic disorder than the warm neutral medium (WNM). We further demonstrate that apparent discrepancies between simulation- and observation-based measures of magnetic disorder arise from whether disorder is quantified per unit path length or per unit mass. Our results support a picture in which CNM structures host relatively ordered magnetic fields, producing higher polarization fractions along CNM-dominated sightlines in the diffuse ISM. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11315 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11315v1 Announce Type: new Abstract: The properties of spiral galaxies in the early universe remain poorly studied and, as such, little is known about their nature and evolution. We use JWST data to measure the pitch angles of spiral galaxies across cosmic time. Our sample consists of 593 spiral galaxies with stellar masses ($M_*$) greater than $10^{10} M_\odot$ up to $z \sim 3.5$, drawn from the CEERS and JADES surveys. Spiral galaxies are identified by fine-tuning a Zoobot deep-learning model. We use SpArcFiRe to identify spiral arms and measure their pitch angles. We find no significant redshift evolution in the average pitch angle across the full sample. However, in the most massive systems (log$(M_*/M_\odot)=11-12$), spiral arms slightly wind up with time. We show that at $z>1.25$, pitch angle does not correlate with some key internal galaxy properties (stellar mass, bulge mass, disk mass, specific star formation rate [sSFR]). In contrast, at $z<1.25$, pitch angle shows a weak but statistically significant negative correlation with stellar mass, bulge mass, and disk mass, and a positive correlation with sSFR at $z<0.75$. We also find no dependence of pitch angle on the tidal strength applied by nearby companions. These results indicate a transition epoch at $z\sim1$: above this redshift, spiral structures appear to be primarily locally driven and not correlated with global galaxy properties; and below this redshift, spiral arms are regulated by global gravitational potential, consistent with the predictions of the density wave theory. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.11313 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11313v1 Announce Type: new Abstract: Low surface brightness tidal debris around galaxies, such as tails, streams, and shells, together with other interaction-driven morphological disturbances, serve as valuable indicators of past or ongoing galaxy mergers. With the growing data volume from surveys like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), automated detection methods are essential. This paper evaluates the performance of two automated methods, a Self-Supervised Learning (SSL) model and the Concentration-Asymmetry-Smoothness (CAS) parameter method, in tracing interaction-driven disturbances and merger signatures, with visual classification used as the benchmark. Visual classification yields a high-confidence disturbance fraction of 25.1 +/- 1.5% in our sample and serves as the reference standard for assessing the completeness and precision of the automated approaches. Visual classification is affected by galaxy distance and image resolution, which limit the detectability of faint low surface brightness structures. The SSL model achieves high recall (0.86 +/- 0.04) and low contamination (0.2) by retraining only its linear classifier on a small labelled dataset, making it suitable for identifying a broad set of disturbed systems, including faint tidal debris and other interaction-driven morphological disturbances, thereby providing a more complete census of merger-related features. The CAS method, using the traditional threshold A > 0.35, shows higher precision (0.77) but lower recall (0.20), indicating a conservative approach that captures cleaner but less complete samples. Visual classification and the SSL model show a significant positive correlation between stellar mass and disturbance fraction, while the CAS method exhibits a much weaker trend. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2510.08699 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2510.08699v2 Announce Type: replace Abstract: The number of observed gravitational wave (GW) events is growing fast thanks to rapidly improving detector sensitivities. GWs from compact binary coalescences like Black Holes or Neutron Stars behave like standard sirens and can be used as cosmological probes. To this aim, generally, the observation of an electromagnetic counterpart and the measurement of the redshift are needed. However, even when those are not available, it is still possible to exploit these "dark sirens" via statistical methods. In this work, we explore a method that exploits the information contained in the cross-correlation of samples of GW events with matter over-density tracers like galaxy catalogues. Contrary to other currently employed dark-sirens methods, this approach does not suffer from systematic errors related to the incompleteness of the galaxy catalogue. To further enhance the technique, we implement tomography in redshift space for the galaxy catalogue and luminosity distance space for the GWs. We simulate future data collected by the array of currently existing detectors, namely LIGO, Virgo, and Kagra, as well as planned third-generation ones such as the Einstein Telescope and Cosmic Explorers. We cross-correlate these data with those from upcoming photometric galaxy surveys such as Euclid. We perform a sensitivity forecast employing a full-likelihood approach and explore the parameter space with Monte Carlo Markov Chains. We find that with this method, third-generation detectors will be able to determine the Hubble constant $H_0$ with an error of only 0.7%, which is enough to provide decisive information to shed light on the Hubble tension. Furthermore, for the other cosmological parameters, we find that the GWs and galaxy surveys information are highly complementary, and the use of both significantly improves the ability to constrain the underlying cosmology. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2510.04179 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2510.04179v4 Announce Type: replace Abstract: We perform a consistency check of DESI DR2 BAO constraints ($D_M/r_d, D_H/r_d)$ by reconstructing the same quantities from DES supernovae (SNe) in bins with the same effective redshift $z_{\textrm{eff}} \in \{ 0.510, 0.706, 0.934 \}$ and a Planck $r_d$ prior. Through mock analysis we show that $D_M(z_{\rm eff})$ and $D_{H}(z_{\rm eff})$ can be locally reconstructed model agnostically from $\Lambda$CDM and extended models, but only if one employs frequentist methods; purely Bayesian reconstructions from Markov Chain Monte Carlo (MCMC) exhibit bias. We find that the ratio of the three $D_M/r_d$ values at different $z_{\textrm{eff}}$ are consistent with a horizontal, thus confirming that the distance duality relation holds up to calibration. However, the $D_H/r_d$ ratio shows a decreasing trend driven by the $z_{\textrm{eff}} = 0.934$ bin, the significance of which varies from $2.5 \sigma$ with Bayesian methods down to $1.4 \sigma$ with frequentist methods. We show that replacing DES with DES-Dovekie SNe reduces the significance to $1.7 \sigma$ and $1.2 \sigma$ in Bayesian and frequentist approaches, respectively. We conclude that distances reconstructed from SNe show good agreement with DESI BAO distances across the redshifts studied. We also note that $D_M(z_{\rm eff} = 0.510)/r_d$ reconstructed from SNe favours DESI BAO over transversal BAO against a backdrop of a $3.7 \sigma$ disagreement. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2509.09665 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2509.09665v3 Announce Type: replace Abstract: One of the most pressing problems in current cosmology is the cause of the Hubble tension. We revisit a two-rung distance ladder, composed only of Cepheid periods and magnitudes, anchor distances in the Milky Way, Large Magellanic Cloud, NGC 4258, and host galaxy redshifts. We adopt the SH0ES data for the most up-to-date and carefully vetted measurements, where the Cepheid hosts were selected to harbour also Type Ia supernovae. We introduce two important improvements: a rigorous selection modelling and a state-of-the-art density and peculiar velocity model using Manticore-Local, based on the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. We infer $H_0 = 71.1 \pm 1.4~\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$, assuming the Cepheid host sample was selected by supernova magnitudes. However, the actual selection criteria are not clear, and other assumptions can increase $H_0$ by up to one statistical standard deviation. The posterior has a lower central value and a 41 per cent smaller uncertainty than a previous study using the same distance-ladder data. This result is lower than the supernova-based SH0ES inferred value of $H_0 = 73.2 \pm 0.9~\mathrm{km}\,\mathrm{s}^{-1}\,\mathrm{Mpc}^{-1}$ at about $1.3\sigma$, and is in $2.8\sigma$ tension with the latest cosmic microwave background results in the standard cosmological model. These results demonstrate that a measurement of $H_0$ of sufficient precision to weigh in on the Hubble tension is achievable using second-rung data alone, underscoring the importance of robust and accurate statistical and velocity-field modelling. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12408 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12408v1 Announce Type: cross Abstract: Recent results from the DAMIC-M and PandaX collaborations have excluded the standard freeze-in production of dark matter for masses in the range $3~\mathrm{MeV} \lesssim m_\chi \lesssim 1~\mathrm{GeV}$ in the context of extensions of the Standard Model featuring an additional ultra-light $U(1)_{\rm X}$ gauge boson. In this work, we analyze the constraints induced by DAMIC-M and PandaX results on the reheating temperature in freeze-in models at stronger coupling, or when a non-thermal source (such as inflaton decay) comes into play. We identify viable scenarios in which the DM relic abundance is correctly reproduced while evading current experimental bounds on the electron-scattering cross section, $\overline{\sigma}_\mathrm{e}$. In particular, we show that for reheating temperatures below the electroweak scale, Boltzmann suppressed production can be compensated by stronger couplings, bringing freeze-in scenarios within present experimental reach. Finally, we study a hybrid scenario in which a small branching ratio of inflaton decay seeds a nonzero initial dark-matter abundance. We show that such contributions can significantly modify freeze-in predictions across broad regions of parameter space, offering an additional pathway for probing extremely feeble interactions. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12297 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12297v1 Announce Type: cross Abstract: The origin of cosmic acceleration remains a central problem in cosmology, commonly attributed to a cosmological constant within the $\Lambda$CDM model or to dynamical dark energy. Here, we develop an alternative approach in which acceleration emerges from quantum post-selection, a standard feature of quantum theory that is not usually incorporated into cosmological modelling. While quantum theory admits both pre-selected and post-selected ensembles, quantum cosmological models are almost exclusively formulated in terms of initial conditions. Building on previous work on post-selected quasiclassical dynamics, we construct a minimal predictive cosmological model in which post-selection and coarse-graining generate effective late-time acceleration without introducing a cosmological constant, dark energy, or modifications of general relativity. The resulting expansion history is highly constrained theoretically and depends on at most two parameters beyond standard Friedmann evolution. Confrontation with type Ia supernova and cosmic chronometer data yields statistically competitive fits while naturally avoiding the coincidence problem. The model also reproduces the standard radiation- and matter-dominated behaviour at early times and predicts a present-day jerk parameter significantly different from the $\Lambda$CDM value. These results suggest that cosmic acceleration may arise as a macroscopic quantum cosmological effect rather than from additional cosmological fluids or modified gravitational dynamics. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11923 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11923v1 Announce Type: cross Abstract: The propagation of very-high-energy (VHE; $E_{\gamma} \geq 100$ GeV) gamma rays from extragalactic sources is affected by interactions with photons of the extragalactic background light (EBL), resulting in pair production that attenuates the intrinsic gamma-ray flux. This interaction renders the Universe increasingly opaque to VHE photons at high energies and redshifts. New physics scenarios involving axion-like particles (ALPs) could modify this expected optical depth. In particular, ALPs with masses $m_a \sim 10$ eV can decay into two photons over cosmological timescales, thereby contributing to the diffuse EBL. If such ALPs constitute a significant fraction of the dark matter density, their decay would enhance the EBL intensity and consequently increase the gamma-ray optical depth. In this study, we investigate this scenario using a large sample of gamma-ray spectra observed with the High Energy Stereoscopic System (H.E.S.S.) and the Fermi Large Area Telescope. We model the contribution of decaying ALPs to the EBL and assess their impact on the spectra of blazars across redshifts. By comparing these observations with standard EBL models, we place constraints on the properties of heavy ALPs, specifically their mass and photon coupling, and evaluate their viability as a dark matter candidate capable of modifying the gamma-ray transparency of the Universe. From the combined analysis, and under the assumption that ALPs constitute the entire dark matter density, we derive 95% confidence exclusion limits on the photon-ALP coupling down to $g_{a\gamma} \sim 7 \times 10^{-12}$ GeV$^{-1}$ for masses $m_a\sim 15$ eV. These constraints are competitive with existing astrophysical bounds and provide complementary sensitivity to other techniques, closing a previously unconstrained region of parameter space in the $m_a \sim 2.5$-$20$ eV range. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11305 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11305v1 Announce Type: cross Abstract: For broadband imaging surveys, filter-substrate refraction causes light at different wavelengths to follow slightly different paths through the filter substrate before reaching the detector. This effect produces two chromatic perturbations to the point spread function (PSF): a shift in the effective focal position along the optical axis (longitudinal shift), which manifests as a defocus-like perturbation, and a wavelength-dependent displacement of the image position in the focal plane (lateral shift), which manifests as image decentering. Using image simulations, we provide the first study of these two effects independently across all eight Roman imaging bands and over the full focal plane. We compute the resulting PSF and photometric errors from images with and without the effect included, and compare the magnitude of the effect to the Roman science requirements. We find that the lateral shift is the dominant contribution, producing PSF size and ellipticity residuals in most bands of order ~0.3-0.4%. These exceed the Roman science requirements for weak lensing by roughly an order of magnitude. The effect is also strongly field dependent, increasing toward the edges of the focal plane. By contrast, flux residuals remain below one third of the 1% requirement for most bands, except in R062 and W146. We find the longitudinal shift to be subdominant and negligible in most bands, including the weak lensing bands. Finally, we implement the dominant lateral-shift effect in a framework suitable for large-scale image simulations and validate that the resulting PSF size and shape changes are accurately reproduced. Overall, we find that filter-substrate refraction is a relevant chromatic effect for Roman PSF modeling, and we provide tools to model and incorporate it in large-scale image simulations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12405 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12405v1 Announce Type: new Abstract: Small-scale galaxy clustering is expected to contain substantial cosmological information, but the extent to which this information constrains halo-based cosmologies independent of an assumed galaxy--halo connection remains unclear. We quantify this dependence using LRG-like mock galaxy catalogs built from 81 cosmologies in the {\tt \textsc{AbacusSummit}} suite. We analyze two-point correlation function multipoles on scales ranging from $5$--$80$ Mpc/$h$ and compare two limiting treatments, the \enquote{floor} and \enquote{ceiling}, of the standard five-parameter HOD model. In the conservative floor case, we impose only broad initial HOD bounds and profile over HOD parameters to determine the minimum constraining power available; we accomplish this with {\tt HODmin}, a two-stage global optimization algorithm written for minimizing $\chi^2$ in HOD space. In the optimistic ceiling case, we assume the HOD parameters are known exactly. We find a significant difference between the floor and ceiling when comparing against the same Planck $\Lambda$CDM mock data vector with identical modeling assumptions: for the floor, $25\%$ of the discrete {\tt \textsc{AbacusSummit}} cosmologies tested are excluded at $3\sigma$, whereas for the ceiling, $\sim81\%$ are excluded. Many cosmologies agree well with data in the floor, and yet in the ceiling are excluded by multiple orders of magnitude in $\chi^2$. We therefore observe the strength of small-scale clustering constraints depends heavily on the amount of prior HOD information assumed. We compare the sensitivity of this effect to various choices like scale cut, angle cut, multipole inclusion, mock phase, and mock HOD model. Our wide floor--ceiling bracket indicates that informative galaxy--halo priors are necessary for extracting strong small-scale clustering constraints. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12389 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12389v1 Announce Type: new Abstract: Weak lensing by large-scale structure is a powerful cosmological probe. While most analyses rely on second-order correlations, these are primarily sensitive to the parameter combination $S_8 = \sigma_8 (\Omega_m/0.3)^{0.5}$, limiting their ability to constrain $\Omega_m$ and other cosmological parameters independently. Higher-order statistics capture non-Gaussian features of the density field and can therefore break parameter degeneracies and extract more cosmological information from weak lensing surveys. We present a joint analysis of second- and third-order cosmic shear in the final data release of the Kilo-Degree Survey (KiDS-Legacy). We combine COSEBIs (Complete Orthogonal Sets of E-/B-mode Integrals) at scales between 2' and 300' with third-order aperture mass moments at scales between 4' and 32' to perform a joint analysis of second- and third-order statistics. Compared to previous KiDS analyses, we implement several methodological advances: an intrinsic alignment model with redshift and mass dependence, a baryon correction model validated on multiple hydrodynamical simulations, and corrections for reduced shear and source clustering. Combining COSEBIs with third-order aperture mass statistics in KiDS-Legacy yields $\Omega_m = 0.297^{+0.056}_{-0.040}$ and $S_8 = 0.806^{+0.025}_{-0.023}$, significantly tightening the $\Omega_m$ constraints and more than doubling the figure of merit in the $\Omega_m$--$S_8$ plane compared to the two-point analysis alone. The third-order measurements pass stringent internal consistency tests, are fully compatible with the KiDS-Legacy 2-point constraints, other 2+3-point lensing results and with Planck CMB measurements within $1\sigma$, providing no evidence for an $S_8$ tension and demonstrating the maturity of 3-point cosmic shear as a key probe for forthcoming surveys. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12265 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12265v1 Announce Type: new Abstract: Quasars can serve as standard candles through an empirical scaling relation between their ultraviolet (UV) and X-ray luminosities. As high-redshift probes, it is critical to test whether this relation evolves with redshift. In this work, we reconstruct the Hubble diagram of the Pantheon+ sample using the deep learning--based LADDER algorithm and use it as a reference to investigate the quasar scaling relation. Our results, which are consistent with those from Gaussian process regression and narrow-bin analyses, show that the potentially contaminated sample at $z 0.7$ sample; thus, it should be further screened or excluded when quasars are used as cosmological probes. We find that the scaling relation exhibits a non-linear redshift dependence that cannot be accounted for by a simple linear correction, and that this behavior is a feature of the current data sample rather than a consequence of cosmological model misspecification. To use quasars as standardizable candles, further modeling of the scaling relation and intrinsic dispersion, or more advanced data processing techniques, is required. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12255 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12255v1 Announce Type: new Abstract: Nonlinear structure growth generates higher-order correlations and morphological features in the cosmic density field that cannot be fully characterized by two-point statistics. Upcoming surveys will measure these features with greater precision, making it essential to develop methods capable of extracting as much cosmological information as possible from them. Field-level inference (FLI) is one such approach, in which cosmological parameters are constrained by comparing observed maps to forward-modeled maps, either directly or through learned summaries that retain map-level information. In this work, we compare FLI with power-spectrum-based inference using the same forward-modeling pipeline for generating weak lensing maps, with the goal of quantifying the gain from map-level analysis relative to two-point statistics. We perform this comparison with both implicit and explicit inference methods, using 8-million-parameter forward models based on Lagrangian perturbation theory and particle-mesh (PM) N-body evolution. The two FLI approaches yield closely consistent posteriors; this agreement, together with coverage tests confirming the calibration of the implicit analyses, gives us confidence in the recovered field-level constraints. Relative to the power-spectrum-based analyses, these results show significant gains in cosmological information, especially when small scales are included in the PM-based forward model. We then discuss the remaining challenges that must be addressed before PM-based explicit FLI can be applied to observational datasets. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12170 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12170v1 Announce Type: new Abstract: We develop a stochastic framework for the stationary spherical Jeans equation, motivated by the field-dependent nature of the gravitational coupling in scalar--tensor theories. We model unresolved spatial fluctuations of the scalar sector as an effective stochastic contribution to the gravitational coupling, $\Geff(r,\omega)=\Gbar(r)+\Gamma_G(r)\xi(r,\omega)$. This approach induces a linear It\^o stochastic differential equation for the radial velocity dispersion $y(r)=\sigma_r^2(r)$, defining a nonautonomous radial random flow rather than a time-evolution problem. We derive the associated Fokker--Planck equation and obtain integral expressions for the mean, variance, and covariance of the radial velocity dispersion. Because the noise is additive, the deterministic Jeans solution is recovered as the mean profile, while the stochastic sector produces a probability band around it. We specialize the construction to Navarro--Frenk--White, Hernquist, and Einasto halo models and propagate the radial covariance to the projected line-of-sight velocity dispersion. This provides a semi-analytical framework for assessing how effective gravitational fluctuations can affect halo kinematic observables in the stationary Jeans regime. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.12137 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.12137v1 Announce Type: new Abstract: We measure the dark matter halo mass function, with backsplash halos removed, from a wide range of cosmological-box and zoom-in simulations. These include the MultiDark Planck boxes, along with a suite of zoom-in simulations of Group, Milky Way, and LMC-mass halos. The Milky Way simulations include both CDM and non-CDM initial conditions. Using these measurements, we calibrate the parameters of flexible fitting functions for the halo mass function and the window function, along with parameterized models for various systematics, including finite box size effects, halo isolation criteria, halo detection efficiency, and contamination by artificial halos (objects forming from particle noise in the initial conditions). We show that this model shows remarkable consistency with N-body simulations over a broad range of redshifts, and ten orders of magnitude in halo mass ($10^6\mathrm{M}_\odot$ to $10^{16}\mathrm{M}_\odot$). Our model typically maintains a high precision of 12% and captures complex behaviors, including small-scale cut-offs, oscillations, and enhancements. In specific mass intervals for certain power spectra, we see larger deviations of 40-50%. Furthermore, when integrated with a simple model for environmental dependence, this fitting function provides a robust description of how environmental density influences the halo mass function. This precision model captures a wide variety of dark matter paradigms (including thermal relics, axions, and models with dark-sector interactions), is accurate for halo masses down to $10^7\mathrm{M}_\odot$, and is a critical ingredient for model-independent dark-matter inference from forthcoming data. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11929 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11929v1 Announce Type: new Abstract: We study the effects of dimension-four and dimension-six nonminimal Higgs couplings to the Ricci scalar $R$ in the $R^2$-Higgs inflation model in light of the recent ACT and SPT observations. We show that the dimension-six operators $|\Phi|^2 R^2$ and $|\Phi|^4 R$ can accommodate the enhanced scalar spectral index $n_s$ preferred by the combined CMB+BAO analyses. Using a doubly covariant formalism, we find that the same region of parameter space that explains the observed value of $n_s$ can also induce rapid preheating through the production of the Goldstone modes. If thermalization proceeds efficiently through this preheating mechanism, it may help match the inflationary scale with the CMB reference scale. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11725 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11725v1 Announce Type: new Abstract: We perform a Bayesian inference analysis of an inflationary model based on an inverse-tangent potential, incorporating reheating dynamics in both constant and dynamical equation-of-state (DEOS) frameworks. Using Planck and ACT constraints on the scalar spectral index, we find preferred values $\kappa\simeq0.5-0.6$ and $N_k\simeq40-60$, leading to reheating temperatures $T_{RH}\sim10^{10}-10^{14}$ GeV and reheating durations $N_{RH}\sim3-36$ e-folds. Reheating weighted $H_0$ posteriors shift the Planck inference towards the ACT preferred region through the intrinsic $n_s-H_0$ degeneracy of the CMB likelihood. In the DEOS framework, reheating with a constant decay rate yields $N_{RH}\simeq4-8$ e-folds and $T_{RH}\simeq10^{13}$ GeV, while a dynamical decay rate produces a strong dependence on the Yukawa coupling $y$, with $N_{RH}$ varying from $\mathcal{O}(30)$ to $\mathcal{O}(1)$ e-folds and the reheating temperature spanning $\sim10^{-2}-10^{14}$ GeV. Imposing inflation-reheating consistency significantly restricts the viable parameter space to a narrow region around $n_s\simeq0.9720-0.9725$ and $r\simeq0.026-0.060$, demonstrating that reheating dynamics provide a nontrivial bridge between early-universe inflation and late-time cosmological parameter inference. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11545 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11545v1 Announce Type: new Abstract: We investigate stationary halo-like solutions of the Gross-Pitaevskii-Poisson (GPP) system, which describes self-gravitating Bose-Einstein condensates with repulsive self-interactions, as a dark matter model. The boson mass $m_\phi$, scattering length $a_s$, and total particle number $N$ are kept explicit, with $N$ treated as an independent macroscopic control parameter. Solving the stationary GPP equations over a broad parameter space, we identify ground-state, excited-state, and unbound solution branches according to their binding properties and nodal structure. The ground-state branch occupies a well-defined region of the $(m_\phi,N)$ plane whose location depends strongly on the self-interaction strength, whereas the excited-state and unbound regions are largely insensitive to the initial ansatz. From the converged solutions, we derive empirical scaling relations connecting the characteristic halo radius $R_{99}$ to $m_\phi$, $a_s$, and $N$. In the weakly interacting regime, the results reproduce the standard Schrodinger-Poisson mass-radius relation, while finite self-interactions reveal an intermediate regime in which gravity, quantum pressure, and repulsive interactions jointly determine the equilibrium structure. As an astrophysical application, we show that ground-state solutions can reproduce representative dwarf-galaxy rotation curves using only the solitonic component. We also examine the implications of current Lyman-$\alpha$ forest constraints and find that, although increasing $a_s$ shifts equilibrium solutions toward larger boson masses compatible with existing bounds, the resulting configurations do not reproduce the observed dwarf-galaxy kinematics. These results provide a systematic characterization of stationary GPP halos and establish a direct connection between microscopic particle properties and observable galactic quantities. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11368 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11368v1 Announce Type: new Abstract: Following our previous work constraining interacting dark energy (IDE) models, which showed their potential to alleviate the Hubble tension, in this work we investigate the non-linear effects of the IDE scenario favoured by CMB and DESI observations. The implications of IDE for the $S_8$ tension remain unclear, since current weak-lensing and large-scale-structure analyses either exclude highly non-linear scales or model the non-linear regime using prescriptions calibrated within $\Lambda$CDM. We address this issue by implementing a fully self-consistent IDE pipeline. We perform N-body simulations of the IDE model with a transfer rate $Q=\xi {\cal H}\rho_x$ using a modified implementation of RAMSES. Since the dark matter Euler equation remains unchanged with respect to $\Lambda$CDM, the interaction can be incorporated through the modified background evolution and an effective time-dependent dark matter particle mass. We find scale-dependent deviations in the quasi-linear and non-linear regimes of the matter power spectrum, together with modifications to the density-field morphology and halo abundance. Our results show that the impact of IDE on quasi-linear and non-linear structure formation cannot be captured by standard $\Lambda$CDM-calibrated prescriptions, highlighting the importance of model-consistent non-linear modelling for future weak-lensing and large-scale-structure constraints on interacting dark energy cosmologies. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11312 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11312v1 Announce Type: new Abstract: Although measurements of the Cosmic Microwave Background (CMB) are consistent with a nearly scale-invariant primordial spectrum of adiabatic perturbations, in which the energy densities of different components (radiation, baryons, and dark matter) fluctuate proportionally, there could also exist isocurvature perturbations, in which density fluctuations of the individual components differ from the adiabatic mode. Cold dark matter isocurvature (CDI) perturbations with a variety of spectral tilts generated in pre-inflationary axion models provide one such example. In this article, we present the most updated constraints on these axion CDI perturbations using the latest CMB anisotropy measurements from Planck, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT). We study both fixed spectral indices with values ranging from red- to blue-tilted spectra as well as the case with a free index. We find that the constraint on the spectral index gets moderately improved with the combined datasets compared to Planck alone, while the bounds on the isocurvature amplitudes for the fixed spectral indices we consider do not get tighter. We also discuss the theoretical implications of our constraints, in particular for models giving rise to blue-tilted spectra. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11309 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11309v1 Announce Type: new Abstract: We present cosmological constraints from the Dark Energy Survey Year 3 (DES Y3) weak lensing data using hierarchical hybrid statistics within a Bayesian simulation-based inference framework that is based on the Gower Street simulations. To maximize the precision of the inference, we have developed a new, information-theory based, data compression of the weak lensing maps to just seven highly informative summary statistics. The hybrid scheme exploits the high information content of the power spectrum, compressing both the power spectrum and neural-based summaries that are designed to extract further information. Our simulation-based approach enables principled forward modelling of all major sources of systematic uncertainty and survey properties into realistic mock observations, including the survey mask, photometric redshift uncertainties, intrinsic galaxy alignments, multiplicative shear calibration bias, source galaxy clustering, non-Gaussian shape noise, and non-linear structure formation. The summary statistics are then used in a Bayesian simulation-based inference pipeline. The inference is validated through coverage tests and checks for robustness against baryonic feedback. Assuming a $w$CDM cosmology, our analysis yields $S_8 = 0.808 \pm 0.017$, $\Omega_{\rm m} = 0.325 \pm 0.024$, and $w < -0.766$ (marginalized posterior 68 per cent credible intervals). This rigorous combination of information theory, physics- and neural network-based extreme data compression, and principled Bayesian analysis improves the figure of merit for $(\Omega_{\rm m}, S_8, w)$ by 60 per cent over the previous state-of-the-art, and by almost a factor of 3 over two-point analyses of the same data. They are the most precise joint constraints on $(\Omega_{\rm m}, S_8, w)$ from weak gravitational lensing data alone of any survey to date. We intend to apply this analysis to the more recent DES Y6 data. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.11300 Thu, 11 Jun 2026 00:00:00 -0400 arXiv:2606.11300v1 Announce Type: new Abstract: Parity-violating physics in the Universe can generate correlations between the Cosmic Microwave Background (CMB) $E$- and $B$-modes, but detecting such signals requires extremely accurate calibration of instruments. We describe a data-driven method to calibrate the relative polarisation angle between CMB experiments using cross-correlations of observations over a common sky region. Unlike standard self-calibration approaches, this method does not assume vanishing isotropic cosmic birefringence or primordial $EB$ correlations when estimating the relative misalignment angle, and therefore preserves sensitivity to parity-violating physics. As a proof of concept, we forecast the performance of this method using the Simons Observatory (SO) Small Aperture Telescopes (SATs) as a calibrated reference. If they can be calibrated to an uncertainty of $0.08^\circ$, as anticipated from the SO wire grid calibration system, we show that the SO Large Aperture Telescope and Planck could be calibrated to uncertainties of $0.10^\circ$ and $0.17^\circ$, respectively, at $\sim 145$ GHz. This approach relies on the availability of at least one well-calibrated instrument, and provides a complementary path to improving polarisation calibration across experiments, enabling more robust searches for parity-violating physics in the CMB, such as cosmic birefringence. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10116 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10116v1 Announce Type: new Abstract: In this work, we study winds for a representative sample of 86 star-forming galaxies (SFGs) at z~1 with $M_\star = 10^{9.0}-10^{11.5} M_\odot$, by measuring the Mg II line profiles in deep Keck spectra. A total of 50 (58\%) are found to have winds. Unlike local starburst galaxies, the wind detection rate does not exhibit a threshold in star-formation rate (SFR) density $\Sigma_\mathrm{SFR}$ at 0.1 Msun/yr/kpc$^2$, but shows a gradual decline around this value. We find correlations between wind velocity $v_\mathrm{wind}$ and SFR, $\Sigma_\mathrm{SFR}$, and stellar mass, as per previous studies. Intriguingly, the z~1 SFGs appear to follow the same $v_\mathrm{wind}$-SFR relation as local starbursts. A combined fit gives: log $v_\mathrm{wind}$ = 0.16 log SFR + 2.4 (3-sigma significance). This unified relation spans over 4 dex in SFR and agrees with Illustris-TNG. No unified relation is found between $v_\mathrm{wind}$ and stellar mass, sSFR, or $\Sigma_\mathrm{SFR}$. This suggests winds might be most closely associated with SFR. We examine whether winds in z~1 SFGs are driven by their most compact star-forming regions. To do so, we consider whether the relation between $v_\mathrm{wind}$ and the $\Sigma_\mathrm{SFR}$ measured from only these regions is stronger than that for the galaxy-wide $\Sigma_\mathrm{SFR}$. We do not find a stronger correlation, suggesting that winds are most related to $\Sigma_\mathrm{SFR}$ of the entire galaxy. Collectively, these findings suggest a picture in which galaxy-wide star formation plays an important role in driving winds at z~1. Wind bubbles from all star-forming regions could combine momentum and help lift their entrained gas out of the galaxy. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10117 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10117v1 Announce Type: new Abstract: We employ a simulated sample of galaxies drawn from the IllustrisTNG suite to study the emergence of the diffuse and extended nature of $\sim12,000$ low surface brightness galaxies (LSBGs) within a wide stellar mass range (${M}_{*}=10^{9}-10^{12} \rm{M}_{\odot}$). We employ merger trees to follow the evolution of their physical properties such as stellar surface density, specific angular momentum and halo spin parameter, finding that the central low density nature of LSBGs is mainly a consequence of an increase in their angular momentum and (inner) halo spin parameter. We also find that star formation histories of LSBGs are quite similar to their high surface brightness (HSBGs) counterparts, with significant differences not in the time, but in the spatial distribution in which new stars are forming. We conclude that the mechanisms that favor the emergence of the low surface brightness nature are strongly related with variations in the spin parameter of host halos and their angular momentum, deviating the stellar distribution of galaxies from their inner regions to their outskirts, leading to a decrease in their central surface brightness. Once the LSBG nature is established, galaxies are less likely to experience strong variations in their central surface densities and morphology. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10160 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10160v1 Announce Type: new Abstract: We present James Webb Space Telescope (JWST) NIRSpec integral field unit (IFU) observations of six galaxies at $z \sim 6$, obtained as part of the Aether project (General Observers program 5645). The targets were originally identified by the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) survey, as candidate obscured quasars with luminous ($\gtrsim10^{43}$ erg s$^{-1}$) but narrow ($\lesssim500$ km s$^{-1}$) Ly$\alpha$ emission. Two objects exhibit a broad component in their Balmer lines (FWHM $>3000$ km s$^{-1}$), indicating the presence of active galactic nuclei (AGNs), while the remaining four show similar profiles in permitted and forbidden lines. Combining these data with similar SHELLQs objects reported previously, we find that the presence of broad lines is strongly correlated with Ly$\alpha$ luminosity ($L_{\rm Ly\alpha}$); the inferred AGN fraction is $>$77 % and $<$15 % above and below $L_{\rm Ly\alpha} =10^{44}$ erg s$^{-1}$, respectively. Dust-extinction corrections inferred from the Balmer decrement would imply unrealistically high Ly$\alpha$ luminosities, suggesting that the line-emitting gas consists of multiple zones. The IFU data reveal diverse spatial structures. The AGN hosts are compact, whereas the other galaxies show extended ionized gas on scales up to 10 kpc and star formation rates of 60 - 600 $M_\odot$ yr$^{-1}$. One of the extended objects exhibits a signature of rotation, while most of the others show little ordered kinematics, with velocity widths (FWHM) up to 200 - 300 km s$^{-1}$. These objects populate the intermediate luminosity regime between classical luminous quasars and the low-luminosity AGNs discovered by JWST, including Little Red Dots, potentially linking the two populations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10197 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10197v1 Announce Type: new Abstract: Integral field unit (IFU) spectroscopy provides spatially resolved spectra across galaxies, offering crucial insights into their evolution. However, its high observational cost limits current IFU datasets to $\sim 10^4$ objects. We present a multi-modal, probabilistic foundation model that predicts high-resolution spectra with calibrated uncertainties at arbitrary spatial locations within a galaxy directly from broadband images. Built on a masked autoencoder framework, our architecture injects fiber positional encodings and redshift aware wavelength encodings, enabling spatially conditioned predictions. Trained on 4.7 million images and single fiber spectroscopic observations from the Dark Energy Spectroscopic Instrument (DESI) survey, our model exploits the natural variance of fiber placements and the morphological self-similarity of galaxies to achieve IFU-like capabilities without any IFU training data. Predicted emission line flux maps match independent IFU observations from the Mapping Nearby Galaxies at APO (MaNGA) survey, with performance comparable to a supervised baseline trained directly on IFU data. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10235 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10235v1 Announce Type: new Abstract: While the presence of the Galactic warp has long been established from observations of \HI\, gas, the \textit{Gaia} measurements of over 1 billion stars with parallaxes have enabled much more detailed studies using stellar populations. Here, we demonstrate that asymptotic giant branch (AGB) stars, an evolved phase of low- and intermediate-mass stars, can serve as an effective tracer of the Galactic warp. We use two distinct AGB populations: C-rich AGB stars, representing stars of about 1~Gyr in age with main-sequence masses of 2--2.5~\Msun, and intermediate-mass (3--5~\Msun) O-rich AGB stars, corresponding to ages of 100--300~Myr. The downward warp traced by O-rich AGB stars is consistent with that found from Cepheids, which is expected given their similar ages. The more numerous C-rich AGB stars clearly reveal the Galactic warp over a wide range of azimuthal angles. Their warp appears to reach larger amplitudes than that of Cepheids across azimuthal angles. Our results show that C-rich AGB stars, together with intermediate-mass O-rich AGB stars, provide new constraints on the Galactic warp at intermediate stellar ages, offering a new insight into the stellar age and warp amplitude relation. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10271 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10271v1 Announce Type: new Abstract: Galactic winds are considered a likely driver of rapid quenching in early massive galaxies, but until now there has been no direct evidence that such systems drive winds powerful enough to meaningfully suppress their star-formation. We present resolved cold gas and ionized gas observations of a powerful supernova-driven wind in a massive galaxy 1.1 billion years after the Big Bang (at $z$=5.3). The outflow, likely triggered by ongoing merger activity, is removing gas at twice the rate of star-formation and could plausibly eject all the cold gas from the galaxy within 100 Myr. Our results suggest that powerful merger-driven outflows may be a key mechanism to produce abundant massive quiescent galaxies in the early Universe when a large fraction of massive galaxies are interacting. The mass and energetics of this distant outflow are consistent with nearby starburst-driven superwinds, suggesting that the efficiency of stellar feedback has remained relatively constant over the last 12 billion years of cosmic history. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10447 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10447v1 Announce Type: new Abstract: Narrow-line Seyfert 1 (NLSy1) galaxies are peculiar active galactic nuclei (AGN) known to exhibit a variety of intriguing observational features from low-frequency radio waves to high-energy $\gamma$~rays. As of now, NLSy1 catalogs are primarily based on optical spectroscopic observations from the Sloan Digital Sky Survey (SDSS). Here we report, for the first time, a new catalog of NLSy1 galaxies using the high-quality optical spectroscopic observations made public in the first data release of the Dark Energy Spectroscopic Instrument (DESI). We performed a detailed spectral decomposition of more than 71,000 optical spectra of AGN not included in the SDSS catalog and located at $z<0.9$. From this sample, we identify 18749 objects as NLSy1 galaxies for the first time. We also supplement the NLSy1 catalog with a sample of broad-line Seyfert 1 galaxies. The NLSy1 galaxies identified in the DESI data tend to have slightly higher bolometric luminosities and lower black hole masses (though with large dispersions), leading to the higher Eddington ratios than those of the SDSS-NLSy1 sample matched in redshifts and absolute $B$-band magnitudes. Moreover, the fraction of DESI-NLSy1 galaxies detected in the radio, X-ray, and $\gamma$-ray catalogs was found to be lower than that of SDSS-NLSy1 sources. We conclude that deeper multiwavelength investigations of these enigmatic AGN will help unravel the low-luminosity end of the NLSy1 population. The catalog has been made available at https://www.ucm.es/blazars/seyfert and Zenodo https://doi.org/10.5281/zenodo.20484681. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10455 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10455v1 Announce Type: new Abstract: The quasar main sequence, or Eigenvector 1 (EV1), describes the optical diversity of active galactic nuclei (AGN), with Narrow-Line Seyfert 1 (NLSy1) galaxies anchoring the high-accretion end. Recent discoveries of overly massive black holes in the early Universe highlight the need to study local, low-mass super-Eddington accretors as analogs of rapid black hole growth. We map a population of 18,749 NLSy1 galaxies identified in the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) onto the EV1 plane to determine whether they represent a distinct population of super-accretors. We compare the spectral properties of the DESI DR1 NLSy1 sample with the SDSS DR17 NLSy1 catalog. We extract key parameters, including the broad H-beta full width at half maximum (FWHM) and Fe II strength (R4570). To evaluate their accretion states, we derive single-epoch virial black hole masses using an Fe II strength-dependent scaling relation and an Eddington rate-dependent fundamental plane. The DESI DR1 NLSy1 population shows a shift toward the extreme end of the EV1 parameter space, with stronger Fe II emission (median log R4570 = -0.03) than the SDSS sample (-0.31). Furthermore, the DESI sources host less massive black holes (median log black hole mass ~6.73) than the SDSS objects (6.77-6.91). Given comparable continuum luminosities, a larger fraction of the DESI sample (43.8%-47.7%) exceeds the Eddington limit (log Eddington ratio > 0) than the SDSS sample (20.6%-37.4%). The sensitivity of DESI has unveiled a large population of low-mass, super-Eddington accreting AGN largely missing from previous surveys. These extreme EV1 objects naturally produce the observed intense Fe II emission. This unique sample provides a statistical dataset of local super-Eddington accretors for understanding early-Universe black hole growth. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10557 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10557v1 Announce Type: new Abstract: We present $^{12}$CO(1-0) mapping across the entire system of Stephan's Quintet, a well-known compact galaxy group, observed by Atacama Compact Array (7\,m array + Total Power) of the Atacama Large Millimeter/submillimeter Array. These observations provide the first large-scale ($137\,\mathrm{kpc}\times119\,\mathrm{kpc}$), spatially resolved ($\sim$5.5\,$\mathrm{kpc}$) molecular gas map of a compact group. Our CO map revealed that most of the molecular gas resides in the disk of the member galaxy NGC~7319 and in the intergalactic regions, including components along the shocked filament and the optically identified tidal tail extending from NGC~7319. Along the tidal tail and its surroundings, we found not only an extended molecular gas component but also four discrete CO clumps, with velocity dispersions of $\sim$10-30 $\mathrm{km\,s^{-1}}$ and molecular gas masses of order $10^7$-$10^8\,M_\odot$. Three of these clumps spatially overlap with H\,{\sc i}, whereas the remaining clump shows no associated H\,{\sc i} or counterparts at optical and infrared wavelengths. Using star formation rates derived from H$\alpha$ luminosities of H\,{\sc ii} regions, we found that star formation efficiencies (SFEs) span $\sim$2.2\,dex ($\sim$0.02--4\,Gyr$^{-1}$) and negatively correlate with CO velocity dispersion. While regions with small velocity dispersion exhibit SFEs comparable to those of nearby disk galaxies, those with large velocity dispersion ($\sim$50-150$\,\mathrm{km\,s^{-1}}$) around the shocked filament show strongly suppressed star formation. These results suggest that turbulence plays a significant role in regulating star formation in interacting systems. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10558 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10558v1 Announce Type: new Abstract: The stellar initial mass function (IMF) is a fundamental ingredient in galaxy evolution, linking observed integrated light to galaxy properties. Constraining the full IMF shape beyond the Milky Way remains challenging, as most studies focus either on the low-mass end of quiescent galaxies or the high-mass end of star-forming galaxies. Here we present the first simultaneous analysis of both ends of the IMF in 214 star-forming galaxies from the Hector survey. We estimate the low-mass end slope using a stellar population approach that fits IMF-sensitive absorption features with extended star formation histories, while the high-mass end slope is derived via the Kennicutt diagnostic, which compares the observed H-alpha equivalent width and g-r colour with stellar population synthesis model predictions. We find substantial diversity in IMF shapes and a weak but statistically robust correlation between the low- and high-mass IMF slopes. Both IMF slopes show significant correlations with stellar mass, star formation activity, and stellar metallicity ([M/H]). In general, higher stellar mass, stronger star formation activity, and higher metallicity are associated with both bottom-heavy and top-heavy IMFs. Partial correlation analysis reveals that the low-mass end slope is primarily driven by [M/H], whereas the high-mass end is mainly linked to stellar mass and recent star formation. Because the low-mass end slope traces the IMF over long-term averages and the high-mass end slope captures only recent star formation, the processes shaping each end likely occur over different and possibly decoupled timescales. Our findings challenge the universality of the IMF and emphasise the need for galaxy evolution and stellar population models to incorporate a flexible IMF prescription. Accounting for these variations is essential to build an IMF-consistent picture of galaxy evolution across cosmic time. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10623 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10623v1 Announce Type: new Abstract: Classical Cepheids (DCEPs) are excellent standard candles expected to trace the spatial and kinematic distribution of the Galaxy's young and dynamically cold stellar disc. Using the most precise mid-infrared DCEP distances to date combined with Gaia-DR3 astrometry & line-of-sight velocities, we perform a comprehensive 6D dynamical census of the Milky Way's DCEP population. While the vast majority exhibit the expected disc-like kinematics, we identify 18 kinematically anomalous Cepheids. These `rogue' stars reside on highly inclined orbits, including two in retrograde motion and one with a total velocity of ~480 km/s. Despite their extreme trajectories, their optical light curves are consistent with DCEP classifications. We explore whether these anomalies originate from classification systematics or physical processes. Re-deriving distances under the assumption that these are misclassified older Type II Cepheids (T2C) fails to reconcile their extreme kinematics, placing them at the tail of the T2C angular momentum distribution. Dynamical comparison with Galactic Globular Clusters (GC) suggests that at least one anomaly (OGLE-GD-CEP-0507) was possibly scattered into its current orbit via an interaction with the GC E3. Assuming a runaway scenario we derive dynamical ages for the kinematic anomalies, which we find highly consistent with their Cepheid ages. Spectroscopic follow-up would be insightful as one source in particular is exceptionally metal poor ([Fe/H] ~-1.6 dex), which is highly atypical for a DCEP. Integrating photometric classification with 6D kinematics will help fully characterise the Galaxy's variable star populations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10648 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10648v1 Announce Type: new Abstract: Star formation in galaxies is intrinsically stochastic, driven by physical processes operating across a wide range of scales. The scatter in the star-forming main sequence relation provides a window into this variability, but interpreting this scatter in terms of underlying physical mechanisms remains challenging. We present a study of star-formation variability during reionization (redshift z=3-8) using power spectral density (PSD) models to characterize fluctuations in star formation rates (SFRs). We use estimates of the intrinsic scatter in main sequence SFRs at six averaging timescales (10-100 Myr) from a catalogue of ~17000 galaxies presented in Simmonds et al. 2025 to constrain two PSD models, the Simple Harmonic Oscillator (SHO) and the Extended Regulator (ExtReg), with nested sampling and neural network emulators. We find that the regulator component of the ExtReg model is poorly constrained by the present data. However, both the dynamical component of the ExtReg model and the single-component SHO model favour characteristic variability timescales of ~10-30 Myr, comparable to expected galactic dynamical and stellar feedback timescales. At least in the SHO model, and most clearly at z~3-4, the inferred PSD power on ~10 Myr timescales decreases with stellar mass, indicating more bursty, rapidly varying star formation in lower-mass galaxies than in higher-mass systems. We find weak evidence for a transition from a two-component ExtReg-like PSD at lower redshift to a single-component SHO-like PSD at higher redshift in the lowest stellar-mass bin, log M*/M$\odot$ = 8-8.5, although the Bayes factors are small and selection effects at high redshift prevent strong conclusions. Overall, our results suggest that the observed 10-100 Myr scatter of the high-redshift star-forming main sequence is governed primarily by short-timescale variability, consistent with galactic dynamical timescales. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10655 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10655v1 Announce Type: new Abstract: Context. Several studies have shown that host-galaxy structure or extended optical morphology in AGNs can induce spurious parallaxes and proper motions in Gaia DR3. However, it remains unclear whether source morphology also introduces systematic errors into the celestial reference frame constructed from Gaia data. Aims. We aim to provide a Gaia-independent external morphological indicator for Gaia-CRF3 sources and to use it to quantify the astrometric systematics associated with source morphology. Methods. Using morphological parameters derived from DESI, SDSS, and SkyMapper, together with the PS1-PSC point-source score as a common reference scale, we used XGBoost to infer external morphological scores for Gaia-CRF3 sources. We then developed a multi-survey fusion scheme to combine the four survey-based point-source scores into a single composite score that measures the degree to which each source departs from the morphology of an ideal point source. Results. We obtained morphological scores for 1,607,490 Gaia-CRF3 sources, corresponding to a completeness of 99.59\% with respect to the full Gaia-CRF3 catalogue. The score ranges from 0 to 1 and remains reliable for sources with $G 0.95, the total frame spin amplitude is reduced by 15.8\% relative to that of the full Gaia-CRF3 sample. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10823 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10823v1 Announce Type: new Abstract: Active galactic nuclei (AGNs) have been proposed as efficient environments for the formation of binary black holes (BBHs). We present an updated semi-analytical framework for BBH formation and evolution in AGN disks, following the capture, migration, pair-up, gas-driven hardening, binary--single encounters, and merger of stellar-origin black holes. We systematically explore the dependence of the resulting BBH merger population on the main AGN parameters, namely the supermassive black hole mass $M_\bullet$, the Eddington ratio $\lambda_\bullet$, and the disk viscosity parameter $\alpha$, and construct an intrinsic BBH population by weighting the simulations according to observed low-redshift AGN properties. We find that AGN disks can produce repeated mergers and build a high-mass tail extending beyond the pair-instability mass gap and into the intermediate-mass range. Hierarchical growth is more efficient in lower-viscosity disks, with $\alpha=0.01$, while higher-viscosity disks suppress the formation of massive remnants. The merger efficiency generally increases with $\lambda_\bullet$, but its dependence on $M_\bullet$ is non-trivial. The AGN-assisted BBH population is characterized by increasingly unequal mass ratios at high primary mass, a correlation between primary mass and $|\chi_{\rm eff}|$, and an effective-spin distribution that depends strongly on the fraction of binaries born in prograde or retrograde configurations. We find that the AGN channel can reproduce systems broadly consistent with the massive BBH events GW190521 and GW231123. We test several variations of the physical model, including different formalisms for migration torques, gas hardening, and three-body encounters. The general properties of the population are robust across these variations, with the high-mass tail and spin signatures persisting in all cases except when gas hardening is switched off. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10859 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10859v1 Announce Type: new Abstract: Dark matter subhalos and intermediate-mass black holes wandering in the Milky Way and the Andromeda galaxy are difficult to directly detect through electromagnetic observations, yet knowing their abundance is essential for understanding galaxy formation and evolution. We propose parallel stellar streams as dynamical imprints left on stellar streams by dark perturbers, including starless dark matter subhalos and wandering intermediate-mass black holes. We report that a single stream can split into two parallel structures after an encounter with a dark perturber. This scenario is supported by analytical modelling and N-body simulations. We also discuss how we can distinguish parallel stellar streams from other formation processes based on observables. We extend the theoretical picture of stream-subhalo interactions by showing that encounters with dark perturbers can generate density depletions perpendicular to the stream elongation, leading to parallel stellar stream morphologies beyond conventional gap-like signatures. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09992 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09992v1 Announce Type: new Abstract: The explosion of a star is first marked by the shock wave breaking out of the stellar surface, producing a burst of ultraviolet and X-ray radiation. These events are observationally rare, despite likely accompanying the majority of supernovae. Here, we report on our multi-wavelength observing campaign of the closest Einstein Probe fast X-ray transient EP260321a at $z=0.0344$. The thermal ($kT=160$ eV) X-ray emission with peak luminosity $2.2\times10^{44}$ erg s$^{-1}$ points to a shock breakout origin. We demonstrate that EP260321a is accompanied by a broad-lined Type Ic supernova, SN 2026gzf. The supernova properties, including its spectral evolution, lightcurve evolution, and expansion velocities, are all typical of the energetic stripped-envelope supernovae associated with gamma-ray bursts. However, deep X-ray upper limits obtained with the \textit{Chandra X-ray Observatory} do not detect an X-ray afterglow, and instead exclude the afterglow of known gamma-ray bursts or fast X-ray transients. If the stellar explosion launched a successful relativistic jet, we require that it had both a low Lorentz factor $\Gamma_0$\,$<$\,$30$ and a kinetic energy $E_\textrm{kin}$\,$<$\,$10^{49}$ erg for a stellar wind density of $A_*$\,$\gtrsim$\,$1$. We propose that EP260321a originated from a mildly relativistic, weak outflow that was choked by the progenitor star. This scenario is capable of naturally explaining its low X-ray luminosity and lack of prompt gamma-ray emission. EP260321a bridges the gap between SN 2008D and low-luminosity GRBs, suggesting a greater diversity in the physical parameters of stripped stars as they undergo terminal collapse. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10002 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10002v1 Announce Type: new Abstract: A long-standing question in the death of massive stars is the role of relativistic jets. While many gamma-ray bursts and some fast X-ray transients seem to be associated with broad-lined type Ic supernovae, the opposite is not true. The lack of observable jet emission in those Ic-BL SNe can be explained by invoking off-axis jets, choked jets that inject all their energy into the stellar envelope, baryon-loaded jets for which the prompt high-energy emission is strongly suppressed, or non-jetted SNe. The lack of exact explosion time in the majority of SNe presents an obstacle to distinguish between these scenarios. Here we report the properties of SN 2026gzf associated with the X-ray thermal Einstein Probe shock-breakout EP260321a at z=0.0343. The absence of compelling shocked cocoon and radio emission up to 54 days, combined with initial expansion velocities of ~30,000 km/s and a circumstellar shell of ~0.07 M$_\odot$, favour a scenario for SN 2026gzf in which a jet was choked in the circumstellar shell. Our high-spatial resolution images of the SN environment show that the progenitor was located between two highly star-forming regions with a metallicity lower than any previously known Ic-BL SN. As the first case of a Ic-BL SN associated with high-energy prompt emission without the signature of a jet, SN 2026gzf provides a unique perspective to understand the successful launch of relativistic jets during the deaths of massive stars. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10009 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10009v1 Announce Type: new Abstract: When a massive star explodes as a supernova, crucial information about its immediate environment is lost within hours. Here we report rapid optical observations from Lulin Observatory of the broad-lined Type Ic supernova SN 2026gzf, beginning 1.25 hours after Einstein Probe detected the X-ray transient EP260321a. Our data led to the discovery of the optical counterpart and showed a luminous blue first-day excess that cannot be reproduced by standard radioactive models. We find that interaction between the ejecta and $\approx 0.02$ M$_{\odot}$ of circumstellar material accounts for the early excess. Archival Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) images show variability at the explosion site over the previous $\sim 12$ years, with the source brightening by a factor of $\sim 1.5$ in the final $\sim 3$ years before explosion, providing rare evidence for pre-explosion activity in a stripped-envelope progenitor system. The precursor brightening suggests enhanced eruptive mass loss during late-stage oxygen burning before core collapse, while an additional silicon-burning episode shortly before explosion may have created the compact nearby material responsible for the X-ray shock-breakout signal. SN 2026gzf therefore offers the first view of how a stripped progenitor modifies its immediate environment shortly before death, linking long-term precursor variability, circumstellar interaction and the explosion itself. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10011 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10011v1 Announce Type: new Abstract: In March 2026, the Einstein Probe (EP) discovered its most nearby (z = 0.0343) Fast X-ray Transient (FXT), EP260321a, the first EP FXT to provide a strong match to expectations for X-ray ''shock breakout'' (SBO) emission. Here, we present our multi-wavelength follow-up campaign of EP260321a and its broad-line Type Ic (Ic-BL) supernova (SN) counterpart, SN 2026gzf, the first Type Ic-BL SN with a definitive X-ray SBO. We show that our radio follow-up extending over 5.8 - 54.5 days post-FXT rules out an on-axis jet counterpart of isotropic-equivalent kinetic energy $E_{K} > 10^{49}$ erg for circumburst densities $n > 10^{-2}~{\rm cm}^{-3}$ and constrains radio synchrotron emission from the fastest-moving SN ejecta. In addition, we derive the properties of SN 2026gzf and its host galaxy from our well-sampled optical data and compare them with those of optically discovered Type Ic-BL SNe, finding that SN2026gzf is well within the 90% confidence interval across all properties. We further fit SN 2026gzf's light curve with five different physical models, and determine that combined emission from both interaction with circumstellar material (CSM) and $^{56}$Ni radioactive decay provides the best fit with plausible model parameters. Finally, using the rate of Ic-BL SNe from the ZTF Bright Transient Survey and assuming all Type Ic-BL SNe produce EP260321a-like FXTs, we infer an expected rate of EP-detected SBOs of 4.4 - 16 year$^{-1}$. This is inconsistent at the 90% confidence level with current EP detection rates, potentially indicating that most Type Ic-BL SNe produce less luminous X-ray SBO signals compared to EP 260321a. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10014 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10014v1 Announce Type: new Abstract: Massive stars die as energetic supernova explosions, but the physical processes during and before such explosions are poorly studied observationally. The first electromagnetic signals from core-collapse events are predicted to be a flash of soft X-ray and ultraviolet (UV) light, produced as a result of a shock wave breaking out of the star and its surrounding medium. Such shock breakout (SBO) events often carry essential information about the explosion energetics, the progenitor star, and its immediate environment. However, they are difficult to catch because of their very short durations and a historical lack of sensitive wide-field monitors. Only two SBO events have been detected so far in X-rays, but their emission spectra are modified from the simple thermal form by complicated physical factors, however. Here we report the discovery of a fast X-ray transient, EP260321a, followed by a broad-lined Type Ic supernova (SN Ic-BL) emerging days later, suggesting its progenitor as a Wolf-Rayet star with its hydrogen and helium envelopes stripped. Its X-ray emission is soft and best modeled by blackbody radiation, making it a bona fide SBO. The observed long duration and large total energy output of the X-ray event jointly indicate a shock breaking out from a surrounding shell at a radius of about 300 solar radii, rather than from the progenitor star's surface. This provides direct evidence of abrupt mass ejection within a month prior to core collapse, suggesting intense pre-explosion activity for a massive star. The real-time detection of SBOs yields precise timing of stellar core-collapse, allowing for efficient searches for associated neutrinos and potential gravitational-wave signals. These, together with timely multi-wavelength observations, may uncover how massive stars end their lives. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10118 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10118v1 Announce Type: new Abstract: Context. Determining the internal constitution of the outer crust of magnetars is important for interpreting several of their astrophysical manifestations. In particular, the crustal composition is a key input for simulations of r-process nucleosynthesis in giant flare ejecta. However, traditional methods are computationally expensive, limiting their use in large-scale studies. Although faster iterative approaches exist, they are restricted to unmagnetized matter and strongly quantizing magnetic fields, leaving the intermediate field strengths characteristic of observed magnetars without an efficient treatment. Aims. We developed the program magcrust to extend these existing iterative approaches, enabling the rapid computation of the outer-crust composition of cold, non-accreted magnetars over the full range of the magnetic-field strengths inferred for these objects. Methods. Transitions between adjacent crustal layers are computed by solving approximate equilibrium conditions at the interface. Nuclear abundances and layer depths are estimated from approximate solutions of Einstein's equations of general relativity. Results. The performance and accuracy of the program were assessed against detailed numerical calculations. Relative deviations from exact transition properties remain within a few percent, and crustal compositions are well reproduced across 17 nuclear mass tables and 1300 magnetic-field strengths from 1E13 to 1E16 G. Computation times are reduced by factors of 1E3-1E7 compared to traditional approaches. Conclusions. This program provides a robust and efficient tool for determining the stratification of magnetars' outer crust over the full range of astrophysically relevant magnetic-field strengths. Its computational speed makes it well suited to systematic calculations, including sensitivity analyses, uncertainty quantification, and ensemble studies. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10189 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10189v1 Announce Type: new Abstract: Kilohertz perturbations in active magnetars evolve into monster radiative shocks at radii $r\sim 10^8$ cm. The shock generates X-rays and a semi-coherent radio precursor, which strongly interacts with the magnetospheric plasma ahead of the shock. We show that this interaction self-regulates the precursor emission and find its self-consistent frequency and luminosity. The precursor frequency falls in the GHz band and its production peaks when the shock expands to $r\approx 10^9$ cm. The resulting GHz burst has a sub-millisecond duration and energy ${\cal E}_{\rm FRB}\approx 10^{34}{\cal E}_{38}^{0.2}$ erg where ${\cal E}$ is the energy of the primary magnetosonic disturbance that launched the shock. As the GHz burst propagates to the light cylinder $R_{\rm LC}\sim 10^{10}$ cm, it faces a threat of being absorbed by the magnetosphere. The burst escapes if the local plasma density at $R_{\rm LC}$ is $\sim 30$ times lower than typically expected for active magnetars, so distant observers need some luck to see the radio burst. The shock X-rays follow the radio waves with a millisecond delay. Shocks from kilohertz disturbances with energies ${\cal E}\sim 10^{38}$ erg generate X-ray and radio bursts similar to the activity detected in SGR 1935+2154. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10292 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10292v1 Announce Type: new Abstract: In this work, we perform an indirect search for axion-like particles (ALPs) through their hypothesized mixing with photons in the presence of magnetic fields. ALPs are a well-motivated dark-matter candidate class, and the photon-ALP conversion mechanism provides a unique channel to constrain their mass and coupling constant using very-high-energy gamma-ray observations. The photon-ALP mixing could alter the observed gamma-ray spectrum from extragalactic sources by effectively reducing the apparent attenuation due to extragalactic-background-light absorption. We analyze 7.5 years of data from the High Altitude Water Cherenkov (HAWC) Observatory, targeting the nearby radio galaxy M87. This source is located within the Virgo cluster and is an ideal environment for photon-ALP conversion due to its low redshift and the large-scale, strongly magnetized medium of the cluster. We find no evidence for a photon-ALP conversion signal and, consequently, set constraints on the ALP mass and photon-ALP coupling constant with emission from M87 which are consistent with previous results. Our analysis places competitive constraints on the ALP parameter space, defining an exclusion region in the mass range of approximately $10^{-8}$ to $10^{-6}$ eV for coupling constants above $5\times10^{-12}$ GeV$^{-1}$, complementing previous constraints from other gamma-ray observatories. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10519 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10519v1 Announce Type: new Abstract: We present a reanalysis of 17 years of Fermi Large Area Telescope (LAT) observations of the Crab pulsar obtained between 2008 August and 2025 August. Using monthly Jodrell Bank radio ephemerides, we assigned pulse phases to the LAT events and aligned the phase zero across the full data set. From this phase-aligned data set, we derived pulse profiles over 100 MeV to 300 GeV. The pulsed emission remains clearly detectable in the 10 to 20 GeV and 20 to 30 GeV bands, with H-test significances of 32.36 sigma and 11.59 sigma, respectively, but is not significantly detected in the 30 to 300 GeV band. Phase-resolved likelihood analysis was performed over 100 MeV to 30 GeV using 14 phase bins with comparable pulsed statistics. The fixed-window fractional fluxes show that the contribution of Peak 1 (P1) decreases steadily with energy, while those of Peak 2 (P2) and the Bridge increase, with P2 exceeding P1 above 10 GeV. Finally, the same phase-assignment framework also enables an off-pulse analysis from 100 MeV to 1 TeV, confirming the synchrotron and inverse-Compton components that dominate the emission in the selected off-pulse interval. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10527 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10527v1 Announce Type: new Abstract: Axions and axion-like particles (ALPs) are compelling candidates for dark matter and new physics beyond the Standard Model. Photon-axion mixing in external magnetic fields modifies the photon energy spectrum and linear polarization state, and also induces circular polarization signals. Compared to spectral and linear polarization methods, circular polarization benefits from lower astrophysical background contamination, providing an independent probe for axion searches. In this work, we study the circular polarization induced by photon-axion mixing within the chiral basis framework. By analytically solving the evolution equations under the single-domain approximation, we derive an expression for the circular polarization degree P_C, applicable in the resonant, strong coupling, and weak coupling regimes. Within single-domain magnetic field models, we compare the energy-dependent circular polarization in four astrophysical environments (AGN jets, intracluster medium, intergalactic medium, and Galactic magnetic fields). We find that the X-ray to MeV band represents the most sensitive observational window. Using the blazar S4 0954+65 as a case study, phase accumulation in random magnetic domains causes the circular polarization degree to fluctuate with redshift and exhibit pronounced energy structures. Using the optical circular polarization upper limit P_C < 0.184% from this source, we constrain g_{a{\gamma}{\gamma}} <= 5 x 10^{-12} GeV^{-1} for m_a ~ 10^{-16}--10^{-10} eV, with the strongest constraint near m_a ~ 10^{-14} eV. These results establish circular polarization as a complementary axion probe. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10538 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10538v1 Announce Type: new Abstract: Over a hundred fast radio burst (FRB) host galaxies have now been identified, enabling both comparisons of host redshift with FRB dispersion measure to study the cosmological distribution of ionised gas, and analyses of host properties in order to identify FRB progenitors. The standard method for determining the most likely FRB host galaxy in an optical image is the Bayesian framework Probabilistic Association of Transients to their Hosts (PATH), which accounts for uncertainties in the radio localisation, and simplified prior distributions on the host being observable. In this work we extend PATH, incorporating physically-motivated priors that are based on expectations about FRB host galaxy magnitudes. We develop three different models for the apparent r-band magnitude distribution based on an FRB's expected host galaxy redshift, $P(m_r|z)$ and combine these with expectations for redshift based on an FRB's dispersion measure, $P(z|DM)$. We fit the parameters of these prior models using host galaxy candidates for 32 FRBs detected by the Australian SKA Pathfinder (ASKAP) in incoherent sum (ICS) mode by the Commensal Real-time ASKAP Fast Transients (CRAFT) survey. Employing PATH with the new priors on the host magnitudes, we find increased confidence in the most probable hosts of all ASKAP ICS FRB host galaxies. All three models predict similar distributions of FRB host magnitudes at low redshift $(z \sim 0.1)$, and we confirm previous results that the true FRB host galaxy distribution is fainter than expected for a star-formation-weighted distribution (p-value of 0.12%). However, a mass-weighted distribution provides an even worse fit (p-value of $10^{-9}$). Tests against more FRBs in the $z > 0.5$ range, where the models differ, and extensions of the models to account for e.g. host metallicity, may help to resolve these uncertainties in the FRB host distribution. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10566 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10566v1 Announce Type: new Abstract: We report the discovery of a new X-ray transient, EP~J175257.3--351923 (EP250916a), by the \textit{Einstein Probe} (EP) near the Galactic plane. The outburst lasted for at least $\gtrsim 40$~days, reached a peak 2--10 keV flux of $\sim 4 \times 10^{-10}$~erg~cm$^{-2}$~s$^{-1}$, and exhibited a fast-rise, exponential-decay (FRED) profile typical of X-ray binary outbursts. The source remained in the hard state throughout the outburst, with only modest variations in the photon index ($\sim 1.6$--$2.2$) and no evidence for a spectral state transition. Broadband spectral modeling suggests a truncated disk, a weak reflection component, and a high-energy cutoff at $\sim 217$~keV, consistent with hard-state accretion in black-hole systems. No reliable optical counterpart is detected within the Swift/XRT error circle in SVOM/VT, Swift/UVOT and GROND observations, and the inferred X-ray-to-optical flux ratio, $\xi \gtrsim 21.75$, is consistent with a low-mass companion. No pulsations or significant aperiodic variability are detected. Although the compact object cannot yet be firmly identified, the timing, spectral, and optical evidence favors EP~J175257.3--351923 as a black-hole low-mass X-ray binary candidate, highlighting EP's potential to uncover a faint, previously hidden population of X-ray binaries. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10710 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10710v1 Announce Type: new Abstract: How stellar-mass black holes are formed is an open question in astrophysics, with very limited observational constraints. It is not known which types of stars are more likely to produce black holes, and whether the formation process is accompanied by strong or weak electromagnetic transients - or none at all - and this issue remains a critical missing piece in the puzzle of the fate of massive stars. Recent theoretical work predicts that many stellar-mass black holes form from hot, UV-luminous massive stars, including Wolf-Rayet-like progenitors, and searches focused primarily on luminous cool supergiants may therefore miss a substantial fraction of black-hole formation events. While the coming decade will bring major advances in time-domain astronomy through Rubin/LSST, Roman, JWST, and wide-field transient surveys, none of these combines UV sensitivity, sub-arcsecond imaging, and decade-long continuity. HST uniquely enables direct searches for disappearing hot massive stars associated with black-hole formation. We outline a roadmap for extending HST's role in this area into the 2030s through a dedicated, large program to re-image nearby galaxies in the UV and identify candidate disappearing stars and unusual low-luminosity transients identified by complementary surveys. Theoretical event rates imply that the nearby galaxy population accessible to HST should yield of order one detectable black-hole-forming disappearance event per year. Extending HST operations into the 2030s would therefore provide crucial insights into the unsolved problem of black hole formation. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10739 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10739v1 Announce Type: new Abstract: We present a broadband spectral analysis of the neutron star LMXB GRS 1747-312 using $\sim 40$ ks AstroSat data. The source was observed during the decay phase of the 2017 outburst, with an absorbed 1.0--5.5 keV flux of $1.67^{+0.04}*{-0.07} \times 10^{-11}$ erg s$^{-1}$ cm$^{-2}$, corresponding to a luminosity of $\sim (0.9-1.80) \times 10^{35}$ erg s$^{-1}$. The continuum is modeled with thermal Comptonization of blackbody emission and interstellar absorption. A mildly broad iron line at $\sim 6.4$ keV is fitted with a disc reflection component. Narrow lines below 2 keV are described by a hot plasma using the XSPEC model APEC. Additionally, there is a potential detection of an emission line at $4.19^{+0.12}*{-0.10}$ keV with width $\sigma = 0.2 \pm 0.2~\mathrm{keV}$ and line flux = $13^{+10}*{-9} \times 10^{-5}$ erg s$^{-1}$ cm$^{-2}$. Examination of several short duration ($\sim$ few kiloseconds) Swift observations at few times the AstroSat source flux, provided upper limits to the line flux $< 30 \times 10^{-5}$ erg s$^{-1}$ cm$^{-2}$. The 4.2 keV line likely originates from reflection off the neutron star surface. Shifting the neutral Fe $K*\alpha$ line from its rest energy of 6.4 to 4.2 keV requires a redshift of $z \sim 0.6$, consistent with that expected from the surface of a non-spinning $1.4 M_\odot$, 10 km radius neutron star. If confirmed, this feature provides a potential direct measurement of gravitational redshift, allowing us to place strong constraints on the neutron star's mass-to-radius ratio and gain valuable insights into the equation of state (EOS) of dense matter. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10807 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10807v1 Announce Type: new Abstract: We present the Thousand Pulsar Array (TPA) single-pulse data set, obtained with the MeerKAT radio telescope and comprising time-series observations of 1192 pulsars, typically containing ~1000 consecutive pulses per source. We describe the MeerTime Single Pulse software pipeline which calibrates the data and automatically excises interference signals to produce data products suitable for typical single-pulse studies. To demonstrate the capabilities of the dataset, we carry out a population-level study of phase-averaged single-pulse energy distributions and nulling behaviour. Pulse energy distributions are modelled within a Bayesian framework choosing from a range of intrinsic energy distributions, and including an explicit nulling fraction. We find that approximately half of the pulsars require multi-component intrinsic energy distributions, while the remainder are consistent with single-component models. Nulling is detected or constrained for most pulsars in the sample, and both the occurrence and inferred nulling fraction show systematic variation across the P-$\dot{P}$ diagram. In particular, nulling fractions increase with spin period and exhibit only a weak dependence on period derivative. We also examine trends in the preferred forms of pulse energy distributions as a function of spin-down luminosity, finding modest evidence for population-level evolution. Estimates of single-pulse luminosities indicate that individual pulses can exceed the long-term average luminosity by large factors, particularly for low-$\dot{E}$ pulsars. These results characterise the statistical properties of single-pulse emission across a large pulsar sample and highlight the limitations of phase-averaged energy distributions for capturing the full complexity of pulsar emission variability. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10828 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10828v1 Announce Type: new Abstract: We present a new study on the MeV-TeV gamma-ray origin of HESS J1857+026 using data collected from the Fermi-LAT, VERITAS, and HAWC observatories. A spatial and spectral study of HESS J1857+026 including radiative modeling of the MeV-TeV spectrum determines the likely dominant gamma-ray origin as a pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1856+0245. The MeV-TeV spectrum is further characterized through basic evolutionary radiative modeling assuming a PWN origin to constrain the physical properties of the system such as the magnetic field strength and PWN age. The results of the PWN evolutionary model are consistent with the observational constraints of the system, finding an age of the system between t = [16,21]kyr and a magnetic field strength between B = [0.4,1.6]muG. These estimates support an evolved PWN scenario where the observed gamma-ray emission is generated by the relativistic electrons inverse Compton scattering (ICS) off local photon fields, however the low-energy (E < 10GeV) spectral component could be dominated by hadronic emission originating from a supernova remnant (SNR). For a PWN component above 10GeV, we measure the conditions for particle diffusion, finding that the local diffusion (D(50TeV) ~ $10^{28}cm^{-2}s^{-1}$) is suppressed compared to the interstellar medium (ISM) value, in agreement with similar TeV PWNe. By measuring the radial surface brightness profiles of the gamma-ray source across multiple instruments, we demonstrate that the combined MeV-TeV spatial information is a powerful tool to constrain particle diffusion properties. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10840 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10840v1 Announce Type: new Abstract: A second extragalactic pulsar wind nebula (PWN) is discovered in the MeV-GeV band using the Fermi-LAT. Faint, point-like gamma-ray emission is detected at the location of the composite supernova remnant (SNR) B0453-685 from energies 300MeV-2TeV. The Fermi-LAT data analysis of the new gamma-ray source is presented together with a detailed multi-wavelength investigation to understand the nature of the observed emission. The observational evidence and physical implications from broadband modeling do not support an SNR gamma-ray origin. Semi-analytic radiative evolutionary models are explored to understand the potential for any pulsar or PWN component responsible for the observed gamma-ray emission. The modeling results favor an evolved PWN ($\tau\sim 14,000$ years) that has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below $5$GeV. The particle acceleration mechanisms and their efficiency within B0453-685 have important implications for the role PWNe play in generating Cosmic Rays (CRs), but constraints on the synchrotron cut-off are required to accurately characterize the underlying particle properties. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10855 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10855v1 Announce Type: new Abstract: Pulsar Wind Nebulae (PWNe) are relativistic, magnetic winds comprised of radiating electrons and positrons, powered by an energetic pulsar. The pulsar continuously injects particles into the PWN that are accelerated at the termination shock. As the relativistic particles enter the PWN, they radiate away the energy received at the shock as they interact with the PWN environment, generating synchrotron emission from interactions with the magnetic field of the PWN and Inverse Compton Scattering (ICS) from interactions with the local photon fields. Synchrotron emission is observed from the majority of known PWNe from radio to X-ray energies, and the ICS is observed in the $\gamma$-ray bands, from MeV to TeV energies. The particle acceleration processes at the termination shock and elsewhere within the PWN remain to be understood. Recent progress in theoretical studies have provided the capability to explain broadband observations of several PWNe including their spectral and spatial features. This work reviews some of the most compelling outcomes of recent literature, outlining the outstanding questions that remain to be answered, and how the future prospects of $\gamma$-ray astronomy will be instrumental in advancing the current understanding of PWNe. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10926 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10926v1 Announce Type: new Abstract: Positive lags in gamma-ray bursts (GRBs), where hard photons anticipate softer ones, provide a unique window into the temporal evolution of their prompt emission. Negative lags, when hard photons are delayed, are instead more enigmatic to interpret. Disentangling the effects that produce both kinds of lags is critical for identifying the physical mechanisms at work in the prompt and early afterglow phases of GRBs. We investigate the potential of time lags for distinguishing different emission components at different energy bands. Using data from the Fermi Gamma-ray Burst Monitor (GBM) and the LAT Low Energy(LLE) technique, we perform a time-resolved joint spectral analysis in the range 10 keV-100 MeV for two exceptionally bright bursts, GRB 160625B and GRB 190114C. Time lags between the lowest-energy band (10-100 keV) and progressively higher-energy bands up to 30-100 MeV were computed across their distinct emission episodes via the cross-correlation function. For GRB 160625B, the spectra are described by a single component with clear hard-to-soft evolution, and the time lags are always positive. Analysis of the high-energy exponential cutoff, likely originating above the photosphere, yields bulk Lorentz factor estimates of $\Gamma \sim 120-250$. GRB 190114C exhibits negative lags in the 30-100 MeV band, coinciding with a delayed high-energy powerlaw component that dominates the LLE range after ~2.5 s. Comparison with multi-wavelength observations shows some compatibility with the early afterglow, though its origin remains open, leaving room for external shocks or internal dissipation. Time lags are effective diagnostic tools for the spectral evolution of GRBs: positive lags trace the softening of the prompt emission, whereas negative lags indicate the appearance of a new, independent high-energy spectral component. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10964 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10964v1 Announce Type: new Abstract: We have recently shown evidence that the most relativistic jets (with Lorentz factor >2) from stellar-mass black holes in X-ray binary systems may be locked to a fixed axis, likely the spin axis of the black hole. Slower, mildly relativistic jets (with velocities typically ~ 0.3c) are often seen to precess and can be associated with both neutron stars and black holes. In this paper we demonstrate an additional clear link between highly obscured systems and these lower-velocity, precessing jets. We speculate that this link may be due to mass-loading of the jets close to their launch sites, since these obscured systems are likely to be examples of (sometimes persistent, other times transient) super-Eddington accretion. The fastest relativistic jets are now seen to be both locked to a fixed direction, likely the black hole spin axis, and to be launched in low-density environments, while jets launched in dense environments are generally slower and very likely to precess. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09974 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09974v1 Announce Type: new Abstract: Slitless spectroscopy enables efficient, large-area surveys without target pre-selection, yet it faces challenges from source blending, higher noise, and lost spatial-spectral information. We present an advanced, non-parametric, data-driven algorithm that leverages multiple dispersion angles to reconstruct three-dimensional flux distributions, providing low-resolution Integral Field Unit (IFU) capabilities from slitless data. By treating each pixel as an independent element, our method naturally handles source confusion without requiring prior assumptions regarding redshifts, templates, or model libraries. We validate the algorithm using simulated Roman Space Telescope wide-field slitless spectroscopy images that are equivalent to what is expected from the High-Latitude Time-Domain Survey. First, we demonstrate that a host-galaxy model reconstructed from multiple dispersion angles can be used to accurately subtract host light from a transient, recovering a Type Ia supernova spectrum with minimal bias. Second, we showcase a high-fidelity flux-cube reconstruction of a complex galaxy, successfully measuring the redshift and recovering continuum, emission, and absorption features. This approach highlights the potential of multi-dispersion-angle slitless data to provide spatially resolved spectral information in a non-parametric way, which is traditionally accessible only with integral field spectroscopy, opening a new window into large, unbiased, and spatially-resolved studies of galaxy evolution. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10076 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10076v1 Announce Type: new Abstract: Modeled gravitational wave searches correlate the strain data with a bank of gravitational wave template waveforms to make detections of gravitational wave candidates, and these results are processed by downstream tools to calculate the likely sky location and distance of the source of the candidates. This is crucial for multi-messenger efforts, since it informs astronomers where to point their telescopes to facilitate electromagnetic follow-up of the gravitational wave candidates. We present a novel method to improve the low-latency results of the GstLAL gravitational wave search pipeline, and thus improving sky location estimates of low-latency candidates. This method involves ingesting the GstLAL low-latency results, and performing a small targeted hierarchical search to recover the candidates with more accurate parameters, in a medium-latency timescale (few seconds to five minutes). To test our method, we perform a GstLAL low-latency analysis on forty days of data from the third observing run of LIGO, Virgo, and KAGRA, and show that our method improves the GstLAL results by 5.38% and the subsequent sky location results by 16.75% on average. In addition to this increase in precision, we also show that these results are more accurate as compared to the GstLAL results. This method has been adopted by GstLAL for the fourth observing run. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10171 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10171v1 Announce Type: new Abstract: A high-resolution near-IR spectroscopy capability on the Habitable Worlds Observatory (HWO) could strongly and efficiently advance many of the mission's goals. The technical barriers that made such a capability unfeasible on previous missions have largely been eliminated. Many HWO science case development documents require high spectral resolution in the IR and others would benefit significantly from it. High resolution improves the detectability of weak, unresolved features, aids identification of those features and provides additional information about radial velocity and line shape. It will be significantly easier to remove contaminating stellar features from high-resolution data. Silicon diffractive optics, immersion gratings and grisms, together with the new generation of low-noise, low dark-current avalanche photodiode arrays, make it possible to design a very compact high-resolution spectrograph that can cover the entire 1.1-2.0 micron band in a single exposure that would realize all of these advantages. We outline here the case for such an instrument and the technology development pathway needed to mature it in preparation for the HWO mission. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10712 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10712v1 Announce Type: new Abstract: DIffuse X-ray Explorer (DIXE) is a proposed high-resolution X-ray spectroscopic surveyor aimed at studying large structures of hot gas in the Milky Way. Its payload is designed to have a field of view (FoV) of $10^\circ$ (half-power diameter) and an energy resolution of better than 6 eV, covering an energy range of 0.1-10 keV. It will be mounted on the China Space Station (CSS) and follow the CSS orbit to conduct the survey with fixed zenith pointing in order to optimize the coverage of key science targets. The payload will avoid the Sun passively via an operable sunshade, where a minimum $25^\circ$ angular separation between the pointing axis and the direction of the Sun is required. Two Sun-avoidance strategies are considered: one focusing on minimizing mechanical risk and the other on maximizing exposure time. The one-year exposure maps indicate that DIXE will cover approximately $72.5\%$ of the sky, with typical exposure times of 26 ks and 68 ks for the two strategies, respectively. Although mechanically collimated, the imaging performance of the payload can be enhanced with a demodulation method based on Markov Chain Monte Carlo sampling using the collimator response. Through simulation, we found that the method could achieve a localization accuracy of $1^\circ$ for point-like sources and a spatial resolution of $3^\circ$ for the extended sources of complex surface brightness distribution, both of which are significantly smaller than the FoV. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10750 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10750v1 Announce Type: new Abstract: As new observational technologies reveal increasingly detailed properties of neutron star surfaces, the demand for accessible and extensible theoretical modeling tools continues to grow. We present UnReal-B, a real-space Density Functional Theory solver for one-dimensional chains of matter in extreme magnetic fields $B \approx 10^{12} - 10^{15},\mathrm{G}$. By employing the adiabatic approximation, UnReal-B, provides a streamlined numerical framework for calculating the electronic structure of strongly magnetized condensed matter. The solver is benchmarked against published results for several astrophysically relevant elements, demonstrating excellent agreement while maintaining a comparatively simple and transparent implementation. Released as open-source software, UnReal-B facilitates reproducible and community-driven investigations of neutron-star surface matter and provides a foundation for future developments motivated by emerging observational constraints. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10771 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10771v1 Announce Type: new Abstract: Reinforcement learning (RL)-based algorithms have recently emerged as a promising approach for adaptive optics (AO) control. In simulations and laboratory experiments, they have demonstrated robustness to real-world effects such as photon and detector noise, misregistration, vibrations, and rapid variations in seeing conditions. However, their performance has not yet been validated on sky. We report the first on-sky demonstration of a reinforcement learning controller for adaptive optics, named Policy Optimization for AO (PO4AO). We further analyze its on-sky behavior and identify directions for improving the algorithm and its implementation.PO4AO was implemented and deployed on the Papyrus adaptive optics system installed at the Coud\'e focus of the 1.52 m telescope (T152) at the OHP. A Python-based implementation was interfaced with the existing real-time controller (DAO RTC) via shared-memory buffers. The performance of PO4AO was compared to that of a standard integrator controller over several nights, covering a range of flux levels and atmospheric conditions. PO4AO consistently outperformed the standard integrator in all tested configurations. The controller successfully learned and compensated for vibration patterns and demonstrated strong robustness to measurement noise. Once tuned for Papyrus, PO4AO operated in a turnkey fashion, using a single set of hyperparameters across varying observing conditions and science targets. These performance gains were achieved despite a non-optimized Python implementation introducing approximately $750\,\mu\text{s}$ of additional latency, along with control jitter and occasional frame drops. When properly implemented and optimized, PO4AO constitutes a robust and high-performance turnkey controller for single-conjugate adaptive optics systems, paving the way for broader adoption of reinforcement learning strategies in on-sky AO operations. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11097 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11097v1 Announce Type: new Abstract: The accuracy of particle counting in highly segmented detectors is limited by the corner-clipping effect, in which a single ionizing particle generates signals in adjacent detection elements. This phenomenon introduces a direction-dependent overcounting bias that distorts reconstructed observables and is commonly corrected using Monte-Carlo simulations, thereby inheriting modeling uncertainties. We present a fully data-driven method to directly measure the single-particle corner-clipping probability, exploiting the nanosecond timing resolution of modern detectors to statistically distinguish genuine corner-clipping events from random coincidences, with non-neighboring detection elements serving as an intrinsic control sample. The technique is validated using detailed simulations of the Underground Muon Detector of the Pierre Auger Observatory, reproducing the true angular dependence of the corner-clipping probability with absolute deviations below 0.01. To parameterize the results, we introduce a compact analytical model incorporating detector geometry, minimum detectable path length, and orientation-independent contributions. The proposed methodology and parameterization enable the direct incorporation of data-driven corner-clipping corrections into reconstruction algorithms, mitigating the overcounting bias and ultimately yielding a more accurate determination of the muonic component of extensive air showers. These developments are broadly applicable to any segmented detector with sufficient timing resolution, making them relevant to a wide range of experiments in high-energy and astroparticle physics. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11102 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11102v1 Announce Type: new Abstract: The Ohio State University Radio Observatory (OSURO), known as the Big Ear, played a pivotal role in both radio astronomy and the Search for Extraterrestrial Intelligence (SETI). Following the completion of the Ohio Sky Survey, the facility was repurposed in 1973 as the world's first full-time dedicated SETI observatory and operated continuously until its decommissioning in 1998. During this period, the Ohio SETI Program evolved from an 8-channel hydrogen-line receiver into increasingly sophisticated survey systems. Over three decades, these surveys covered approximately 70% of the radio sky using a largely consistent instrumental configuration, creating one of the most extensive long-term radio astronomy archives ever assembled. The program is best known for the detection of the Wow! Signal in 1977, but it also accumulated an archive of over 40,000 transient narrowband events, revealed unusual concentrations of radio bursts near the Galactic Center, and established one of the longest continuous radio monitoring records in astronomy. Following the closure of the Big Ear, its scientific legacy continued through Project Argus and, more recently, the Arecibo Wow! project. This paper provides an overview of the final decades of the Ohio SETI Program, including its instrumentation, survey strategies, scientific discoveries, and enduring impact on SETI, time-domain radio astronomy, and the preservation of historical astronomical data. Despite its scientific significance, most of the data collected by the Ohio SETI Program remains unexplored, leaving a unique archive available for future research. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10686 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10686v1 Announce Type: cross Abstract: The pulsar magnetosphere has only recently been addressed using Physics-Informed Neural Networks (PINNs), by deploying a domain-decomposition approach and treating the separatrix and equatorial current sheet as infinitesimally thin discontinuities. However, this baseline requires extensive manual hyperparameter tuning, achieves limited final accuracy and demands several hours of training. We refine this framework by introducing domain-specific neural architectures based on Kolmogorov-Arnold networks, an automated adaptive training pipeline and a physics-based convergence criterion that eliminate the need for manual calibration. The proposed methodology delivers self-consistent axisymmetric magnetosphere solutions with mean squared errors of the PDE residuals at O(1e-6) in double precision - an improvement of two orders of magnitude over the baseline - while achieving convergence in under 20 minutes in single precision. Importantly, the method reliably resolves stellar radii reduced by up to 80% compared to the baseline, overcoming the severe spatial scale disparities that also challenge traditional solvers. Furthermore, by varying the flux that opens to infinity, we provide a correction to the equation that connects it to the equatorial T-point's position. The complete framework is released as the open-source library PulsarX. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10762 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10762v1 Announce Type: cross Abstract: Colliding-wind binaries (CWBs), which are systems of two massive stars whose supersonic winds collide into bow shocks, encode rich information about stellar wind properties in their multi-frequency emission, e.g. images in the H$\alpha$, X-ray, and radio wavelengths. Inferring physical parameters (mass-loss rates, terminal wind velocities, orbital elements) from short time-series observations is a compelling but challenging inverse problem, because the forward hydrodynamic simulator is computationally expensive and the likelihood is intractable. We adopt a factorized spatio-temporal architecture for amortized posterior inference that separates spatial encoding from temporal aggregation. This design aligns with the structure of the underlying physical process of local morphology and global dynamical evolution, induces time-translation equivariance in the learned representation, and improves identifiability in low-signal regimes. Coupled with a neural spline flow conditioned on these spatio-temporal embeddings of 10-frame H$\alpha$ photon-count time series, we present a complete simulation-based inference pipeline for CWBs. Our method jointly infers seven physical parameters from synthetic observations under realistic detector noise, with posteriors verified as well-calibrated via TARP and SBC diagnostics. The approach naturally expands posterior width in information-poor regimes (low photon counts) and robustly recovers orbital parameters and mass-loss rates, demonstrating the feasibility of amortized likelihood-free inference for this challenging astrophysical inverse problem. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10868 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10868v1 Announce Type: cross Abstract: Long-horizon autoregressive forecasting of oscillatory physical signals, such as seismograms, gravitational-wave strain, and similar wavefields is limited by error accumulation: as a causal model is fed its own outputs over hundreds of steps, small per-step errors compound into phase drift that pointwise metrics fail to detect. We ask when such rollout stays stable, using synthetic three-component seismograms as a physically structured testbed and the \textsc{SeismoGPT} autoregressive forecaster as the model under study. Through controlled, intra-architecture ablations evaluated on free-running rollout with paired significance tests, we isolate the contribution of each design choice. Multi-token prediction is the dominant stabilizer, accounting for almost the entire improvement over a single-token baseline ($+0.040$ median NCC); a horizon-embedding hybrid prediction head and a cross-horizon STFT-magnitude coherence loss each add a small but consistent further gain. Performance depends sharply on a context-ratio threshold near one, roughly the full P-S interval of observed signal, below which rollout generalization collapses. The dominant residual failure is a polarity inversion that a magnitude-based spectral loss cannot, by construction, penalize, identifying phase-aware objectives as the natural next step. We frame this as a controlled study of rollout stability on oscillatory wavefields, not a benchmark of forecasting architectures. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11059 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11059v1 Announce Type: cross Abstract: Amorphous tantala is an important optical material used in a number of high-precision optical applications, including gravitational wave interferometry. In this paper, we study in-situ the structural changes that occur in amorphous ion-beam sputtered coatings during an annealing treatment by means of a synchrotron radiation scattering experiment. The scattering signal is measured as a function of time on a large range of the Q-space. X-Ray diffraction and Rietveld analysis are used to study crystallization during the annealing treatment, whereas pair distribution function analysis allows to inspect the structural changes occurring during the amorphous to crystalline transition. Our findings indicate that several structural rearrangements occur in parallel, namely a first quick establishment of a backbone structure in the cationic substructure appearing on a rather extended range (up to 100 Angstrom), followed by a progressive rearrangement of the oxygen atoms environment which gradually increases the crystallinity of the structure. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11161 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11161v1 Announce Type: cross Abstract: We present AutoClassMK, a simple, fully-connected, five-layer double-headed neural network written entirely in Python and Numpy that classifies normal stellar spectra conforming to the libr18 MK atlas in the 2D MK classification system with a high degree of precision and recall. AutoClassMK has the distinction of having transparent basic code with no calls to specialized libraries. In this paper we take care to explicitly describe in detail the ideas and operations that enable the network. Training AutoClassMK required us to develop large, noisy artificial training and test sets by augmenting the libr18 and libr18_27 MK atlases and to simplify the luminosity classification so that every combination of spectral- and luminosity-class is represented in the training set. We then test the network's ability to predict the MK spectral type of noisy augmentations of spectra in the libr18_225 MK atlas. We then implemented the same architecture in PyTorch to gain further insight and to enable execution on CUDA GPU's. All codes and the training and test sets are available from the OpenStars www site: www.ap.smu.ca/OpenStars. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2605.31402 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.31402v2 Announce Type: replace Abstract: The Gaia Data Release 3 (GDR3) parallaxes are affected by a complex bias that depends on stellar magnitude, color, and celestial position, with amplitudes reaching tens of microarcseconds ($\mu$as). Standard global parametric models (e.g., Lindegren et al. 2021, hereafter L21) effectively remove large-scale trends but struggle to resolve small-scale spatial systematics due to functional rigidity. We aim to construct a flexible, data-driven calibration map that eliminates these residual local systematics without imposing rigid functional forms. We propose a "Global Pre-correction + Local Refinement" hybrid strategy. First, we utilize the L21 model as a baseline to remove the dominant magnitude and color-dependent biases. Second, we model the residual zero-point using a Local Non-parametric method based on a Sliding Window technique. This approach fits local trends using k-nearest neighbors from quasars (for faint stars, G>18) and wide binaries combined with Large Magellanic Cloud (LMC) (for bright stars, G < 18). Our hybrid model demonstrates significant improvements over the standard L21 solution. Validation against different samples reveals a remarkably flat residual map with near-zero bias across the full sky. Our mathematical attempt at calibrating the parallax zero-point is expected to provide a useful reference for the zero-point correction in future Gaia DR4, and to help move towards a physical resolution of this issue. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2509.17372 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2509.17372v2 Announce Type: replace-cross Abstract: The DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a planned space-based, next-generation gravitational wave detector aimed at observing primordial gravitational waves originating form cosmic inflation. This work focuses on reducing the quantum noise, in the instrument's observation band of 0.1 to 10 Hz, by employing optical springs and a homodyne detection scheme. Although detuning 1000\,km long arm cavities was previously considered ineffective due to quantum state degradation from diffraction losses, we revisit this problem by formulating a new, rigorous model for quantum state of light by accounting for the vacuum state mixing as a result of diffraction losses. This work shows that high sensitivities can be achieved by employing optimal configurations of optical springs and homodyne detection schemes even with diffraction losses. These improvements alone are still not sufficient to achieve sensitivities to detect primordial gravitational waves as other technical noises limit further improvement. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10411 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10411v1 Announce Type: new Abstract: Solar eruptions are powered by the release of magnetic energy stored in the lower solar atmosphere, but the pre-eruptive magnetic configuration of filament channels remains difficult to determine. A central question is whether this energy is stored in a pre-existing magnetic flux rope or in a sheared arcade that forms a flux rope only during eruption. Resolving this ambiguity is critical for identifying instability thresholds and eruption triggers, yet photosphere-based extrapolations often provide insufficient constraints on the three-dimensional coronal field. Here, we introduce a data-driven magnetic field extrapolation framework that combines photospheric and chromospheric vector magnetograms in a unified multi-height optimization, while accounting for variable chromospheric formation heights and the 180{\deg} azimuthal ambiguity. Tests with radiative magnetohydrodynamic simulations show that photosphere-only extrapolations can misidentify the pre-eruptive magnetic configuration, whereas chromospheric vector constraints recover the three-dimensional structure substantially more accurately. Applied to multi-line spectropolarimetric observations of an active region filament obtained with the Swedish Solar Telescope, the method reveals a reconstructed magnetic field consistent with a pre-eruptive flux-rope configuration. These results show that chromospheric vector magnetic measurements can provide decisive constraints on filament magnetic configuration and open a path toward diagnosing magnetic-energy storage and instability in eruptive solar active regions. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2604.03429 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2604.03429v2 Announce Type: replace-cross Abstract: We aim to confirm the compact nature and constrain the radio spectra of candidate persistent radio sources (PRSs) associated with repeating fast radio bursts (FRBs). We performed European VLBI Network (EVN) observations at 5 and 8 GHz targeting two candidates identified in a recent VLA survey. We measured flux densities and upper limits at milliarcsecond resolution and combined them with published VLBI data at lower frequencies to derive spectral constraints. We detect a compact source associated with FRB 20190417A at 5 GHz with a flux density of $150\pm45$ uJy, while no detection is obtained at 8 GHz. The source is unresolved and has a brightness temperature $T_{\rm b}>10^{5}$ K, confirming its non-thermal nature. Combining our measurement with VLBI data at 1.4 GHz, we derive a spectral index $\alpha = -0.19 \pm 0.29$, consistent with a nearly flat spectrum. This makes FRB 20190417A only the second PRS with a spectral index constrained using VLBI data. The inferred luminosity places the source on the proposed $L_{\nu}$-|RM| relation. Including this source yields a scatter of $\sigma_\Delta = 0.65$, corresponding to $\hat{\alpha}|\epsilon| = 1.5 \pm 0.7$, consistent with forward shocks in the free-expansion phase or young pulsar wind nebulae. For the candidate PRS associated with FRB 20181030A, we report upper limits of 80 uJy at 5 GHz and 150 uJy at 8 GHz, corresponding to $L_{5\,\mathrm{GHz}} \lesssim 3.8 \times 10^{25}\ {\rm erg\ s^{-1}\ Hz^{-1}}$, and implying a steep spectral index ($\alpha \lesssim -1.2$) if the VLA emission arises from a compact component. Our results highlight the importance of VLBI in isolating compact emission from FRB engines and provide one of the few spectral constraints for PRSs at milliarcsecond resolution. The consistency of FRB 20190417A with the $L_{\nu}$-|RM| relation supports a nebular origin for the persistent emission. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2603.26353 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2603.26353v2 Announce Type: replace-cross Abstract: An X-ray background in the early Universe enhances molecular hydrogen formation, the main coolant of primordial gas, thereby lowering the threshold for Pop III star formation. Continuing our series on X-ray impacts on Pop III star formation, we investigate how a soft X-ray background promotes Pop III star formation using cosmological zoom-in simulations of ten cosmic volumes spanning a range of halo number densities. Each volume is irradiated by the Lyman-Warner (LW) H$_{2}$ dissociating background and a weak (J$_{21} \sim 10^{-5}$), soft ($E \sim 0.2-2.0$ keV) X-ray background produced by pair-instability SNe (PISNe) from Pop III stars and calculated self-consistently as described in a companion paper. We also compare the same simulations with and without X-rays to isolate the X-ray effect. The background promotes Pop III star formation in two ways: (1) by reducing the mean host halo mass by a factor of $\sim 2-3$, and (2) by enabling Pop III star formation in haloes that would otherwise remain sterile, thereby increasing the halo occupation fraction. The resulting gain in Pop III number density is largest in underdense regions (a factor of $\approx 3$ on average, reaching up to 7). In the most extreme case, Pop II stars form only in the presence of X-rays and the gas-phase metallicity rises by an order of magnitude, suggesting that dwarf galaxies in underdense regions may be significantly influenced by an early X-ray background. We also provide fitting functions for the halo occupation probability of Pop III stars as a function of redshift for both X-ray and LW-only simulations, which can serve as inputs for semi-analytic models. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2512.13783 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2512.13783v2 Announce Type: replace-cross Abstract: We use the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) to identify stellar members of the Local Group dwarf galaxies. We cross-match DESI targets with candidate members that are based on Gaia proper motions, positions, and photometry. The addition of DESI radial velocities enables secure membership determination in 15 systems. Our results confirm that Gaia-based selection algorithms are effective in minimising foreground contamination. Two stars are found to be associated with DES~J0225$+$0304; if this is the case, then it leads to the first determination of the systemic radial velocity (RV$_{\rm{sys}}=-150.0\pm7.0$~km~s$^{-1}$). Draco and Sextans are the galaxies with the largest number of members. We focus on Sextans and, for the first time with DESI, trace its stellar kinematics to large radii (up to $\sim$10~half-light radii). We find that the metal-poor population exhibits a higher velocity dispersion and extends to larger radii, whereas the metal-rich population is kinematically colder and centrally concentrated. The metallicity gradient is steeper in the inner regions of Sextans ($\sim -12\times 10^{-3}$~dex~arcmin$^{-1}$ or $\sim -0.36$~dex~kpc$^{-1}$), while almost no gradient in the outskirts, hinting for an ex-situ halo or for an ``outside-in'' star formation. Although DESI [$\alpha$/Fe] ratios for Sextans stars with $\FeH\gtrsim-2.0$ are in line with literature values, those for very metal-poor stars ($\FeH\lesssim-2.0$) present a large scatter and strong anti-correlation with metallicity, warranting a caution for using DESI abundances in this regime. With a less strict selection, we identify 8 ultra metal-poor ([Fe/H]~$< -4$) candidates that require higher signal-to-noise ratio spectroscopic observations to determine their metallicities. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2007.08493 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2007.08493v3 Announce Type: replace-cross Abstract: In the context of the massive secondary object recently observed in the compact-star merger GW190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. Our work shows that state-of-the-art relativistic mean field models can generate massive stars reaching $\gtrsim 2.05\,\Msun$, while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and non-standard self-vector interactions are introduced. In particular, we present a new version of the Chiral Mean Field (CMF) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. When rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass $2.5\,\Msun$. We find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the non-rotating stars. This is not the case for pure quark stars, which can easily reach $2.5\,\Msun$ and still possess approximately the same amount of baryons as stable non-rotating stars. We also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event GW190814 can be associated with a star containing quarks as one of its progenitors. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2605.20660 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.20660v2 Announce Type: replace Abstract: Extremely low-mass white dwarfs (ELM WDs) are helium (He) WDs with masses below $\sim 0.3\ M_{\odot}$, mainly formed through binary interaction. ELM WD binaries typically are formed from two channels, namely the stable Roche lobe overflow (RLOF) channel and the common envelope ejection channel. For ELM WD binaries produced from RLOF channel, the ELM WD mass has a strong correlation with the orbital period, i.e., the so-called WD mass-orbital period relation. However, the observations in the ELM Survey show that the orbital periods of ELM WD binaries from the RLOF channel are typically shorter than the theoretically predicted values. Extra angular momentum loss (AML) may be needed to explain such a phenomenon. In this work, we assumed that part of the transferred mass from the donor is lost at the outer Lagrangian point and simulated the formation of ELM WD binaries. Enhanced AML enables more mass to be lost during thermal-timescale mass transfer, thereby affecting nuclear burning in the transfer phase and producing ELM WDs with distinct internal structures. These structural differences alter the (pre-)He WD mass-radius relation at the end of mass transfer, which in turn shifts the WD mass-orbital period relation downward. These adjustments enable our model to successfully reproduce the majority of observed systems from the relevant survey projects. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11165 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11165v1 Announce Type: cross Abstract: Recently, a chemically depleted young massive stellar population was identified using the spectroscopic catalogue of Gaia DR3. To explain its characteristics, a recent enhanced star formation event, via a third infall occurring within the last 2 Gyr, has been evoked. In this paper we reassess the low alpha sequence of massive stars identified in the Gaia spectroscopic catalog and investigate their presence in other Milky Way spectroscopic survey catalogs. We select massive sequence stars and RGB stars from the Gaia DR3 catalogue using the same filtering strategy adopted in previous chemical cartography studies. These samples are then cross matched with APOGEE DR17, GALAH DR4, and Gaia CNN to enable a detailed comparison of stellar parameters and alpha abundances. Stellar masses are estimated by projecting their atmospheric parameters and infrared magnitudes onto PARSEC isochrones. For the massive star sample, we find large discrepancies in stellar parameters and calcium abundances between Gaia DR3 and the three external surveys. The external catalogues do not show a low ca sequence but rather resemble those of thin disc RGB stars. Other alpha elements (si in APOGEE and GALAH, and mg in GALAH) also do not show depleted values. In APOGEE, however, massive sequence stars with metallicities above -0.5 dex display lower mg abundances. We attribute this to APOGEE's use of macroturbulence velocities calibrated solely on metallicity. Our analysis does not show any evidence for alpha element depletion in massive sequence stars. Alpha abundances of massive sequence stars derived from the Gaia RVS spectra should therefore be used with caution. Nevertheless, the previously proposed three infall chemical evolution models remain plausible: even without a chemically depleted young massive population, scenarios involving only mild dilution could still account for recent star formation episodes. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10283 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10283v1 Announce Type: cross Abstract: The Expanding Box Model (EBM) has been widely employed to simulate multiscale plasma phenomena in the expanding solar wind by transforming the MHD equations to a co-moving, non-inertial frame. However, traditional formulations have suffered from historical ambiguity regarding the physical separation between the co-moving and inertial reference frames, primarily arising from a classical approximation of an invariant magnetic field between them. To resolve this inconsistency, we reformulate the EBM from first principles using a fully covariant approach. Here, we model the expanding solar wind frame as an anisotropic expanding spacetime metric, allowing us to incorporate radial acceleration profiles and differential transverse expansion, ensuring that all physical fields are correctly transformed by expansion. We demonstrate that the mathematical artifacts and structural asymmetries identified in previous EBM-MHD literature are direct consequences of neglecting the tensorial scaling of the magnetic field. Our covariant treatment eliminates these residues, restoring symmetry in the co-moving frame. Projecting our system back into the inertial frame recovers the established observational scaling and analogous physics, clarifies the mathematical distinction between local plasma dynamics and global expansion, and reveals the macroscopic anisotropy of the Parker spiral as a purely geometric projection. Furthermore, linear wave analysis demonstrates that macroscopic acceleration governs the evolution of Alfv\'en wave amplitude, acting either as geometric damping or as an energy source. Further, we write the EBM-MHD system using compressible Els\"asser variables. This formulation provides a consistent and clean foundation for future numerical simulations of accelerating astrophysical plasmas. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10090 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10090v1 Announce Type: cross Abstract: We investigate the crust-core transition in neutron stars using both thermodynamic and dynamical descriptions of the instability. In the thermodynamic approach, the transition is identified through the vanishing of a generalized incompressibility coefficient signaling the onset of a bulk spinodal instability. In contrast, the dynamical approach based on the relativistic random-phase approximation (RPA) incorporates Coulomb screening and finite-size effects that determine the instability at finite wavelength. Using a family of covariant energy density functionals spanning a broad range of symmetry-energy slopes, we show that the dynamical treatment systematically predicts lower transition densities and pressures compared to the thermodynamic approach. We further demonstrate that the RPA instability develops at a characteristic length scale set by the competition among bulk, Coulomb, and surface effects. Most importantly, we show that these differences propagate directly into neutron-star observables. Because the thermodynamic approach predicts larger transition pressures, it generates thicker crusts and significantly larger crustal fractions of the stellar moment of inertia than the dynamical-RPA framework -- with important implications for the interpretation of pulsar glitches and other crust-sensitive neutron-star observables. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.03740 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.03740v1 Announce Type: cross Abstract: While recent JWST observations of mature super-Earths and sub-Neptunes have frequently revealed featureless transmission spectra, their inflated progenitors offer a unique window into understanding their primordial compositions. As part of the KRONOS (Keys to Revealing the Origin and Nature Of sub-neptune Systems) JWST program, we present the NIRISS/SOSS transmission spectrum of V1298 Tau c, a $\sim$23 Myr super-Earth progenitor orbiting a young Solar analog. We detect H$_2$O in V1298 Tau c's atmosphere with a $\log_{10}$ volume mixing ratio of $-1.83^{+0.68}_{-0.77}$, but no additional molecules from these data alone. We find consistent results for the planetary atmospheric properties in both retrievals with and without informed priors on stellar heterogeneities based on the observed stellar spectrum. We infer an atmospheric metallicity [O/H] of $14.8^{+56.0}_{-12.28}\times$ the Solar value. This metallicity is similar to literature measurements for other young planets, including its massive outer companion V1298~Tau~b. In contrast, this measured metallicity is systematically lower than the metallicities of mature planets of similar mass and temperature. Altogether, these results provide tentative but growing evidence that the exoplanet mass--metallicity relation evolves with planetary age. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11121 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11121v1 Announce Type: new Abstract: Models of stellar structure and evolution describe the global and internal properties of stars throughout their lifetimes and are indispensable for studies of stellar clusters and Galactic evolution. However, most 1D evolutionary calculations rely on simplified treatment of convection, resulting in inaccurate near-surface structures and non-negligible uncertainties in the predicted fundamental parameters of low-mass stars. In a series of previous works, a novel approach was developed to couple 1D stellar interior models with 3D model atmospheres throughout the evolutionary calculation. This 1D-3D coupling method makes predicted stellar properties effectively independent of the mixing-length parameter. To expand this framework to ensemble studies of stars and age determinations of clusters, we present the GASTAG stellar evolutionary tracks and isochrones constructed using the 1D-3D coupling approach. Comparing effective temperatures from the APOGEE-Kepler catalog with GASTAG predictions, we find the theoretical temperatures are cooler by about 70 K near solar metallicity. Our isochrones are compared with observed color-magnitude diagrams of star clusters spanning from $\rm [Fe/H] = 0.3$ to $-1.9$. In all cases, the synthesized and observed diagrams agree excellently in the main-sequence, turn-off, and subgiant regions, while isochrones predict systematically cooler red giant branches. Taking these independent findings together reveals that the temperature mismatch is most likely due to deficiencies in stellar models. Because GASTAG is constructed using a method that substantially reduces uncertainties associated with surface boundary conditions and the mixing-length parameter, the difference between modeling and observation can be more confidently attributed to other ingredients in the models, such as $\alpha$-element abundances or uncertainties in low-temperature opacities. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11006 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11006v1 Announce Type: new Abstract: Stellar clusters are crucial tools for studying the age, spatial distribution, dynamics, kinematics, and chemical composition of different Galactic stellar populations. In this work, we used red giant stars from open clusters to better understand the extra-mixing process through the CNO abundances and $^{12}$C/$^{13}$C, $^{16}$O/$^{17}$O and $^{16}$O/$^{18}$O isotopic ratios determined using high-quality spectra in the visible and near-infrared regions. We analysed the radial velocities and chemical composition of 22 K-type giant stars from nine open clusters (NGC188, NGC2682, NGC3680, NGC5822, IC4756, NGC6633, NGC3532, NGC6281, and NGC5460). High-resolution and high signal-to-noise spectra of stars in the NGC188 cluster were obtained with the ESPaDOnS spectrograph at the CFHT in the visible region. The stars in the other clusters were observed with the CRIRES spectrograph at the VLT. We used IRAF to compute radial velocities and Turbospectrum and MOOG for the chemical analysis. The values obtained for the radial velocities and abundances of the sample are similar to those found in the literature. The results in the visible and infrared support the occurrence and predicted mass dependence of thermohaline mixing on the red giant branch and of rotation-induced mixing on the main sequence. Variations of the initial abundances of $^{17}$O and $^{18}$O may be needed to explain the dispersion of the oxygen isotopic ratios in red giant stars. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10981 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10981v1 Announce Type: new Abstract: V838 Mon is the remnant of a stellar merger that occurred in 2002. Twenty-four years after the merger, the remnant closely resembles a red supergiant, but its luminosity is sustained by core H burning and continued contraction toward hydrostatic equilibrium. In late 2025, the system entered the deepest dimming event observed since 2006. We characterize the 2026 dimming using multiband photometry and high-resolution spectroscopy spanning from the dimming minimum through the recovery phase. The photometric color evolution during the dimming can be well reproduced by dust extinction with $A_V=1.26$ mag and $R_V=1.8$, consistent with a transiting clump of freshly formed circumstellar dust composed of small silicate or alumina grains. The photospheric effective temperature changed by no more than ~200 K during the event. During the recovery phase, H recombination lines from the Balmer, Paschen, and Brackett series appeared in emission, with anomalous line ratios matching those of pulsating Mira stars near maximum light. These features are interpreted as arising from a sub-photospheric pulsation shock. Simultaneously, low-ionization metal lines appeared blueshifted by 90 km/s relative to the stellar rest frame, tracing shock-affected gas on the near side of the stellar disk. The spectroscopic sequence suggests that the 2026 dimming was itself triggered by a preceding pulsation shock that occurred earlier in 2025. We present the first observational evidence for pulsations in a stellar merger remnant. Twenty-four years after the coalescence, V838 Mon exhibits pulsation shocks qualitatively identical to those of red supergiants and Mira stars, confirming predictions of pulsational instability in post-merger objects. A further dimming event, triggered by the observed shock, is predicted to start in northern summer 2026. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10512 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10512v1 Announce Type: new Abstract: Due to solar wind turbulence, Parker spirals are stochastic. The dispersion of magnetic field lines is described by a convection-diffusion equation for the field line density distribution which is a function of the two heliographic angles in addition to the radial distance. Taking into account the radial evolution of the turbulence, the three-dimensional convection-diffusion equation is transformed into a set {of} stochastic differential equations which is solved numerically using both a forward and backward formulation. By tracing a large number of stochastic Parker spirals, the field line density distribution is constructed at any point in the heliosphere. It is shown that the angular part of the distribution function can be well-fitted by a two-dimensional Gaussian with standard deviation close to $ 25^{\circ}$ at 1 AU. The simulations also confirm that the magnetic field lines are underwound, on average, for strong enough turbulence intensity. Applying the backward approach, magnetic field lines are traced from an observer at 1 AU back to the Sun, quantifying the probability of magnetic connection when interplanetary turbulence is accounted for. It is shown that the angular uncertainty of $\sim 25^{\circ}$ is sharply reduced to $\sim 4^{\circ}$ when the field lines are traced back to the solar wind source surface from 0.25 AU. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10506 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10506v1 Announce Type: new Abstract: Recent multi-wavelength observations of solar flares have provided new constraints on the physical origin of quasi-periodic pulsations (QPPs). In an X-class flare, we detect a short-lived $\sim$5-minute QPP simultaneously in hard X-rays, extreme-ultraviolet (EUV), and soft X-ray emissions, exhibiting a clear phase-drifting behavior with emitting plasma temperature. Based on phase-resolved timing analysis, it is found that (i) the QPPs in all diagnostics share nearly identical oscillation periods, (ii) a systematic temperature-dependent phase drifting is present, with the phase delay relative to the hard X-ray emission increases systematically from the hottest to cooler EUV channels, and (iii) the QPP persists for only a few cycles during the impulsive phase. These properties imply that periodic magnetic reconnection, possibly triggered by the leakage of 5-minute oscillations from the lower atmosphere, modulates the non-thermal electrons responsible for the leading Hard X-ray QPPs. Subsequently, plasma heating and cooling processes manifest sequentially across passbands with different temperature responses, resulting in the observed temperature-dependent phase drifting. These results provide novel observational evidence supporting the use of multi-temperature, multi-wavelength phase relationships to constrain the temporal evolution of flare energy release and the origins of QPPs. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10505 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10505v1 Announce Type: new Abstract: A part of the magnetic energy released during a flare is transported to the lower atmosphere. High-resolution observations show that flare ribbons, sites of energy deposition at the footpoints of flaring loops which appear bright in the chromosphere and transition region, are structured on small spatial scales on the order of 100 km. Based on idealized numerical models of flares it is suggested that the ribbon fine-structures could originate from a tearing instability and the development of plasmoids in current sheets. Here we report on Fe I 5250.6 {\AA} and Mg I b2 5173 {\AA} spectral observations of a solar flare from the Tunable Magnetograph onboard the SUNRISE III balloon-borne mission that reveal an intricate link between the flare ribbon structure and the ambient chromosphere. We identified uncombed chromospheric loops and non-flaring fine-structures that are interspersed among brighter flare ribbon threads. These loops remain stable on timescales of minutes. Spectral lines from these regions show reduced emission or self-reversal in the line core compared with the immediately adjacent flare ribbons. We discuss the potential role of these structures in the onset of a flare. Furthermore, we suggest that irrespective of the complexities in the flaring current sheet, uncombed chromospheric loops and nonflaring fine-structure might play a role in spatially modulating the flare energy deposition in the lower atmosphere. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09997 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09997v1 Announce Type: new Abstract: The formation histories of halos set the baseline rate at which galaxies accrete gas over cosmic time. While a number of models describe these histories and their derivative, the mass accretion rate (MAR), a simple and universal formula has remained elusive. Here we measure the median MARs and half-mass formation times of halos in dark matter-only and hydrodynamical simulations, in extremely different cosmologies ($\Lambda$CDM and Einstein-de Sitter), and across a wide range of redshifts ($z = 0$-$14$). We confirm that MARs increase with mass and redshift, and that they are virtually identical in hydrodynamical and dark matter-only simulations. We show that MARs are accurately described by a universal six-parameter function of three physical variables: the peak height $\nu$, the slope of the linear power spectrum $n_{\rm eff}$, and the effective linear growth rate $\alpha_{\rm eff}$. A complementary two-parameter fit for the formation redshift improves on the function of Lacey \& Cole by fixing one parameter to its physical value and adding a dependence on $n_{\rm eff}$. Our model is broadly consistent with some prescriptions from the literature but provides a larger range and higher accuracy at high redshifts and low masses. Our fitting functions are implemented in the publicly available \textsc{Colossus} toolkit. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10006 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10006v1 Announce Type: new Abstract: The Standard Model of particle physics contains a diverse set of particle species, motivating the possibility of a similarly complex dark sector. Here we study two-component dark matter (DM) mixtures, in which one component behaves as standard CDM while the other suppresses the formation of small-scale structure, either through an astrophysically relevant de~Broglie wavelength (fuzzy DM; FDM) or collisional damping from temperature-independent scattering (interacting DM; IDM). Using the observed population of Milky Way satellite galaxies, we derive new leading constraints on the parameter spaces of mixed FDM and of mixed IDM coupled to photons ($\gamma$-DM), neutrinos ($\nu$-DM), or baryons ($p$-DM), for beyond-CDM fractions down to $50\%$. We require that the linear matter power spectra of allowed models remain less suppressed than a constrained reference model. The resulting $95\%$ confidence bounds on FDM mass and IDM cross section weaken systematically with decreasing fraction, following distinct power-law scalings. At $50\%$ fraction, IDM cross section bounds weaken by a factor of $\sim$2--6 and FDM mass bounds by $\sim$1.5, relative to the $100\%$ case. We forecast that idealized future satellite surveys, which adopt approximate LSST sensitivity thresholds, can improve these $100\%$ bounds by a factor of $\sim$1.6--14 for IDM and $\sim$3 for FDM. Self-consistent cosmological simulations of mixed DM scenarios will be essential to more robustly characterize the degeneracy between particle physics parameters and fractional contribution, to extend constraints to lower fractions, and to identify signatures beyond satellite abundance to further inform these models. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10020 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10020v1 Announce Type: new Abstract: We present Manticore-Deep, a high-resolution Bayesian field-level inference of cosmic large-scale structure spanning a comoving volume of $(4~h^{-1}\mathrm{Gpc})^{3}$ out to $z \approx 0.7$, at ${\sim}4$~Mpc/h resolution. Building on the inference framework established in the companion Manticore-Local analysis (P1), Manticore-Deep jointly constrains five galaxy redshift surveys (2M++, 6dFGS, 2dFGRS, SDSS, and BOSS) within a single hierarchical Bayesian framework using the BORG algorithm. The method infers initial conditions that are evolved forward under gravitational dynamics, delivering a full posterior ensemble of three-dimensional density and velocity fields that causally reproduce the observed large-scale structure. A novel tiled inference strategy makes this computation feasible, extending the reconstructed volume by more than an order of magnitude beyond P1. The posterior realisations are statistically consistent with LCDM, exhibiting Gaussian, isotropic initial conditions and evolving into late-time structures that reproduce the expected $z=0$ matter power spectrum, bispectrum, and halo mass function across the resolved scales tested. We validate the physical fidelity of the reconstruction through two independent, template-free posterior-predictive tests against observations not used in the inference. Cross-correlation of the reconstructed matter field with the Planck PR3 CMB lensing map yields a conservative cumulative detection significance of 7.4$\sigma$, while velocity-weighted stacking of $64750$ galaxy clusters on the Planck 217~GHz map produces a kSZ detection at $3.5\sigma$, with a model-independent approach--recession split confirming that the inferred velocities are statistically aligned with the true cluster motions. As a case study, we show that the BOSS Great Wall is recovered as a ${\sim}3\sigma$ overdensity consistent with LCDM across all posterior realisations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10023 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10023v1 Announce Type: new Abstract: Accurate posterior estimation is central to scientific inference, as uncertainties determine what can be reliably learned from observational data. While Markov chain Monte Carlo methods provide asymptotic convergence guarantees, they are computationally demanding in high-dimensional settings. Neural network-based generative models for entire discretized 3D fields enable fast amortized inference but often lack convergence guarantees and principled accuracy assessment. Using Hamiltonian Monte Carlo to obtain reference posterior samples, we conduct a controlled field-level evaluation of an implicit generative model (Stochastic Interpolants) and an explicit likelihood-based model (GLOW normalizing flows). This comparison, unavailable in typical applications, enables the detection of posterior geometry failures that standard metrics cannot capture. As a case study, we consider the cosmological inverse problem of inferring cosmic initial conditions from present-day large-scale structure. To match the precision of modern cosmological data, this problem increasingly relies on complex, non-linear, and non-differentiable simulators, which are incompatible with gradient-based inference frameworks. Generative models offer a route to address these challenges, provided their inferred posteriors are reliable. In this work, we show that matching posterior means, marginal distributions, or achieving high cross-correlation does not imply correct uncertainty structure, as revealed by posterior variance fields and sample-based evaluations. Through this work, we aim to raise awareness of the challenges of uncertainty estimation in high-dimensional field-level settings, highlighting the importance of careful design and validation of neural generative approaches for scientific applications. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10024 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10024v1 Announce Type: new Abstract: Learning cosmology from galaxy surveys requires large suites of simulations spanning the cosmological and astrophysical parameter space, yet hydrodynamical simulations of galaxy formation remain prohibitively expensive. Semi-analytic models offer an inexpensive, physically grounded alternative, but still require halo merger trees from $N$-body simulations, and densely sampling cosmological parameters in sufficient volume remains expensive. We address this by extending cosmological rescaling to operate directly on merger trees and applying it in the $\Omega_{\rm m}$-$\sigma_8$ plane, running the Santa Cruz semi-analytic model for galaxy formation on the rescaled trees to produce galaxy populations across new cosmological and astrophysical parameters at negligible additional cost. A novel halo-profile-based correction, controlled by a single free parameter, suppresses systematic bias in rescaled halo masses to below the per cent level. We apply the method to parameter estimation of $\Omega_{\rm m}$ and $\sigma_8$ given either the stellar mass function or the two-point correlation function, finding that as few as 64, and potentially fewer, base $N$-body simulations, rescaled to $\sim1000$ training samples, match the accuracy of 750 dedicated $N$-body simulations; rescaling to 3200 realisations improves the prediction of $\Omega_{\rm m}$ by $\sim25\%$. Rescaling all merger trees from a single CAMELS-SAM $N$-body simulation costs $\sim0.1$ CPUh, compared to several thousand CPUh to run the simulation itself. We demonstrate a practical route to obtaining predictions of galaxy summary statistics across cosmological and astrophysical parameters, even with a relatively small number of base $N$-body simulations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10028 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10028v1 Announce Type: new Abstract: We present a suite of 50 high-fidelity simulations of Coma cluster analogues constructed from BORG/MANTICORE constrained initial conditions and evolved with the IllustrisTNG galaxy formation model. Regions predicted to form massive clusters comparable to Coma in mass and environment are selected and followed through cosmic time, producing realistic galaxy populations and intracluster medium properties. The ensemble captures both cosmic variance and uncertainties in the local initial conditions, providing a statistically robust framework for interpreting Coma in a cosmological context. We focus on direct comparisons with observed thermodynamical profiles of the intracluster medium. Specifically, we extract X-ray surface brightness profiles from the simulated clusters and confront them with measurements from eROSITA, as well as compute the thermal Sunyaev--Zel'dovich effect via integrated Compton-$y$ profiles for comparison with Planck satellite data. The simulations reproduce the broad shape and normalisation of both observables, while also highlighting the range of scatter expected from environmental and assembly history differences. This enables us to assess how feedback processes, merger activity, and large-scale environment shape observable cluster properties. Our results demonstrate that combining constrained cosmological initial conditions with state-of-the-art galaxy formation physics provides an effective strategy for generating targeted, observation-driven analogues of specific clusters. The resulting dataset offers a valuable resource for testing models of intracluster medium physics, calibrating scaling relations, and interpreting upcoming joint X-ray and Sunyaev--Zel'dovich observations of nearby massive clusters. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10038 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10038v1 Announce Type: new Abstract: We present a new set of 1,192 cosmological simulations as part of the CAMELS project, in which a space of 35 cosmological, astrophysical, and numerical parameters is explored around the fiducial IllustrisTNG model. The volume of each of these simulations is (50Mpc/h)^3, eight times larger than that of previous CAMELS simulations. This provides lower sample variance as well as access to more massive halos and more diverse environments. We focus this work on exploring the advantages these differences provide for parameter inference powered by neural networks. We generate training sets based on the matter power spectra, projected maps of the volumes, graphs representing galaxy spatial distributions, and thermodynamical properties of massive halos. We employ multilayer perceptrons, convolutional neural networks, graph neural networks, and Gaussian processes, respectively, to extract information on the simulation parameters from these inputs while comparing systematically to analogous results from our previous generation of (25Mpc/h)^3 simulations. We generally find that the new, larger volumes produce tighter marginal constraints on the parameters, to degrees that vary between the different inputs. The improvements, however, scale more weakly than with the square root of the increase in the amount of data (i.e., physical volume). We interpret this as originating either from information loss due to mode coupling or from complex degeneracies in parameter space. We also discuss the effects on statistics of the intergalactic medium temperature from four new parameters that are varied in these simulations, which control the amplitude and timing of the ionizing background radiation. We publicly release the simulation outputs and ancillary data at https://camels.readthedocs.io. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10483 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10483v1 Announce Type: new Abstract: Merging galaxy clusters represent the ideal laboratory to test our understanding of the large scale structure formation history and the processes involved. While many merging clusters have been identified, only a limited number have been studied in detail through multi-wavelength analysis and dynamical reconstruction, this type of analysis being crucial to account for projection degeneracies. This work investigates the merger dynamics of the massive and complex cluster MACS0600 using high spatial, $\sim 15$ arcsec, radio and X-ray datasets in combination with ancillary optical data. We analyze the cluster morphology and the thermodynamic properties of the intracluster medium (ICM) through XMM-Newton and Chandra X-ray observations, and explore the non-thermal component via diffuse radio emission observed with Meerkat. We find a disturbed X-ray morphology with multiple substructures and a clear offset between the bulk of the radio emission and the X-ray peak. At the location of the X-ray peak, we detect a compact cool core surrounded by hotter gas and associated with a surface brightness discontinuity consistent with a cold front. The central region exhibits elevated temperatures and hosts most of the diffuse radio emission, suggesting merger-driven turbulence. Optical data further support a relative motion between the cool core and the main cluster along the line of sight. We conclude that MACS0600 is undergoing a merger in which a compact cool core has crossed the main, more massive cluster without being completely disrupted, while significantly perturbing the surrounding ICM. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10597 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10597v1 Announce Type: new Abstract: We test gravity by exploiting the synergy between the gravitational potential decay rate ($\mathit{DR}$) and complementary structure-growth probes: these observables respond to MG parameters with different degeneracy directions, so their combination yields stronger constraints than any single probe. We adopt the tomographic $\mathit{DR}$ measurements reported in \citep{2025ApJ...982...99D} and combine them with CMB-lensing-tomography $\Sigma_8$ constraints and $f\sigma_8$ measurements from DESI DR1 full-shape analyses and the DESI peculiar-velocity field. We apply this joint data vector to two representative frameworks: phenomenological parameterizations and the Effective Field Theory (EFT) $\alpha$-basis. For the phenomenological form $P_{\rm MG}(a)=1+P_{{\rm MG},0}\,\Omega_{\rm DE}(a)/\Omega_{\rm DE}(0)$, where $P_{\rm MG}$ denotes $\mu$, $\eta$, or $\Sigma$, we obtain $\mu_0=0.09\pm0.35$ and $\Sigma_0=0.01\pm0.06$. Compared to the measurements combination $\Sigma_8+f\sigma_8$, including $\mathit{DR}$ tightens the constraint on $\Sigma_0$ by a factor of $\sim2$. For the $(\mu_0,\eta_0)$ case we find $\mu_0=0.06^{+0.17}_{-0.23}$ and $\eta_0=-0.03^{+0.36}_{-0.46}$; relative to $\Sigma_8+f\sigma_8$, adding $\mathit{DR}$ improves the constraints on both parameters by a factor of $\sim1.5$. In the EFT $\alpha$-basis, adopting the parameterization $\alpha_i(a)=c_i\,\Omega_{\rm DE}(a)$ with $i\in\{{\rm M,B}\}$, we find $c_{\rm M}=0.64^{+0.32}_{-0.72}$ and $c{\rm B}=0.31^{+0.19}_{-0.29}$. The corresponding EFT uncertainties are about a factor of $\sim2$ smaller than those reported in \citep{2025JCAP...09..053I}, which combined DESI full-shape and BAO measurements with DES-SN5YR and CMB data. These results demonstrate the capability of $\mathit{DR}$ and the necessity of including the $\mathit{DR}$ measurements in testing gravity. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10679 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10679v1 Announce Type: new Abstract: Stage IV surveys such as LSST will probe deeply into the nonlinear regime, where systematic effects from galaxy bias and baryonic feedback become dominant and poorly constrained nuisance parameters can lead to degeneracies. In this work we present a $3\times2$pt analysis for LSST Y1 and Y10 data using the BACCO emulator for modelling both the hybrid-effective field theory (HEFT) for nonlinear galaxy bias and the baryonic feedback using the baryonification mechanism. We aim to find a balance between model complexity and scale cuts, with particular attention to parameter degeneracies and baryonic feedback effects on the galaxy--matter and galaxy--galaxy power spectra. First, we find that a linear bias model delivers percent-level, unbiased constraints on $\Omega_{\rm m}$ and $\sigma_8$ only up to $k_{\rm max}=0.1\,h/$Mpc, but pushing to smaller scales requires a perturbative approach. Second, we compare HEFT with a minimal bias variant with fixed higher-order terms, and find that the latter is unbiased in $\Lambda$CDM even at $k_{\rm max}=0.7\,h/$Mpc. We show that higher-order bias can mimic baryonic suppression, but baryons cannot reproduce the full range of higher-order bias behaviour. Third, we find that a detection of the total neutrino mass $M_\nu$ is possible for both Y1 and Y10 for $k\geq0.3\,h/$Mpc, at least when photo-$z$ uncertainties and related nuisance parameters are precisely known. However, the specific measured value is not robust across equally plausible mock scenarios: the inferred $M_\nu$ can be significantly biased by adopting the minimal bias model. The entire analysis is conducted with a new independent, open source pipeline (MGL) that we present for the first time in this work. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10863 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10863v1 Announce Type: new Abstract: During the radiation-dominated era of the Universe, a primordial magnetic field undergoes a turbulent decay while its length scale increases due to an inverse cascade. At later times, the size of the largest processed eddy scales with the Alfv\'en speed and it describes an isochrone that moves toward larger scales with increasing time. Different magnetogenesis mechanisms produce different initial length scales and field strengths, independently of the nominal generation time. However, we show that for any initial field, a proper time can be determined such that the isochrones at early times are parallel to those at late times. We use two-dimensional numerical simulations of decaying MHD turbulence and vary the initial position of the peak of the magnetic energy spectrum. In this case, the evolution is governed by the conservation of anastrophy. A fit to the Alfv\'en time yields an accurate estimate of the factor by which the decay time is longer than the Alfv\'en time, while the offset in the fit provides an additional estimate of the proper time that needs to be added to the nominal time since the beginning of each simulation. We also find that the presence of an initial velocity field of realistic strength helps producing a more straight track. The magnetic field parameters lie on universal isochrones even for early times. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09938 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09938v1 Announce Type: cross Abstract: The Vera C. Rubin Observatory began commissioning its camera, LSSTCam, in April 2025, with the Legacy Survey of Space and Time (LSST) scheduled to start in 2026. A primary science goal is constraining Dark Energy through weak gravitational lensing of the large-scale structure (cosmic shear). After a full year of data from LSST, these measurements are expected to reach precision comparable to recent Dark Energy Spectroscopic Instrument (DESI), providing an independent test of hints that Dark Energy may evolve over time. However, cosmic shear requires exquisite control of instrumental systematics. This proceeding presents an overview of the Rubin Observatory commissioning -- the successes achieved and the systematic issues we are working to resolve. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09945 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09945v1 Announce Type: cross Abstract: The generalized cosmological time (GCT) framework introduces a modified lapse function, N(t)\propto a^{b/4}, as a geometric extension of the standard FLRW description. Like other departures from $\Lambda$CDM, such constructions must remain compatible with the observed stability of local gravitational and laboratory physics. In scalar--tensor theories, this compatibility is usually achieved through dynamical screening mechanisms that suppress additional degrees of freedom in dense environments. In this work, we examine whether a locally static spacetime region can be consistently embedded within a cosmological background described by a time-dependent lapse. By embedding a static Schwarzschild interior into an expanding GCT--FLRW exterior, the Israel junction conditions are used to determine the class of background expansions that admit such a matching in the absence of a thin shell. The continuity of the extrinsic curvature yields a Friedmann-type relation that coincides with the GCT background equations of motion. This relation should be interpreted not as a new dynamical equation, but as a geometric consistency condition (GCC) associated with the matching of the two spacetime regions. In this sense, the junction does not introduce new dynamics, but provides a GCC under which a region with fixed local clocks can be embedded in a cosmological spacetime with an evolving lapse. Therefore, the analysis clarifies how locally static gravitational systems can remain compatible with a cosmological time normalization that differs from that of local proper time while preserving the standard description of local physics. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09968 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09968v1 Announce Type: cross Abstract: High-frequency gravitational waves (HFGWs) in the MHz to GHz regime can convert into radio photons in the presence of astrophysical magnetic fields through the inverse Gertsenshtein effect. We show that existing radio telescopes like CHIME and FAST are excellent tools for detecting HFGW sources, significantly outperforming many existing experiments at detecting primordial black hole (PBH) mergers, the most realistic sources of transient HFGWs. Radio telescopes are also uniquely sensitive to sources of monochromatic HFGW emission, such as ultralight boson clouds formed through superradiance around PBHs, and are likely to have excellent sensitivity to generic sources of detectable HFGWs. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09981 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09981v1 Announce Type: cross Abstract: We present a systematic X-ray analysis of the narrow-line Type 1 quasar PHL 1811, which has long been regarded as the prototype of intrinsically X-ray weak quasars. A critical breakthrough came with the first detection of a bright X-ray flare from this source by the Einstein Probe (EP) in 2024. We utilize archival X-ray observations spanning 2001-2024, including the post-flare EP and Swift data. We confirm that PHL 1811 shows X-ray weakness factors $f_{\rm weak} \approx 23$-179 across all epochs before 2024. The 2024 EP flare marks the first detection of an X-ray nominal state with $f_{\rm weak} \approx 0.63$, followed by a rapid flux decline. We identify three key observational signatures that strongly support heavy obscuration: (1) a significant hard X-ray excess above $\approx5$ keV in the 2015 XMM-Newton spectrum; (2) relatively flat spectral shapes in two Swift observations; and (3) transitions between X-ray nominal and multiple X-ray weak states without corresponding optical/infrared variability, consistent with expectations from obscuration by a clumpy dust-free absorber. Fitting with a partial-covering obscuration model reproduces all multi-epoch spectra well. The observed steep spectra are dominated by a small leaked/scattered fraction of the intrinsic continuum, and variability is driven by changes in the leakage fraction and column density. Our results strongly favor the scenario where PHL 1811 is obscured by a radiatively driven accretion-disk wind from super-Eddington accretion, unifying PHL 1811 with the broader population of super-Eddington accreting AGNs under a single obscuration framework. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10005 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10005v1 Announce Type: cross Abstract: We have simulated Ly{\alpha}, H{\alpha}, H{\beta}, [OII], and [OIII] intensity maps which are observable by SPHEREx during cosmic reionization. We simulate these intensity maps including all significant sources of emission for each line, and include radiative transfer for the Ly{\alpha} intensity maps. We also include a simple model of dust extinction based on observations of galaxies at z 6 will require more sensitive instruments, such as the Cosmic Dawn Intensity Mapper. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10013 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10013v1 Announce Type: cross Abstract: Primordial black holes (PBHs), possibly formed from the collapse of early universe perturbations, will evaporate via Hawking radiation with a lifetime comparable to the age of the universe, if their mass is $O(10^{14})$ g. Such black holes can contribute to the observed gamma-ray fluxes in the MeV and GeV range. Using the observed extragalactic gamma-ray background (EGRB) from the \textit{Fermi} Large Area Telescope, the \textit{EGRET}, and the \textit{COMPTEL} telescopes that cover gamma-ray energies from 0.5 MeV to 1 TeV, we evaluate limits on the abundance of PBHs with masses of $10^{14}$ to $10^{17}$ g. We study both monochromatic and extended mass distributions of PBHs. To model the EGRB spectrum, we calculate the contribution from extragalactic sources including blazars, star-forming galaxies and radio galaxies and also account for ultra-high-energy cosmic rays that produce gamma rays when interacting with the infrared background. Our EGRB modeling uses information from the \textit{Fermi} gamma-ray point sources catalog, from observations at X-rays, the visible spectrum, the infrared and radio waves, and also accounts for modeling uncertainties and variations on the properties within each class of these sources. Moreover, we use recent work on the modeling of the PBHs' gamma-ray emission, that includes the direct Hawking radiation, gamma rays produced in the hadronization and decay of unstable particles, final state radiation and gamma rays from pair annihilations in the interstellar medium. As the contribution of final state radiation and the annihilation of positrons enhances the low-energy part of the produced gamma-ray spectra from PBHs, we find that the EGRB observations can set the tightest limits on their abundance among all indirect dark matter probes, within the mass range of interest.[abridged] Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10017 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10017v1 Announce Type: cross Abstract: We provide the cosmic-ray (CR) fluxes of antiprotons and antideuterons produced by the Galactic annihilation or decay of weak-scale dark matter (DM) particles of masses in the range from a few GeV to 100 TeV. We estimate these fluxes based on the updated models for the propagation of charged particles in the Galaxy and using the improved $\bar{p}$ and $\bar{d}$ spectra provided by $\texttt{CosmiXs}$. For the updated propagation models we consider the MIN/MED/MAX sets under the new SLIM/BIG/QUAINT schemes. We treat the Galactic propagation in a semi-analytic way including different possible effects such as spatial diffusion, energy-losses, convection and diffusive reacceleration. For the DM distribution in the Galactic halo we consider NFW, Einasto and Burkert profiles with the most updated parameters. Moreover, we also incorporate the latest models for the inelastic cross-sections of $\bar{p}$ and $\bar{d}$ based on ALICE data. We validate our calculations with those available in the literature or those obtained from other publicly available numerical packages. We compare the CR fluxes obtained in this work with those provided previously by $\texttt{PPPC4DMID}$ which were based on old propagation scenarios. We find that the CR fluxes obtained here with the new propagation models are much more robust (compared to the older ones) under the variation MIN - MAX. We also discuss the impact of this in the improvement of the discovery potential of a possible DM signal in the light of the present and upcoming CR observations. We provide all our results for the DM-induced interstellar CR fluxes in a tabulated format (for the kinetic energy range 0.1 GeV - 100 TeV) in the $\texttt{GitHub}$ repository of the newly created $\href{https://github.com/CosmiXsPPPC}{\texttt{CosmiXsPPPC}}$ project. The results are ready to be used for studies related to DM indirect searches. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10026 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10026v1 Announce Type: cross Abstract: We present a new subgrid model for interstellar gas evolution in cosmological simulations of galaxy formation, based on the pressure-regulated, feedback-modulated (PRFM) theory of star formation. In contrast to the empirically pegged star formation prescriptions employed in current cosmological simulations, the PRFM model links the local star formation rate to the dynamic balance achieved in galactic interstellar gas between gravity and stellar feedback effects. With this formulation, both the star formation efficiency and the effective equation of state may be directly calibrated using numerical simulations, such as TIGRESS, which resolve physics of the interstellar medium and star formation at parsec scales. We develop, and implement in the Arepo moving-mesh code, two complementary classes of the subgrid model: a volumetric version (PRFM-vol) applicable when the gas disk scale height of a galaxy is numerically resolved in a simulation, and an integrated version (PRFM-int) that reconstructs the mid-plane density and pressure from vertical equilibrium considerations when the true gas scale height cannot be numerically resolved. Using isolated Milky-Way-like disk simulations across mass resolutions $10^5$-$10^7~{\rm M}_\odot$, we show that both implementations yield shorter gas depletion times than the IllustrisTNG prescription, especially in regions where pressure and density are large. At high resolution, PRFM-vol and PRFM-int agree closely with each other and with TIGRESS for the star formation rate; PRFM-int remains robust at all resolutions tested. These results demonstrate that PRFM-derived subgrid prescriptions provide a physically grounded and numerically stable framework for star formation across the dynamic range of galaxy formation simulations, paving the way for future cosmological applications. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10027 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10027v1 Announce Type: cross Abstract: Dust attenuation is a major source of systematic uncertainty in both SED fitting and forward modeling of galaxy populations, yet the functional form used to parameterize attenuation curves has received surprisingly little systematic scrutiny. Particular unanswered questions include: how many free parameters are genuinely needed, and which analytic expression best captures the full diversity of attenuation curve shapes in galaxies across cosmic time? Using a large library of synthetic attenuation curves from TNG50 and TNG100 galaxies post-processed with the SKIRT radiative transfer code using three dust mixtures (Milky Way, SMC, and stellar dust), we show via Information-Ordered Bottleneck analysis that exactly four parameters are needed to capture the diversity of attenuation curves. Guided by this result, we use symbolic regression to derive a new, interpretable four-parameter attenuation model that outperforms existing parameterizations in recovering both attenuation curves and emergent fluxes across all dust mixtures explored. The four parameters of this model have clear physical interpretations: UV bump strength, FUV slope, UV-bump transition curvature, and large-scale optical slope. Their correlations with galaxy properties are primarily regulated by star-formation rate surface density, metallicity, and stellar-dust geometry, and are largely preserved across dust mixtures -- except for the bump-sensitive parameters, which retain a stronger dependence on grain composition. We further provide symbolic-regression scaling relations linking all four parameters to quasi-observable galaxy properties, offering a physically motivated route to assign realistic attenuation curves in SED fitting and forward modeling without radiative-transfer calculations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09979 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09979v1 Announce Type: new Abstract: The formation mechanism(s) of substellar objects, such as brown dwarfs and free-floating planets, remains an ongoing puzzle in stellar and planetary physics. Recent observational and theoretical work points towards a star-like origin for brown dwarfs, though several authors posit that they could form like planets in a circumstellar disc, and then subsequently be ejected into a star-forming region or the Galactic field. Recently, JWST observations have discovered nine substellar objects in the IC348 star-forming region with a spectral absorption feature at 3.4$\mu$m from an unidentified aliphatic hydrocarbon, detected for the first time in planetary atmospheres outside of the Solar System. It is unclear whether these hydrocarbon absorption features in these 'H-type' objects indicate a different formation mechanism compared to more massive brown dwarfs. We quantify the spatial distribution of these objects and find they are indistinguishable from the spatial distribution of stars and other brown dwarfs in IC348. We use N-body simulations to test whether the H-type objects could have formed as planets in circumstellar discs and then been dynamically ejected by stellar fly-bys. We show that a similar number of free-floating planets could be produced if those planets initially resided at ~5au from their host stars. However, these free-floating planets have a much more dispersed spatial distribution than the stars and brown dwarfs, inconsistent with the spatial distribution of the H-type objects in IC348. We therefore conclude that the H-type objects are unlikely to have a planetary-like origin. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10012 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10012v1 Announce Type: new Abstract: Non-ideal magnetohydrodynamic simulations of protoplanetary disks show a plethora of complex gas structures, including winds, rings, and gaps. These affect dust transport and help form dust traps, which are essential for planetesimal formation. Although studies have explored the evolution of dust in such systems, they have done so either in 1D or without dust coagulation, and the effect of such systems on dust growth is still an active area of research. This work aims to investigate the effect of a complex gas flow architecture on global dust evolution, including dust growth and transport. We examine the timescales of different processes impacting dust evolution and discuss prospects of forming planetesimals. We post-process gas velocity output from a 2D non-ideal magnetohydrodynamic simulation using a 2D (r-z) Monte Carlo dust coagulation code to perform global simulations of dust growth and evolution. We perform three runs, one with a typical steady-state disk and two with the gas velocity from the MHD simulation, where we vary the fragmentation velocity. Our results show that the advection of small particles by the gas due to strong gas velocities can play an important role in setting the dust size distributions around protoplanetary disks. The gas flow structure has a transition region, and this region acts as a location of a dust pile-up, increasing the pebble-to-gas ratio by a factor of 2.5 when compared to the steady state disk. Lowering the fragmentation velocity improves the stability of the pile-up, but the pebble concentration is not as high. This scenario acts as a way to form a dust trap in a disk without a pressure bump. We discuss the possibilities for planetesimal formation in such a trap. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10624 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10624v1 Announce Type: new Abstract: The HD 135344B (SAO 206462) disk exhibits strong signposts of planet formation. ALMA images in the sub-mm revealed a gap-crossing dust filament whose position coincides with a twist detected in the scattered-light spiral structure. Analysis of the spirals in polarized light also hints at a spiral-driving protoplanet in the sub-mm gap. We aim to study the spirals dynamics, as well as the twist, over a 10-year baseline, in different bands. We also seek to assess the authenticity of a recently claimed candidate protoplanet. We use high-fidelity post-processing algorithms such as IPCA to minimize the biases induced by ADI on extended sources and analyze archival VLT/NACO, VLT/SPHERE, VLT/ERIS and JWST/NIRCam datasets to obtain the spiral traces and measure their orbital motion in multiple scattered light bands. We measure an average spiral orbital motion of 0.81$\pm$0.05 deg/yr, in agreement with the literature value of about 0.85$\pm$0.05 deg/yr at all wavelengths. With simple modeling of the twist morphology, we confirm that it is co-moving with the spiral in which it is embedded. While the position angle of the twist coincides with the dust filament, it is located at a smaller angular separation from the star, which we attribute to the fact that the spiral trace moves away from the central star with increasing wavelength. We find that a recently claimed protoplanet candidate can be explained as a post-processing artifact. Our confirmation that the motion of the scattered light twist is consistent with the orbital velocity of a planet at 69$\pm$4 au over a 10-year baseline suggests that the spirals, the gap, the dust filament, and the twist, could indeed be attributed to the same hypothetical protoplanet embedded within the spiral. A perplexing trend for a wavelength-dependence of the angular distance of the spiral traces to the central star remains to be explained. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10676 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10676v1 Announce Type: new Abstract: We present a Smoothed Particle Hydrodynamics (SPH) implementation of the full one-fluid dusty gas algorithm for multiple dust species, generalising our previous terminal velocity approach to handle arbitrary drag regimes. By construction, mass, momentum, angular momentum, and energy are all conserved. We benchmark our method against a suite of tests -- DUSTYBOX, DUSTYWAVE, DUSTYSHOCK, DUSTYSETTLE, and DUSTYDISC -- each probing different aspects of the algorithm. Compared to the terminal velocity approximation, the full one-fluid approach incurs a computational cost increase of a factor of five to ten due to the added overhead of evolving the differential velocities and solving the drag terms implicitly. However, it accurately recovers analytic behaviour in regimes where the terminal velocity approximation fails. In such cases, errors from the terminal velocity approximation accumulate and propagate to other dust phases. We show that the stopping-time limiter commonly used in the terminal velocity approximation for numerical stability can substantially affect simulations containing large grains (Stokes numbers $\gtrsim 1$). While disabling the limiter leads to different outcomes, the discrepancy with the full one-fluid solution remains comparable, underscoring the importance of using a more general formulation for large grains. The full one-fluid formalism may be useful when including processes such as coagulation and fragmentation, where accurate treatment of large grains becomes essential. While the inability to model orbit-crossing dust trajectories remains a key limitation of the one-fluid formalism, this may eventually be addressed through the introduction of an effective dust pressure, mirroring how fluid models encapsulate microscopic velocity dispersion in gases. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10690 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10690v1 Announce Type: new Abstract: We present a calibrated catalog of Cassini Visible and Infrared Mapping Spectrometer (VIMS) observations of Jupiter, together with the processing workflow used to generate the final publicly available products. Starting from the raw VIMS cubes, the workflow produces radiometrically consistent multi-extension FITS files and includes a revised visible-channel calibration, a revised infrared-channel calibration that resolves a subset of problematic cases not satisfactorily treated by the standard ISIS pipeline, corrections for pointing-related misalignments between spectral cubes and geometric backplanes, and customized dark signal correction strategies. The final products include calibrated spectral cubes together with geometry backplanes and wavelength information for subsequent scientific analysis. We assess the consistency of the calibrated products through internal validation tests and comparisons with independent reference spectra from the literature. The resulting products provide a uniform and validated data set of Cassini VIMS Jupiter observations for community use. The full catalog is available as a public data set at Zenodo: doi:10.5281/zenodo.19223781. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10888 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10888v1 Announce Type: new Abstract: Protoplanetary disks are the birthplace of planets and planetary systems. Investigating the molecular inventory of disks is key to linking the chemical evolution of the interstellar medium and the makeup of planets and their atmospheres. In particular, tracing the history of the deuterium enrichment of water along the journey from interstellar clouds through protoplanetary disks to planetary systems provides critical insights into the chemical inheritance. We aim to investigate the chemical composition of ices in protoplanetary disks; specifically, the presence of HDO ice that ought to be present, but has not been detected in disks thus far. We analyzed JWST/NIRSpec observations of the 132-1832 edge-on disk located in the Orion Nebula Cluster using the ENIIGMA fitting tool and unique laboratory data. We report on the first detections of HDO ice in a protoplanetary disk. The estimated upper limit for the HDO/H$_2$O ratio for 132-1832 is much higher, compared to HDO/H$_2$O ratios obtained for chondrites, comets, and embedded young stellar objects. In the disk ices, beyond HDO, we detected H$_2$O, CO$_2$, $^{13}$CO$_2$, CO, OCN$^-$, and OCS, species, whose presence has also been detected in other disks. The HDO ice detection may point to the efficient ice processing in the disk and confirm the findings of laboratory experiments on deuterated ices. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10108 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10108v1 Announce Type: cross Abstract: (Extract from the Executive Summary) Humanity stands at the threshold of answering one of its most profound questions: Does life exist beyond Earth? Ongoing and upcoming space missions, together with powerful ground-based instruments, have prepared the way for a transformational next step - the detailed characterization of Earth analogs orbiting Sun-like and other stars and the search for atmospheric biosignatures that may indicate life. Within this context, the European Space Agency's Voyage 2050 process has identified the direct detection of thermal emission from temperate terrestrial exoplanets in the mid-infrared (mid-IR) as a top scientific priority. The Large Interferometer For Exoplanets (LIFE) - a space-based, mid-IR nulling interferometer - is designed to meet this goal. LIFE will be capable of detecting climate-relevant gases such as CO$_2$ and H$_2$O, identifying classical biosignatures like O$_3$ and CH$_4$, and probing additional, non-classical biosignatures. It will also provide key data for determining planetary radius, albedo, and temperature, which are essential for assessing habitability. In parallel, the U.S. National Academy has recommended a complementary mission now called the Habitable Worlds Observatory (HWO) - a ~6-meter space telescope equipped with advanced coronagraphs to suppress starlight by a factor of ~10$^{10}$ across the visible and possibly into the near-infrared and near-ultraviolet. Together, LIFE and HWO offer synergistic capabilities, enabling a comprehensive and robust assessment of the prevalence of life-bearing exoplanets in our galactic neighbourhood - a first in human history. By uniting an international and interdisciplinary community of scientists and engineers, LIFE offers a credible pathway toward the direct detection and characterization of potentially habitable - and even inhabited - worlds. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10140 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10140v1 Announce Type: cross Abstract: Extraterrestrial civilizations might place large, lightweight mirrors into orbit around an exoplanet, either to alter its climate or to provide illumination to the planet's dark side. We previously analyzed the detectability of a fleet of 1km x 1km, 1000 kg mirrors (Korpela, Sallmen, & Leystra Greene 2015). Because these mirrors are large and lightweight, their orbits are significantly affected by the star's radiation pressure (RP). We created a simulation package based on the REBOUND N-body simulator, incorporating RP that directs starlight towards the planet's center. RP can always affect mirror orbits, or only during orbital night. We have simulated mirrors in initially circular orbits around exoplanets at various locations in the habitable zones of eight types of main-sequence stars. Initial mirror orbit sizes range from 2 to 10 planet radii, and we included 4 different initial mirror orbit orientations. For each simulation, we have the mirror's survival time, trajectory, distance from the planet center at each time, and velocity relative to the planet at each time. We present an analysis of trends in mirror orbit stability, and relate these to the ratios of RP and gravitational accelerations, as well as the ratio of planet orbit period to mirror orbit period. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10760 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10760v1 Announce Type: cross Abstract: The vortex coronagraph is one of the most promising candidates for the Habitable Worlds Observatory (HWO) due to its excellent theoretical performance for an off-axis telescope. A practical realization can be achieved using liquid-crystal polymers to form a vector vortex coronagraph (VVC). Reaching the $10^{-10}$ contrast required for Earth-like planet detection is, however, limited by polarization leakage caused by wavelength-dependent deviations from half-wave retardance. This effect can be mitigated using multi-layer twisted retarders to minimize leakage, and by combining the VVC with multiple polarization gratings (mgVVC) to diffract the polarization leakage out of the science path. We present recent progress within the ESA-funded SUPPPPRESS project, which aims to advance the manufacturing, assembly, and testing of high-performance VVCs. Central singularities of 2 and 6 $\mu$m have been achieved for charge 2 and charge 6 VVCs, respectively, with patterning accuracies better than 1 degree root-mean-square error. Fabrication procedures have been developed to produce individual components with a polarization leakage of $3\times10^{-4}$ over a 10% bandwidth and $8\times10^{-4}$ over a 20% bandwidth. We also report on the development of assembly and alignment procedures for mgVVCs and their metrology. Furthermore, we present initial high-contrast tests at the THD2 bench for both regular VVCs and a double-grating VVC. The double-grating VVC reaches an average contrast between 3 and 10 $\lambda$/D of $2 \times 10^{-8}$ over a small bandwidth and $6\times 10^{-8}$ over a 10% bandwidth. Finally, we report on successful space-environment tests of the assembled liquid-crystal masks. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10816 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10816v1 Announce Type: cross Abstract: Observations of (giant) planets accreting material within their natal environment are crucial to constrain models for their formation. WRAY 15-1880 (aka RX J1842.9-3532) in the Corona Australis (CrA) complex has a prominent pre-transitional disk, and an age of ~2.8+-0.7 Myr, computed by comparison with isochrones using the accurate dynamical mass derived from disk kinematics. Hence, this star is in the late phases of disk evolution and might host accreting planets. We acquire new polarimetric imaging data with VLT-SPHERE and analyze archive observations taken with VLT-SPHERE, VLT-MUSE, and ALMA, finding a candidate Jupiter-like companion within the disk gap from high-contrast imaging. The mass estimates of the candidate companion, derived from various methods, are consistent with an object in the range of 0.3-7.6 MJup. The spectrum of the candidate companion is consistent with a T3 spectral type, in agreement with expectations of an object of a few Jupiter masses. We find an emission blob North-West of the star in the ALMA data rotating solidly with the candidate companion, that can be interpreted as a vortex/dust trap at the m=1 Lindblad resonance of the planet. Accretion on the candidate planet is not detected from the VLT-MUSE archival data. This may be due to insufficient contrast, an observational geometry that is unfavorable for viewing the planet's surface, or it could indicate that we are merely observing irregularities within the disk. Finally, we identify a microjet extending from the star perpendicular to the disk in these data. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.11026 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11026v1 Announce Type: cross Abstract: Context. Silicates are key constituents of planet-forming disks and major building blocks of rocky planets. Mid-infrared spectral features of micron-sized silicate grains trace grain growth, mineralogy, and disk chemistry. Aims. We characterized the dust mineralogy in T Tauri disks using James Webb Space Telescope (JWST)/Mid-Infrared Instrument (MIRI) observations and investigated the connections between the dust and molecular gas compositions. Methods. We analyzed JWST/MIRI spectra of 26 disks from the MIRI mid-Infrared Disk Survey (MINDS). Using our DustComp spectral decomposition tool, we inferred the mass fractions of individual dust species. The fits included Mg$_2$SiO$_4$ (forsterite), MgSiO$_3$ (enstatite), and SiO$_2$ (silica), together with amorphous silicates of corresponding stoichiometry. Results. Mg-rich (and Fe-poor) silicates reproduce the data well, with residuals typically within $\pm3\%$. Grain size distributions are skewed toward sizes larger than $2\mu$m, indicating significant growth. The average dust composition is dominated by Mg$_2$SiO$_4$-stoichiometry grains ($\sim60\%$), followed by MgSiO$_3$ ($\sim30\%$) and SiO$_2$ ($\sim10\%$). Crystalline mass fractions are typically in the $5$-$24\%$ range, with a mean of $14\%$. Annealed silica is robustly detected in nine objects, with cristobalite as the main polymorph. We found a correlation between dust and molecular gas composition: disks with strong annealed silica features show stronger CO$_2$ emission, while forsterite-rich disks display stronger H$_2$O emission. Disks with annealed silica features may also have elevated gas-phase C/O ratios. Conclusions. The observed dust-gas correlation may provide the first indication that the molecular gas composition regulates the availability of dust species in the inner disk. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2509.10947 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2509.10947v3 Announce Type: replace Abstract: K2-18b, a sub-Neptune orbiting in the habitable zone of an M dwarf, has attracted significant interest following observations with the Hubble Space Telescope (HST) and, more recently, with the James Webb Space Telescope (JWST), which reveal detectable atmospheric features across the near- and mid-infrared. Using free-chemistry Bayesian retrievals, we investigate whether hydrocarbon hazes can explain the apparent mismatch of spectral feature amplitudes between the JWST NIRISS/NIRSpec and MIRI LRS datasets. We additionally assess the impact of stellar parameter uncertainties on the derived bulk properties of the planet and explore how planetary mass uncertainties affect atmospheric retrievals. We find that hazy scenarios can reproduce the combined JWST spectrum and provide a consistent explanation for the reduced NIRISS/NIRSpec feature amplitudes relative to the stronger MIRI features. Across all retrievals, the atmosphere remains consistent with an H$_2$-dominated sub-Neptune, with CH$_4$ and CO$_2$ as the dominant absorbers. Our hazy models retrieve systematically lower molecular abundances compared to haze-free models, reflecting the degeneracy between haze opacity and mean molecular weight. In addition, we identify strong degeneracies between planetary mass, temperature, and mean molecular weight. The retrieved planetary mass is particularly poorly constrained, with $2\sigma$ uncertainties reaching up to $\sim71\%$. We demonstrate that different mass assumptions can significantly bias the inferred atmospheric properties, with higher masses favouring warmer and lower mean molecular weight atmospheres. Breaking these degeneracies will require improved stellar characterisation to obtain more precise mass measurements. More laboratory-focused studies and future JWST observations are essential for interpreting these temperate sub-Neptune atmospheres. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2601.14254 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2601.14254v2 Announce Type: replace Abstract: The internal composition of sub-Neptunes remains a prominent unresolved question in exoplanetary science. We present a technique to place constraints on envelope mean molecular weight that utilises observations of escaping hydrogen or helium exospheres. This method is based on a simple timescale argument, which states that sub-Neptunes require a sufficiently large hydrogen or helium reservoir to explain on-going escape at their observed rates. This then naturally leads to an upper limit on atmospheric mean molecular weight. We formalise this argument within a Bayesian inference model and apply it to the archetypal sub-Neptunes GJ-436 b, TOI-776 b and TOI-776 c, which have all been observed to be losing significant hydrogen content as well as relatively featureless transit spectra when observed with JWST. Combining constraints from atmospheric escape and transit spectroscopy in the case of TOI-776 c allows us to tentatively rule out the high mean molecular weight scenario, pointing towards a low mean molecular weight atmosphere with high-altitude aerosols muting spectral features in the infra-red. Finally, we reframe our analysis to the hycean candidate K2-18 b, which has also been shown to host a tentative escaping hydrogen exosphere. If such a detection is robust, we infer a hydrogen-rich envelope mass fraction of $\log_{10} f_\text{env} = -1.67\pm0.78$, which is inconsistent with the hycean scenario at the $\sim 4\sigma$ level. This latter result requires further observational follow-up to confirm. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2603.07718 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2603.07718v3 Announce Type: replace Abstract: We present multi-epoch optical spectroscopy of the interstellar comet 3I/ATLAS obtained between December 2025 and January 2026 (heliocentric distances 1.8-3.3 au), yielding post-perihelion production rates and mixing ratios for CN, C$_3$, C$_2$, CH, and gaseous metals (Fe I and Ni I). Our results show that the coma is less depleted in C$_2$ after perihelion than before, indicative of subsurface activation or compositional heterogeneity. The outgassing profiles reveal a pronounced perihelion asymmetry: CN and metal production rates decline more gradually outbound than inbound, consistent with the reported behavior of H$_2$O and implying a change in the comet's activity pattern across perihelion. Despite being metal-rich relative to its H$_2$O content, 3I follows the metal-CO correlation observed in comets of diverse origins, suggesting that gaseous metal release is more closely linked to a CO-bearing volatile reservoir than to H$_2$O, potentially in the form of metal carbonyls. In addition, the [O I] $\lambda6300$ emission shows a significant residual after subtracting the expected contributions from H$_2$O, CO$_2$, and CO, which may reflect systematic uncertainties in the photodissociation yields of those molecules or a contribution from additional oxygen-bearing parents. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2605.19635 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.19635v3 Announce Type: replace Abstract: We perform a comprehensive analysis of lunar impact flash (LIF) light curve shapes and their dependence on the lunar terrain, using the large sample of LIFs detected by NELIOTA over the last 9 years. We classified 124 multi-frame light curves into mare, highland and `border' regions. Subsequently, we derived analytical expressions for single-size and dual-size ejecta cooling models, which were fitted to the observational data to estimate their physical properties. While impacts on both terrains yield similar peak magnitude distributions, their decay behaviour differs significantly; highland LIFs exhibit a shallower and longer-lasting decay compared to mare flashes, which are faster and steeper. The dual-size model suggests this extended duration is primarily driven by the fine droplets of the ejecta. The profile and duration of the LIF light curves represent the initial stages of the impact cratering process. The observed dichotomy between highland and mare LIFs demonstrates that the initial stages of the impact cratering process are fundamentally dependent on lunar lithology. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2604.17554 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2604.17554v2 Announce Type: replace-cross Abstract: A primary goal of the Habitable Worlds Observatory (HWO) is to detect and measure the abundance of biosignature molecules, such as water (H2O) and oxygen (O2), in the atmosphere of Earth analogs. This is expected to require deep spectroscopic observations lasting hundreds of hours per planet. In this context, it is essential to optimize the spectral resolution of the spectrograph to both maximize the number of planets that can be studied over the lifetime of the mission, and also to reduce the risks of false detections. The purpose of this work is to provide a framework to explore the spectral resolution design trade-space for HWO. This framework must be valid and comparable across all spectral resolutions from low (R 10,000), and account for the spectral correlation of the residual starlight (i.e., speckle noise chromaticity). Leveraging the concept of "template matching", we develop a simulation toolkit based on the Python package EXOSIMS to compute the detection significance of planets and molecules. We then simulate observations of Earth analogs around 164 stars using representative mission parameters to explore the effects of the detector noise and the correlated speckle noise floor. Our findings suggest that a moderate or high resolution spectrograph (R>1,000) will provide higher sensitivity to critical molecules compared to a low resolution spectroscopy mode (e.g., R~140). The correlated speckle noise may also entirely suppress our ability to detect bio-signatures at low spectral resolutions. We conclude that a more comprehensive study combined with detailed models of its stability, and other sources of correlated noise, is necessary to fully explore the trade space of spectral resolution and detectability of key species. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.09975 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09975v1 Announce Type: new Abstract: We present the discovery of a compact Milky Way satellite in the constellation of Gemini. This system was discovered by cross-matching detections from two independent search algorithms applied to Blanco/DECam data from the third data release of the DECam Local Volume Exploration survey (DELVE DR3), and confirmed with deeper imaging from Gemini/GMOS-N. Based on these data, we determine that the system is an ultra-faint ($M_V = -2.1^{+0.4}_{-0.6}$), compact ($r_{1/2} = 8.6^{+1.4}_{-1.2}$ pc) system located at a heliocentric distance of $120^{+7}_{-6}$ kpc. These physical properties place the system in the regime of ambiguous, ultra-faint compact Milky Way halo satellites that cannot be confidently classified as dwarf galaxies or star clusters from morphology alone; we therefore name the system DELVE 8/Gemini I. From medium-resolution Keck/DEIMOS spectroscopy, we securely identify four members including two blue horizontal branch stars, confirming the system as a bound satellite moving at a mean radial velocity of $v_{\rm hel} = -82.7^{+3.7}_{-3.9} {\rm km\,s}^{-1}$. We also use these spectra to place an upper limit of $\rm [Fe/H] \lesssim -2.5$ on the metallicity of DELVE 8/Gemini I's brightest star, supporting the classification of the system as either an ancient star cluster or ultra-faint dwarf galaxy. The discovery of faint, distant systems similar to DELVE 8/Gemini I is expected to become more common with upcoming surveys. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09999 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09999v1 Announce Type: new Abstract: In modern simulations that include star formation, it is common to use a universal and invariant initial mass function (IMF) to represent star populations or sample individual stars. However, stellar masses are determined by local and environmental processes that operate over a wide dynamical range and remain unresolved in simulations. We introduce a semi-deterministic (SDT) scheme for sampling individual stars from star-forming gas in numerical simulations. We represent unresolved molecular cores and protostellar disks with reservoir particles (RsvPs) and employ an on-the-fly friends-of-friends algorithm to identify star clusters. The instantaneous IMF for newly formed stars is then derived from the current cluster mass. We test the performance of this method in simulations of isolated molecular clouds and a major merger between two dwarf galaxies. Compared to existing IMF sampling methods, our SDT scheme naturally reproduces the observed $m_{\star,\text{max}}$-$M_\text{ecl}$ relation and yields numbers of massive stars consistent with optimal sampling theory. It also exhibits the smallest run-to-run variation among simulations with different random seeds. The regulated star formation results in a small ($\sim0.15$ Myr) but coherent time delay in the emergence of massive stars, reduces the large scatter arising from Poisson noise, and produces initial mass segregation within the clusters. On galactic scales, the SDT method predicts a steeper high-mass IMF slope at low star formation rates (SFRs), with the slope negatively correlated with the SFR. As the specific abundance of massive stars declines, we predict that H$\alpha$-based SFR diagnostics will systematically underestimate the intrinsic SFR due to IMF sampling effects. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10000 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10000v1 Announce Type: new Abstract: A population of dense stellar systems at high redshift has recently been uncovered by the JWST. To investigate the formation of supermassive black hole (SMBH) seeds in these dense environments without invoking any \textit{ad hoc} seeding mechanisms, we present star cluster-scale simulations performed with an updated version of the hydrodynamics code \texttt{Enzo-Abyss}, which self-consistently integrates the gravity using a direct $N$-body method coupled with stellar evolution. By modeling initially dense, metal-poor gas clouds with varying turbulence, we consistently find the formation of dense clusters resembling early-stage nuclear star clusters (NSCs), as well as the formation of very massive stars (VMSs) ranging from $343\;\mathrm{M_\odot}$ to $5108\;\mathrm{M_\odot}$ via runaway collisions, irrespective of stellar wind feedback strength. Following the direct collapse of these VMSs, the resulting intermediate-mass black holes (IMBHs) grow through Eddington-limited gas accretion and tidal disruption events (TDEs). In our most optimistic model, we find a mass accretion rate of $1.64\times10^{-4}\;\mathrm{M_\odot\;yr^{-1}}$, with TDEs contributing $23\%$ of the total accretion over $\sim10\;\mathrm{Myr}$. Assuming a steady gas supply into the NSC driven by rapid structural assembly in the high-redshift environment, together with a constant TDE rate, we project that an IMBH with an initial mass of $6747\;\mathrm{M_\odot}$ at the center of the NSC can grow to $\sim62000\;\mathrm{M_\odot}$ within $100\;\mathrm{Myr}$ of its formation. Our numerical study, conducted within a single self-consistent framework that incorporates the essential physical processes, suggests that VMSs can form in dense gas clouds, collapse into IMBHs, and subsequently provide viable seeds for the SMBHs observed at high redshift. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10022 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10022v1 Announce Type: new Abstract: We introduce PRFM-vol, a new subgrid model for star formation in cosmological simulations that aims to increase the physical realism of cosmological simulations by leveraging results obtained with focused ISM simulations. We deploy a modified effective equation of state and calculate the star formation rate for each gas cell as a function of the ambient densities of gas, dark matter, and stars, based on the pressure-regulated feedback-modulated (PRFM) theory of star formation. Test simulations of our model in isolated galaxies show that we match PRFM predictions and TIGRESS scaling relations remarkably well, provided sufficiently high resolution is available. In particular, we are able to clearly demonstrate the impact of the stellar potential on the star formation rate, thereby retaining an important prediction of PRFM. We then apply our new model to cosmological multizoom simulations and find, compared to our previous TIGRESS/Schmidt model, a significant increase in the stellar scale heights and a slight increase in stellar mass. We demonstrate that modifying the effective equation of state significantly affects the morphology of simulated galaxies. Pronounced stellar clumps appear if the effective pressure at low hydrogen number densities is low, and disappear for higher pressure. We show that the formation of clumps is a result of Toomre instabilities, and conclude that simulated galaxy morphologies can be used to constrain effective equation of state models. Overall, our results establish PRFM-vol as a new self-consistent, physics-motivated subgrid model for star formation in high-resolution cosmological simulations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10036 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10036v1 Announce Type: new Abstract: JWST discoveries of the earliest ($z \gtrsim 9$) supermassive black holes (BHs, $M_\bullet \gtrsim 10^6\,\rm{M}_\odot$) challenge the BH seeding and accretion models of most cosmological simulations. In this work, we compare early BH growth arising from three different accretion prescriptions characterized by distinct scalings between the accretion rate ($\dot{M}_{\rm \bullet}$) and the BH mass ($M_{\rm \bullet}$): the commonly used Bondi-Hoyle model ($\dot{M}_{\rm \bullet}\propto M_{\rm \bullet}^2$), and two free-fall models with shallower scalings ($\dot{M}_{\rm \bullet}\propto M_{\rm \bullet}^{1/2}$ and $M_{\rm \bullet}$). Bondi accretion tends to produce stronger runaway growth than the free-fall models when using heavy ($\sim10^5\,\rm{M}_\odot$) seeds owing to the steeper $M_\bullet$ scaling, but its sensitivity to the local gas sound speed makes it more susceptible to suppression from temperature increases due to AGN and stellar feedback. The free-fall models tend to produce stronger growth for lower-mass seeds ($\sim10^{3-4}\,\rm{M}_\odot$) as they are less dependent on the BH's mass to accrete effectively, however in this regime BH growth remains negligible for all accretion models in the presence of fiducial stellar feedback. Enhancing early BH growth via many BH-BH mergers disproportionately enhances subsequent accretion-driven growth for Bondi due to the steeper $M_{\rm \bullet}$ dependence. Our simulations can thus assemble BHs with masses of $\sim10^6-10^7 M_{\odot}$ at $z\gtrsim9$, as inferred by JWST, under two circumstances: 1) abundant heavy-seed formation that drives BH-BH mergers, or 2) Bondi accretion with weak feedback. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2509.17372 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2509.17372v2 Announce Type: replace-cross Abstract: The DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO) is a planned space-based, next-generation gravitational wave detector aimed at observing primordial gravitational waves originating form cosmic inflation. This work focuses on reducing the quantum noise, in the instrument's observation band of 0.1 to 10 Hz, by employing optical springs and a homodyne detection scheme. Although detuning 1000\,km long arm cavities was previously considered ineffective due to quantum state degradation from diffraction losses, we revisit this problem by formulating a new, rigorous model for quantum state of light by accounting for the vacuum state mixing as a result of diffraction losses. This work shows that high sensitivities can be achieved by employing optimal configurations of optical springs and homodyne detection schemes even with diffraction losses. These improvements alone are still not sufficient to achieve sensitivities to detect primordial gravitational waves as other technical noises limit further improvement. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10411 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10411v1 Announce Type: new Abstract: Solar eruptions are powered by the release of magnetic energy stored in the lower solar atmosphere, but the pre-eruptive magnetic configuration of filament channels remains difficult to determine. A central question is whether this energy is stored in a pre-existing magnetic flux rope or in a sheared arcade that forms a flux rope only during eruption. Resolving this ambiguity is critical for identifying instability thresholds and eruption triggers, yet photosphere-based extrapolations often provide insufficient constraints on the three-dimensional coronal field. Here, we introduce a data-driven magnetic field extrapolation framework that combines photospheric and chromospheric vector magnetograms in a unified multi-height optimization, while accounting for variable chromospheric formation heights and the 180{\deg} azimuthal ambiguity. Tests with radiative magnetohydrodynamic simulations show that photosphere-only extrapolations can misidentify the pre-eruptive magnetic configuration, whereas chromospheric vector constraints recover the three-dimensional structure substantially more accurately. Applied to multi-line spectropolarimetric observations of an active region filament obtained with the Swedish Solar Telescope, the method reveals a reconstructed magnetic field consistent with a pre-eruptive flux-rope configuration. These results show that chromospheric vector magnetic measurements can provide decisive constraints on filament magnetic configuration and open a path toward diagnosing magnetic-energy storage and instability in eruptive solar active regions. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2604.03429 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2604.03429v2 Announce Type: replace-cross Abstract: We aim to confirm the compact nature and constrain the radio spectra of candidate persistent radio sources (PRSs) associated with repeating fast radio bursts (FRBs). We performed European VLBI Network (EVN) observations at 5 and 8 GHz targeting two candidates identified in a recent VLA survey. We measured flux densities and upper limits at milliarcsecond resolution and combined them with published VLBI data at lower frequencies to derive spectral constraints. We detect a compact source associated with FRB 20190417A at 5 GHz with a flux density of $150\pm45$ uJy, while no detection is obtained at 8 GHz. The source is unresolved and has a brightness temperature $T_{\rm b}>10^{5}$ K, confirming its non-thermal nature. Combining our measurement with VLBI data at 1.4 GHz, we derive a spectral index $\alpha = -0.19 \pm 0.29$, consistent with a nearly flat spectrum. This makes FRB 20190417A only the second PRS with a spectral index constrained using VLBI data. The inferred luminosity places the source on the proposed $L_{\nu}$-|RM| relation. Including this source yields a scatter of $\sigma_\Delta = 0.65$, corresponding to $\hat{\alpha}|\epsilon| = 1.5 \pm 0.7$, consistent with forward shocks in the free-expansion phase or young pulsar wind nebulae. For the candidate PRS associated with FRB 20181030A, we report upper limits of 80 uJy at 5 GHz and 150 uJy at 8 GHz, corresponding to $L_{5\,\mathrm{GHz}} \lesssim 3.8 \times 10^{25}\ {\rm erg\ s^{-1}\ Hz^{-1}}$, and implying a steep spectral index ($\alpha \lesssim -1.2$) if the VLA emission arises from a compact component. Our results highlight the importance of VLBI in isolating compact emission from FRB engines and provide one of the few spectral constraints for PRSs at milliarcsecond resolution. The consistency of FRB 20190417A with the $L_{\nu}$-|RM| relation supports a nebular origin for the persistent emission. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2603.26353 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2603.26353v2 Announce Type: replace-cross Abstract: An X-ray background in the early Universe enhances molecular hydrogen formation, the main coolant of primordial gas, thereby lowering the threshold for Pop III star formation. Continuing our series on X-ray impacts on Pop III star formation, we investigate how a soft X-ray background promotes Pop III star formation using cosmological zoom-in simulations of ten cosmic volumes spanning a range of halo number densities. Each volume is irradiated by the Lyman-Warner (LW) H$_{2}$ dissociating background and a weak (J$_{21} \sim 10^{-5}$), soft ($E \sim 0.2-2.0$ keV) X-ray background produced by pair-instability SNe (PISNe) from Pop III stars and calculated self-consistently as described in a companion paper. We also compare the same simulations with and without X-rays to isolate the X-ray effect. The background promotes Pop III star formation in two ways: (1) by reducing the mean host halo mass by a factor of $\sim 2-3$, and (2) by enabling Pop III star formation in haloes that would otherwise remain sterile, thereby increasing the halo occupation fraction. The resulting gain in Pop III number density is largest in underdense regions (a factor of $\approx 3$ on average, reaching up to 7). In the most extreme case, Pop II stars form only in the presence of X-rays and the gas-phase metallicity rises by an order of magnitude, suggesting that dwarf galaxies in underdense regions may be significantly influenced by an early X-ray background. We also provide fitting functions for the halo occupation probability of Pop III stars as a function of redshift for both X-ray and LW-only simulations, which can serve as inputs for semi-analytic models. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2512.13783 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2512.13783v2 Announce Type: replace-cross Abstract: We use the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) to identify stellar members of the Local Group dwarf galaxies. We cross-match DESI targets with candidate members that are based on Gaia proper motions, positions, and photometry. The addition of DESI radial velocities enables secure membership determination in 15 systems. Our results confirm that Gaia-based selection algorithms are effective in minimising foreground contamination. Two stars are found to be associated with DES~J0225$+$0304; if this is the case, then it leads to the first determination of the systemic radial velocity (RV$_{\rm{sys}}=-150.0\pm7.0$~km~s$^{-1}$). Draco and Sextans are the galaxies with the largest number of members. We focus on Sextans and, for the first time with DESI, trace its stellar kinematics to large radii (up to $\sim$10~half-light radii). We find that the metal-poor population exhibits a higher velocity dispersion and extends to larger radii, whereas the metal-rich population is kinematically colder and centrally concentrated. The metallicity gradient is steeper in the inner regions of Sextans ($\sim -12\times 10^{-3}$~dex~arcmin$^{-1}$ or $\sim -0.36$~dex~kpc$^{-1}$), while almost no gradient in the outskirts, hinting for an ex-situ halo or for an ``outside-in'' star formation. Although DESI [$\alpha$/Fe] ratios for Sextans stars with $\FeH\gtrsim-2.0$ are in line with literature values, those for very metal-poor stars ($\FeH\lesssim-2.0$) present a large scatter and strong anti-correlation with metallicity, warranting a caution for using DESI abundances in this regime. With a less strict selection, we identify 8 ultra metal-poor ([Fe/H]~$< -4$) candidates that require higher signal-to-noise ratio spectroscopic observations to determine their metallicities. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2007.08493 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2007.08493v3 Announce Type: replace-cross Abstract: In the context of the massive secondary object recently observed in the compact-star merger GW190814, we investigate the possibility of producing massive neutron stars from a few different equation of state models that contain exotic degrees of freedom, such as hyperons and quarks. Our work shows that state-of-the-art relativistic mean field models can generate massive stars reaching $\gtrsim 2.05\,\Msun$, while being in good agreement with gravitational-wave events and x-ray pulsar observations, when quark vector interactions and non-standard self-vector interactions are introduced. In particular, we present a new version of the Chiral Mean Field (CMF) model in which a different quark-deconfinement potential allows for stable stars with a pure quark core. When rapid rotation is considered, our models generate stellar masses that approach, and in some cases surpass $2.5\,\Msun$. We find that in such cases fast rotation does not necessarily suppress exotic degrees of freedom due to changes in stellar central density, but require a larger amount of baryons than what is allowed in the non-rotating stars. This is not the case for pure quark stars, which can easily reach $2.5\,\Msun$ and still possess approximately the same amount of baryons as stable non-rotating stars. We also briefly discuss possible origins for fast rotating stars with a large amount of baryons and their stability, showing how the event GW190814 can be associated with a star containing quarks as one of its progenitors. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2605.20660 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.20660v2 Announce Type: replace Abstract: Extremely low-mass white dwarfs (ELM WDs) are helium (He) WDs with masses below $\sim 0.3\ M_{\odot}$, mainly formed through binary interaction. ELM WD binaries typically are formed from two channels, namely the stable Roche lobe overflow (RLOF) channel and the common envelope ejection channel. For ELM WD binaries produced from RLOF channel, the ELM WD mass has a strong correlation with the orbital period, i.e., the so-called WD mass-orbital period relation. However, the observations in the ELM Survey show that the orbital periods of ELM WD binaries from the RLOF channel are typically shorter than the theoretically predicted values. Extra angular momentum loss (AML) may be needed to explain such a phenomenon. In this work, we assumed that part of the transferred mass from the donor is lost at the outer Lagrangian point and simulated the formation of ELM WD binaries. Enhanced AML enables more mass to be lost during thermal-timescale mass transfer, thereby affecting nuclear burning in the transfer phase and producing ELM WDs with distinct internal structures. These structural differences alter the (pre-)He WD mass-radius relation at the end of mass transfer, which in turn shifts the WD mass-orbital period relation downward. These adjustments enable our model to successfully reproduce the majority of observed systems from the relevant survey projects. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11165 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11165v1 Announce Type: cross Abstract: Recently, a chemically depleted young massive stellar population was identified using the spectroscopic catalogue of Gaia DR3. To explain its characteristics, a recent enhanced star formation event, via a third infall occurring within the last 2 Gyr, has been evoked. In this paper we reassess the low alpha sequence of massive stars identified in the Gaia spectroscopic catalog and investigate their presence in other Milky Way spectroscopic survey catalogs. We select massive sequence stars and RGB stars from the Gaia DR3 catalogue using the same filtering strategy adopted in previous chemical cartography studies. These samples are then cross matched with APOGEE DR17, GALAH DR4, and Gaia CNN to enable a detailed comparison of stellar parameters and alpha abundances. Stellar masses are estimated by projecting their atmospheric parameters and infrared magnitudes onto PARSEC isochrones. For the massive star sample, we find large discrepancies in stellar parameters and calcium abundances between Gaia DR3 and the three external surveys. The external catalogues do not show a low ca sequence but rather resemble those of thin disc RGB stars. Other alpha elements (si in APOGEE and GALAH, and mg in GALAH) also do not show depleted values. In APOGEE, however, massive sequence stars with metallicities above -0.5 dex display lower mg abundances. We attribute this to APOGEE's use of macroturbulence velocities calibrated solely on metallicity. Our analysis does not show any evidence for alpha element depletion in massive sequence stars. Alpha abundances of massive sequence stars derived from the Gaia RVS spectra should therefore be used with caution. Nevertheless, the previously proposed three infall chemical evolution models remain plausible: even without a chemically depleted young massive population, scenarios involving only mild dilution could still account for recent star formation episodes. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10283 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10283v1 Announce Type: cross Abstract: The Expanding Box Model (EBM) has been widely employed to simulate multiscale plasma phenomena in the expanding solar wind by transforming the MHD equations to a co-moving, non-inertial frame. However, traditional formulations have suffered from historical ambiguity regarding the physical separation between the co-moving and inertial reference frames, primarily arising from a classical approximation of an invariant magnetic field between them. To resolve this inconsistency, we reformulate the EBM from first principles using a fully covariant approach. Here, we model the expanding solar wind frame as an anisotropic expanding spacetime metric, allowing us to incorporate radial acceleration profiles and differential transverse expansion, ensuring that all physical fields are correctly transformed by expansion. We demonstrate that the mathematical artifacts and structural asymmetries identified in previous EBM-MHD literature are direct consequences of neglecting the tensorial scaling of the magnetic field. Our covariant treatment eliminates these residues, restoring symmetry in the co-moving frame. Projecting our system back into the inertial frame recovers the established observational scaling and analogous physics, clarifies the mathematical distinction between local plasma dynamics and global expansion, and reveals the macroscopic anisotropy of the Parker spiral as a purely geometric projection. Furthermore, linear wave analysis demonstrates that macroscopic acceleration governs the evolution of Alfv\'en wave amplitude, acting either as geometric damping or as an energy source. Further, we write the EBM-MHD system using compressible Els\"asser variables. This formulation provides a consistent and clean foundation for future numerical simulations of accelerating astrophysical plasmas. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10090 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10090v1 Announce Type: cross Abstract: We investigate the crust-core transition in neutron stars using both thermodynamic and dynamical descriptions of the instability. In the thermodynamic approach, the transition is identified through the vanishing of a generalized incompressibility coefficient signaling the onset of a bulk spinodal instability. In contrast, the dynamical approach based on the relativistic random-phase approximation (RPA) incorporates Coulomb screening and finite-size effects that determine the instability at finite wavelength. Using a family of covariant energy density functionals spanning a broad range of symmetry-energy slopes, we show that the dynamical treatment systematically predicts lower transition densities and pressures compared to the thermodynamic approach. We further demonstrate that the RPA instability develops at a characteristic length scale set by the competition among bulk, Coulomb, and surface effects. Most importantly, we show that these differences propagate directly into neutron-star observables. Because the thermodynamic approach predicts larger transition pressures, it generates thicker crusts and significantly larger crustal fractions of the stellar moment of inertia than the dynamical-RPA framework -- with important implications for the interpretation of pulsar glitches and other crust-sensitive neutron-star observables. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.03740 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.03740v1 Announce Type: cross Abstract: While recent JWST observations of mature super-Earths and sub-Neptunes have frequently revealed featureless transmission spectra, their inflated progenitors offer a unique window into understanding their primordial compositions. As part of the KRONOS (Keys to Revealing the Origin and Nature Of sub-neptune Systems) JWST program, we present the NIRISS/SOSS transmission spectrum of V1298 Tau c, a $\sim$23 Myr super-Earth progenitor orbiting a young Solar analog. We detect H$_2$O in V1298 Tau c's atmosphere with a $\log_{10}$ volume mixing ratio of $-1.83^{+0.68}_{-0.77}$, but no additional molecules from these data alone. We find consistent results for the planetary atmospheric properties in both retrievals with and without informed priors on stellar heterogeneities based on the observed stellar spectrum. We infer an atmospheric metallicity [O/H] of $14.8^{+56.0}_{-12.28}\times$ the Solar value. This metallicity is similar to literature measurements for other young planets, including its massive outer companion V1298~Tau~b. In contrast, this measured metallicity is systematically lower than the metallicities of mature planets of similar mass and temperature. Altogether, these results provide tentative but growing evidence that the exoplanet mass--metallicity relation evolves with planetary age. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11121 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11121v1 Announce Type: new Abstract: Models of stellar structure and evolution describe the global and internal properties of stars throughout their lifetimes and are indispensable for studies of stellar clusters and Galactic evolution. However, most 1D evolutionary calculations rely on simplified treatment of convection, resulting in inaccurate near-surface structures and non-negligible uncertainties in the predicted fundamental parameters of low-mass stars. In a series of previous works, a novel approach was developed to couple 1D stellar interior models with 3D model atmospheres throughout the evolutionary calculation. This 1D-3D coupling method makes predicted stellar properties effectively independent of the mixing-length parameter. To expand this framework to ensemble studies of stars and age determinations of clusters, we present the GASTAG stellar evolutionary tracks and isochrones constructed using the 1D-3D coupling approach. Comparing effective temperatures from the APOGEE-Kepler catalog with GASTAG predictions, we find the theoretical temperatures are cooler by about 70 K near solar metallicity. Our isochrones are compared with observed color-magnitude diagrams of star clusters spanning from $\rm [Fe/H] = 0.3$ to $-1.9$. In all cases, the synthesized and observed diagrams agree excellently in the main-sequence, turn-off, and subgiant regions, while isochrones predict systematically cooler red giant branches. Taking these independent findings together reveals that the temperature mismatch is most likely due to deficiencies in stellar models. Because GASTAG is constructed using a method that substantially reduces uncertainties associated with surface boundary conditions and the mixing-length parameter, the difference between modeling and observation can be more confidently attributed to other ingredients in the models, such as $\alpha$-element abundances or uncertainties in low-temperature opacities. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.11006 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11006v1 Announce Type: new Abstract: Stellar clusters are crucial tools for studying the age, spatial distribution, dynamics, kinematics, and chemical composition of different Galactic stellar populations. In this work, we used red giant stars from open clusters to better understand the extra-mixing process through the CNO abundances and $^{12}$C/$^{13}$C, $^{16}$O/$^{17}$O and $^{16}$O/$^{18}$O isotopic ratios determined using high-quality spectra in the visible and near-infrared regions. We analysed the radial velocities and chemical composition of 22 K-type giant stars from nine open clusters (NGC188, NGC2682, NGC3680, NGC5822, IC4756, NGC6633, NGC3532, NGC6281, and NGC5460). High-resolution and high signal-to-noise spectra of stars in the NGC188 cluster were obtained with the ESPaDOnS spectrograph at the CFHT in the visible region. The stars in the other clusters were observed with the CRIRES spectrograph at the VLT. We used IRAF to compute radial velocities and Turbospectrum and MOOG for the chemical analysis. The values obtained for the radial velocities and abundances of the sample are similar to those found in the literature. The results in the visible and infrared support the occurrence and predicted mass dependence of thermohaline mixing on the red giant branch and of rotation-induced mixing on the main sequence. Variations of the initial abundances of $^{17}$O and $^{18}$O may be needed to explain the dispersion of the oxygen isotopic ratios in red giant stars. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10981 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10981v1 Announce Type: new Abstract: V838 Mon is the remnant of a stellar merger that occurred in 2002. Twenty-four years after the merger, the remnant closely resembles a red supergiant, but its luminosity is sustained by core H burning and continued contraction toward hydrostatic equilibrium. In late 2025, the system entered the deepest dimming event observed since 2006. We characterize the 2026 dimming using multiband photometry and high-resolution spectroscopy spanning from the dimming minimum through the recovery phase. The photometric color evolution during the dimming can be well reproduced by dust extinction with $A_V=1.26$ mag and $R_V=1.8$, consistent with a transiting clump of freshly formed circumstellar dust composed of small silicate or alumina grains. The photospheric effective temperature changed by no more than ~200 K during the event. During the recovery phase, H recombination lines from the Balmer, Paschen, and Brackett series appeared in emission, with anomalous line ratios matching those of pulsating Mira stars near maximum light. These features are interpreted as arising from a sub-photospheric pulsation shock. Simultaneously, low-ionization metal lines appeared blueshifted by 90 km/s relative to the stellar rest frame, tracing shock-affected gas on the near side of the stellar disk. The spectroscopic sequence suggests that the 2026 dimming was itself triggered by a preceding pulsation shock that occurred earlier in 2025. We present the first observational evidence for pulsations in a stellar merger remnant. Twenty-four years after the coalescence, V838 Mon exhibits pulsation shocks qualitatively identical to those of red supergiants and Mira stars, confirming predictions of pulsational instability in post-merger objects. A further dimming event, triggered by the observed shock, is predicted to start in northern summer 2026. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10512 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10512v1 Announce Type: new Abstract: Due to solar wind turbulence, Parker spirals are stochastic. The dispersion of magnetic field lines is described by a convection-diffusion equation for the field line density distribution which is a function of the two heliographic angles in addition to the radial distance. Taking into account the radial evolution of the turbulence, the three-dimensional convection-diffusion equation is transformed into a set {of} stochastic differential equations which is solved numerically using both a forward and backward formulation. By tracing a large number of stochastic Parker spirals, the field line density distribution is constructed at any point in the heliosphere. It is shown that the angular part of the distribution function can be well-fitted by a two-dimensional Gaussian with standard deviation close to $ 25^{\circ}$ at 1 AU. The simulations also confirm that the magnetic field lines are underwound, on average, for strong enough turbulence intensity. Applying the backward approach, magnetic field lines are traced from an observer at 1 AU back to the Sun, quantifying the probability of magnetic connection when interplanetary turbulence is accounted for. It is shown that the angular uncertainty of $\sim 25^{\circ}$ is sharply reduced to $\sim 4^{\circ}$ when the field lines are traced back to the solar wind source surface from 0.25 AU. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10506 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10506v1 Announce Type: new Abstract: Recent multi-wavelength observations of solar flares have provided new constraints on the physical origin of quasi-periodic pulsations (QPPs). In an X-class flare, we detect a short-lived $\sim$5-minute QPP simultaneously in hard X-rays, extreme-ultraviolet (EUV), and soft X-ray emissions, exhibiting a clear phase-drifting behavior with emitting plasma temperature. Based on phase-resolved timing analysis, it is found that (i) the QPPs in all diagnostics share nearly identical oscillation periods, (ii) a systematic temperature-dependent phase drifting is present, with the phase delay relative to the hard X-ray emission increases systematically from the hottest to cooler EUV channels, and (iii) the QPP persists for only a few cycles during the impulsive phase. These properties imply that periodic magnetic reconnection, possibly triggered by the leakage of 5-minute oscillations from the lower atmosphere, modulates the non-thermal electrons responsible for the leading Hard X-ray QPPs. Subsequently, plasma heating and cooling processes manifest sequentially across passbands with different temperature responses, resulting in the observed temperature-dependent phase drifting. These results provide novel observational evidence supporting the use of multi-temperature, multi-wavelength phase relationships to constrain the temporal evolution of flare energy release and the origins of QPPs. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.10505 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10505v1 Announce Type: new Abstract: A part of the magnetic energy released during a flare is transported to the lower atmosphere. High-resolution observations show that flare ribbons, sites of energy deposition at the footpoints of flaring loops which appear bright in the chromosphere and transition region, are structured on small spatial scales on the order of 100 km. Based on idealized numerical models of flares it is suggested that the ribbon fine-structures could originate from a tearing instability and the development of plasmoids in current sheets. Here we report on Fe I 5250.6 {\AA} and Mg I b2 5173 {\AA} spectral observations of a solar flare from the Tunable Magnetograph onboard the SUNRISE III balloon-borne mission that reveal an intricate link between the flare ribbon structure and the ambient chromosphere. We identified uncombed chromospheric loops and non-flaring fine-structures that are interspersed among brighter flare ribbon threads. These loops remain stable on timescales of minutes. Spectral lines from these regions show reduced emission or self-reversal in the line core compared with the immediately adjacent flare ribbons. We discuss the potential role of these structures in the onset of a flare. Furthermore, we suggest that irrespective of the complexities in the flaring current sheet, uncombed chromospheric loops and nonflaring fine-structure might play a role in spatially modulating the flare energy deposition in the lower atmosphere. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09997 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09997v1 Announce Type: new Abstract: The formation histories of halos set the baseline rate at which galaxies accrete gas over cosmic time. While a number of models describe these histories and their derivative, the mass accretion rate (MAR), a simple and universal formula has remained elusive. Here we measure the median MARs and half-mass formation times of halos in dark matter-only and hydrodynamical simulations, in extremely different cosmologies ($\Lambda$CDM and Einstein-de Sitter), and across a wide range of redshifts ($z = 0$-$14$). We confirm that MARs increase with mass and redshift, and that they are virtually identical in hydrodynamical and dark matter-only simulations. We show that MARs are accurately described by a universal six-parameter function of three physical variables: the peak height $\nu$, the slope of the linear power spectrum $n_{\rm eff}$, and the effective linear growth rate $\alpha_{\rm eff}$. A complementary two-parameter fit for the formation redshift improves on the function of Lacey \& Cole by fixing one parameter to its physical value and adding a dependence on $n_{\rm eff}$. Our model is broadly consistent with some prescriptions from the literature but provides a larger range and higher accuracy at high redshifts and low masses. Our fitting functions are implemented in the publicly available \textsc{Colossus} toolkit. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10006 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10006v1 Announce Type: new Abstract: The Standard Model of particle physics contains a diverse set of particle species, motivating the possibility of a similarly complex dark sector. Here we study two-component dark matter (DM) mixtures, in which one component behaves as standard CDM while the other suppresses the formation of small-scale structure, either through an astrophysically relevant de~Broglie wavelength (fuzzy DM; FDM) or collisional damping from temperature-independent scattering (interacting DM; IDM). Using the observed population of Milky Way satellite galaxies, we derive new leading constraints on the parameter spaces of mixed FDM and of mixed IDM coupled to photons ($\gamma$-DM), neutrinos ($\nu$-DM), or baryons ($p$-DM), for beyond-CDM fractions down to $50\%$. We require that the linear matter power spectra of allowed models remain less suppressed than a constrained reference model. The resulting $95\%$ confidence bounds on FDM mass and IDM cross section weaken systematically with decreasing fraction, following distinct power-law scalings. At $50\%$ fraction, IDM cross section bounds weaken by a factor of $\sim$2--6 and FDM mass bounds by $\sim$1.5, relative to the $100\%$ case. We forecast that idealized future satellite surveys, which adopt approximate LSST sensitivity thresholds, can improve these $100\%$ bounds by a factor of $\sim$1.6--14 for IDM and $\sim$3 for FDM. Self-consistent cosmological simulations of mixed DM scenarios will be essential to more robustly characterize the degeneracy between particle physics parameters and fractional contribution, to extend constraints to lower fractions, and to identify signatures beyond satellite abundance to further inform these models. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10020 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10020v1 Announce Type: new Abstract: We present Manticore-Deep, a high-resolution Bayesian field-level inference of cosmic large-scale structure spanning a comoving volume of $(4~h^{-1}\mathrm{Gpc})^{3}$ out to $z \approx 0.7$, at ${\sim}4$~Mpc/h resolution. Building on the inference framework established in the companion Manticore-Local analysis (P1), Manticore-Deep jointly constrains five galaxy redshift surveys (2M++, 6dFGS, 2dFGRS, SDSS, and BOSS) within a single hierarchical Bayesian framework using the BORG algorithm. The method infers initial conditions that are evolved forward under gravitational dynamics, delivering a full posterior ensemble of three-dimensional density and velocity fields that causally reproduce the observed large-scale structure. A novel tiled inference strategy makes this computation feasible, extending the reconstructed volume by more than an order of magnitude beyond P1. The posterior realisations are statistically consistent with LCDM, exhibiting Gaussian, isotropic initial conditions and evolving into late-time structures that reproduce the expected $z=0$ matter power spectrum, bispectrum, and halo mass function across the resolved scales tested. We validate the physical fidelity of the reconstruction through two independent, template-free posterior-predictive tests against observations not used in the inference. Cross-correlation of the reconstructed matter field with the Planck PR3 CMB lensing map yields a conservative cumulative detection significance of 7.4$\sigma$, while velocity-weighted stacking of $64750$ galaxy clusters on the Planck 217~GHz map produces a kSZ detection at $3.5\sigma$, with a model-independent approach--recession split confirming that the inferred velocities are statistically aligned with the true cluster motions. As a case study, we show that the BOSS Great Wall is recovered as a ${\sim}3\sigma$ overdensity consistent with LCDM across all posterior realisations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10023 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10023v1 Announce Type: new Abstract: Accurate posterior estimation is central to scientific inference, as uncertainties determine what can be reliably learned from observational data. While Markov chain Monte Carlo methods provide asymptotic convergence guarantees, they are computationally demanding in high-dimensional settings. Neural network-based generative models for entire discretized 3D fields enable fast amortized inference but often lack convergence guarantees and principled accuracy assessment. Using Hamiltonian Monte Carlo to obtain reference posterior samples, we conduct a controlled field-level evaluation of an implicit generative model (Stochastic Interpolants) and an explicit likelihood-based model (GLOW normalizing flows). This comparison, unavailable in typical applications, enables the detection of posterior geometry failures that standard metrics cannot capture. As a case study, we consider the cosmological inverse problem of inferring cosmic initial conditions from present-day large-scale structure. To match the precision of modern cosmological data, this problem increasingly relies on complex, non-linear, and non-differentiable simulators, which are incompatible with gradient-based inference frameworks. Generative models offer a route to address these challenges, provided their inferred posteriors are reliable. In this work, we show that matching posterior means, marginal distributions, or achieving high cross-correlation does not imply correct uncertainty structure, as revealed by posterior variance fields and sample-based evaluations. Through this work, we aim to raise awareness of the challenges of uncertainty estimation in high-dimensional field-level settings, highlighting the importance of careful design and validation of neural generative approaches for scientific applications. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10024 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10024v1 Announce Type: new Abstract: Learning cosmology from galaxy surveys requires large suites of simulations spanning the cosmological and astrophysical parameter space, yet hydrodynamical simulations of galaxy formation remain prohibitively expensive. Semi-analytic models offer an inexpensive, physically grounded alternative, but still require halo merger trees from $N$-body simulations, and densely sampling cosmological parameters in sufficient volume remains expensive. We address this by extending cosmological rescaling to operate directly on merger trees and applying it in the $\Omega_{\rm m}$-$\sigma_8$ plane, running the Santa Cruz semi-analytic model for galaxy formation on the rescaled trees to produce galaxy populations across new cosmological and astrophysical parameters at negligible additional cost. A novel halo-profile-based correction, controlled by a single free parameter, suppresses systematic bias in rescaled halo masses to below the per cent level. We apply the method to parameter estimation of $\Omega_{\rm m}$ and $\sigma_8$ given either the stellar mass function or the two-point correlation function, finding that as few as 64, and potentially fewer, base $N$-body simulations, rescaled to $\sim1000$ training samples, match the accuracy of 750 dedicated $N$-body simulations; rescaling to 3200 realisations improves the prediction of $\Omega_{\rm m}$ by $\sim25\%$. Rescaling all merger trees from a single CAMELS-SAM $N$-body simulation costs $\sim0.1$ CPUh, compared to several thousand CPUh to run the simulation itself. We demonstrate a practical route to obtaining predictions of galaxy summary statistics across cosmological and astrophysical parameters, even with a relatively small number of base $N$-body simulations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10028 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10028v1 Announce Type: new Abstract: We present a suite of 50 high-fidelity simulations of Coma cluster analogues constructed from BORG/MANTICORE constrained initial conditions and evolved with the IllustrisTNG galaxy formation model. Regions predicted to form massive clusters comparable to Coma in mass and environment are selected and followed through cosmic time, producing realistic galaxy populations and intracluster medium properties. The ensemble captures both cosmic variance and uncertainties in the local initial conditions, providing a statistically robust framework for interpreting Coma in a cosmological context. We focus on direct comparisons with observed thermodynamical profiles of the intracluster medium. Specifically, we extract X-ray surface brightness profiles from the simulated clusters and confront them with measurements from eROSITA, as well as compute the thermal Sunyaev--Zel'dovich effect via integrated Compton-$y$ profiles for comparison with Planck satellite data. The simulations reproduce the broad shape and normalisation of both observables, while also highlighting the range of scatter expected from environmental and assembly history differences. This enables us to assess how feedback processes, merger activity, and large-scale environment shape observable cluster properties. Our results demonstrate that combining constrained cosmological initial conditions with state-of-the-art galaxy formation physics provides an effective strategy for generating targeted, observation-driven analogues of specific clusters. The resulting dataset offers a valuable resource for testing models of intracluster medium physics, calibrating scaling relations, and interpreting upcoming joint X-ray and Sunyaev--Zel'dovich observations of nearby massive clusters. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10038 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10038v1 Announce Type: new Abstract: We present a new set of 1,192 cosmological simulations as part of the CAMELS project, in which a space of 35 cosmological, astrophysical, and numerical parameters is explored around the fiducial IllustrisTNG model. The volume of each of these simulations is (50Mpc/h)^3, eight times larger than that of previous CAMELS simulations. This provides lower sample variance as well as access to more massive halos and more diverse environments. We focus this work on exploring the advantages these differences provide for parameter inference powered by neural networks. We generate training sets based on the matter power spectra, projected maps of the volumes, graphs representing galaxy spatial distributions, and thermodynamical properties of massive halos. We employ multilayer perceptrons, convolutional neural networks, graph neural networks, and Gaussian processes, respectively, to extract information on the simulation parameters from these inputs while comparing systematically to analogous results from our previous generation of (25Mpc/h)^3 simulations. We generally find that the new, larger volumes produce tighter marginal constraints on the parameters, to degrees that vary between the different inputs. The improvements, however, scale more weakly than with the square root of the increase in the amount of data (i.e., physical volume). We interpret this as originating either from information loss due to mode coupling or from complex degeneracies in parameter space. We also discuss the effects on statistics of the intergalactic medium temperature from four new parameters that are varied in these simulations, which control the amplitude and timing of the ionizing background radiation. We publicly release the simulation outputs and ancillary data at https://camels.readthedocs.io. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10483 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10483v1 Announce Type: new Abstract: Merging galaxy clusters represent the ideal laboratory to test our understanding of the large scale structure formation history and the processes involved. While many merging clusters have been identified, only a limited number have been studied in detail through multi-wavelength analysis and dynamical reconstruction, this type of analysis being crucial to account for projection degeneracies. This work investigates the merger dynamics of the massive and complex cluster MACS0600 using high spatial, $\sim 15$ arcsec, radio and X-ray datasets in combination with ancillary optical data. We analyze the cluster morphology and the thermodynamic properties of the intracluster medium (ICM) through XMM-Newton and Chandra X-ray observations, and explore the non-thermal component via diffuse radio emission observed with Meerkat. We find a disturbed X-ray morphology with multiple substructures and a clear offset between the bulk of the radio emission and the X-ray peak. At the location of the X-ray peak, we detect a compact cool core surrounded by hotter gas and associated with a surface brightness discontinuity consistent with a cold front. The central region exhibits elevated temperatures and hosts most of the diffuse radio emission, suggesting merger-driven turbulence. Optical data further support a relative motion between the cool core and the main cluster along the line of sight. We conclude that MACS0600 is undergoing a merger in which a compact cool core has crossed the main, more massive cluster without being completely disrupted, while significantly perturbing the surrounding ICM. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10597 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10597v1 Announce Type: new Abstract: We test gravity by exploiting the synergy between the gravitational potential decay rate ($\mathit{DR}$) and complementary structure-growth probes: these observables respond to MG parameters with different degeneracy directions, so their combination yields stronger constraints than any single probe. We adopt the tomographic $\mathit{DR}$ measurements reported in \citep{2025ApJ...982...99D} and combine them with CMB-lensing-tomography $\Sigma_8$ constraints and $f\sigma_8$ measurements from DESI DR1 full-shape analyses and the DESI peculiar-velocity field. We apply this joint data vector to two representative frameworks: phenomenological parameterizations and the Effective Field Theory (EFT) $\alpha$-basis. For the phenomenological form $P_{\rm MG}(a)=1+P_{{\rm MG},0}\,\Omega_{\rm DE}(a)/\Omega_{\rm DE}(0)$, where $P_{\rm MG}$ denotes $\mu$, $\eta$, or $\Sigma$, we obtain $\mu_0=0.09\pm0.35$ and $\Sigma_0=0.01\pm0.06$. Compared to the measurements combination $\Sigma_8+f\sigma_8$, including $\mathit{DR}$ tightens the constraint on $\Sigma_0$ by a factor of $\sim2$. For the $(\mu_0,\eta_0)$ case we find $\mu_0=0.06^{+0.17}_{-0.23}$ and $\eta_0=-0.03^{+0.36}_{-0.46}$; relative to $\Sigma_8+f\sigma_8$, adding $\mathit{DR}$ improves the constraints on both parameters by a factor of $\sim1.5$. In the EFT $\alpha$-basis, adopting the parameterization $\alpha_i(a)=c_i\,\Omega_{\rm DE}(a)$ with $i\in\{{\rm M,B}\}$, we find $c_{\rm M}=0.64^{+0.32}_{-0.72}$ and $c{\rm B}=0.31^{+0.19}_{-0.29}$. The corresponding EFT uncertainties are about a factor of $\sim2$ smaller than those reported in \citep{2025JCAP...09..053I}, which combined DESI full-shape and BAO measurements with DES-SN5YR and CMB data. These results demonstrate the capability of $\mathit{DR}$ and the necessity of including the $\mathit{DR}$ measurements in testing gravity. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10679 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10679v1 Announce Type: new Abstract: Stage IV surveys such as LSST will probe deeply into the nonlinear regime, where systematic effects from galaxy bias and baryonic feedback become dominant and poorly constrained nuisance parameters can lead to degeneracies. In this work we present a $3\times2$pt analysis for LSST Y1 and Y10 data using the BACCO emulator for modelling both the hybrid-effective field theory (HEFT) for nonlinear galaxy bias and the baryonic feedback using the baryonification mechanism. We aim to find a balance between model complexity and scale cuts, with particular attention to parameter degeneracies and baryonic feedback effects on the galaxy--matter and galaxy--galaxy power spectra. First, we find that a linear bias model delivers percent-level, unbiased constraints on $\Omega_{\rm m}$ and $\sigma_8$ only up to $k_{\rm max}=0.1\,h/$Mpc, but pushing to smaller scales requires a perturbative approach. Second, we compare HEFT with a minimal bias variant with fixed higher-order terms, and find that the latter is unbiased in $\Lambda$CDM even at $k_{\rm max}=0.7\,h/$Mpc. We show that higher-order bias can mimic baryonic suppression, but baryons cannot reproduce the full range of higher-order bias behaviour. Third, we find that a detection of the total neutrino mass $M_\nu$ is possible for both Y1 and Y10 for $k\geq0.3\,h/$Mpc, at least when photo-$z$ uncertainties and related nuisance parameters are precisely known. However, the specific measured value is not robust across equally plausible mock scenarios: the inferred $M_\nu$ can be significantly biased by adopting the minimal bias model. The entire analysis is conducted with a new independent, open source pipeline (MGL) that we present for the first time in this work. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10863 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10863v1 Announce Type: new Abstract: During the radiation-dominated era of the Universe, a primordial magnetic field undergoes a turbulent decay while its length scale increases due to an inverse cascade. At later times, the size of the largest processed eddy scales with the Alfv\'en speed and it describes an isochrone that moves toward larger scales with increasing time. Different magnetogenesis mechanisms produce different initial length scales and field strengths, independently of the nominal generation time. However, we show that for any initial field, a proper time can be determined such that the isochrones at early times are parallel to those at late times. We use two-dimensional numerical simulations of decaying MHD turbulence and vary the initial position of the peak of the magnetic energy spectrum. In this case, the evolution is governed by the conservation of anastrophy. A fit to the Alfv\'en time yields an accurate estimate of the factor by which the decay time is longer than the Alfv\'en time, while the offset in the fit provides an additional estimate of the proper time that needs to be added to the nominal time since the beginning of each simulation. We also find that the presence of an initial velocity field of realistic strength helps producing a more straight track. The magnetic field parameters lie on universal isochrones even for early times. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09938 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09938v1 Announce Type: cross Abstract: The Vera C. Rubin Observatory began commissioning its camera, LSSTCam, in April 2025, with the Legacy Survey of Space and Time (LSST) scheduled to start in 2026. A primary science goal is constraining Dark Energy through weak gravitational lensing of the large-scale structure (cosmic shear). After a full year of data from LSST, these measurements are expected to reach precision comparable to recent Dark Energy Spectroscopic Instrument (DESI), providing an independent test of hints that Dark Energy may evolve over time. However, cosmic shear requires exquisite control of instrumental systematics. This proceeding presents an overview of the Rubin Observatory commissioning -- the successes achieved and the systematic issues we are working to resolve. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09945 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09945v1 Announce Type: cross Abstract: The generalized cosmological time (GCT) framework introduces a modified lapse function, N(t)\propto a^{b/4}, as a geometric extension of the standard FLRW description. Like other departures from $\Lambda$CDM, such constructions must remain compatible with the observed stability of local gravitational and laboratory physics. In scalar--tensor theories, this compatibility is usually achieved through dynamical screening mechanisms that suppress additional degrees of freedom in dense environments. In this work, we examine whether a locally static spacetime region can be consistently embedded within a cosmological background described by a time-dependent lapse. By embedding a static Schwarzschild interior into an expanding GCT--FLRW exterior, the Israel junction conditions are used to determine the class of background expansions that admit such a matching in the absence of a thin shell. The continuity of the extrinsic curvature yields a Friedmann-type relation that coincides with the GCT background equations of motion. This relation should be interpreted not as a new dynamical equation, but as a geometric consistency condition (GCC) associated with the matching of the two spacetime regions. In this sense, the junction does not introduce new dynamics, but provides a GCC under which a region with fixed local clocks can be embedded in a cosmological spacetime with an evolving lapse. Therefore, the analysis clarifies how locally static gravitational systems can remain compatible with a cosmological time normalization that differs from that of local proper time while preserving the standard description of local physics. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09968 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09968v1 Announce Type: cross Abstract: High-frequency gravitational waves (HFGWs) in the MHz to GHz regime can convert into radio photons in the presence of astrophysical magnetic fields through the inverse Gertsenshtein effect. We show that existing radio telescopes like CHIME and FAST are excellent tools for detecting HFGW sources, significantly outperforming many existing experiments at detecting primordial black hole (PBH) mergers, the most realistic sources of transient HFGWs. Radio telescopes are also uniquely sensitive to sources of monochromatic HFGW emission, such as ultralight boson clouds formed through superradiance around PBHs, and are likely to have excellent sensitivity to generic sources of detectable HFGWs. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09981 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09981v1 Announce Type: cross Abstract: We present a systematic X-ray analysis of the narrow-line Type 1 quasar PHL 1811, which has long been regarded as the prototype of intrinsically X-ray weak quasars. A critical breakthrough came with the first detection of a bright X-ray flare from this source by the Einstein Probe (EP) in 2024. We utilize archival X-ray observations spanning 2001-2024, including the post-flare EP and Swift data. We confirm that PHL 1811 shows X-ray weakness factors $f_{\rm weak} \approx 23$-179 across all epochs before 2024. The 2024 EP flare marks the first detection of an X-ray nominal state with $f_{\rm weak} \approx 0.63$, followed by a rapid flux decline. We identify three key observational signatures that strongly support heavy obscuration: (1) a significant hard X-ray excess above $\approx5$ keV in the 2015 XMM-Newton spectrum; (2) relatively flat spectral shapes in two Swift observations; and (3) transitions between X-ray nominal and multiple X-ray weak states without corresponding optical/infrared variability, consistent with expectations from obscuration by a clumpy dust-free absorber. Fitting with a partial-covering obscuration model reproduces all multi-epoch spectra well. The observed steep spectra are dominated by a small leaked/scattered fraction of the intrinsic continuum, and variability is driven by changes in the leakage fraction and column density. Our results strongly favor the scenario where PHL 1811 is obscured by a radiatively driven accretion-disk wind from super-Eddington accretion, unifying PHL 1811 with the broader population of super-Eddington accreting AGNs under a single obscuration framework. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10005 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10005v1 Announce Type: cross Abstract: We have simulated Ly{\alpha}, H{\alpha}, H{\beta}, [OII], and [OIII] intensity maps which are observable by SPHEREx during cosmic reionization. We simulate these intensity maps including all significant sources of emission for each line, and include radiative transfer for the Ly{\alpha} intensity maps. We also include a simple model of dust extinction based on observations of galaxies at z 6 will require more sensitive instruments, such as the Cosmic Dawn Intensity Mapper. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10013 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10013v1 Announce Type: cross Abstract: Primordial black holes (PBHs), possibly formed from the collapse of early universe perturbations, will evaporate via Hawking radiation with a lifetime comparable to the age of the universe, if their mass is $O(10^{14})$ g. Such black holes can contribute to the observed gamma-ray fluxes in the MeV and GeV range. Using the observed extragalactic gamma-ray background (EGRB) from the \textit{Fermi} Large Area Telescope, the \textit{EGRET}, and the \textit{COMPTEL} telescopes that cover gamma-ray energies from 0.5 MeV to 1 TeV, we evaluate limits on the abundance of PBHs with masses of $10^{14}$ to $10^{17}$ g. We study both monochromatic and extended mass distributions of PBHs. To model the EGRB spectrum, we calculate the contribution from extragalactic sources including blazars, star-forming galaxies and radio galaxies and also account for ultra-high-energy cosmic rays that produce gamma rays when interacting with the infrared background. Our EGRB modeling uses information from the \textit{Fermi} gamma-ray point sources catalog, from observations at X-rays, the visible spectrum, the infrared and radio waves, and also accounts for modeling uncertainties and variations on the properties within each class of these sources. Moreover, we use recent work on the modeling of the PBHs' gamma-ray emission, that includes the direct Hawking radiation, gamma rays produced in the hadronization and decay of unstable particles, final state radiation and gamma rays from pair annihilations in the interstellar medium. As the contribution of final state radiation and the annihilation of positrons enhances the low-energy part of the produced gamma-ray spectra from PBHs, we find that the EGRB observations can set the tightest limits on their abundance among all indirect dark matter probes, within the mass range of interest.[abridged] Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10017 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10017v1 Announce Type: cross Abstract: We provide the cosmic-ray (CR) fluxes of antiprotons and antideuterons produced by the Galactic annihilation or decay of weak-scale dark matter (DM) particles of masses in the range from a few GeV to 100 TeV. We estimate these fluxes based on the updated models for the propagation of charged particles in the Galaxy and using the improved $\bar{p}$ and $\bar{d}$ spectra provided by $\texttt{CosmiXs}$. For the updated propagation models we consider the MIN/MED/MAX sets under the new SLIM/BIG/QUAINT schemes. We treat the Galactic propagation in a semi-analytic way including different possible effects such as spatial diffusion, energy-losses, convection and diffusive reacceleration. For the DM distribution in the Galactic halo we consider NFW, Einasto and Burkert profiles with the most updated parameters. Moreover, we also incorporate the latest models for the inelastic cross-sections of $\bar{p}$ and $\bar{d}$ based on ALICE data. We validate our calculations with those available in the literature or those obtained from other publicly available numerical packages. We compare the CR fluxes obtained in this work with those provided previously by $\texttt{PPPC4DMID}$ which were based on old propagation scenarios. We find that the CR fluxes obtained here with the new propagation models are much more robust (compared to the older ones) under the variation MIN - MAX. We also discuss the impact of this in the improvement of the discovery potential of a possible DM signal in the light of the present and upcoming CR observations. We provide all our results for the DM-induced interstellar CR fluxes in a tabulated format (for the kinetic energy range 0.1 GeV - 100 TeV) in the $\texttt{GitHub}$ repository of the newly created $\href{https://github.com/CosmiXsPPPC}{\texttt{CosmiXsPPPC}}$ project. The results are ready to be used for studies related to DM indirect searches. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10026 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10026v1 Announce Type: cross Abstract: We present a new subgrid model for interstellar gas evolution in cosmological simulations of galaxy formation, based on the pressure-regulated, feedback-modulated (PRFM) theory of star formation. In contrast to the empirically pegged star formation prescriptions employed in current cosmological simulations, the PRFM model links the local star formation rate to the dynamic balance achieved in galactic interstellar gas between gravity and stellar feedback effects. With this formulation, both the star formation efficiency and the effective equation of state may be directly calibrated using numerical simulations, such as TIGRESS, which resolve physics of the interstellar medium and star formation at parsec scales. We develop, and implement in the Arepo moving-mesh code, two complementary classes of the subgrid model: a volumetric version (PRFM-vol) applicable when the gas disk scale height of a galaxy is numerically resolved in a simulation, and an integrated version (PRFM-int) that reconstructs the mid-plane density and pressure from vertical equilibrium considerations when the true gas scale height cannot be numerically resolved. Using isolated Milky-Way-like disk simulations across mass resolutions $10^5$-$10^7~{\rm M}_\odot$, we show that both implementations yield shorter gas depletion times than the IllustrisTNG prescription, especially in regions where pressure and density are large. At high resolution, PRFM-vol and PRFM-int agree closely with each other and with TIGRESS for the star formation rate; PRFM-int remains robust at all resolutions tested. These results demonstrate that PRFM-derived subgrid prescriptions provide a physically grounded and numerically stable framework for star formation across the dynamic range of galaxy formation simulations, paving the way for future cosmological applications. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.10027 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10027v1 Announce Type: cross Abstract: Dust attenuation is a major source of systematic uncertainty in both SED fitting and forward modeling of galaxy populations, yet the functional form used to parameterize attenuation curves has received surprisingly little systematic scrutiny. Particular unanswered questions include: how many free parameters are genuinely needed, and which analytic expression best captures the full diversity of attenuation curve shapes in galaxies across cosmic time? Using a large library of synthetic attenuation curves from TNG50 and TNG100 galaxies post-processed with the SKIRT radiative transfer code using three dust mixtures (Milky Way, SMC, and stellar dust), we show via Information-Ordered Bottleneck analysis that exactly four parameters are needed to capture the diversity of attenuation curves. Guided by this result, we use symbolic regression to derive a new, interpretable four-parameter attenuation model that outperforms existing parameterizations in recovering both attenuation curves and emergent fluxes across all dust mixtures explored. The four parameters of this model have clear physical interpretations: UV bump strength, FUV slope, UV-bump transition curvature, and large-scale optical slope. Their correlations with galaxy properties are primarily regulated by star-formation rate surface density, metallicity, and stellar-dust geometry, and are largely preserved across dust mixtures -- except for the bump-sensitive parameters, which retain a stronger dependence on grain composition. We further provide symbolic-regression scaling relations linking all four parameters to quasi-observable galaxy properties, offering a physically motivated route to assign realistic attenuation curves in SED fitting and forward modeling without radiative-transfer calculations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09979 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09979v1 Announce Type: new Abstract: The formation mechanism(s) of substellar objects, such as brown dwarfs and free-floating planets, remains an ongoing puzzle in stellar and planetary physics. Recent observational and theoretical work points towards a star-like origin for brown dwarfs, though several authors posit that they could form like planets in a circumstellar disc, and then subsequently be ejected into a star-forming region or the Galactic field. Recently, JWST observations have discovered nine substellar objects in the IC348 star-forming region with a spectral absorption feature at 3.4$\mu$m from an unidentified aliphatic hydrocarbon, detected for the first time in planetary atmospheres outside of the Solar System. It is unclear whether these hydrocarbon absorption features in these 'H-type' objects indicate a different formation mechanism compared to more massive brown dwarfs. We quantify the spatial distribution of these objects and find they are indistinguishable from the spatial distribution of stars and other brown dwarfs in IC348. We use N-body simulations to test whether the H-type objects could have formed as planets in circumstellar discs and then been dynamically ejected by stellar fly-bys. We show that a similar number of free-floating planets could be produced if those planets initially resided at ~5au from their host stars. However, these free-floating planets have a much more dispersed spatial distribution than the stars and brown dwarfs, inconsistent with the spatial distribution of the H-type objects in IC348. We therefore conclude that the H-type objects are unlikely to have a planetary-like origin. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10012 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10012v1 Announce Type: new Abstract: Non-ideal magnetohydrodynamic simulations of protoplanetary disks show a plethora of complex gas structures, including winds, rings, and gaps. These affect dust transport and help form dust traps, which are essential for planetesimal formation. Although studies have explored the evolution of dust in such systems, they have done so either in 1D or without dust coagulation, and the effect of such systems on dust growth is still an active area of research. This work aims to investigate the effect of a complex gas flow architecture on global dust evolution, including dust growth and transport. We examine the timescales of different processes impacting dust evolution and discuss prospects of forming planetesimals. We post-process gas velocity output from a 2D non-ideal magnetohydrodynamic simulation using a 2D (r-z) Monte Carlo dust coagulation code to perform global simulations of dust growth and evolution. We perform three runs, one with a typical steady-state disk and two with the gas velocity from the MHD simulation, where we vary the fragmentation velocity. Our results show that the advection of small particles by the gas due to strong gas velocities can play an important role in setting the dust size distributions around protoplanetary disks. The gas flow structure has a transition region, and this region acts as a location of a dust pile-up, increasing the pebble-to-gas ratio by a factor of 2.5 when compared to the steady state disk. Lowering the fragmentation velocity improves the stability of the pile-up, but the pebble concentration is not as high. This scenario acts as a way to form a dust trap in a disk without a pressure bump. We discuss the possibilities for planetesimal formation in such a trap. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10624 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10624v1 Announce Type: new Abstract: The HD 135344B (SAO 206462) disk exhibits strong signposts of planet formation. ALMA images in the sub-mm revealed a gap-crossing dust filament whose position coincides with a twist detected in the scattered-light spiral structure. Analysis of the spirals in polarized light also hints at a spiral-driving protoplanet in the sub-mm gap. We aim to study the spirals dynamics, as well as the twist, over a 10-year baseline, in different bands. We also seek to assess the authenticity of a recently claimed candidate protoplanet. We use high-fidelity post-processing algorithms such as IPCA to minimize the biases induced by ADI on extended sources and analyze archival VLT/NACO, VLT/SPHERE, VLT/ERIS and JWST/NIRCam datasets to obtain the spiral traces and measure their orbital motion in multiple scattered light bands. We measure an average spiral orbital motion of 0.81$\pm$0.05 deg/yr, in agreement with the literature value of about 0.85$\pm$0.05 deg/yr at all wavelengths. With simple modeling of the twist morphology, we confirm that it is co-moving with the spiral in which it is embedded. While the position angle of the twist coincides with the dust filament, it is located at a smaller angular separation from the star, which we attribute to the fact that the spiral trace moves away from the central star with increasing wavelength. We find that a recently claimed protoplanet candidate can be explained as a post-processing artifact. Our confirmation that the motion of the scattered light twist is consistent with the orbital velocity of a planet at 69$\pm$4 au over a 10-year baseline suggests that the spirals, the gap, the dust filament, and the twist, could indeed be attributed to the same hypothetical protoplanet embedded within the spiral. A perplexing trend for a wavelength-dependence of the angular distance of the spiral traces to the central star remains to be explained. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10676 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10676v1 Announce Type: new Abstract: We present a Smoothed Particle Hydrodynamics (SPH) implementation of the full one-fluid dusty gas algorithm for multiple dust species, generalising our previous terminal velocity approach to handle arbitrary drag regimes. By construction, mass, momentum, angular momentum, and energy are all conserved. We benchmark our method against a suite of tests -- DUSTYBOX, DUSTYWAVE, DUSTYSHOCK, DUSTYSETTLE, and DUSTYDISC -- each probing different aspects of the algorithm. Compared to the terminal velocity approximation, the full one-fluid approach incurs a computational cost increase of a factor of five to ten due to the added overhead of evolving the differential velocities and solving the drag terms implicitly. However, it accurately recovers analytic behaviour in regimes where the terminal velocity approximation fails. In such cases, errors from the terminal velocity approximation accumulate and propagate to other dust phases. We show that the stopping-time limiter commonly used in the terminal velocity approximation for numerical stability can substantially affect simulations containing large grains (Stokes numbers $\gtrsim 1$). While disabling the limiter leads to different outcomes, the discrepancy with the full one-fluid solution remains comparable, underscoring the importance of using a more general formulation for large grains. The full one-fluid formalism may be useful when including processes such as coagulation and fragmentation, where accurate treatment of large grains becomes essential. While the inability to model orbit-crossing dust trajectories remains a key limitation of the one-fluid formalism, this may eventually be addressed through the introduction of an effective dust pressure, mirroring how fluid models encapsulate microscopic velocity dispersion in gases. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10690 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10690v1 Announce Type: new Abstract: We present a calibrated catalog of Cassini Visible and Infrared Mapping Spectrometer (VIMS) observations of Jupiter, together with the processing workflow used to generate the final publicly available products. Starting from the raw VIMS cubes, the workflow produces radiometrically consistent multi-extension FITS files and includes a revised visible-channel calibration, a revised infrared-channel calibration that resolves a subset of problematic cases not satisfactorily treated by the standard ISIS pipeline, corrections for pointing-related misalignments between spectral cubes and geometric backplanes, and customized dark signal correction strategies. The final products include calibrated spectral cubes together with geometry backplanes and wavelength information for subsequent scientific analysis. We assess the consistency of the calibrated products through internal validation tests and comparisons with independent reference spectra from the literature. The resulting products provide a uniform and validated data set of Cassini VIMS Jupiter observations for community use. The full catalog is available as a public data set at Zenodo: doi:10.5281/zenodo.19223781. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10888 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10888v1 Announce Type: new Abstract: Protoplanetary disks are the birthplace of planets and planetary systems. Investigating the molecular inventory of disks is key to linking the chemical evolution of the interstellar medium and the makeup of planets and their atmospheres. In particular, tracing the history of the deuterium enrichment of water along the journey from interstellar clouds through protoplanetary disks to planetary systems provides critical insights into the chemical inheritance. We aim to investigate the chemical composition of ices in protoplanetary disks; specifically, the presence of HDO ice that ought to be present, but has not been detected in disks thus far. We analyzed JWST/NIRSpec observations of the 132-1832 edge-on disk located in the Orion Nebula Cluster using the ENIIGMA fitting tool and unique laboratory data. We report on the first detections of HDO ice in a protoplanetary disk. The estimated upper limit for the HDO/H$_2$O ratio for 132-1832 is much higher, compared to HDO/H$_2$O ratios obtained for chondrites, comets, and embedded young stellar objects. In the disk ices, beyond HDO, we detected H$_2$O, CO$_2$, $^{13}$CO$_2$, CO, OCN$^-$, and OCS, species, whose presence has also been detected in other disks. The HDO ice detection may point to the efficient ice processing in the disk and confirm the findings of laboratory experiments on deuterated ices. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10108 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10108v1 Announce Type: cross Abstract: (Extract from the Executive Summary) Humanity stands at the threshold of answering one of its most profound questions: Does life exist beyond Earth? Ongoing and upcoming space missions, together with powerful ground-based instruments, have prepared the way for a transformational next step - the detailed characterization of Earth analogs orbiting Sun-like and other stars and the search for atmospheric biosignatures that may indicate life. Within this context, the European Space Agency's Voyage 2050 process has identified the direct detection of thermal emission from temperate terrestrial exoplanets in the mid-infrared (mid-IR) as a top scientific priority. The Large Interferometer For Exoplanets (LIFE) - a space-based, mid-IR nulling interferometer - is designed to meet this goal. LIFE will be capable of detecting climate-relevant gases such as CO$_2$ and H$_2$O, identifying classical biosignatures like O$_3$ and CH$_4$, and probing additional, non-classical biosignatures. It will also provide key data for determining planetary radius, albedo, and temperature, which are essential for assessing habitability. In parallel, the U.S. National Academy has recommended a complementary mission now called the Habitable Worlds Observatory (HWO) - a ~6-meter space telescope equipped with advanced coronagraphs to suppress starlight by a factor of ~10$^{10}$ across the visible and possibly into the near-infrared and near-ultraviolet. Together, LIFE and HWO offer synergistic capabilities, enabling a comprehensive and robust assessment of the prevalence of life-bearing exoplanets in our galactic neighbourhood - a first in human history. By uniting an international and interdisciplinary community of scientists and engineers, LIFE offers a credible pathway toward the direct detection and characterization of potentially habitable - and even inhabited - worlds. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10140 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10140v1 Announce Type: cross Abstract: Extraterrestrial civilizations might place large, lightweight mirrors into orbit around an exoplanet, either to alter its climate or to provide illumination to the planet's dark side. We previously analyzed the detectability of a fleet of 1km x 1km, 1000 kg mirrors (Korpela, Sallmen, & Leystra Greene 2015). Because these mirrors are large and lightweight, their orbits are significantly affected by the star's radiation pressure (RP). We created a simulation package based on the REBOUND N-body simulator, incorporating RP that directs starlight towards the planet's center. RP can always affect mirror orbits, or only during orbital night. We have simulated mirrors in initially circular orbits around exoplanets at various locations in the habitable zones of eight types of main-sequence stars. Initial mirror orbit sizes range from 2 to 10 planet radii, and we included 4 different initial mirror orbit orientations. For each simulation, we have the mirror's survival time, trajectory, distance from the planet center at each time, and velocity relative to the planet at each time. We present an analysis of trends in mirror orbit stability, and relate these to the ratios of RP and gravitational accelerations, as well as the ratio of planet orbit period to mirror orbit period. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10760 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10760v1 Announce Type: cross Abstract: The vortex coronagraph is one of the most promising candidates for the Habitable Worlds Observatory (HWO) due to its excellent theoretical performance for an off-axis telescope. A practical realization can be achieved using liquid-crystal polymers to form a vector vortex coronagraph (VVC). Reaching the $10^{-10}$ contrast required for Earth-like planet detection is, however, limited by polarization leakage caused by wavelength-dependent deviations from half-wave retardance. This effect can be mitigated using multi-layer twisted retarders to minimize leakage, and by combining the VVC with multiple polarization gratings (mgVVC) to diffract the polarization leakage out of the science path. We present recent progress within the ESA-funded SUPPPPRESS project, which aims to advance the manufacturing, assembly, and testing of high-performance VVCs. Central singularities of 2 and 6 $\mu$m have been achieved for charge 2 and charge 6 VVCs, respectively, with patterning accuracies better than 1 degree root-mean-square error. Fabrication procedures have been developed to produce individual components with a polarization leakage of $3\times10^{-4}$ over a 10% bandwidth and $8\times10^{-4}$ over a 20% bandwidth. We also report on the development of assembly and alignment procedures for mgVVCs and their metrology. Furthermore, we present initial high-contrast tests at the THD2 bench for both regular VVCs and a double-grating VVC. The double-grating VVC reaches an average contrast between 3 and 10 $\lambda$/D of $2 \times 10^{-8}$ over a small bandwidth and $6\times 10^{-8}$ over a 10% bandwidth. Finally, we report on successful space-environment tests of the assembled liquid-crystal masks. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.10816 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10816v1 Announce Type: cross Abstract: Observations of (giant) planets accreting material within their natal environment are crucial to constrain models for their formation. WRAY 15-1880 (aka RX J1842.9-3532) in the Corona Australis (CrA) complex has a prominent pre-transitional disk, and an age of ~2.8+-0.7 Myr, computed by comparison with isochrones using the accurate dynamical mass derived from disk kinematics. Hence, this star is in the late phases of disk evolution and might host accreting planets. We acquire new polarimetric imaging data with VLT-SPHERE and analyze archive observations taken with VLT-SPHERE, VLT-MUSE, and ALMA, finding a candidate Jupiter-like companion within the disk gap from high-contrast imaging. The mass estimates of the candidate companion, derived from various methods, are consistent with an object in the range of 0.3-7.6 MJup. The spectrum of the candidate companion is consistent with a T3 spectral type, in agreement with expectations of an object of a few Jupiter masses. We find an emission blob North-West of the star in the ALMA data rotating solidly with the candidate companion, that can be interpreted as a vortex/dust trap at the m=1 Lindblad resonance of the planet. Accretion on the candidate planet is not detected from the VLT-MUSE archival data. This may be due to insufficient contrast, an observational geometry that is unfavorable for viewing the planet's surface, or it could indicate that we are merely observing irregularities within the disk. Finally, we identify a microjet extending from the star perpendicular to the disk in these data. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.11026 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11026v1 Announce Type: cross Abstract: Context. Silicates are key constituents of planet-forming disks and major building blocks of rocky planets. Mid-infrared spectral features of micron-sized silicate grains trace grain growth, mineralogy, and disk chemistry. Aims. We characterized the dust mineralogy in T Tauri disks using James Webb Space Telescope (JWST)/Mid-Infrared Instrument (MIRI) observations and investigated the connections between the dust and molecular gas compositions. Methods. We analyzed JWST/MIRI spectra of 26 disks from the MIRI mid-Infrared Disk Survey (MINDS). Using our DustComp spectral decomposition tool, we inferred the mass fractions of individual dust species. The fits included Mg$_2$SiO$_4$ (forsterite), MgSiO$_3$ (enstatite), and SiO$_2$ (silica), together with amorphous silicates of corresponding stoichiometry. Results. Mg-rich (and Fe-poor) silicates reproduce the data well, with residuals typically within $\pm3\%$. Grain size distributions are skewed toward sizes larger than $2\mu$m, indicating significant growth. The average dust composition is dominated by Mg$_2$SiO$_4$-stoichiometry grains ($\sim60\%$), followed by MgSiO$_3$ ($\sim30\%$) and SiO$_2$ ($\sim10\%$). Crystalline mass fractions are typically in the $5$-$24\%$ range, with a mean of $14\%$. Annealed silica is robustly detected in nine objects, with cristobalite as the main polymorph. We found a correlation between dust and molecular gas composition: disks with strong annealed silica features show stronger CO$_2$ emission, while forsterite-rich disks display stronger H$_2$O emission. Disks with annealed silica features may also have elevated gas-phase C/O ratios. Conclusions. The observed dust-gas correlation may provide the first indication that the molecular gas composition regulates the availability of dust species in the inner disk. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2509.10947 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2509.10947v3 Announce Type: replace Abstract: K2-18b, a sub-Neptune orbiting in the habitable zone of an M dwarf, has attracted significant interest following observations with the Hubble Space Telescope (HST) and, more recently, with the James Webb Space Telescope (JWST), which reveal detectable atmospheric features across the near- and mid-infrared. Using free-chemistry Bayesian retrievals, we investigate whether hydrocarbon hazes can explain the apparent mismatch of spectral feature amplitudes between the JWST NIRISS/NIRSpec and MIRI LRS datasets. We additionally assess the impact of stellar parameter uncertainties on the derived bulk properties of the planet and explore how planetary mass uncertainties affect atmospheric retrievals. We find that hazy scenarios can reproduce the combined JWST spectrum and provide a consistent explanation for the reduced NIRISS/NIRSpec feature amplitudes relative to the stronger MIRI features. Across all retrievals, the atmosphere remains consistent with an H$_2$-dominated sub-Neptune, with CH$_4$ and CO$_2$ as the dominant absorbers. Our hazy models retrieve systematically lower molecular abundances compared to haze-free models, reflecting the degeneracy between haze opacity and mean molecular weight. In addition, we identify strong degeneracies between planetary mass, temperature, and mean molecular weight. The retrieved planetary mass is particularly poorly constrained, with $2\sigma$ uncertainties reaching up to $\sim71\%$. We demonstrate that different mass assumptions can significantly bias the inferred atmospheric properties, with higher masses favouring warmer and lower mean molecular weight atmospheres. Breaking these degeneracies will require improved stellar characterisation to obtain more precise mass measurements. More laboratory-focused studies and future JWST observations are essential for interpreting these temperate sub-Neptune atmospheres. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2601.14254 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2601.14254v2 Announce Type: replace Abstract: The internal composition of sub-Neptunes remains a prominent unresolved question in exoplanetary science. We present a technique to place constraints on envelope mean molecular weight that utilises observations of escaping hydrogen or helium exospheres. This method is based on a simple timescale argument, which states that sub-Neptunes require a sufficiently large hydrogen or helium reservoir to explain on-going escape at their observed rates. This then naturally leads to an upper limit on atmospheric mean molecular weight. We formalise this argument within a Bayesian inference model and apply it to the archetypal sub-Neptunes GJ-436 b, TOI-776 b and TOI-776 c, which have all been observed to be losing significant hydrogen content as well as relatively featureless transit spectra when observed with JWST. Combining constraints from atmospheric escape and transit spectroscopy in the case of TOI-776 c allows us to tentatively rule out the high mean molecular weight scenario, pointing towards a low mean molecular weight atmosphere with high-altitude aerosols muting spectral features in the infra-red. Finally, we reframe our analysis to the hycean candidate K2-18 b, which has also been shown to host a tentative escaping hydrogen exosphere. If such a detection is robust, we infer a hydrogen-rich envelope mass fraction of $\log_{10} f_\text{env} = -1.67\pm0.78$, which is inconsistent with the hycean scenario at the $\sim 4\sigma$ level. This latter result requires further observational follow-up to confirm. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2603.07718 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2603.07718v3 Announce Type: replace Abstract: We present multi-epoch optical spectroscopy of the interstellar comet 3I/ATLAS obtained between December 2025 and January 2026 (heliocentric distances 1.8-3.3 au), yielding post-perihelion production rates and mixing ratios for CN, C$_3$, C$_2$, CH, and gaseous metals (Fe I and Ni I). Our results show that the coma is less depleted in C$_2$ after perihelion than before, indicative of subsurface activation or compositional heterogeneity. The outgassing profiles reveal a pronounced perihelion asymmetry: CN and metal production rates decline more gradually outbound than inbound, consistent with the reported behavior of H$_2$O and implying a change in the comet's activity pattern across perihelion. Despite being metal-rich relative to its H$_2$O content, 3I follows the metal-CO correlation observed in comets of diverse origins, suggesting that gaseous metal release is more closely linked to a CO-bearing volatile reservoir than to H$_2$O, potentially in the form of metal carbonyls. In addition, the [O I] $\lambda6300$ emission shows a significant residual after subtracting the expected contributions from H$_2$O, CO$_2$, and CO, which may reflect systematic uncertainties in the photodissociation yields of those molecules or a contribution from additional oxygen-bearing parents. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2605.19635 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.19635v3 Announce Type: replace Abstract: We perform a comprehensive analysis of lunar impact flash (LIF) light curve shapes and their dependence on the lunar terrain, using the large sample of LIFs detected by NELIOTA over the last 9 years. We classified 124 multi-frame light curves into mare, highland and `border' regions. Subsequently, we derived analytical expressions for single-size and dual-size ejecta cooling models, which were fitted to the observational data to estimate their physical properties. While impacts on both terrains yield similar peak magnitude distributions, their decay behaviour differs significantly; highland LIFs exhibit a shallower and longer-lasting decay compared to mare flashes, which are faster and steeper. The dual-size model suggests this extended duration is primarily driven by the fine droplets of the ejecta. The profile and duration of the LIF light curves represent the initial stages of the impact cratering process. The observed dichotomy between highland and mare LIFs demonstrates that the initial stages of the impact cratering process are fundamentally dependent on lunar lithology. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2604.17554 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2604.17554v2 Announce Type: replace-cross Abstract: A primary goal of the Habitable Worlds Observatory (HWO) is to detect and measure the abundance of biosignature molecules, such as water (H2O) and oxygen (O2), in the atmosphere of Earth analogs. This is expected to require deep spectroscopic observations lasting hundreds of hours per planet. In this context, it is essential to optimize the spectral resolution of the spectrograph to both maximize the number of planets that can be studied over the lifetime of the mission, and also to reduce the risks of false detections. The purpose of this work is to provide a framework to explore the spectral resolution design trade-space for HWO. This framework must be valid and comparable across all spectral resolutions from low (R 10,000), and account for the spectral correlation of the residual starlight (i.e., speckle noise chromaticity). Leveraging the concept of "template matching", we develop a simulation toolkit based on the Python package EXOSIMS to compute the detection significance of planets and molecules. We then simulate observations of Earth analogs around 164 stars using representative mission parameters to explore the effects of the detector noise and the correlated speckle noise floor. Our findings suggest that a moderate or high resolution spectrograph (R>1,000) will provide higher sensitivity to critical molecules compared to a low resolution spectroscopy mode (e.g., R~140). The correlated speckle noise may also entirely suppress our ability to detect bio-signatures at low spectral resolutions. We conclude that a more comprehensive study combined with detailed models of its stability, and other sources of correlated noise, is necessary to fully explore the trade space of spectral resolution and detectability of key species. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.09975 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09975v1 Announce Type: new Abstract: We present the discovery of a compact Milky Way satellite in the constellation of Gemini. This system was discovered by cross-matching detections from two independent search algorithms applied to Blanco/DECam data from the third data release of the DECam Local Volume Exploration survey (DELVE DR3), and confirmed with deeper imaging from Gemini/GMOS-N. Based on these data, we determine that the system is an ultra-faint ($M_V = -2.1^{+0.4}_{-0.6}$), compact ($r_{1/2} = 8.6^{+1.4}_{-1.2}$ pc) system located at a heliocentric distance of $120^{+7}_{-6}$ kpc. These physical properties place the system in the regime of ambiguous, ultra-faint compact Milky Way halo satellites that cannot be confidently classified as dwarf galaxies or star clusters from morphology alone; we therefore name the system DELVE 8/Gemini I. From medium-resolution Keck/DEIMOS spectroscopy, we securely identify four members including two blue horizontal branch stars, confirming the system as a bound satellite moving at a mean radial velocity of $v_{\rm hel} = -82.7^{+3.7}_{-3.9} {\rm km\,s}^{-1}$. We also use these spectra to place an upper limit of $\rm [Fe/H] \lesssim -2.5$ on the metallicity of DELVE 8/Gemini I's brightest star, supporting the classification of the system as either an ancient star cluster or ultra-faint dwarf galaxy. The discovery of faint, distant systems similar to DELVE 8/Gemini I is expected to become more common with upcoming surveys. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09999 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09999v1 Announce Type: new Abstract: In modern simulations that include star formation, it is common to use a universal and invariant initial mass function (IMF) to represent star populations or sample individual stars. However, stellar masses are determined by local and environmental processes that operate over a wide dynamical range and remain unresolved in simulations. We introduce a semi-deterministic (SDT) scheme for sampling individual stars from star-forming gas in numerical simulations. We represent unresolved molecular cores and protostellar disks with reservoir particles (RsvPs) and employ an on-the-fly friends-of-friends algorithm to identify star clusters. The instantaneous IMF for newly formed stars is then derived from the current cluster mass. We test the performance of this method in simulations of isolated molecular clouds and a major merger between two dwarf galaxies. Compared to existing IMF sampling methods, our SDT scheme naturally reproduces the observed $m_{\star,\text{max}}$-$M_\text{ecl}$ relation and yields numbers of massive stars consistent with optimal sampling theory. It also exhibits the smallest run-to-run variation among simulations with different random seeds. The regulated star formation results in a small ($\sim0.15$ Myr) but coherent time delay in the emergence of massive stars, reduces the large scatter arising from Poisson noise, and produces initial mass segregation within the clusters. On galactic scales, the SDT method predicts a steeper high-mass IMF slope at low star formation rates (SFRs), with the slope negatively correlated with the SFR. As the specific abundance of massive stars declines, we predict that H$\alpha$-based SFR diagnostics will systematically underestimate the intrinsic SFR due to IMF sampling effects. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10000 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10000v1 Announce Type: new Abstract: A population of dense stellar systems at high redshift has recently been uncovered by the JWST. To investigate the formation of supermassive black hole (SMBH) seeds in these dense environments without invoking any \textit{ad hoc} seeding mechanisms, we present star cluster-scale simulations performed with an updated version of the hydrodynamics code \texttt{Enzo-Abyss}, which self-consistently integrates the gravity using a direct $N$-body method coupled with stellar evolution. By modeling initially dense, metal-poor gas clouds with varying turbulence, we consistently find the formation of dense clusters resembling early-stage nuclear star clusters (NSCs), as well as the formation of very massive stars (VMSs) ranging from $343\;\mathrm{M_\odot}$ to $5108\;\mathrm{M_\odot}$ via runaway collisions, irrespective of stellar wind feedback strength. Following the direct collapse of these VMSs, the resulting intermediate-mass black holes (IMBHs) grow through Eddington-limited gas accretion and tidal disruption events (TDEs). In our most optimistic model, we find a mass accretion rate of $1.64\times10^{-4}\;\mathrm{M_\odot\;yr^{-1}}$, with TDEs contributing $23\%$ of the total accretion over $\sim10\;\mathrm{Myr}$. Assuming a steady gas supply into the NSC driven by rapid structural assembly in the high-redshift environment, together with a constant TDE rate, we project that an IMBH with an initial mass of $6747\;\mathrm{M_\odot}$ at the center of the NSC can grow to $\sim62000\;\mathrm{M_\odot}$ within $100\;\mathrm{Myr}$ of its formation. Our numerical study, conducted within a single self-consistent framework that incorporates the essential physical processes, suggests that VMSs can form in dense gas clouds, collapse into IMBHs, and subsequently provide viable seeds for the SMBHs observed at high redshift. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10022 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10022v1 Announce Type: new Abstract: We introduce PRFM-vol, a new subgrid model for star formation in cosmological simulations that aims to increase the physical realism of cosmological simulations by leveraging results obtained with focused ISM simulations. We deploy a modified effective equation of state and calculate the star formation rate for each gas cell as a function of the ambient densities of gas, dark matter, and stars, based on the pressure-regulated feedback-modulated (PRFM) theory of star formation. Test simulations of our model in isolated galaxies show that we match PRFM predictions and TIGRESS scaling relations remarkably well, provided sufficiently high resolution is available. In particular, we are able to clearly demonstrate the impact of the stellar potential on the star formation rate, thereby retaining an important prediction of PRFM. We then apply our new model to cosmological multizoom simulations and find, compared to our previous TIGRESS/Schmidt model, a significant increase in the stellar scale heights and a slight increase in stellar mass. We demonstrate that modifying the effective equation of state significantly affects the morphology of simulated galaxies. Pronounced stellar clumps appear if the effective pressure at low hydrogen number densities is low, and disappear for higher pressure. We show that the formation of clumps is a result of Toomre instabilities, and conclude that simulated galaxy morphologies can be used to constrain effective equation of state models. Overall, our results establish PRFM-vol as a new self-consistent, physics-motivated subgrid model for star formation in high-resolution cosmological simulations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10036 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10036v1 Announce Type: new Abstract: JWST discoveries of the earliest ($z \gtrsim 9$) supermassive black holes (BHs, $M_\bullet \gtrsim 10^6\,\rm{M}_\odot$) challenge the BH seeding and accretion models of most cosmological simulations. In this work, we compare early BH growth arising from three different accretion prescriptions characterized by distinct scalings between the accretion rate ($\dot{M}_{\rm \bullet}$) and the BH mass ($M_{\rm \bullet}$): the commonly used Bondi-Hoyle model ($\dot{M}_{\rm \bullet}\propto M_{\rm \bullet}^2$), and two free-fall models with shallower scalings ($\dot{M}_{\rm \bullet}\propto M_{\rm \bullet}^{1/2}$ and $M_{\rm \bullet}$). Bondi accretion tends to produce stronger runaway growth than the free-fall models when using heavy ($\sim10^5\,\rm{M}_\odot$) seeds owing to the steeper $M_\bullet$ scaling, but its sensitivity to the local gas sound speed makes it more susceptible to suppression from temperature increases due to AGN and stellar feedback. The free-fall models tend to produce stronger growth for lower-mass seeds ($\sim10^{3-4}\,\rm{M}_\odot$) as they are less dependent on the BH's mass to accrete effectively, however in this regime BH growth remains negligible for all accretion models in the presence of fiducial stellar feedback. Enhancing early BH growth via many BH-BH mergers disproportionately enhances subsequent accretion-driven growth for Bondi due to the steeper $M_{\rm \bullet}$ dependence. Our simulations can thus assemble BHs with masses of $\sim10^6-10^7 M_{\odot}$ at $z\gtrsim9$, as inferred by JWST, under two circumstances: 1) abundant heavy-seed formation that drives BH-BH mergers, or 2) Bondi accretion with weak feedback. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10116 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10116v1 Announce Type: new Abstract: In this work, we study winds for a representative sample of 86 star-forming galaxies (SFGs) at z~1 with $M_\star = 10^{9.0}-10^{11.5} M_\odot$, by measuring the Mg II line profiles in deep Keck spectra. A total of 50 (58\%) are found to have winds. Unlike local starburst galaxies, the wind detection rate does not exhibit a threshold in star-formation rate (SFR) density $\Sigma_\mathrm{SFR}$ at 0.1 Msun/yr/kpc$^2$, but shows a gradual decline around this value. We find correlations between wind velocity $v_\mathrm{wind}$ and SFR, $\Sigma_\mathrm{SFR}$, and stellar mass, as per previous studies. Intriguingly, the z~1 SFGs appear to follow the same $v_\mathrm{wind}$-SFR relation as local starbursts. A combined fit gives: log $v_\mathrm{wind}$ = 0.16 log SFR + 2.4 (3-sigma significance). This unified relation spans over 4 dex in SFR and agrees with Illustris-TNG. No unified relation is found between $v_\mathrm{wind}$ and stellar mass, sSFR, or $\Sigma_\mathrm{SFR}$. This suggests winds might be most closely associated with SFR. We examine whether winds in z~1 SFGs are driven by their most compact star-forming regions. To do so, we consider whether the relation between $v_\mathrm{wind}$ and the $\Sigma_\mathrm{SFR}$ measured from only these regions is stronger than that for the galaxy-wide $\Sigma_\mathrm{SFR}$. We do not find a stronger correlation, suggesting that winds are most related to $\Sigma_\mathrm{SFR}$ of the entire galaxy. Collectively, these findings suggest a picture in which galaxy-wide star formation plays an important role in driving winds at z~1. Wind bubbles from all star-forming regions could combine momentum and help lift their entrained gas out of the galaxy. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10117 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10117v1 Announce Type: new Abstract: We employ a simulated sample of galaxies drawn from the IllustrisTNG suite to study the emergence of the diffuse and extended nature of $\sim12,000$ low surface brightness galaxies (LSBGs) within a wide stellar mass range (${M}_{*}=10^{9}-10^{12} \rm{M}_{\odot}$). We employ merger trees to follow the evolution of their physical properties such as stellar surface density, specific angular momentum and halo spin parameter, finding that the central low density nature of LSBGs is mainly a consequence of an increase in their angular momentum and (inner) halo spin parameter. We also find that star formation histories of LSBGs are quite similar to their high surface brightness (HSBGs) counterparts, with significant differences not in the time, but in the spatial distribution in which new stars are forming. We conclude that the mechanisms that favor the emergence of the low surface brightness nature are strongly related with variations in the spin parameter of host halos and their angular momentum, deviating the stellar distribution of galaxies from their inner regions to their outskirts, leading to a decrease in their central surface brightness. Once the LSBG nature is established, galaxies are less likely to experience strong variations in their central surface densities and morphology. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10160 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10160v1 Announce Type: new Abstract: We present James Webb Space Telescope (JWST) NIRSpec integral field unit (IFU) observations of six galaxies at $z \sim 6$, obtained as part of the Aether project (General Observers program 5645). The targets were originally identified by the Subaru High-$z$ Exploration of Low-Luminosity Quasars (SHELLQs) survey, as candidate obscured quasars with luminous ($\gtrsim10^{43}$ erg s$^{-1}$) but narrow ($\lesssim500$ km s$^{-1}$) Ly$\alpha$ emission. Two objects exhibit a broad component in their Balmer lines (FWHM $>3000$ km s$^{-1}$), indicating the presence of active galactic nuclei (AGNs), while the remaining four show similar profiles in permitted and forbidden lines. Combining these data with similar SHELLQs objects reported previously, we find that the presence of broad lines is strongly correlated with Ly$\alpha$ luminosity ($L_{\rm Ly\alpha}$); the inferred AGN fraction is $>$77 % and $<$15 % above and below $L_{\rm Ly\alpha} =10^{44}$ erg s$^{-1}$, respectively. Dust-extinction corrections inferred from the Balmer decrement would imply unrealistically high Ly$\alpha$ luminosities, suggesting that the line-emitting gas consists of multiple zones. The IFU data reveal diverse spatial structures. The AGN hosts are compact, whereas the other galaxies show extended ionized gas on scales up to 10 kpc and star formation rates of 60 - 600 $M_\odot$ yr$^{-1}$. One of the extended objects exhibits a signature of rotation, while most of the others show little ordered kinematics, with velocity widths (FWHM) up to 200 - 300 km s$^{-1}$. These objects populate the intermediate luminosity regime between classical luminous quasars and the low-luminosity AGNs discovered by JWST, including Little Red Dots, potentially linking the two populations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10197 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10197v1 Announce Type: new Abstract: Integral field unit (IFU) spectroscopy provides spatially resolved spectra across galaxies, offering crucial insights into their evolution. However, its high observational cost limits current IFU datasets to $\sim 10^4$ objects. We present a multi-modal, probabilistic foundation model that predicts high-resolution spectra with calibrated uncertainties at arbitrary spatial locations within a galaxy directly from broadband images. Built on a masked autoencoder framework, our architecture injects fiber positional encodings and redshift aware wavelength encodings, enabling spatially conditioned predictions. Trained on 4.7 million images and single fiber spectroscopic observations from the Dark Energy Spectroscopic Instrument (DESI) survey, our model exploits the natural variance of fiber placements and the morphological self-similarity of galaxies to achieve IFU-like capabilities without any IFU training data. Predicted emission line flux maps match independent IFU observations from the Mapping Nearby Galaxies at APO (MaNGA) survey, with performance comparable to a supervised baseline trained directly on IFU data. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10235 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10235v1 Announce Type: new Abstract: While the presence of the Galactic warp has long been established from observations of \HI\, gas, the \textit{Gaia} measurements of over 1 billion stars with parallaxes have enabled much more detailed studies using stellar populations. Here, we demonstrate that asymptotic giant branch (AGB) stars, an evolved phase of low- and intermediate-mass stars, can serve as an effective tracer of the Galactic warp. We use two distinct AGB populations: C-rich AGB stars, representing stars of about 1~Gyr in age with main-sequence masses of 2--2.5~\Msun, and intermediate-mass (3--5~\Msun) O-rich AGB stars, corresponding to ages of 100--300~Myr. The downward warp traced by O-rich AGB stars is consistent with that found from Cepheids, which is expected given their similar ages. The more numerous C-rich AGB stars clearly reveal the Galactic warp over a wide range of azimuthal angles. Their warp appears to reach larger amplitudes than that of Cepheids across azimuthal angles. Our results show that C-rich AGB stars, together with intermediate-mass O-rich AGB stars, provide new constraints on the Galactic warp at intermediate stellar ages, offering a new insight into the stellar age and warp amplitude relation. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10271 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10271v1 Announce Type: new Abstract: Galactic winds are considered a likely driver of rapid quenching in early massive galaxies, but until now there has been no direct evidence that such systems drive winds powerful enough to meaningfully suppress their star-formation. We present resolved cold gas and ionized gas observations of a powerful supernova-driven wind in a massive galaxy 1.1 billion years after the Big Bang (at $z$=5.3). The outflow, likely triggered by ongoing merger activity, is removing gas at twice the rate of star-formation and could plausibly eject all the cold gas from the galaxy within 100 Myr. Our results suggest that powerful merger-driven outflows may be a key mechanism to produce abundant massive quiescent galaxies in the early Universe when a large fraction of massive galaxies are interacting. The mass and energetics of this distant outflow are consistent with nearby starburst-driven superwinds, suggesting that the efficiency of stellar feedback has remained relatively constant over the last 12 billion years of cosmic history. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10447 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10447v1 Announce Type: new Abstract: Narrow-line Seyfert 1 (NLSy1) galaxies are peculiar active galactic nuclei (AGN) known to exhibit a variety of intriguing observational features from low-frequency radio waves to high-energy $\gamma$~rays. As of now, NLSy1 catalogs are primarily based on optical spectroscopic observations from the Sloan Digital Sky Survey (SDSS). Here we report, for the first time, a new catalog of NLSy1 galaxies using the high-quality optical spectroscopic observations made public in the first data release of the Dark Energy Spectroscopic Instrument (DESI). We performed a detailed spectral decomposition of more than 71,000 optical spectra of AGN not included in the SDSS catalog and located at $z<0.9$. From this sample, we identify 18749 objects as NLSy1 galaxies for the first time. We also supplement the NLSy1 catalog with a sample of broad-line Seyfert 1 galaxies. The NLSy1 galaxies identified in the DESI data tend to have slightly higher bolometric luminosities and lower black hole masses (though with large dispersions), leading to the higher Eddington ratios than those of the SDSS-NLSy1 sample matched in redshifts and absolute $B$-band magnitudes. Moreover, the fraction of DESI-NLSy1 galaxies detected in the radio, X-ray, and $\gamma$-ray catalogs was found to be lower than that of SDSS-NLSy1 sources. We conclude that deeper multiwavelength investigations of these enigmatic AGN will help unravel the low-luminosity end of the NLSy1 population. The catalog has been made available at https://www.ucm.es/blazars/seyfert and Zenodo https://doi.org/10.5281/zenodo.20484681. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10455 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10455v1 Announce Type: new Abstract: The quasar main sequence, or Eigenvector 1 (EV1), describes the optical diversity of active galactic nuclei (AGN), with Narrow-Line Seyfert 1 (NLSy1) galaxies anchoring the high-accretion end. Recent discoveries of overly massive black holes in the early Universe highlight the need to study local, low-mass super-Eddington accretors as analogs of rapid black hole growth. We map a population of 18,749 NLSy1 galaxies identified in the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) onto the EV1 plane to determine whether they represent a distinct population of super-accretors. We compare the spectral properties of the DESI DR1 NLSy1 sample with the SDSS DR17 NLSy1 catalog. We extract key parameters, including the broad H-beta full width at half maximum (FWHM) and Fe II strength (R4570). To evaluate their accretion states, we derive single-epoch virial black hole masses using an Fe II strength-dependent scaling relation and an Eddington rate-dependent fundamental plane. The DESI DR1 NLSy1 population shows a shift toward the extreme end of the EV1 parameter space, with stronger Fe II emission (median log R4570 = -0.03) than the SDSS sample (-0.31). Furthermore, the DESI sources host less massive black holes (median log black hole mass ~6.73) than the SDSS objects (6.77-6.91). Given comparable continuum luminosities, a larger fraction of the DESI sample (43.8%-47.7%) exceeds the Eddington limit (log Eddington ratio > 0) than the SDSS sample (20.6%-37.4%). The sensitivity of DESI has unveiled a large population of low-mass, super-Eddington accreting AGN largely missing from previous surveys. These extreme EV1 objects naturally produce the observed intense Fe II emission. This unique sample provides a statistical dataset of local super-Eddington accretors for understanding early-Universe black hole growth. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10557 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10557v1 Announce Type: new Abstract: We present $^{12}$CO(1-0) mapping across the entire system of Stephan's Quintet, a well-known compact galaxy group, observed by Atacama Compact Array (7\,m array + Total Power) of the Atacama Large Millimeter/submillimeter Array. These observations provide the first large-scale ($137\,\mathrm{kpc}\times119\,\mathrm{kpc}$), spatially resolved ($\sim$5.5\,$\mathrm{kpc}$) molecular gas map of a compact group. Our CO map revealed that most of the molecular gas resides in the disk of the member galaxy NGC~7319 and in the intergalactic regions, including components along the shocked filament and the optically identified tidal tail extending from NGC~7319. Along the tidal tail and its surroundings, we found not only an extended molecular gas component but also four discrete CO clumps, with velocity dispersions of $\sim$10-30 $\mathrm{km\,s^{-1}}$ and molecular gas masses of order $10^7$-$10^8\,M_\odot$. Three of these clumps spatially overlap with H\,{\sc i}, whereas the remaining clump shows no associated H\,{\sc i} or counterparts at optical and infrared wavelengths. Using star formation rates derived from H$\alpha$ luminosities of H\,{\sc ii} regions, we found that star formation efficiencies (SFEs) span $\sim$2.2\,dex ($\sim$0.02--4\,Gyr$^{-1}$) and negatively correlate with CO velocity dispersion. While regions with small velocity dispersion exhibit SFEs comparable to those of nearby disk galaxies, those with large velocity dispersion ($\sim$50-150$\,\mathrm{km\,s^{-1}}$) around the shocked filament show strongly suppressed star formation. These results suggest that turbulence plays a significant role in regulating star formation in interacting systems. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10558 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10558v1 Announce Type: new Abstract: The stellar initial mass function (IMF) is a fundamental ingredient in galaxy evolution, linking observed integrated light to galaxy properties. Constraining the full IMF shape beyond the Milky Way remains challenging, as most studies focus either on the low-mass end of quiescent galaxies or the high-mass end of star-forming galaxies. Here we present the first simultaneous analysis of both ends of the IMF in 214 star-forming galaxies from the Hector survey. We estimate the low-mass end slope using a stellar population approach that fits IMF-sensitive absorption features with extended star formation histories, while the high-mass end slope is derived via the Kennicutt diagnostic, which compares the observed H-alpha equivalent width and g-r colour with stellar population synthesis model predictions. We find substantial diversity in IMF shapes and a weak but statistically robust correlation between the low- and high-mass IMF slopes. Both IMF slopes show significant correlations with stellar mass, star formation activity, and stellar metallicity ([M/H]). In general, higher stellar mass, stronger star formation activity, and higher metallicity are associated with both bottom-heavy and top-heavy IMFs. Partial correlation analysis reveals that the low-mass end slope is primarily driven by [M/H], whereas the high-mass end is mainly linked to stellar mass and recent star formation. Because the low-mass end slope traces the IMF over long-term averages and the high-mass end slope captures only recent star formation, the processes shaping each end likely occur over different and possibly decoupled timescales. Our findings challenge the universality of the IMF and emphasise the need for galaxy evolution and stellar population models to incorporate a flexible IMF prescription. Accounting for these variations is essential to build an IMF-consistent picture of galaxy evolution across cosmic time. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10623 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10623v1 Announce Type: new Abstract: Classical Cepheids (DCEPs) are excellent standard candles expected to trace the spatial and kinematic distribution of the Galaxy's young and dynamically cold stellar disc. Using the most precise mid-infrared DCEP distances to date combined with Gaia-DR3 astrometry & line-of-sight velocities, we perform a comprehensive 6D dynamical census of the Milky Way's DCEP population. While the vast majority exhibit the expected disc-like kinematics, we identify 18 kinematically anomalous Cepheids. These `rogue' stars reside on highly inclined orbits, including two in retrograde motion and one with a total velocity of ~480 km/s. Despite their extreme trajectories, their optical light curves are consistent with DCEP classifications. We explore whether these anomalies originate from classification systematics or physical processes. Re-deriving distances under the assumption that these are misclassified older Type II Cepheids (T2C) fails to reconcile their extreme kinematics, placing them at the tail of the T2C angular momentum distribution. Dynamical comparison with Galactic Globular Clusters (GC) suggests that at least one anomaly (OGLE-GD-CEP-0507) was possibly scattered into its current orbit via an interaction with the GC E3. Assuming a runaway scenario we derive dynamical ages for the kinematic anomalies, which we find highly consistent with their Cepheid ages. Spectroscopic follow-up would be insightful as one source in particular is exceptionally metal poor ([Fe/H] ~-1.6 dex), which is highly atypical for a DCEP. Integrating photometric classification with 6D kinematics will help fully characterise the Galaxy's variable star populations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10648 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10648v1 Announce Type: new Abstract: Star formation in galaxies is intrinsically stochastic, driven by physical processes operating across a wide range of scales. The scatter in the star-forming main sequence relation provides a window into this variability, but interpreting this scatter in terms of underlying physical mechanisms remains challenging. We present a study of star-formation variability during reionization (redshift z=3-8) using power spectral density (PSD) models to characterize fluctuations in star formation rates (SFRs). We use estimates of the intrinsic scatter in main sequence SFRs at six averaging timescales (10-100 Myr) from a catalogue of ~17000 galaxies presented in Simmonds et al. 2025 to constrain two PSD models, the Simple Harmonic Oscillator (SHO) and the Extended Regulator (ExtReg), with nested sampling and neural network emulators. We find that the regulator component of the ExtReg model is poorly constrained by the present data. However, both the dynamical component of the ExtReg model and the single-component SHO model favour characteristic variability timescales of ~10-30 Myr, comparable to expected galactic dynamical and stellar feedback timescales. At least in the SHO model, and most clearly at z~3-4, the inferred PSD power on ~10 Myr timescales decreases with stellar mass, indicating more bursty, rapidly varying star formation in lower-mass galaxies than in higher-mass systems. We find weak evidence for a transition from a two-component ExtReg-like PSD at lower redshift to a single-component SHO-like PSD at higher redshift in the lowest stellar-mass bin, log M*/M$\odot$ = 8-8.5, although the Bayes factors are small and selection effects at high redshift prevent strong conclusions. Overall, our results suggest that the observed 10-100 Myr scatter of the high-redshift star-forming main sequence is governed primarily by short-timescale variability, consistent with galactic dynamical timescales. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10655 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10655v1 Announce Type: new Abstract: Context. Several studies have shown that host-galaxy structure or extended optical morphology in AGNs can induce spurious parallaxes and proper motions in Gaia DR3. However, it remains unclear whether source morphology also introduces systematic errors into the celestial reference frame constructed from Gaia data. Aims. We aim to provide a Gaia-independent external morphological indicator for Gaia-CRF3 sources and to use it to quantify the astrometric systematics associated with source morphology. Methods. Using morphological parameters derived from DESI, SDSS, and SkyMapper, together with the PS1-PSC point-source score as a common reference scale, we used XGBoost to infer external morphological scores for Gaia-CRF3 sources. We then developed a multi-survey fusion scheme to combine the four survey-based point-source scores into a single composite score that measures the degree to which each source departs from the morphology of an ideal point source. Results. We obtained morphological scores for 1,607,490 Gaia-CRF3 sources, corresponding to a completeness of 99.59\% with respect to the full Gaia-CRF3 catalogue. The score ranges from 0 to 1 and remains reliable for sources with $G 0.95, the total frame spin amplitude is reduced by 15.8\% relative to that of the full Gaia-CRF3 sample. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10823 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10823v1 Announce Type: new Abstract: Active galactic nuclei (AGNs) have been proposed as efficient environments for the formation of binary black holes (BBHs). We present an updated semi-analytical framework for BBH formation and evolution in AGN disks, following the capture, migration, pair-up, gas-driven hardening, binary--single encounters, and merger of stellar-origin black holes. We systematically explore the dependence of the resulting BBH merger population on the main AGN parameters, namely the supermassive black hole mass $M_\bullet$, the Eddington ratio $\lambda_\bullet$, and the disk viscosity parameter $\alpha$, and construct an intrinsic BBH population by weighting the simulations according to observed low-redshift AGN properties. We find that AGN disks can produce repeated mergers and build a high-mass tail extending beyond the pair-instability mass gap and into the intermediate-mass range. Hierarchical growth is more efficient in lower-viscosity disks, with $\alpha=0.01$, while higher-viscosity disks suppress the formation of massive remnants. The merger efficiency generally increases with $\lambda_\bullet$, but its dependence on $M_\bullet$ is non-trivial. The AGN-assisted BBH population is characterized by increasingly unequal mass ratios at high primary mass, a correlation between primary mass and $|\chi_{\rm eff}|$, and an effective-spin distribution that depends strongly on the fraction of binaries born in prograde or retrograde configurations. We find that the AGN channel can reproduce systems broadly consistent with the massive BBH events GW190521 and GW231123. We test several variations of the physical model, including different formalisms for migration torques, gas hardening, and three-body encounters. The general properties of the population are robust across these variations, with the high-mass tail and spin signatures persisting in all cases except when gas hardening is switched off. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.10859 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10859v1 Announce Type: new Abstract: Dark matter subhalos and intermediate-mass black holes wandering in the Milky Way and the Andromeda galaxy are difficult to directly detect through electromagnetic observations, yet knowing their abundance is essential for understanding galaxy formation and evolution. We propose parallel stellar streams as dynamical imprints left on stellar streams by dark perturbers, including starless dark matter subhalos and wandering intermediate-mass black holes. We report that a single stream can split into two parallel structures after an encounter with a dark perturber. This scenario is supported by analytical modelling and N-body simulations. We also discuss how we can distinguish parallel stellar streams from other formation processes based on observables. We extend the theoretical picture of stream-subhalo interactions by showing that encounters with dark perturbers can generate density depletions perpendicular to the stream elongation, leading to parallel stellar stream morphologies beyond conventional gap-like signatures. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09992 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09992v1 Announce Type: new Abstract: The explosion of a star is first marked by the shock wave breaking out of the stellar surface, producing a burst of ultraviolet and X-ray radiation. These events are observationally rare, despite likely accompanying the majority of supernovae. Here, we report on our multi-wavelength observing campaign of the closest Einstein Probe fast X-ray transient EP260321a at $z=0.0344$. The thermal ($kT=160$ eV) X-ray emission with peak luminosity $2.2\times10^{44}$ erg s$^{-1}$ points to a shock breakout origin. We demonstrate that EP260321a is accompanied by a broad-lined Type Ic supernova, SN 2026gzf. The supernova properties, including its spectral evolution, lightcurve evolution, and expansion velocities, are all typical of the energetic stripped-envelope supernovae associated with gamma-ray bursts. However, deep X-ray upper limits obtained with the \textit{Chandra X-ray Observatory} do not detect an X-ray afterglow, and instead exclude the afterglow of known gamma-ray bursts or fast X-ray transients. If the stellar explosion launched a successful relativistic jet, we require that it had both a low Lorentz factor $\Gamma_0$\,$<$\,$30$ and a kinetic energy $E_\textrm{kin}$\,$<$\,$10^{49}$ erg for a stellar wind density of $A_*$\,$\gtrsim$\,$1$. We propose that EP260321a originated from a mildly relativistic, weak outflow that was choked by the progenitor star. This scenario is capable of naturally explaining its low X-ray luminosity and lack of prompt gamma-ray emission. EP260321a bridges the gap between SN 2008D and low-luminosity GRBs, suggesting a greater diversity in the physical parameters of stripped stars as they undergo terminal collapse. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10002 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10002v1 Announce Type: new Abstract: A long-standing question in the death of massive stars is the role of relativistic jets. While many gamma-ray bursts and some fast X-ray transients seem to be associated with broad-lined type Ic supernovae, the opposite is not true. The lack of observable jet emission in those Ic-BL SNe can be explained by invoking off-axis jets, choked jets that inject all their energy into the stellar envelope, baryon-loaded jets for which the prompt high-energy emission is strongly suppressed, or non-jetted SNe. The lack of exact explosion time in the majority of SNe presents an obstacle to distinguish between these scenarios. Here we report the properties of SN 2026gzf associated with the X-ray thermal Einstein Probe shock-breakout EP260321a at z=0.0343. The absence of compelling shocked cocoon and radio emission up to 54 days, combined with initial expansion velocities of ~30,000 km/s and a circumstellar shell of ~0.07 M$_\odot$, favour a scenario for SN 2026gzf in which a jet was choked in the circumstellar shell. Our high-spatial resolution images of the SN environment show that the progenitor was located between two highly star-forming regions with a metallicity lower than any previously known Ic-BL SN. As the first case of a Ic-BL SN associated with high-energy prompt emission without the signature of a jet, SN 2026gzf provides a unique perspective to understand the successful launch of relativistic jets during the deaths of massive stars. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10009 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10009v1 Announce Type: new Abstract: When a massive star explodes as a supernova, crucial information about its immediate environment is lost within hours. Here we report rapid optical observations from Lulin Observatory of the broad-lined Type Ic supernova SN 2026gzf, beginning 1.25 hours after Einstein Probe detected the X-ray transient EP260321a. Our data led to the discovery of the optical counterpart and showed a luminous blue first-day excess that cannot be reproduced by standard radioactive models. We find that interaction between the ejecta and $\approx 0.02$ M$_{\odot}$ of circumstellar material accounts for the early excess. Archival Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) images show variability at the explosion site over the previous $\sim 12$ years, with the source brightening by a factor of $\sim 1.5$ in the final $\sim 3$ years before explosion, providing rare evidence for pre-explosion activity in a stripped-envelope progenitor system. The precursor brightening suggests enhanced eruptive mass loss during late-stage oxygen burning before core collapse, while an additional silicon-burning episode shortly before explosion may have created the compact nearby material responsible for the X-ray shock-breakout signal. SN 2026gzf therefore offers the first view of how a stripped progenitor modifies its immediate environment shortly before death, linking long-term precursor variability, circumstellar interaction and the explosion itself. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10011 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10011v1 Announce Type: new Abstract: In March 2026, the Einstein Probe (EP) discovered its most nearby (z = 0.0343) Fast X-ray Transient (FXT), EP260321a, the first EP FXT to provide a strong match to expectations for X-ray ''shock breakout'' (SBO) emission. Here, we present our multi-wavelength follow-up campaign of EP260321a and its broad-line Type Ic (Ic-BL) supernova (SN) counterpart, SN 2026gzf, the first Type Ic-BL SN with a definitive X-ray SBO. We show that our radio follow-up extending over 5.8 - 54.5 days post-FXT rules out an on-axis jet counterpart of isotropic-equivalent kinetic energy $E_{K} > 10^{49}$ erg for circumburst densities $n > 10^{-2}~{\rm cm}^{-3}$ and constrains radio synchrotron emission from the fastest-moving SN ejecta. In addition, we derive the properties of SN 2026gzf and its host galaxy from our well-sampled optical data and compare them with those of optically discovered Type Ic-BL SNe, finding that SN2026gzf is well within the 90% confidence interval across all properties. We further fit SN 2026gzf's light curve with five different physical models, and determine that combined emission from both interaction with circumstellar material (CSM) and $^{56}$Ni radioactive decay provides the best fit with plausible model parameters. Finally, using the rate of Ic-BL SNe from the ZTF Bright Transient Survey and assuming all Type Ic-BL SNe produce EP260321a-like FXTs, we infer an expected rate of EP-detected SBOs of 4.4 - 16 year$^{-1}$. This is inconsistent at the 90% confidence level with current EP detection rates, potentially indicating that most Type Ic-BL SNe produce less luminous X-ray SBO signals compared to EP 260321a. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10014 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10014v1 Announce Type: new Abstract: Massive stars die as energetic supernova explosions, but the physical processes during and before such explosions are poorly studied observationally. The first electromagnetic signals from core-collapse events are predicted to be a flash of soft X-ray and ultraviolet (UV) light, produced as a result of a shock wave breaking out of the star and its surrounding medium. Such shock breakout (SBO) events often carry essential information about the explosion energetics, the progenitor star, and its immediate environment. However, they are difficult to catch because of their very short durations and a historical lack of sensitive wide-field monitors. Only two SBO events have been detected so far in X-rays, but their emission spectra are modified from the simple thermal form by complicated physical factors, however. Here we report the discovery of a fast X-ray transient, EP260321a, followed by a broad-lined Type Ic supernova (SN Ic-BL) emerging days later, suggesting its progenitor as a Wolf-Rayet star with its hydrogen and helium envelopes stripped. Its X-ray emission is soft and best modeled by blackbody radiation, making it a bona fide SBO. The observed long duration and large total energy output of the X-ray event jointly indicate a shock breaking out from a surrounding shell at a radius of about 300 solar radii, rather than from the progenitor star's surface. This provides direct evidence of abrupt mass ejection within a month prior to core collapse, suggesting intense pre-explosion activity for a massive star. The real-time detection of SBOs yields precise timing of stellar core-collapse, allowing for efficient searches for associated neutrinos and potential gravitational-wave signals. These, together with timely multi-wavelength observations, may uncover how massive stars end their lives. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10118 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10118v1 Announce Type: new Abstract: Context. Determining the internal constitution of the outer crust of magnetars is important for interpreting several of their astrophysical manifestations. In particular, the crustal composition is a key input for simulations of r-process nucleosynthesis in giant flare ejecta. However, traditional methods are computationally expensive, limiting their use in large-scale studies. Although faster iterative approaches exist, they are restricted to unmagnetized matter and strongly quantizing magnetic fields, leaving the intermediate field strengths characteristic of observed magnetars without an efficient treatment. Aims. We developed the program magcrust to extend these existing iterative approaches, enabling the rapid computation of the outer-crust composition of cold, non-accreted magnetars over the full range of the magnetic-field strengths inferred for these objects. Methods. Transitions between adjacent crustal layers are computed by solving approximate equilibrium conditions at the interface. Nuclear abundances and layer depths are estimated from approximate solutions of Einstein's equations of general relativity. Results. The performance and accuracy of the program were assessed against detailed numerical calculations. Relative deviations from exact transition properties remain within a few percent, and crustal compositions are well reproduced across 17 nuclear mass tables and 1300 magnetic-field strengths from 1E13 to 1E16 G. Computation times are reduced by factors of 1E3-1E7 compared to traditional approaches. Conclusions. This program provides a robust and efficient tool for determining the stratification of magnetars' outer crust over the full range of astrophysically relevant magnetic-field strengths. Its computational speed makes it well suited to systematic calculations, including sensitivity analyses, uncertainty quantification, and ensemble studies. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10189 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10189v1 Announce Type: new Abstract: Kilohertz perturbations in active magnetars evolve into monster radiative shocks at radii $r\sim 10^8$ cm. The shock generates X-rays and a semi-coherent radio precursor, which strongly interacts with the magnetospheric plasma ahead of the shock. We show that this interaction self-regulates the precursor emission and find its self-consistent frequency and luminosity. The precursor frequency falls in the GHz band and its production peaks when the shock expands to $r\approx 10^9$ cm. The resulting GHz burst has a sub-millisecond duration and energy ${\cal E}_{\rm FRB}\approx 10^{34}{\cal E}_{38}^{0.2}$ erg where ${\cal E}$ is the energy of the primary magnetosonic disturbance that launched the shock. As the GHz burst propagates to the light cylinder $R_{\rm LC}\sim 10^{10}$ cm, it faces a threat of being absorbed by the magnetosphere. The burst escapes if the local plasma density at $R_{\rm LC}$ is $\sim 30$ times lower than typically expected for active magnetars, so distant observers need some luck to see the radio burst. The shock X-rays follow the radio waves with a millisecond delay. Shocks from kilohertz disturbances with energies ${\cal E}\sim 10^{38}$ erg generate X-ray and radio bursts similar to the activity detected in SGR 1935+2154. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10292 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10292v1 Announce Type: new Abstract: In this work, we perform an indirect search for axion-like particles (ALPs) through their hypothesized mixing with photons in the presence of magnetic fields. ALPs are a well-motivated dark-matter candidate class, and the photon-ALP conversion mechanism provides a unique channel to constrain their mass and coupling constant using very-high-energy gamma-ray observations. The photon-ALP mixing could alter the observed gamma-ray spectrum from extragalactic sources by effectively reducing the apparent attenuation due to extragalactic-background-light absorption. We analyze 7.5 years of data from the High Altitude Water Cherenkov (HAWC) Observatory, targeting the nearby radio galaxy M87. This source is located within the Virgo cluster and is an ideal environment for photon-ALP conversion due to its low redshift and the large-scale, strongly magnetized medium of the cluster. We find no evidence for a photon-ALP conversion signal and, consequently, set constraints on the ALP mass and photon-ALP coupling constant with emission from M87 which are consistent with previous results. Our analysis places competitive constraints on the ALP parameter space, defining an exclusion region in the mass range of approximately $10^{-8}$ to $10^{-6}$ eV for coupling constants above $5\times10^{-12}$ GeV$^{-1}$, complementing previous constraints from other gamma-ray observatories. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10519 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10519v1 Announce Type: new Abstract: We present a reanalysis of 17 years of Fermi Large Area Telescope (LAT) observations of the Crab pulsar obtained between 2008 August and 2025 August. Using monthly Jodrell Bank radio ephemerides, we assigned pulse phases to the LAT events and aligned the phase zero across the full data set. From this phase-aligned data set, we derived pulse profiles over 100 MeV to 300 GeV. The pulsed emission remains clearly detectable in the 10 to 20 GeV and 20 to 30 GeV bands, with H-test significances of 32.36 sigma and 11.59 sigma, respectively, but is not significantly detected in the 30 to 300 GeV band. Phase-resolved likelihood analysis was performed over 100 MeV to 30 GeV using 14 phase bins with comparable pulsed statistics. The fixed-window fractional fluxes show that the contribution of Peak 1 (P1) decreases steadily with energy, while those of Peak 2 (P2) and the Bridge increase, with P2 exceeding P1 above 10 GeV. Finally, the same phase-assignment framework also enables an off-pulse analysis from 100 MeV to 1 TeV, confirming the synchrotron and inverse-Compton components that dominate the emission in the selected off-pulse interval. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10527 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10527v1 Announce Type: new Abstract: Axions and axion-like particles (ALPs) are compelling candidates for dark matter and new physics beyond the Standard Model. Photon-axion mixing in external magnetic fields modifies the photon energy spectrum and linear polarization state, and also induces circular polarization signals. Compared to spectral and linear polarization methods, circular polarization benefits from lower astrophysical background contamination, providing an independent probe for axion searches. In this work, we study the circular polarization induced by photon-axion mixing within the chiral basis framework. By analytically solving the evolution equations under the single-domain approximation, we derive an expression for the circular polarization degree P_C, applicable in the resonant, strong coupling, and weak coupling regimes. Within single-domain magnetic field models, we compare the energy-dependent circular polarization in four astrophysical environments (AGN jets, intracluster medium, intergalactic medium, and Galactic magnetic fields). We find that the X-ray to MeV band represents the most sensitive observational window. Using the blazar S4 0954+65 as a case study, phase accumulation in random magnetic domains causes the circular polarization degree to fluctuate with redshift and exhibit pronounced energy structures. Using the optical circular polarization upper limit P_C < 0.184% from this source, we constrain g_{a{\gamma}{\gamma}} <= 5 x 10^{-12} GeV^{-1} for m_a ~ 10^{-16}--10^{-10} eV, with the strongest constraint near m_a ~ 10^{-14} eV. These results establish circular polarization as a complementary axion probe. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10538 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10538v1 Announce Type: new Abstract: Over a hundred fast radio burst (FRB) host galaxies have now been identified, enabling both comparisons of host redshift with FRB dispersion measure to study the cosmological distribution of ionised gas, and analyses of host properties in order to identify FRB progenitors. The standard method for determining the most likely FRB host galaxy in an optical image is the Bayesian framework Probabilistic Association of Transients to their Hosts (PATH), which accounts for uncertainties in the radio localisation, and simplified prior distributions on the host being observable. In this work we extend PATH, incorporating physically-motivated priors that are based on expectations about FRB host galaxy magnitudes. We develop three different models for the apparent r-band magnitude distribution based on an FRB's expected host galaxy redshift, $P(m_r|z)$ and combine these with expectations for redshift based on an FRB's dispersion measure, $P(z|DM)$. We fit the parameters of these prior models using host galaxy candidates for 32 FRBs detected by the Australian SKA Pathfinder (ASKAP) in incoherent sum (ICS) mode by the Commensal Real-time ASKAP Fast Transients (CRAFT) survey. Employing PATH with the new priors on the host magnitudes, we find increased confidence in the most probable hosts of all ASKAP ICS FRB host galaxies. All three models predict similar distributions of FRB host magnitudes at low redshift $(z \sim 0.1)$, and we confirm previous results that the true FRB host galaxy distribution is fainter than expected for a star-formation-weighted distribution (p-value of 0.12%). However, a mass-weighted distribution provides an even worse fit (p-value of $10^{-9}$). Tests against more FRBs in the $z > 0.5$ range, where the models differ, and extensions of the models to account for e.g. host metallicity, may help to resolve these uncertainties in the FRB host distribution. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10566 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10566v1 Announce Type: new Abstract: We report the discovery of a new X-ray transient, EP~J175257.3--351923 (EP250916a), by the \textit{Einstein Probe} (EP) near the Galactic plane. The outburst lasted for at least $\gtrsim 40$~days, reached a peak 2--10 keV flux of $\sim 4 \times 10^{-10}$~erg~cm$^{-2}$~s$^{-1}$, and exhibited a fast-rise, exponential-decay (FRED) profile typical of X-ray binary outbursts. The source remained in the hard state throughout the outburst, with only modest variations in the photon index ($\sim 1.6$--$2.2$) and no evidence for a spectral state transition. Broadband spectral modeling suggests a truncated disk, a weak reflection component, and a high-energy cutoff at $\sim 217$~keV, consistent with hard-state accretion in black-hole systems. No reliable optical counterpart is detected within the Swift/XRT error circle in SVOM/VT, Swift/UVOT and GROND observations, and the inferred X-ray-to-optical flux ratio, $\xi \gtrsim 21.75$, is consistent with a low-mass companion. No pulsations or significant aperiodic variability are detected. Although the compact object cannot yet be firmly identified, the timing, spectral, and optical evidence favors EP~J175257.3--351923 as a black-hole low-mass X-ray binary candidate, highlighting EP's potential to uncover a faint, previously hidden population of X-ray binaries. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10710 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10710v1 Announce Type: new Abstract: How stellar-mass black holes are formed is an open question in astrophysics, with very limited observational constraints. It is not known which types of stars are more likely to produce black holes, and whether the formation process is accompanied by strong or weak electromagnetic transients - or none at all - and this issue remains a critical missing piece in the puzzle of the fate of massive stars. Recent theoretical work predicts that many stellar-mass black holes form from hot, UV-luminous massive stars, including Wolf-Rayet-like progenitors, and searches focused primarily on luminous cool supergiants may therefore miss a substantial fraction of black-hole formation events. While the coming decade will bring major advances in time-domain astronomy through Rubin/LSST, Roman, JWST, and wide-field transient surveys, none of these combines UV sensitivity, sub-arcsecond imaging, and decade-long continuity. HST uniquely enables direct searches for disappearing hot massive stars associated with black-hole formation. We outline a roadmap for extending HST's role in this area into the 2030s through a dedicated, large program to re-image nearby galaxies in the UV and identify candidate disappearing stars and unusual low-luminosity transients identified by complementary surveys. Theoretical event rates imply that the nearby galaxy population accessible to HST should yield of order one detectable black-hole-forming disappearance event per year. Extending HST operations into the 2030s would therefore provide crucial insights into the unsolved problem of black hole formation. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10739 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10739v1 Announce Type: new Abstract: We present a broadband spectral analysis of the neutron star LMXB GRS 1747-312 using $\sim 40$ ks AstroSat data. The source was observed during the decay phase of the 2017 outburst, with an absorbed 1.0--5.5 keV flux of $1.67^{+0.04}*{-0.07} \times 10^{-11}$ erg s$^{-1}$ cm$^{-2}$, corresponding to a luminosity of $\sim (0.9-1.80) \times 10^{35}$ erg s$^{-1}$. The continuum is modeled with thermal Comptonization of blackbody emission and interstellar absorption. A mildly broad iron line at $\sim 6.4$ keV is fitted with a disc reflection component. Narrow lines below 2 keV are described by a hot plasma using the XSPEC model APEC. Additionally, there is a potential detection of an emission line at $4.19^{+0.12}*{-0.10}$ keV with width $\sigma = 0.2 \pm 0.2~\mathrm{keV}$ and line flux = $13^{+10}*{-9} \times 10^{-5}$ erg s$^{-1}$ cm$^{-2}$. Examination of several short duration ($\sim$ few kiloseconds) Swift observations at few times the AstroSat source flux, provided upper limits to the line flux $< 30 \times 10^{-5}$ erg s$^{-1}$ cm$^{-2}$. The 4.2 keV line likely originates from reflection off the neutron star surface. Shifting the neutral Fe $K*\alpha$ line from its rest energy of 6.4 to 4.2 keV requires a redshift of $z \sim 0.6$, consistent with that expected from the surface of a non-spinning $1.4 M_\odot$, 10 km radius neutron star. If confirmed, this feature provides a potential direct measurement of gravitational redshift, allowing us to place strong constraints on the neutron star's mass-to-radius ratio and gain valuable insights into the equation of state (EOS) of dense matter. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10807 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10807v1 Announce Type: new Abstract: We present the Thousand Pulsar Array (TPA) single-pulse data set, obtained with the MeerKAT radio telescope and comprising time-series observations of 1192 pulsars, typically containing ~1000 consecutive pulses per source. We describe the MeerTime Single Pulse software pipeline which calibrates the data and automatically excises interference signals to produce data products suitable for typical single-pulse studies. To demonstrate the capabilities of the dataset, we carry out a population-level study of phase-averaged single-pulse energy distributions and nulling behaviour. Pulse energy distributions are modelled within a Bayesian framework choosing from a range of intrinsic energy distributions, and including an explicit nulling fraction. We find that approximately half of the pulsars require multi-component intrinsic energy distributions, while the remainder are consistent with single-component models. Nulling is detected or constrained for most pulsars in the sample, and both the occurrence and inferred nulling fraction show systematic variation across the P-$\dot{P}$ diagram. In particular, nulling fractions increase with spin period and exhibit only a weak dependence on period derivative. We also examine trends in the preferred forms of pulse energy distributions as a function of spin-down luminosity, finding modest evidence for population-level evolution. Estimates of single-pulse luminosities indicate that individual pulses can exceed the long-term average luminosity by large factors, particularly for low-$\dot{E}$ pulsars. These results characterise the statistical properties of single-pulse emission across a large pulsar sample and highlight the limitations of phase-averaged energy distributions for capturing the full complexity of pulsar emission variability. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10828 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10828v1 Announce Type: new Abstract: We present a new study on the MeV-TeV gamma-ray origin of HESS J1857+026 using data collected from the Fermi-LAT, VERITAS, and HAWC observatories. A spatial and spectral study of HESS J1857+026 including radiative modeling of the MeV-TeV spectrum determines the likely dominant gamma-ray origin as a pulsar wind nebula (PWN) powered by the energetic pulsar PSR J1856+0245. The MeV-TeV spectrum is further characterized through basic evolutionary radiative modeling assuming a PWN origin to constrain the physical properties of the system such as the magnetic field strength and PWN age. The results of the PWN evolutionary model are consistent with the observational constraints of the system, finding an age of the system between t = [16,21]kyr and a magnetic field strength between B = [0.4,1.6]muG. These estimates support an evolved PWN scenario where the observed gamma-ray emission is generated by the relativistic electrons inverse Compton scattering (ICS) off local photon fields, however the low-energy (E < 10GeV) spectral component could be dominated by hadronic emission originating from a supernova remnant (SNR). For a PWN component above 10GeV, we measure the conditions for particle diffusion, finding that the local diffusion (D(50TeV) ~ $10^{28}cm^{-2}s^{-1}$) is suppressed compared to the interstellar medium (ISM) value, in agreement with similar TeV PWNe. By measuring the radial surface brightness profiles of the gamma-ray source across multiple instruments, we demonstrate that the combined MeV-TeV spatial information is a powerful tool to constrain particle diffusion properties. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10840 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10840v1 Announce Type: new Abstract: A second extragalactic pulsar wind nebula (PWN) is discovered in the MeV-GeV band using the Fermi-LAT. Faint, point-like gamma-ray emission is detected at the location of the composite supernova remnant (SNR) B0453-685 from energies 300MeV-2TeV. The Fermi-LAT data analysis of the new gamma-ray source is presented together with a detailed multi-wavelength investigation to understand the nature of the observed emission. The observational evidence and physical implications from broadband modeling do not support an SNR gamma-ray origin. Semi-analytic radiative evolutionary models are explored to understand the potential for any pulsar or PWN component responsible for the observed gamma-ray emission. The modeling results favor an evolved PWN ($\tau\sim 14,000$ years) that has been impacted by the return of the SNR reverse shock with a possible substantial pulsar component below $5$GeV. The particle acceleration mechanisms and their efficiency within B0453-685 have important implications for the role PWNe play in generating Cosmic Rays (CRs), but constraints on the synchrotron cut-off are required to accurately characterize the underlying particle properties. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10855 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10855v1 Announce Type: new Abstract: Pulsar Wind Nebulae (PWNe) are relativistic, magnetic winds comprised of radiating electrons and positrons, powered by an energetic pulsar. The pulsar continuously injects particles into the PWN that are accelerated at the termination shock. As the relativistic particles enter the PWN, they radiate away the energy received at the shock as they interact with the PWN environment, generating synchrotron emission from interactions with the magnetic field of the PWN and Inverse Compton Scattering (ICS) from interactions with the local photon fields. Synchrotron emission is observed from the majority of known PWNe from radio to X-ray energies, and the ICS is observed in the $\gamma$-ray bands, from MeV to TeV energies. The particle acceleration processes at the termination shock and elsewhere within the PWN remain to be understood. Recent progress in theoretical studies have provided the capability to explain broadband observations of several PWNe including their spectral and spatial features. This work reviews some of the most compelling outcomes of recent literature, outlining the outstanding questions that remain to be answered, and how the future prospects of $\gamma$-ray astronomy will be instrumental in advancing the current understanding of PWNe. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10926 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10926v1 Announce Type: new Abstract: Positive lags in gamma-ray bursts (GRBs), where hard photons anticipate softer ones, provide a unique window into the temporal evolution of their prompt emission. Negative lags, when hard photons are delayed, are instead more enigmatic to interpret. Disentangling the effects that produce both kinds of lags is critical for identifying the physical mechanisms at work in the prompt and early afterglow phases of GRBs. We investigate the potential of time lags for distinguishing different emission components at different energy bands. Using data from the Fermi Gamma-ray Burst Monitor (GBM) and the LAT Low Energy(LLE) technique, we perform a time-resolved joint spectral analysis in the range 10 keV-100 MeV for two exceptionally bright bursts, GRB 160625B and GRB 190114C. Time lags between the lowest-energy band (10-100 keV) and progressively higher-energy bands up to 30-100 MeV were computed across their distinct emission episodes via the cross-correlation function. For GRB 160625B, the spectra are described by a single component with clear hard-to-soft evolution, and the time lags are always positive. Analysis of the high-energy exponential cutoff, likely originating above the photosphere, yields bulk Lorentz factor estimates of $\Gamma \sim 120-250$. GRB 190114C exhibits negative lags in the 30-100 MeV band, coinciding with a delayed high-energy powerlaw component that dominates the LLE range after ~2.5 s. Comparison with multi-wavelength observations shows some compatibility with the early afterglow, though its origin remains open, leaving room for external shocks or internal dissipation. Time lags are effective diagnostic tools for the spectral evolution of GRBs: positive lags trace the softening of the prompt emission, whereas negative lags indicate the appearance of a new, independent high-energy spectral component. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.10964 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10964v1 Announce Type: new Abstract: We have recently shown evidence that the most relativistic jets (with Lorentz factor >2) from stellar-mass black holes in X-ray binary systems may be locked to a fixed axis, likely the spin axis of the black hole. Slower, mildly relativistic jets (with velocities typically ~ 0.3c) are often seen to precess and can be associated with both neutron stars and black holes. In this paper we demonstrate an additional clear link between highly obscured systems and these lower-velocity, precessing jets. We speculate that this link may be due to mass-loading of the jets close to their launch sites, since these obscured systems are likely to be examples of (sometimes persistent, other times transient) super-Eddington accretion. The fastest relativistic jets are now seen to be both locked to a fixed direction, likely the black hole spin axis, and to be launched in low-density environments, while jets launched in dense environments are generally slower and very likely to precess. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09974 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.09974v1 Announce Type: new Abstract: Slitless spectroscopy enables efficient, large-area surveys without target pre-selection, yet it faces challenges from source blending, higher noise, and lost spatial-spectral information. We present an advanced, non-parametric, data-driven algorithm that leverages multiple dispersion angles to reconstruct three-dimensional flux distributions, providing low-resolution Integral Field Unit (IFU) capabilities from slitless data. By treating each pixel as an independent element, our method naturally handles source confusion without requiring prior assumptions regarding redshifts, templates, or model libraries. We validate the algorithm using simulated Roman Space Telescope wide-field slitless spectroscopy images that are equivalent to what is expected from the High-Latitude Time-Domain Survey. First, we demonstrate that a host-galaxy model reconstructed from multiple dispersion angles can be used to accurately subtract host light from a transient, recovering a Type Ia supernova spectrum with minimal bias. Second, we showcase a high-fidelity flux-cube reconstruction of a complex galaxy, successfully measuring the redshift and recovering continuum, emission, and absorption features. This approach highlights the potential of multi-dispersion-angle slitless data to provide spatially resolved spectral information in a non-parametric way, which is traditionally accessible only with integral field spectroscopy, opening a new window into large, unbiased, and spatially-resolved studies of galaxy evolution. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10076 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10076v1 Announce Type: new Abstract: Modeled gravitational wave searches correlate the strain data with a bank of gravitational wave template waveforms to make detections of gravitational wave candidates, and these results are processed by downstream tools to calculate the likely sky location and distance of the source of the candidates. This is crucial for multi-messenger efforts, since it informs astronomers where to point their telescopes to facilitate electromagnetic follow-up of the gravitational wave candidates. We present a novel method to improve the low-latency results of the GstLAL gravitational wave search pipeline, and thus improving sky location estimates of low-latency candidates. This method involves ingesting the GstLAL low-latency results, and performing a small targeted hierarchical search to recover the candidates with more accurate parameters, in a medium-latency timescale (few seconds to five minutes). To test our method, we perform a GstLAL low-latency analysis on forty days of data from the third observing run of LIGO, Virgo, and KAGRA, and show that our method improves the GstLAL results by 5.38% and the subsequent sky location results by 16.75% on average. In addition to this increase in precision, we also show that these results are more accurate as compared to the GstLAL results. This method has been adopted by GstLAL for the fourth observing run. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10171 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10171v1 Announce Type: new Abstract: A high-resolution near-IR spectroscopy capability on the Habitable Worlds Observatory (HWO) could strongly and efficiently advance many of the mission's goals. The technical barriers that made such a capability unfeasible on previous missions have largely been eliminated. Many HWO science case development documents require high spectral resolution in the IR and others would benefit significantly from it. High resolution improves the detectability of weak, unresolved features, aids identification of those features and provides additional information about radial velocity and line shape. It will be significantly easier to remove contaminating stellar features from high-resolution data. Silicon diffractive optics, immersion gratings and grisms, together with the new generation of low-noise, low dark-current avalanche photodiode arrays, make it possible to design a very compact high-resolution spectrograph that can cover the entire 1.1-2.0 micron band in a single exposure that would realize all of these advantages. We outline here the case for such an instrument and the technology development pathway needed to mature it in preparation for the HWO mission. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10712 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10712v1 Announce Type: new Abstract: DIffuse X-ray Explorer (DIXE) is a proposed high-resolution X-ray spectroscopic surveyor aimed at studying large structures of hot gas in the Milky Way. Its payload is designed to have a field of view (FoV) of $10^\circ$ (half-power diameter) and an energy resolution of better than 6 eV, covering an energy range of 0.1-10 keV. It will be mounted on the China Space Station (CSS) and follow the CSS orbit to conduct the survey with fixed zenith pointing in order to optimize the coverage of key science targets. The payload will avoid the Sun passively via an operable sunshade, where a minimum $25^\circ$ angular separation between the pointing axis and the direction of the Sun is required. Two Sun-avoidance strategies are considered: one focusing on minimizing mechanical risk and the other on maximizing exposure time. The one-year exposure maps indicate that DIXE will cover approximately $72.5\%$ of the sky, with typical exposure times of 26 ks and 68 ks for the two strategies, respectively. Although mechanically collimated, the imaging performance of the payload can be enhanced with a demodulation method based on Markov Chain Monte Carlo sampling using the collimator response. Through simulation, we found that the method could achieve a localization accuracy of $1^\circ$ for point-like sources and a spatial resolution of $3^\circ$ for the extended sources of complex surface brightness distribution, both of which are significantly smaller than the FoV. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10750 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10750v1 Announce Type: new Abstract: As new observational technologies reveal increasingly detailed properties of neutron star surfaces, the demand for accessible and extensible theoretical modeling tools continues to grow. We present UnReal-B, a real-space Density Functional Theory solver for one-dimensional chains of matter in extreme magnetic fields $B \approx 10^{12} - 10^{15},\mathrm{G}$. By employing the adiabatic approximation, UnReal-B, provides a streamlined numerical framework for calculating the electronic structure of strongly magnetized condensed matter. The solver is benchmarked against published results for several astrophysically relevant elements, demonstrating excellent agreement while maintaining a comparatively simple and transparent implementation. Released as open-source software, UnReal-B facilitates reproducible and community-driven investigations of neutron-star surface matter and provides a foundation for future developments motivated by emerging observational constraints. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10771 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10771v1 Announce Type: new Abstract: Reinforcement learning (RL)-based algorithms have recently emerged as a promising approach for adaptive optics (AO) control. In simulations and laboratory experiments, they have demonstrated robustness to real-world effects such as photon and detector noise, misregistration, vibrations, and rapid variations in seeing conditions. However, their performance has not yet been validated on sky. We report the first on-sky demonstration of a reinforcement learning controller for adaptive optics, named Policy Optimization for AO (PO4AO). We further analyze its on-sky behavior and identify directions for improving the algorithm and its implementation.PO4AO was implemented and deployed on the Papyrus adaptive optics system installed at the Coud\'e focus of the 1.52 m telescope (T152) at the OHP. A Python-based implementation was interfaced with the existing real-time controller (DAO RTC) via shared-memory buffers. The performance of PO4AO was compared to that of a standard integrator controller over several nights, covering a range of flux levels and atmospheric conditions. PO4AO consistently outperformed the standard integrator in all tested configurations. The controller successfully learned and compensated for vibration patterns and demonstrated strong robustness to measurement noise. Once tuned for Papyrus, PO4AO operated in a turnkey fashion, using a single set of hyperparameters across varying observing conditions and science targets. These performance gains were achieved despite a non-optimized Python implementation introducing approximately $750\,\mu\text{s}$ of additional latency, along with control jitter and occasional frame drops. When properly implemented and optimized, PO4AO constitutes a robust and high-performance turnkey controller for single-conjugate adaptive optics systems, paving the way for broader adoption of reinforcement learning strategies in on-sky AO operations. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11097 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11097v1 Announce Type: new Abstract: The accuracy of particle counting in highly segmented detectors is limited by the corner-clipping effect, in which a single ionizing particle generates signals in adjacent detection elements. This phenomenon introduces a direction-dependent overcounting bias that distorts reconstructed observables and is commonly corrected using Monte-Carlo simulations, thereby inheriting modeling uncertainties. We present a fully data-driven method to directly measure the single-particle corner-clipping probability, exploiting the nanosecond timing resolution of modern detectors to statistically distinguish genuine corner-clipping events from random coincidences, with non-neighboring detection elements serving as an intrinsic control sample. The technique is validated using detailed simulations of the Underground Muon Detector of the Pierre Auger Observatory, reproducing the true angular dependence of the corner-clipping probability with absolute deviations below 0.01. To parameterize the results, we introduce a compact analytical model incorporating detector geometry, minimum detectable path length, and orientation-independent contributions. The proposed methodology and parameterization enable the direct incorporation of data-driven corner-clipping corrections into reconstruction algorithms, mitigating the overcounting bias and ultimately yielding a more accurate determination of the muonic component of extensive air showers. These developments are broadly applicable to any segmented detector with sufficient timing resolution, making them relevant to a wide range of experiments in high-energy and astroparticle physics. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11102 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11102v1 Announce Type: new Abstract: The Ohio State University Radio Observatory (OSURO), known as the Big Ear, played a pivotal role in both radio astronomy and the Search for Extraterrestrial Intelligence (SETI). Following the completion of the Ohio Sky Survey, the facility was repurposed in 1973 as the world's first full-time dedicated SETI observatory and operated continuously until its decommissioning in 1998. During this period, the Ohio SETI Program evolved from an 8-channel hydrogen-line receiver into increasingly sophisticated survey systems. Over three decades, these surveys covered approximately 70% of the radio sky using a largely consistent instrumental configuration, creating one of the most extensive long-term radio astronomy archives ever assembled. The program is best known for the detection of the Wow! Signal in 1977, but it also accumulated an archive of over 40,000 transient narrowband events, revealed unusual concentrations of radio bursts near the Galactic Center, and established one of the longest continuous radio monitoring records in astronomy. Following the closure of the Big Ear, its scientific legacy continued through Project Argus and, more recently, the Arecibo Wow! project. This paper provides an overview of the final decades of the Ohio SETI Program, including its instrumentation, survey strategies, scientific discoveries, and enduring impact on SETI, time-domain radio astronomy, and the preservation of historical astronomical data. Despite its scientific significance, most of the data collected by the Ohio SETI Program remains unexplored, leaving a unique archive available for future research. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10686 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10686v1 Announce Type: cross Abstract: The pulsar magnetosphere has only recently been addressed using Physics-Informed Neural Networks (PINNs), by deploying a domain-decomposition approach and treating the separatrix and equatorial current sheet as infinitesimally thin discontinuities. However, this baseline requires extensive manual hyperparameter tuning, achieves limited final accuracy and demands several hours of training. We refine this framework by introducing domain-specific neural architectures based on Kolmogorov-Arnold networks, an automated adaptive training pipeline and a physics-based convergence criterion that eliminate the need for manual calibration. The proposed methodology delivers self-consistent axisymmetric magnetosphere solutions with mean squared errors of the PDE residuals at O(1e-6) in double precision - an improvement of two orders of magnitude over the baseline - while achieving convergence in under 20 minutes in single precision. Importantly, the method reliably resolves stellar radii reduced by up to 80% compared to the baseline, overcoming the severe spatial scale disparities that also challenge traditional solvers. Furthermore, by varying the flux that opens to infinity, we provide a correction to the equation that connects it to the equatorial T-point's position. The complete framework is released as the open-source library PulsarX. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10762 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10762v1 Announce Type: cross Abstract: Colliding-wind binaries (CWBs), which are systems of two massive stars whose supersonic winds collide into bow shocks, encode rich information about stellar wind properties in their multi-frequency emission, e.g. images in the H$\alpha$, X-ray, and radio wavelengths. Inferring physical parameters (mass-loss rates, terminal wind velocities, orbital elements) from short time-series observations is a compelling but challenging inverse problem, because the forward hydrodynamic simulator is computationally expensive and the likelihood is intractable. We adopt a factorized spatio-temporal architecture for amortized posterior inference that separates spatial encoding from temporal aggregation. This design aligns with the structure of the underlying physical process of local morphology and global dynamical evolution, induces time-translation equivariance in the learned representation, and improves identifiability in low-signal regimes. Coupled with a neural spline flow conditioned on these spatio-temporal embeddings of 10-frame H$\alpha$ photon-count time series, we present a complete simulation-based inference pipeline for CWBs. Our method jointly infers seven physical parameters from synthetic observations under realistic detector noise, with posteriors verified as well-calibrated via TARP and SBC diagnostics. The approach naturally expands posterior width in information-poor regimes (low photon counts) and robustly recovers orbital parameters and mass-loss rates, demonstrating the feasibility of amortized likelihood-free inference for this challenging astrophysical inverse problem. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.10868 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.10868v1 Announce Type: cross Abstract: Long-horizon autoregressive forecasting of oscillatory physical signals, such as seismograms, gravitational-wave strain, and similar wavefields is limited by error accumulation: as a causal model is fed its own outputs over hundreds of steps, small per-step errors compound into phase drift that pointwise metrics fail to detect. We ask when such rollout stays stable, using synthetic three-component seismograms as a physically structured testbed and the \textsc{SeismoGPT} autoregressive forecaster as the model under study. Through controlled, intra-architecture ablations evaluated on free-running rollout with paired significance tests, we isolate the contribution of each design choice. Multi-token prediction is the dominant stabilizer, accounting for almost the entire improvement over a single-token baseline ($+0.040$ median NCC); a horizon-embedding hybrid prediction head and a cross-horizon STFT-magnitude coherence loss each add a small but consistent further gain. Performance depends sharply on a context-ratio threshold near one, roughly the full P-S interval of observed signal, below which rollout generalization collapses. The dominant residual failure is a polarity inversion that a magnitude-based spectral loss cannot, by construction, penalize, identifying phase-aware objectives as the natural next step. We frame this as a controlled study of rollout stability on oscillatory wavefields, not a benchmark of forecasting architectures. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11059 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11059v1 Announce Type: cross Abstract: Amorphous tantala is an important optical material used in a number of high-precision optical applications, including gravitational wave interferometry. In this paper, we study in-situ the structural changes that occur in amorphous ion-beam sputtered coatings during an annealing treatment by means of a synchrotron radiation scattering experiment. The scattering signal is measured as a function of time on a large range of the Q-space. X-Ray diffraction and Rietveld analysis are used to study crystallization during the annealing treatment, whereas pair distribution function analysis allows to inspect the structural changes occurring during the amorphous to crystalline transition. Our findings indicate that several structural rearrangements occur in parallel, namely a first quick establishment of a backbone structure in the cationic substructure appearing on a rather extended range (up to 100 Angstrom), followed by a progressive rearrangement of the oxygen atoms environment which gradually increases the crystallinity of the structure. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2606.11161 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2606.11161v1 Announce Type: cross Abstract: We present AutoClassMK, a simple, fully-connected, five-layer double-headed neural network written entirely in Python and Numpy that classifies normal stellar spectra conforming to the libr18 MK atlas in the 2D MK classification system with a high degree of precision and recall. AutoClassMK has the distinction of having transparent basic code with no calls to specialized libraries. In this paper we take care to explicitly describe in detail the ideas and operations that enable the network. Training AutoClassMK required us to develop large, noisy artificial training and test sets by augmenting the libr18 and libr18_27 MK atlases and to simplify the luminosity classification so that every combination of spectral- and luminosity-class is represented in the training set. We then test the network's ability to predict the MK spectral type of noisy augmentations of spectra in the libr18_225 MK atlas. We then implemented the same architecture in PyTorch to gain further insight and to enable execution on CUDA GPU's. All codes and the training and test sets are available from the OpenStars www site: www.ap.smu.ca/OpenStars. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2605.31402 Wed, 10 Jun 2026 00:00:00 -0400 arXiv:2605.31402v2 Announce Type: replace Abstract: The Gaia Data Release 3 (GDR3) parallaxes are affected by a complex bias that depends on stellar magnitude, color, and celestial position, with amplitudes reaching tens of microarcseconds ($\mu$as). Standard global parametric models (e.g., Lindegren et al. 2021, hereafter L21) effectively remove large-scale trends but struggle to resolve small-scale spatial systematics due to functional rigidity. We aim to construct a flexible, data-driven calibration map that eliminates these residual local systematics without imposing rigid functional forms. We propose a "Global Pre-correction + Local Refinement" hybrid strategy. First, we utilize the L21 model as a baseline to remove the dominant magnitude and color-dependent biases. Second, we model the residual zero-point using a Local Non-parametric method based on a Sliding Window technique. This approach fits local trends using k-nearest neighbors from quasars (for faint stars, G>18) and wide binaries combined with Large Magellanic Cloud (LMC) (for bright stars, G < 18). Our hybrid model demonstrates significant improvements over the standard L21 solution. Validation against different samples reveals a remarkably flat residual map with near-zero bias across the full sky. Our mathematical attempt at calibrating the parallax zero-point is expected to provide a useful reference for the zero-point correction in future Gaia DR4, and to help move towards a physical resolution of this issue. Astro/astro-ph.IM_(Instrumentation_and_Methods_for_Astrophysics) https://arxiv.org/abs/2512.16169 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2512.16169v2 Announce Type: replace Abstract: A Bayesian analysis of the astrophysical \(S\) factor for the \(^{12}{\rm C}+{}^{12}{\rm C}\) fusion reaction is presented using available low-energy information at carbon--carbon relative energies \(E <3.5~{\rm MeV}\), including direct measurements and recent inverse-kinematics data. The goal of the global Bayesian fit is not to reproduce the local resonance-by-resonance structure of the \(^{12}{\rm C}+{}^{12}{\rm C}\) system, but rather to constrain the smooth global component of \(S^{*}(E)\) using the direct and inverse-kinematics constraints. The resulting posterior \(S^{*}(E)\) lies systematically below the traditional FCZ75 reference normalization over the energy interval considered. For example, at \(E=1.5~{\rm MeV}\) the median posterior value is \(S^{*}(1.5~{\rm MeV})=1.20\times10^{16}~{\rm keV\,b}\), whereas the Fowler--Caughlan--Zimmerman reference value is \(S^{*}_{\rm FCZ75}=3.0\times10^{16}~{\rm keV\,b}\) [W.~A. Fowler, G.~R. Caughlan, and B.~A. Zimmerman, Annu. Rev. Astron. Astrophys. \textbf{13}, 69 (1975)]. Thus, the updated posterior favors a lower smooth low-energy trend and does not support a sharp increase of \(S^{*}(E)\) as the energy decreases. The astrophysical consequence of the analysis is assessed through the thermonuclear reaction rate \(N_A\langle\sigma v\rangle\). The resulting median rate is lower than the CF88 analytic rate [G.~R. Caughlan and W.~A. Fowler, At. Data Nucl. Data Tables \textbf{40}, 283 (1988)] over the temperature interval considered, with \(R_{\rm present}/R_{\rm CF88}\simeq0.33\)--\(0.46\) for \(0.3\leq T_9\leq1.2\). At higher temperatures, where the Gamow window extends above the upper end of the adopted integration interval, the calculated rate should be regarded as a truncated rate rather than a complete stellar rate. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09750 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09750v1 Announce Type: cross Abstract: Many works have attempted to estimate the correlation and integral timescales associated with turbulent fluctuations in the solar wind, which are interpreted as length scales based on Taylor's~Hypothesis. However, accurate estimates of these timescales from spacecraft observations heavily rely on the accurate estimation of autocorrelation functions (ACF), which have been recently shown to depend strongly on the interval length used to estimate them. In this Letter, we show that this dependence on interval length may be artificial because common ACF estimators do not correctly capture the long-lag behavior of the true ACF of the underlying turbulence. We introduce a new ergodicity-based methodology to unambiguously estimate the integral timescale, and a new ACF estimator with better ergodic convergence than current ones. Due to its ergodic properties, the new ACF estimator properly captures the long-lag behavior, and is independent of the interval length. We use this approach to estimate the integral and correlation scales of magnetic fluctuations in the solar wind near $1~{\rm au}$. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09745 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09745v1 Announce Type: cross Abstract: Using the open source MPI-AMRVAC framework, we study oscillatory reconnection in a laboratory plasma, which occurs when a magnetic null is perturbed by incoming fast magnetoacoustic waves driven by an alternating current. The magnetic null region collapses to first form a $y$-directed current sheet that later changes its orientation to the $x$-direction. The $x$-directed current sheet has smaller enhanced thermal pressure and out-of-plane current than the $y$-directed current sheet. The Hall effect produces an out-of-plane plasma flow that evolves with a time lag with respect to the enhanced thermal pressure and out-of-plane current density. Increasing the amplitude of the alternating current produces higher thermal pressure, out-of-plane current density, and out-of-plane plasma flow, while the first peaks of thermal pressure and out-of-plane current density occur earlier. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.07838 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07838v1 Announce Type: cross Abstract: Parker Solar Probe (PSP) observations in the young solar wind reveal new properties of both plasma particle velocity distributions (VDs) and associated electromagnetic (EM) wave fluctuations. The quasilinear (QL) kinetic theory of plasma wave instabilities has recently shown that new hammerhead (HH) proton distributions can be generated by the relaxation of proton beams through the instabilities of right-handed (RH) polarized waves. Such RH waves have indeed been reported in association with HH distributions. In this paper, new results from hybrid simulations of proton-beam-plasma systems with properties typical of those observed to excite EM-RH wave instabilities are presented. From the long-term evolution of these systems, it is found that beam relaxation is driven by instabilities and growing wave fluctuations, leading to HH-type features in the velocity distributions. The production of these features, as well as their prominence, depends on the magnetic power of the waves generated by the instabilities and, therefore, implicitly on the available free energy, quantified by the plasma beta parameter and the relative beam drift. The simulation results capture the self-consistent evolution of the instabilities and their nonlinear development. Linear theory, together with simulations, helps identify the nature of the unstable modes and the plasma conditions under which they arise. The good agreement with quasi-linear (QL) theory further indicates that it can serve as a computationally efficient complementary framework for interpreting the associated wave-particle interactions. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.07566 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07566v1 Announce Type: cross Abstract: Coronal mass ejections (CMEs) are explosive and energetic events consisting of strong magnetic structures erupting from the solar corona. We use superposed epoch analysis to investigate the general properties of CMEs as measured {\it in situ} from 0.2 to 2.2 au based on over 1600 events obtained from the HELIO4CAST catalog. We examine the dependence of the CME global properties on solar cycle phase, and compare the CME parameters derived in the active phase (AP) with the quiet phase (QP). Our findings show that during the AP of the solar cycle, the occurring CMEs are faster and have stronger magnetic field strength than during the QP, which has denser but weaker magnetic strength. These differences in magnetic field strength and density remain even when controlling for the speed. This may indicate that the enhanced profiles observed during the AP are not only a consequence of the CME propagation speed but may also reflect intrinsic differences in the eruption mechanism during different solar cycle phases. We also study how the magnetic field strength and components of the CME magnetic ejecta (ME) structure evolve with heliocentric distance. We find that the toroidal and poloidal ME magnetic field components have a similar power law decrease with distance, indicating a comparable expansion behavior of CMEs in these dimensions. We further quantify the CME magnetic field asymmetry %(often associated with CME aging) using the front-to-rear ratio of the toroidal component across heliocentric distance and find evidence of an increase of this ratio with heliocentric distance. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09814 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09814v1 Announce Type: new Abstract: We present the first Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 (100 GHz) and Band 6 (243 GHz) continuum observations of the Arches cluster, one of the youngest and most massive stellar clusters in the Milky Way. We detect and characterise millimetre emission from 23 massive stars, including WN7-9h Wolf-Rayet stars, O-type supergiants and hypergiants. By combining our ALMA measurements with archival Very Large Array data spanning 5-22.5 GHz, we derive broadband radio-millimetre spectral indices and investigate the radial structure of stellar winds through frequency-dependent clumping diagnostics. The majority of Wolf-Rayet stars exhibit spectral indices clustered around $\alpha \approx 0.7-0.8$, consistent with predominantly thermal free-free emission from dense, partially optically thick winds. In contrast, several O-type stars show flat or negative broadband spectral indices, indicative of non-thermal synchrotron emission likely associated with colliding-wind binaries. Using millimetre flux densities, we derive clumping-scaled mass-loss rates spanning $\log(\dot{M}/\mathrm{M}_{\odot}\,\text{yr}^{-1})\approx-4.1$ to $-4.9$ for the WN stars and $-4.9$ to $-5.4$ for the O super-/hypergiants, consistent with expectations for luminous massive stars in the Galactic Centre environment. We find significant evidence of structured wind clumping at millimetre wavelengths that generally decreases with increasing radius, supporting structured wind models with strong inner-wind inhomogeneities. These results demonstrate the power of combined radio-millimetre observations for constraining mass-loss and wind structure in massive stars, and provide new insight into stellar feedback in extreme cluster environments. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09627 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09627v1 Announce Type: new Abstract: Cataclysmic variable stars (CVs) evolve toward shorter orbital periods ($P_{\rm orb}$) until they reach a minimum $P_{\rm orb}$ near $P_{\rm orb}\sim80$ min. Beyond this point, the donor star becomes out of thermal equilibrium or increasingly degenerate, causing the system to "bounce back" to longer $P_{\rm orb}$ values. Such highly evolved systems are known as period-bouncers. Although 40-80\% of all CVs are expected to have reached this stage, period-bouncers come up for only 3-25\% of the observed CV population. This is likely a consequence of their intrinsic faintness associated with lower mass-transfer rates. Establishing new diagnostics to unveil this missing population is therefore crucial. Two samples of non-magnetic CVs with public SDSS optical spectra were constructed: one of short-period pre-bounce CVs and another of period-bounce CVs. For systems showing Balmer absorption from the white dwarf (WD), hydrogen-dominated atmosphere models were fitted and subtracted to correct for the WD component. H$\alpha$, H$\beta$, and H$\gamma$ fluxes were measured. We then investigated statistical relations between the Balmer decrements, the H$\beta$ line luminosity, and $P_{\rm orb}$, and compared the measured Balmer decrements with theoretical predictions from accretion disc models. Short-period pre-bounce CVs show flat Balmer decrements, that is Balmer line ratios close to unity. In contrast, systems near and beyond the period minimum exhibit progressively steeper decrements (H$\alpha$/H$\beta$>1 and H$\gamma$/H$\beta$<1). This behaviour is attributed to their lower mass accretion rates, as inferred from the H$\beta$ line luminosity. We fitted a linear logistic regression model to the diagram of H$\gamma$/H$\beta$ versus H$\alpha$/H$\beta$. We establish that this diagnostic diagram effectively separates period-bouncers from pre-bounce CVs. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09626 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09626v1 Announce Type: new Abstract: We present analytical model for peristaltic transport within compressible, ideal magnetohydrodynamics (MHD). By employing small-amplitude perturbation expansion, under thin-tube long-wavelength approximation with a uniform axial background magnetic field, we study non-linear coupling between thermodynamic pressure variations and Maxwell's magnetic tension stresses. The resulting net time-averaged volumetric flow rate $\langle Q \rangle$ is calculated. When applied to solar chromospheric spicules under equipartition constraints ($\beta \sim 1$), where sound speed matches the Alfv{\'e}n speed, we find $\langle Q \rangle = 4\epsilon^2/(M^2-1)$. Because the denominator remains positive across all operational supersonic Mach numbers ($M \approx 2\text{--}10$), upward-propagating mechanical disturbances drive a highly directional, collimated upward flow which we interpret as a spicule. Estimates show that for observationally realistic magnetosonic waves with amplitudes of $\approx 10\%$, the peristaltic mechanism generates a localized mass flux $\approx 100$ times that of solar wind. We propose an explicit observational signature of this mechanism, wherein the launch of individual spicular jets is directly preceded by magnetosonic wave trains detectable as localized intensity modulations. Beyond solar chromospheric application, the model may be applicable to traveling magnetic field pinches in laboratory plasma devices and astrophysical mass-loading processes in stellar winds and inner regions of magnetized accretion disks. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09562 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09562v1 Announce Type: new Abstract: Light bridges are commonly observed in active regions and are interpreted as signatures of magnetoconvective processes in sunspots. Several studies have attempted to classify them in the past based on their morphological characteristics. Recent observations have revealed new dynamical properties of light bridges, including their signatures in the upper solar atmosphere, particularly in the chromosphere, and their coupling with coronal features. In this study, we observed two cases of rare and unusual dynamics as light bridges evolve. Using data from the Solar Dynamics Observatory, the evolution of the light bridges is analysed, and the results are reported here. Based on our findings, we propose that the unique movements of the light bridges in the observed sunspot and earlier studies could be an apparent view of the umbral core dynamics. Investigation into these dynamics through signatures in the higher atmosphere reveals a clear coupling to coronal loops and their dynamics. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09485 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09485v1 Announce Type: new Abstract: Accurate stellar ages and masses are essential for interpreting the demographics and physical properties of exoplanets, particularly for intermediate-mass, early-type stars where conventional age indicators are ineffective. Isochrone fitting remains the primary tool for characterising such stars, yet its uncertainties are often underestimated, especially in the presence of rapid rotation and unresolved binarity. We present a population-synthesis framework designed to quantify realistic mass and age uncertainties for intermediate-mass stars (1.4-2.5 M$_{\odot}$), incorporating distributions in rotation rate, mass, metallicity, binarity, inclination, and observational error. Rotational and geometric effects are applied a posteriori to stellar evolutionary models, enabling a continuous treatment of rotation and its impact on effective temperature and luminosity. By comparing synthetic populations against commonly used isochrone grids, we demonstrate that rotation and unresolved companions systematically bias inferred masses and ages, particularly for young stars, and introduce random uncertainties at the $\sim$0.1-M$_{\odot}$ and $\sim$180-Myr level, often exceeding formal fitting errors. The effect is strongest near the zero-age main sequence, where ages are underestimated by a factor of $\geq2$, while for older A stars ($>$10% of their main-sequence lifetime), ages are overestimated by 31% with 27% scatter. Our findings carry important consequences for planet detectability, characterisation, and population studies. We provide a publicly available tool, RAPID, for probabilistic inference of stellar parameters from these synthetic populations, and we demonstrate its application to known exoplanet hosts. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09464 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09464v1 Announce Type: new Abstract: Observations of wide post-interaction binaries show an unexpected feature; orbital eccentricity, which is not understood theoretically. A promising resolution to this long-standing puzzle is eccentric mass transfer (MT). Here the first complete framework for MT in orbits with arbitrary eccentricity, the general mass-transfer (GeMT) model, is confronted with the latest observations of hot subdwarfs of spectral type B (sdB) with main-sequence (MS) companions in wide orbits. SdBs are excellent benchmarks for binary evolution models, since their progenitors provide unique constraints on their formation histories. We show that the GeMT model naturally reproduces all orbital parameters of wide sdB+MS binaries without fine-tuning and that nonzero eccentricity is a natural outcome of MT. We further demonstrate that post-MT eccentricities depend directly on key MT parameters, including transferred mass, accretion efficiency, and angular momentum loss. Given the multitude of eccentric post-MT binaries with components ranging from low- to high-mass stars to compact objects, we propose that post-MT eccentricities offer a new window onto binary evolution, presenting a powerful tool to constrain highly uncertain binary-evolution parameters and mass-transfer formation histories across diverse populations. Post-MT eccentricity should therefore be embraced as a key observable, rather than treated as a problem to be corrected. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09252 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09252v1 Announce Type: new Abstract: We carried out radiometric calibration of the Visible Emission Line Coronagraph (VELC) onboard Aditya-L1 at 5303{\AA} using observations of the Sun itself, a novel approach compared to the calibration using bright stars in the other currently operational space solar coronagraphs. The measured VELC detector count corresponding to the center of Sun's disk is ${\approx}(1.70{\pm}0.12){\times}10^{8}\, \rm sec^{-1}{\AA}^{-1}$, which relates to Sun's flux at 1\,AU in 5303{\AA}, ${\approx}3.0456{\times}10^{6}\, \rm {erg\,sec^{-1} cm^{-2} {\AA}^{-1}}$. We verified the above calibration using observations of the bright star Sirius-A whose estimated flux at 1\,AU in 5303{\AA} is ${\approx}1.44{\times}10^{-8}\,\mathrm{erg\,sec^{-1} cm^{-2} \AA^{-1}}$. The expected detector count with VELC in this case is ${\approx}19{\pm}1.4\, \rm sec^{-1}{\AA}^{-1}$, and the measured count is ${\approx}23{\pm}0.4\, \rm sec^{-1}{\AA}^{-1}$. The reasonable agreement between the expected and observed values for Sirius-A in this initial consistency check after two years of observations with VELC, indicates that measurements of coronal brightness at 5303{\AA} with the VELC and its conversion into absolute physical units using observations of the Sun disk light are in order. Using the Sirius-A observations we measured the point spread function (PSF) of the VELC in its 5303{\AA} channel also. Its full width at half maximum (FWHM) is ${\approx}3.8^{\prime\prime}$. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09226 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09226v1 Announce Type: new Abstract: We examined the applicability of observational data-driven magnetohydrodynamic (MHD) simulations to flare prediction. The target event was the X1.6 flare that occurred in NOAA AR 13663 at 02:22 UT on 3 May 2024. We employed a velocity-driven model, in which the photospheric velocity field was derived from the time-series magnetograms to use as the boundary input. The simulation showed a rapid increase in both thermal and kinetic energy density around the actual onset time and location of the X1.6 flare. We revealed that the flare was triggered by two-step reconnection, in which the initial tether-cutting reconnection facilitated the subsequent breakout reconnection. We further examined whether the flare could be reproduced when the boundary input was stopped prior to the actual flare onset time, assuming the situation in which the flare must be predicted using the data before it actually occurs. When the photospheric magnetic field was fixed more than 1 hour before the actual flare onset time, the flare was not reproduced in the simulations. In contrast, when the photospheric velocity field at the final observation time was incorporated to infer the subsequent magnetic evolution, the prediction lead time could be extended beyond 1 hour. On the other hand, quantitative prediction of the magnitude of flares remains a subject for future study. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.09172 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09172v1 Announce Type: new Abstract: Benchmarking fundamental stellar properties is essential for calibrating evolutionary models and establishing empirical relationships between mass, radius, luminosity and related stellar properties. We determine the current ages and initial equatorial velocities at the Zero-Age Main Sequence (ZAMS) for a well-characterized sample of 108 detached main-sequence eclipsing binaries. Evolutionary tracks from the ZAMS to the present are calculated by accounting for tidal interactions, including meridional circulation, and angular momentum loss via stellar winds, under the assumption of circular orbits. System ages are derived by identifying the evolutionary stage at which the calculated radii of both stellar components best match the observed values. While initial velocities for currently synchronized systems cannot be uniquely constrained, as a wide range of initial states naturally converges to synchronisation over time, we are able to determine unique solutions for ZAMS spin velocities in systems that remain asynchronous today. Our models successfully reproduce observed present-day equatorial velocities with a precision of 1\%. Two systems, HD~71636 and V396~Cas, were found to have primaries with initially retrograde spin at ZAMS. We also find an increasing dispersion of spin velocities with age. Our results demonstrate that tidal and evolutionary effects in binary systems actively counteract rotational deceleration from stellar winds, effectively preventing the substantial spin-down that typically characterizes the evolution of isolated single stars. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.08773 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08773v1 Announce Type: new Abstract: We report the discovery of 11 X-ray flares from 7 M dwarfs previously unknown to exhibit flaring activity, by cross-matching eROSITA observations of bright, nearby M dwarfs with the Chandra telescope archive. To analyze the properties of these flares in a broader context, we compile the sample of all reported X-ray flares from the 15 M dwarfs identified as flaring in the literature. We use this combined sample to derive constraints on the X-ray flare frequency distributions of M0-M6 stars. The average flare occurrence rate we measure is $\sim 10^{-1}\,\rm ks^{-1}$ (corresponding to $\sim 9$ flares per day). The X-ray flares in this sample span energies from $10^{29}\,\rm erg$ to $10^{33}\,\rm erg$ and exhibit a strong correlation between flare strength and duration. The flare properties we characterize include their durations, flux and temperature enhancements, and temporal asymmetries. Using these results and recent simulations of flare-driven atmospheric escape, we derive an upper limit on the time required for habitable Earth-like planets orbiting these M dwarfs to completely lose their atmospheres: 0.5-30 Myr. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.08652 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08652v1 Announce Type: new Abstract: Routine full-disk EUV imaging has been available only since the modern era, such as SOHO and SDO. To extend EUV coronal context into earlier periods, we leverage the multi-decade availability of full-disk \HeI{} observations, whose absorption is modulated by coronal irradiance and magnetic topology and is widely used as a proxy for open-field regions. We present a diffusion-based conditional image translation framework, Coronal Hole-aware Diffusion Model Translator (CH-aware DMT), to reconstruct synthetic SDO/AIA 193 \AA{} EUV images from \HeI{} inputs. The model is trained on temporally co-aligned SOLIS \HeI{} and AIA 193 \AA{} pairs spanning 2011--2015 using a month-based split, where January--October are used for training, November is used for validation, and December for testing. On the held-out test set, the reconstructions preserve dominant full-disk EUV morphology (CC=0.92) and recover CH-related low-intensity structure (CC=0.84). We further assess historical applicability by (1) comparing reconstructed AIA 193 \AA{} morphology with SOHO/EIT 195 \AA{} over 2005--2015; (2) comparing reconstructed AIA 193 \AA{} images generated from KPVT \HeI{} inputs against Yohkoh/SXT soft X-ray observations; and (3) evaluating long-term reconstructed disk-integrated emission statistics against observational EUV series and independent solar activity proxies (sunspot number and F10.7 radio flux over 1974--2015). These results indicate that CH-aware DMT conditioned on \HeI{} can provide a physically plausible synthetic AIA 193 \AA{} coronal proxy for historical studies, supporting multi-decade analyses of large-scale coronal evolution before the direct EUV imaging was available. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.08519 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08519v1 Announce Type: new Abstract: The results of new photometric observations of two SU~UMa type dwarf novae are presented. Superhumps were detected on the light curves of these systems during superoutbursts and their periods and amplitudes determined. The classification of objects as dwarf novae of the ER~UMa subclass (for RZ~LMi) and subclass WZ~Sge (for KV~Dra) has been clarified. Orbital period $0^{d}.0586$ for KV Dra was determined. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.08494 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08494v1 Announce Type: new Abstract: The processes that determine the stellar initial mass function (IMF) and its connection to the core mass function (CMF) are among the major open questions in star formation. The definition of a core remains unclear, yet the way they are extracted from simulations and observations critically shapes the CMF. Nowadays, cores are mostly detected through their density or intensity only. We aim to explore a new way to define cores in 3D numerical simulations based on a direct application of the virial theorem, and break free from some limitations induced by density-based methods. We intend to improve the accuracy and the physical meaning of the extracted cores. We developed vibes, an innovative method that makes full use of the virial theorem to extract overdensities in simulation snapshots. It works by building structures iteratively around density peaks, and applying the virial theorem to the structure at each iteration. Then, the structure boundary is set from the evolution of the its energy as it spatially grows. We used STARFORGE simulations to test the sensitivity of the extraction process to the main working parameters (constraints on the structure shape, iteration step, and peak selection criteria). This sensitivity is observed to be low. We compared our extraction with two density-based extraction algorithms, hop and dendrogram, that are observed to be very sensitive to their input density threshold parameter. Vibes returns structures that are coherent to each other and physically motivated, and it appears much more stable than existing 3D extraction tools. By defining the boundary of the cores on a physical criterion rather than on a user-defined set of density parameters, we expect such extracted cores to be closer to their forsaken definition: gas reservoirs that will form a single star or a close multiple system. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.07989 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07989v1 Announce Type: new Abstract: Sunrise III is a stratospheric balloon-borne solar observatory with a 1-m diameter telescope and three post-focus instruments, along with an image stabilisation system, all within a protective gondola. It samples the lower solar atmosphere, from the solar surface to the middle chromosphere, at a resolution approaching 50~km on the Sun. Sunrise III flew successfully for 6.5 days suspended from a zero-pressure stratospheric balloon from northern Sweden to north-western Canada in July 2024, gathering around 200 TB of data. The present issue of ApJL focuses on the first scientific results from the data collected during that flight. This paper introduces this Focus Issue, providing a very brief overview of the capabilities of the instrumentation, the flight and of the gathered data. Challenges for the measurements, data reduction and interpretation are also briefly touched upon. The paper ends with an overview of the first set of science results obtained from these data, as presented in the current Focus Issue. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.07966 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07966v1 Announce Type: new Abstract: Time-series analysis plays a central role in understanding oscillatory and wave phenomena in solar and stellar atmospheres. However, astrophysical observations are inherently affected by instrumental noise, non-stationary dynamics, and uneven sampling. This review provides a comprehensive overview and comparative analysis of principal methods for detecting and characterizing periodicities in solar and stellar signals. We cover Fourier-transform-based transforms, nonlinear-fitting-based methods (Lomb--Scargle periodogram), time-frequency methods (wavelet and synchrosqueezed transforms), and adaptive decomposition techniques (Empirical Mode Decomposition). Advanced statistical significance tests, including false-alarm probability, autoregressive models, and Bayesian Markov Chain Monte Carlo (MCMC) approaches, are discussed their practical limitations and misuse risks. Through comparative analysis using synthetic benchmarks, we provide guidelines for selecting methods based on signal stationarity, sampling regularity, and noise characteristics. Finally, we outline future directions that integrate Bayesian inference with time-frequency analysis to achieve both statistical rigor and temporal localization in studying non-stationary solar and stellar oscillations. Astro/astro-ph.SR_(Solar_and_Stellar_Astrophysics) https://arxiv.org/abs/2606.07742 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07742v1 Announce Type: cross Abstract: Neutron stars are very dense media in which axions may be produced. This has been used to set limit on the QCD axion mass, usually under the assumption that only neutrons, protons, electrons, and muons appear in the star core. Given the extreme conditions reached within neutron stars, it is reasonable to consider that other particles, such as hyperons and $\Delta$ resonances, may exist on-shell. In this work, we study how the limit on the mass of QCD axions, namely KSVZ and DFSZ invisible axions, is altered when different equations of state are used, allowing for heavier particles to appear in the neutron star core. We find that this dependence is in general mild and thus reinforces the reliability of the known limit. Additionally, in the DFSZ scenario, it may drive the limit within the sensitivity window for IAXO. This would allow this experiment to discern the composition of neutron star cores if an axion were to be observed within that window. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.07731 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07731v1 Announce Type: cross Abstract: We investigate whether current astrophysical data constrain not only the high density continuation of the neutron star equation of state, but also the low density matching procedure itself. To this end, we compare two low density branches propagated through a common high density extension and confront them with direct NICER mass-radius posteriors, a lower bound on the maximum mass, and an effective constraint on $\Lambda_{1.4}$. We find that the observable predictions of the two branches remain strongly overlapping, while the NICER-informed posterior still induces a nontrivial constraint on the matching parameters. Current data therefore constrain primarily the shared continuation above $n_1$, but also indirectly restrict the low-density matching sector. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.07679 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07679v1 Announce Type: cross Abstract: PyCBC Live is a low-latency search pipeline that identifies gravitational waves from compact binary coalescences and provides alerts for electromagnetic follow-up. This paper presents improvements to PyCBC Live that were implemented for the fourth observing run (O4) of the LIGO-Virgo-KAGRA network, which operated from May 2023 to November 2025. The ranking statistic was enhanced to incorporate time-dependent background modeling using data quality streams and daily updates of the noise model. Follow-up capabilities were improved through refined probability of astrophysical origin calculations, optimized SNR recovery with reduced computational cost, and a method to incorporate Virgo as a sky-map-only detector. An Early Warning search was implemented to detect binary neutron star and neutron star-black hole systems before merger, providing pre-merger alerts with a pipeline latency of 2.5-3.5 seconds and warning times up to 60 seconds before coalescence. The autogating procedure was extended to apply to the full strain buffer rather than individual analysis segments, improving rejection of loud and rapidly successive glitches. Performance validation using the Mock Data Challenge showed sensitivity improvements of factors of 1.7 to 2.3 for the coincident search depending on source mass at an inverse false alarm rate of 10 years, and factors of 1.3 to 1.7 for the single-detector search. For injections in two-detector time, the O4 configuration identified 1979 of 2495 injections with a decisive SNR greater than 6 at a false alarm rate below one per year (79.3%), compared to 1262 (50.6%) with the O3 configuration. For injections in single-detector time, the O4 configuration identified 218 of 1174 injections (18.6%), compared to 170 (14.5%) with the O3 configuration. The search maintained a median latency of 15.94 seconds from merger to candidate upload. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09621 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09621v1 Announce Type: new Abstract: The structure and dynamics of neutron stars can be used to probe the physics of extreme matter at nuclear densities and beyond. Nucleonic matter up to ~2-3 times nuclear saturation density is well-studied by nuclear experiments and theoretical modelling. Matter beyond these densities may contain non-nucleonic degrees of freedom that determine the structure of the neutron star inner core and influence bulk observables like stellar radius. Neutron star radius is a key parameter for constraining the core equation of state, but is not a direct gravitational-wave observable during neutron star mergers. Here we show that, if nucleonic physics is well constrained at low densities, the frequency of the asteroseismic crust-core interface mode in a neutron star can be used to infer its radius to within 5-10%, in a way which is notably insensitive to the details of the inner core. This frequency can be measured through multimessenger coincident timing of resonant shattering flares, or direct observation of dynamical tidal resonance with next-generation gravitational-wave detectors. We show that improved constraints on low-density nucleonic physics by nuclear experimental and theoretical efforts will substantially improve such a radius measurement, leveraging low-density efforts for an improved understanding of physics at higher densities. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09604 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09604v1 Announce Type: new Abstract: The recent detection of Galactic neutrinos by the IceCube Observatory constitutes a remarkable achievement for neutrino astrophysics. By means of model dependent analyses based on spatial and spectral templates, a purely diffuse neutrino flux was measured in which no individual source was resolved. We present here a novel theoretical computation about the expected neutrino emission from the Galactic Plane that, differently from previous models, includes both the contributions from cosmic-ray (CR) sea and hadronic sources, represented by star clusters and supernova remnants therein, which are to date believed to be the dominant sources of Galactic CR protons. For the modelling of sources, diffusive particle acceleration is considered at both the collective wind termination shock blown by member stars and at the supernova shocks. The predicted flux of very-high energy neutrinos from individual star clusters is found to be marginally detectable even by cubic kilometer scale detectors, such that their cumulative contribution is expected to appear as an unresolved diffuse component, on top of that guaranteed by the CR sea interacting with the gas along the Plane. The overall neutrino production of the Milky Way star cluster population is computed, based on multiple synthetic realizations of the cluster population reproducing local stellar observations. As a result, we obtain novel neutrino template maps and provide them to the community, to be tested in future neutrino analyses in order to constrain the role of star clusters for extreme CR acceleration and neutrino production. The normalization of our models is consistent with the IceCube best-fit of existing Galactic templates, suggesting that the unresolved contribution from cluster emission may be non-negligible. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09579 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09579v1 Announce Type: new Abstract: X Persei is a classical Be/X-ray binary composed of an O9.5III-B0V Be-type star and a neutron star (NS). The NS exhibits coherent pulsations with a spin period of ~837 s, orbiting the Be star with a ~250 d period. X Persei is notable for its exceptionally hard X-ray emission extending beyond 100 keV. Due to the mild eccentricity of the orbit, ~0.11, the orbital separation varies between roughly 35 R_star at periastron and 44 R_star at apastron. In this work, we analyze five targeted observations obtained with the XMM-Newton and Chandra observatories taken over a 10-year time span, with the aim of investigating the structure and variability of the circumstellar disk surrounding the Be star, in particular the presence of over-dense areas known as clumps. We performed spectral and timing analyses, including average and NS spin-resolved spectroscopy for three of the observations, producing individual spectra at intervals as short as 210 s, corresponding to different epochs of the NS spin, resulting in approximately 1200 spectra. This detailed analysis aimed at resolving emission-line features otherwise diluted in averaged spectra and the evolution of continuum components along the NS spin. The observed spectra are accurately modeled by a two-component continuum comprising a high-temperature blackbody and a power-law component. Phase-resolved spectroscopy reveals transient Fe K alpha emission linked to clumps in the circumstellar disk during high-density epochs, with an 8-9% prevalence. Dips in the X-ray light curve are tied to clump passages. The disk-density modeling, based solely on X-ray data, suggests a compact and dense disk, with a radial density exponent alpha of 2.4-3.3, and a high inner disk density, rho_0 ~ (6-20) x 10^-10 g cm^-3, in agreement with previous studies conducted in the optical and infrared bands. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09417 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09417v1 Announce Type: new Abstract: We demonstrate that in highly magnetized pair plasma nonlinear long-wavelength X-modes experience wave collapse/breaking, whereby the wave undergoes severe spatial steepening, driven by nonlinear modifications of the refractive index and strong ponderomotive forces. The collapse/wave breaking occurs in a narrow parameter regime, when the fluctuating part of the magnetic field exceed the guide field, and plasma magnetization is close to the current starvation regime. This regime is naturally achieved in highly magnetized neutron stars, magnetars. Breaking occurs on the time scale of a fraction of the dynamic time scale, and quickly generates high-k modes. The initial EM energy, spread over large spatial scales, is squeezed into these highly localized, short-wavelength (yet macroscopic) singular pulses. The corresponding electromagnetic ``foam'' spectrum is red, $E_k \propto k^{-2}$, while the particles' spectrum is exceptionally hard, $f(\gamma) \propto \gamma^0$ The wave collapse produces short bright EM pulses - astrophysical Fast Radio Bursts. The highest energy particles may produce short high energy bursts. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09247 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09247v1 Announce Type: new Abstract: The elastic properties of the neutron-star crust are important for the calculations of crustal modes. In particular, the ability of the crust to support shear stresses has been connected to observations of quasi-periodic oscillations and to crust deformations potentially emitting gravitational waves. In this work, we assess the uncertainties in the shear modulus and shear speed in the neutron-star outer and inner crust. To this aim, we performed a Bayesian analysis of the shear properties of the neutron-star crust at zero temperature starting from both a non-informative and a nuclear-physics-informed prior. For the treatment of inhomogeneous matter in the crust, we relied on the one-component plasma approximation, with a (semi-)classical treatment of the ions. We show that the use of a nuclear-physics-informed prior has a non-negligible impact on the prediction of the elastic properties of the crust. The frequency of the fundamental torsional crustal modes we obtain is compatible with the low-frequency range of observed quasi-periodic oscillations, our estimates lying in the interval $\approx 20 - 50$~Hz. Although the different considered priors lead to compatible results, the inclusion of nuclear-physics experimental information in the prior considerably reduces the uncertainties in the prediction of the elastic properties of the crust, potentially constraining the predicted frequency of the crustal modes. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09229 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09229v1 Announce Type: new Abstract: Fallback accretion in collapsar models is often associated with underluminous gamma-ray bursts (GRBs), leading to the widespread view that fallback-fed engines may be intrinsically inefficient at producing high-luminosity events. In this Letter, we present GRB 250706B/C, a luminous long GRB observed by \textit{Insight}-HXMT that exhibits an unusual combination of extreme short-timescale variability and coherent large-scale temporal evolution. The prompt emission contains at least 79 resolved pulses and a minimum variability timescale of $\sim11$ ms. The pulse widths are nearly independent of photon energy and span a broad distribution with a median FWHM of $\sim0.30$ s, while the waiting times between adjacent pulses have a median of $\sim0.38$ s. The prompt-emission envelope exhibits a prolonged rise described by $F(t)\propto (t-t_0)^{0.47\pm0.01}$ followed by a rapid decline. Despite substantial pulse-to-pulse fluctuations, neither the pulse widths nor the waiting times show significant secular evolution during the main emission episode. These features indicate the coexistence of two distinct temporal components, including a slow evolving rising luminosity envelope and rapid stochastic variability. Such behavior is consistent with scenarios in which a time-dependent engine-feeding history regulates the large-scale emission while internal dissipation within the relativistic outflow produces the pulse structure. Within this context, GRB~250706B/C may represent a fallback-fed collapsar operating on a high-luminosity branch, suggesting that fallback itself does not necessarily limit the luminosity scale of GRBs. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08967 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08967v1 Announce Type: new Abstract: The structural properties of bosonic dark matter stars are systematically investigated, presenting precise scaling relations for the mass, radius, central density, and the properties of dark matter particles. The dark matter equation of state is derived from a complex scalar field theory with a quartic self-interaction potential $V(\phi) = \frac{\lambda}{4} |\phi|^4$, considering boson masses $m_{\phi}$ ranging from $10^{-9}$ to $10^{3}$ GeV and self-coupling constants $\lambda$ ranging from $0.01\pi$ to $100\pi$. The scaling relation for the maximum mass of bosonic dark matter stars, the corresponding critical radius and critical central density are obtained as \[ M_{\text{max}} = 0.1 \frac{\sqrt{\lambda}}{m_\phi^2} M_\odot, \qquad R(M_{\text{max}}) = 0.9 \frac{\sqrt{\lambda}}{m_\phi^2} \ \text{km}, \qquad \varepsilon_{\text{max}} = 2.1 \times 10^5 \frac{m_\phi^4}{\lambda} \ \mathrm{MeV/fm^3}, \] where $m_\phi$ is in GeV, the relations for $R(M_{\text{max}})$ and $\varepsilon_{\text{max}}$ are first put forward. The fitting relative error is less than $4\%$. Based on these scaling relations, we further provide global analytical fits for the stable branch. The relationships between mass and central density as well as radius and central density can be described by a unified function of the form: \[ \tilde{Y} = \frac{A}{\left[1 + \left(5\tilde{\varepsilon}\right)^h\right]^s}, \] where for $Y=M$, $\tilde{M} \equiv M/M_{\text{max}}$, $A=1$, $h=-2$, $s=0.42$; for $Y=R$, $\tilde{R} \equiv R/R(M_{\text{max}})$, $A=1.634$, $h=1$, $s=0.28$; and $\tilde{\varepsilon} \equiv \varepsilon_0/\varepsilon_{\text{max}}$. The fitting relative error is less than $0.1\%$. Furthermore, we find a simple quadratic polynomial mass-radius relation for bosonic dark matter stars. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08931 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08931v1 Announce Type: new Abstract: We report the first identification of molecular clumps directly associated with the re-brightening regions of the large-scale X-ray jets of SS 433, based on $^{12}$CO ($J$ = 1--0) observations with the Nobeyama 45-m Radio Telescope. Multiple clumps are detected toward the eastern and western jet heads, showing clear spatial correlation with the X-ray emission. The X-ray emission peaks immediately downstream of the molecular clumps, while the hardness ratio is enhanced at their surfaces, indicating that the observed structures cannot be explained by absorption effects. These results provide direct evidence for shock--cloud interactions between the jets and the surrounding interstellar medium. We suggest that turbulence generated at the jet--cloud interface amplifies magnetic fields, producing the observed non-thermal X-ray emission. Our findings highlight the importance of jet--ISM interactions in shaping the X-ray properties of microquasar jets. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08910 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08910v1 Announce Type: new Abstract: In Scalar-Tensor-Vector Gravity (STVG, also known as MOG), a massive vector field $\phi_\mu$ generates a repulsive fifth force that endows rotating black holes with a gravitational charge $Q \propto \sqrt{\alpha}\,M$, modifying the near-horizon geometry through a single deformation parameter $\alpha$. We investigate how this vector-field coupling imprints itself on the thermal continuum emission of geometrically thin, optically thick accretion disks in the Kerr-MOG black hole. By re-deriving the innermost stable circular orbit (ISCO), the Novikov-Thorne radiative flux, the relativistic energy shift, and the null geodesic structure for the Kerr-MOG spacetime, we compute fully relativistic disk spectra across a broad range of spins, inclinations, and fifth-force strengths using a dedicated \textsc{xspec} spectral model (\texttt{kmspec}). We find that the fifth-force charge pushes the ISCO outward, lowers the peak disk temperature, and systematically softens the thermal continuum relative to its Kerr black hole counterpart at the same spin, with the deviation amplified at high observer inclinations. The resulting spectral modification closely mimics a reduction of spin in the pure Kerr black hole framework, indicating that independent spin measurements from, e.g., iron-line reflection spectroscopy are indispensable for disentangling the vector-field contribution. All results recover the standard Kerr black hole predictions when $\alpha = 0$, and the model is validated against independent analytic and numerical benchmarks to machine precision. Application to a 69.6~ks \textit{XMM-Newton} observation of LMC~X-1 yields $\alpha < 0.044$ at 90\% confidence, consistent with the Kerr metric and general relativity. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08862 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08862v1 Announce Type: new Abstract: We present an X-ray spectro-polarimetric study of the nearby type-1 active galactic nucleus NGC 4151 using two long IXPE observations obtained in 2022 and 2024, supported by simultaneous XMM-Newton and NuSTAR spectroscopy. IXPE measures a polarization degree of $\sim 6-7\%$ above 4 keV, with a polarization angle parallel to the radio jet, and a distinct low-energy component with a different angle, indicating at least two polarized components in the $2-8$ keV band. Previous work interpreted the hard X-ray polarization as evidence for a radially extended slab-like corona. Here we test an alternative scenario in which the observed polarization is produced predominantly by relativistic reflection from an accretion disk illuminated by a compact, lamp-post-like corona. Using recently developed models, we fit the IXPE Stokes spectra with a lamp-post plus distant-torus geometry, including partial-covering absorption and an additional soft polarized power-law component. We find that the data require a low coronal height ($h 45^\circ$ at 3$\sigma$), while the disk reflection contributes $\sim 20\%$ of the 2-8 keV flux. The soft polarized component carries only $\sim 1-5\%$ of the flux but has a high polarization degree ($>10\%$) and a polarization angle around $20^\circ$. The same configuration provides acceptable fits to the $0.4-79$ keV XMM-Newton and NuSTAR spectra, demonstrating that disk reprocessing by a compact corona can simultaneously account for both the polarization and broadband spectral properties of NGC 4151. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08752 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08752v1 Announce Type: new Abstract: We report multi-wavelength studies of the transient EP250916a, detected by the Einstein Probe on 2025 September 16. Located at low Galactic latitude, the source exhibited a rapid X-ray brightening, reaching an unabsorbed 0.5--10 keV flux of $(6.4 \pm 0.1) \times 10^{-10}$ erg cm$^{-2}$ s$^{-1}$, followed by a plateau and a two-stage decay lasting over 40 days. Swift/XRT monitoring shows a persistently hard spectrum ($\Gamma \approx 1.6$--2.2) with only modest softening during decay, while a NuSTAR observation confirms a hard-state continuum extending up to 70 keV. Timing analysis of XMM-Newton data reveals a weak quasi-periodic oscillation (QPO) at $\sim$13 Hz. No other coherent pulsations or thermonuclear bursts are detected. Broadband spectral modeling favors a nonthermal power-law continuum with partial-covering absorption, and shows no significant thermal disk component. Optical imaging obtained with NOT/ALFOSC, LCO, and GaiaDR3 identifies two faint sources within the 2 arcsec Swift/XRT positional uncertainty. A MeerKAT observation at 1.28 GHz yielded no radio counterpart, with a 3$\sigma$ upper limit of 60 $\mu$Jy beam$^{-1}$. The combination of a long-lasting outburst, a hard nonthermal X-ray spectrum, a weak QPO detection, the absence of coherent timing features, and faint potential optical counterparts disfavors a stellar-flare or extragalactic origin and supports an accreting compact-object scenario. Comparisons with similar faint, hard-state transients place EP250916a within a growing population of low-luminosity, hard-state black hole X-ray binary candidates. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08598 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08598v1 Announce Type: new Abstract: We present a broadband X-ray study of the transient hyperluminous X-ray source (HLX), 2SXPS J111416.1+481833, in the galaxy NGC 3583, using archival XMM-Newton, NuSTAR, Chandra data, and long-term Swift/XRT monitoring. The source episodically enters the hyperluminous regime with X-ray luminosities $L_X > 10^{41}$ erg s$^{-1}$ and drops by a factor of $>45$ from its peak into a deep low state. We detect a clear spectral cutoff at $\sim$5-6 keV in the broadband spectra, which are well modeled by a soft thermal component combined with optically thick thermal Comptonization or an inner advection-dominated disk. In the XMM-Newton spectra, we detect a statistically significant ($\gtrsim 3.9 \sigma$) absorption line centered at $E_{\rm line} \approx 1.97 \pm 0.04$ keV with a width of $\sigma_{\rm line} \approx 74 \pm 40$ eV. We primarily interpret the line as a candidate proton Cyclotron Resonance Scattering Feature (CRSF), implying a local magnetic field strength of $B \sim 4 \times 10^{14}$ G. Alternative interpretations, such as an origin in an ionized outflow, were explored and found to be less likely. We do not detect coherent X-ray pulsations, placing 90% confidence upper limits on the pulsed fraction of 19.3% in the 0.3-10 keV band and 36.3% in the 3-15 keV band. The combination of extreme luminosity, a hard spectral state, and the detection of a candidate cyclotron line provides strong evidence for a highly magnetized neutron star accretor. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08522 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08522v1 Announce Type: new Abstract: The high-frequency gravitational waves emitted by a binary neutron star merger remnant carry information on matter at densities and temperatures beyond those reached in isolated neutron stars. We quantify how tightly current multi-messenger constraints already determine the dominant post-merger frequency $f_{2,\rm mean}$. Adopting a set of cold equations of state (EOSs) constrained jointly by gravitational-wave tidal deformability, NICER mass--radius measurements, massive-pulsar masses, chiral effective field theory at low density, and perturbative QCD at asymptotically high density, for each binary mass we select the softest and stiffest models of the multi-messenger posterior and follow their coalescence with fully general-relativistic hydrodynamics simulations. Together with a broad set of EOSs drawn from the literature ($82$ models in total), these simulations show that, once the binary mass and a single measure of the stellar compactness ($\Lambda$ or $R$) are held fixed, the residual spread of $f_{2,\rm mean}$ is only $\sim 100\,{\rm Hz}$, a factor of several below the $\gtrsim 500\,{\rm Hz}$ range spanned by an EOSs set including those already disfavored by the data. This tight calibration of the cold-matter prediction implies that a future high-frequency detection departing from it would point directly to additional physics, such as a hadron--quark transition occurring at finite temperature. We further confirm the quasi-universal relation $(f_1+f_3)/2 \approx f_{2,\rm mean}$ to within $\sim 116\,{\rm Hz}$, which provides a model-independent estimate of $f_{2,\rm mean}$ from the secondary spectral peaks. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08355 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08355v1 Announce Type: new Abstract: Old pulsar wind nebulae are among the foremost galactic high-energy gamma-ray sources. However we still lack a robust approach to their modeling, especially in the light of forthcoming high-energy observatories like Astri or CTAO. Part of the problem is due to the complex interaction that characterizes these systems. Understanding this complexity has then become mandatory for further advancements. We aim to develop a new approach to investigate the role the thermal thick layer of massive filaments, seen in objects like the Crab nebula and 3C 58, but likely present in all pulsar wind nebulae, can exert on the dynamics of the late reverberation phase, and compare results with standard approaches that neglect such a layer. A new formulation of the one-zone thin-shell plus Lagrangian formalism, developed in a series of previous papers, is here extended to the case of a thick layer of filamentary ejecta, complementing our former work, mostly focused on the initial free-expansion phase. We compare the dynamics of reverberation with and without the presence of filaments, and show that in the former case reverberation may be substantially anticipated and the following compression takes much longer. The total compression of the system does not seem to change much, and the qualitative behavior is preserved. Our results suggest that the presence or absence of an extended filamentary layer might affect the duration of both the free-expansion phase (shortening it) and the following compression phase during reverberation (lengthening it), but it does not change much the overall compression of the nebula. While this changes the relative number of systems in these two phases, and their contribution to high-energy emission, some peculiar radiative effects associated with the level of compression in old systems, like the "super-efficiency", might not be much affected. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08116 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08116v1 Announce Type: new Abstract: Pulsar wind nebulae (PWNe) interacting with the host supernova remnants (SNRs) can enter the reverberation phase in which reverse-shock-driven compression amplifies the magnetic field and rapidly reprocesses particles, sometimes producing "superefficiency", where the radiative output in a given frequency band exceeds the pulsar's instantaneous spin-down power. We investigate the prevalence of this phenomenon in the Galactic population by modeling PWNe with the hybrid TIDE+L framework, which self-consistently follows dynamical evolution, particle spectra, and emission from radio to PeV energies. We track superefficiency across frequency bands and evolutionary stages, analyzing both individual objects and ensemble properties, including compression-resolved samples and population spectral energy distributions. Superefficiency is most common in the far-infrared, but emerges across frequencies and evolutionary phases. It is enhanced in systems where accumulated low-energy electrons radiate in magnetically amplified nebulae. We predict substantially more superefficient sources than a purely thin-shell model would, with differences ranging from factors of a few in FIR and GeV bands to more than an order of magnitude in several optical/UV/X-ray bands. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.08023 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08023v1 Announce Type: new Abstract: X-ray thermally emitting isolated neutron stars (XINSs) are a rare population that provides insights into neutron star cooling, magnetic-field evolution, and Galactic demographics. Using more than two decades of observations from the European Space Agency's XMM-Newton Observatory, we searched the 4XMM-DR9 and 4XMM-DR12 catalogues for absorbed XINS candidates down to a flux of $10^{-14}$ erg cm$^{-2}$ s$^{-1}$ in the 0.5--1 keV band. Candidates were selected based on soft X-ray spectra and the absence of catalogued optical, ultraviolet, or infrared counterparts. Follow-up observations with XMM-Newton and FAST were complemented by data from the SRG/eROSITA All-Sky Survey, Chandra, and optical surveys. Of ten sources analysed, five are compelling XINS candidates, one is the known XINS 4XMM J022141.5-735632, two are extragalactic contaminants, and two remain ambiguous because of limited photon statistics. The five candidates exhibit soft ($kT\sim80-100$ eV), moderately absorbed, and stable X-ray emission consistent with distant XINSs. They are located primarily in the Galactic plane, with possible associations at distances of $\sim$1.8 and $\sim$6 kpc. Population-synthesis simulations predict $20\pm5$ XINSs within the 4XMM-DR12 footprint, of which $6^{+2}_{-3}$ exceed our flux threshold, consistent with the observed sample if additional candidates are confirmed. The model further predicts that $\sim$70% of the population remains below the detection threshold. Deep optical and additional X-ray observations are required to establish the nature of the candidates. Future missions such as NewAthena will enable more detailed studies of these distant populations and improve constraints on the Galactic XINS population. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.07733 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07733v1 Announce Type: new Abstract: The Galactic Center (GC) contains a collection of filaments that are typically tens of parsecs in length, illuminated by synchrotron radiation from cosmic rays (CR). The origin of these nonthermal filaments (NTFs) is unclear. We aim to distinguish two injection mechanisms: the first mechanism posits that NTFs are fueled either by jets from pulsar wind nebulae and are lepton-dominated; the second mechanism posits that NTFs are fueled by accelerated particles from interstellar shocks and are proton-dominated. We explore these mechanisms using the magnetohydrodynamics (MHD) code Athena++, modified to account for radiative and collisional losses, to simulate CR propagation with lepton and proton CR species. We vary parameters such as magnetic field strength, plasma density, and the CR diffusion coefficient to determine how the range of conditions present in the GC can affect CRs' propagation, heating, plasma flow, and the observed synchrotron emission. We find few observable differences between the proton- and lepton-dominated cases, but comparing the models with observed filament properties motivates consideration of a third formation mechanism: the generation of NTFs arise from intermittent structures in Galactic Center turbulence. Astro/astro-ph.HE_(High_Energy_Astrophysical_Phenomena) https://arxiv.org/abs/2606.09776 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09776v1 Announce Type: new Abstract: We present a detailed study of the spatial distribution and chemical composition of interstellar ices toward six Class 0 protostars (HOPS-56, HOPS-60, HOPS-73, HOPS-91, HOPS-96, and HOPS-108) in the Orion A molecular cloud. Using high-resolution spectroscopic data from the JWST NIRspec and MIRI MRS instruments (4.3 - 8.1 $\mu$m), we have constructed the first pixel by pixel absorption maps with a resolution of $\sim$100~AU for key ice species, including $^{13}$CO$_2$, OCN$^-$, CO, H$_2$O, NH$_4^+$, and H$_2$CO. CH$_4$ and OCS were analyzed toward the continuum peaks. The column densities were derived by fitting the observed spectra with laboratory ice analogs. We employed radiative transfer modeling, which confirmed the reliability of our column density estimates within the protostellar envelopes. Our analysis reveals significant variations in ice abundances and distributions, reflecting the physical structure and energetic processes within the envelopes. Specifically, we observe the influence of protostellar heating and outflows on the ice mantles, most notably in HOPS-60. The total ice composition is consistent with astrochemical models and covers $\sim$90% of observed ice inventory suggesting that ice is primarily formed during the prestellar stage and subsequently inherited by the protostellar envelope. Based on the abundance relative to water, the sources can be categorized into two distinct groups, possibly indicating evolutionary differences or variations in envelope density and temperature profiles. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09726 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09726v1 Announce Type: new Abstract: We investigate the demography of little red dots (LRDs) using 37 objects at $z\sim3$-$7$ with JWST/NIRSpec PRISM and grating spectra compiled from various JWST programs. We focus on spectroscopic quantities of the broad H$\alpha$ luminosity $L_\mathrm{H\alpha,broad}$ (and the broad H$\beta$ luminosity $L_\mathrm{H\beta,broad}$ where available) and the bolometric luminosity $L_\mathrm{bol}$ represented by modified blackbody emission, avoiding quantities contaminated by host-galaxy emission (e.g., total H$\alpha$ luminosity). We identifiy a tight scaling relation between $L_\mathrm{H\alpha,broad}$ and $L_\mathrm{bol}$, supporting the interpretation that these emissions are primarily powered by the central engine. Interestingly, the $L_\mathrm{H\alpha,broad}$-$L_\mathrm{bol}$ scaling relation of LRDs is enhanced by a factor of $\sim40$ in $L_\mathrm{H\alpha,broad}$ relative to that of low-$z$ Type 1 AGN. A similar trend is found in the $L_\mathrm{H\beta,broad}$-$L_\mathrm{bol}$ relation, although the enhancement in $L_\mathrm{H\beta,broad}$ is smaller, only by a factor of $\sim10$. We explore the physical origin of these enhancements and find that \textsc{Cloudy} photoionization modeling within the classic locally optimally-emitting cloud (LOC) framework can explain them through an increase in the covering factor from $\sim20$\% (Type 1 AGN) to $\sim100$\% (LRDs), together with an increase in the hydrogen column density from $N_\mathrm{H}\sim10^{23}\,\mathrm{cm}^{-2}$ to $\gtrsim10^{24}\,\mathrm{cm}^{-2}$, with a preferred gas density of $\sim10^{10}\,\mathrm{cm}^{-3}$, successfully reproducing the modified blackbody emission. Such a nearly unity covering factor without requiring a gas density increase may result from a significant increase in the BLR filling factor or size, corresponding to a ``stuffed BLR" or ``giant BLR," respectively. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09721 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09721v1 Announce Type: new Abstract: We present a comprehensive study of Little Red Dots (LRDs) at 2.3 90%) of the spectroscopically confirmed LRDs have robust broad-line detection. Our spectroscopic sample of 36 LRDs displays the full range of spectral diversity of LRDs. It includes objects with extreme Balmer breaks similar to the LRD "Cliff", as well as objects with moderately reddened rest-optical continua that can be fit with low-temperature blackbody components in the recent BH* model framework. The broad H$\alpha$ emission is correlated with the continuum emission at 5100 Angstrom, suggesting common origins for these emission components; the narrow [O III] emission, however, is poorly correlated with the optical continuum. We do not find evidence of redshift evolution in these spectral properties. The space density of LRDs declines toward z about 2, opposite to the trend for normal AGNs, although low-luminosity LRDs at z about 2-4 may be more abundant than currently probed by ground-based searches. The clustering of LRDs suggests that they live in dark matter halos of several times $10^{11}\ h^{-1}$ solar masses, albeit with large uncertainties. Overall, these results are consistent with recent observations of LRDs and with the emerging picture of accreting SMBHs enshrouded in dense gas envelopes as the origin of LRDs. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09665 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09665v1 Announce Type: new Abstract: The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to observe active galactic nuclei (AGN) at sky densities of approximately 1000-4000 per sq. deg, enabling photometric reverberation mapping on an unprecedented scale. We present a meta-learning framework for AGN photometric reverberation mapping based on Attentive Latent Neural Processes (ALNP), developed by the SER-SAG-S1 directable software in-kind team for LSST. The framework clusters AGN light curves with similar topologies using Self-Organizing Maps and combines ALNPs with Mixture Density Models to learn light-curve structure, supermassive black hole (SMBH) properties, and accretion-disk transfer functions in an unsupervised manner. We evaluate the framework on simulated AGN light curves spanning a range of cadences and transfer functions, as well as on real data from the Zwicky Transient Facility. The learned latent representations encode information on both transfer functions and SMBH parameters. Relative to ensemble-trained baseline regressors, including Gaussian-process models, the framework improves light-curve reconstruction by 60-70%. The transfer function recovery improves by approximately 35% relative to the training prior in a low-variability cluster, while recovery of intrinsic SMBH and red-noise parameters improves by approximately 34%. We further demonstrate that models trained on simulated data can be applied to real AGN light curves. These results indicate that ALNP-based representations provide a flexible and scalable approach to photometric reverberation mapping and are well suited to the diverse AGN population expected from LSST and future time-domain surveys. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09651 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09651v1 Announce Type: new Abstract: For over a century, the origin of low-energy cosmic rays (LECRs), the dominant heaters and ionizers of dense interstellar gas, remains elusive owing to solar modulation and uncertain transport processes. In this study, we introduce a new astrophysical approach based on HI Narrow Self-Absorption (HINSA) to obtain spatially resolved measurements of LECR ionization rates using high-fidelity HI observations toward the Orion region from the FAST telescope. The LECR ionization rate is found to scale with local star formation rate (SFR) as $log_{10}\zeta = (1.4\pm 0.70)log_{10}\mathrm{SFR} + (-10.5\pm 2.9)$. Moreover, it increases with visual extinction, and is found to exceed, toward active star-forming regions, the value predicted for diffuse regions based on \textit{Voyager} measurements and an external propagation model. These findings demonstrate that LECRs are generated in situ by star-forming activities rather than penetrating from the broader Galactic cosmic-ray population. This is further supported by \textit{Fermi}-LAT gamma-ray observations toward the Orion region. Together, these results resolve a key uncertainty in cosmic-ray origin and establish a new avenue for quantifying the energetic feedback that regulates the interstellar medium. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09629 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09629v1 Announce Type: new Abstract: Stellar streams are a promising way to gravitationally detect low-mass substructure, since their low dynamical temperature makes them retain the imprint of weak gravitational perturbations. We develop a fast, differentiable forward model for perturbed stellar streams in the diffusion regime, where the stream is heated by many small velocity kicks rather than by a few strong encounters. The substructure population enters only through its power spectrum, so the computational cost is insensitive to the number of perturbers, and alternative dark matter models and/or baryonic perturbers can be explored by changing this single input. We validate the simulations against analytical predictions, then forecast the sensitivity of a GD-1-like stream to the substructure power spectrum, adding to the stream density the full kinematics, both proper motions and the radial velocity. Kinematic information tightens the constraints by a factor of $\sim 3$-$5$ relative to density alone, improving the precision on the dark matter free-streaming cutoff scale from $\sim 1.2$ dex to $\sim 0.25$ dex at a fiducial value of $M_{\rm hm} = 10^6 M_\odot$ for a $5$ Gyr stream. A single well-measured stream could thus constrain dark matter competitively with current limits from strong lensing and satellite counts. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09616 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09616v1 Announce Type: new Abstract: We present a spatially resolved analysis of the stellar populations in the inner kiloparsec of NGC 3884, 3C 293, and CGCG 012-070. Using near-infrared spectroscopy, we reconstruct their star formation histories (SFHs) by comparing the M13, XSL, and FSPS stellar population synthesis models. The stellar light is dominated by intermediate-age to old populations (t >= 1 Gyr) with super-solar metallicities (Z >= 1 Z_sun). All models clearly indicate recent star formation (rejuvenation) in these AGN hosts, with young to intermediate-age populations contributing significantly in the nuclear regions. The SFHs from M13 and XSL broadly agree in showing coexisting old and young components, whereas FSPS favours a larger fraction of very young (t < 50 Myr) stars. Moreover, XSL- and FSPS-based SFHs are generally more irregular and "bumpy," while M13 yields smoother, more continuous SFHs. In NGC 3884 and 3C 293, stars with 0.2 < t <= 0.7 Gyr form a ring-like structure around the nucleus. The nuclear spectra further require non-stellar components: a featureless power-law continuum (FC) and hot dust emission (HD). In 3C 293, the FC component appears in two spatially separated regions, possibly indicating a dual active galactic nucleus, though a heavily reddened starburst origin for the secondary component cannot be excluded. Nearly all fits show a central drop in stellar metallicity, consistent with inflow of metal-poor gas that fuels recent accretion and AGN activity. Radial profiles show that HD and FC contributions decrease with radius, while younger stellar populations become more prominent outward. Together, these results support a feeding-feedback scenario in which gas inflows trigger circumnuclear star formation and, via stellar mass loss, help sustain ongoing AGN activity. . Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09576 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09576v1 Announce Type: new Abstract: Stellar streams are thin, elongated collections of stars formed by gravitational disruption of orbiting star clusters or dwarf galaxies and are highly sensitive probes of the Milky Way's dark matter distribution and formation history. We present $\texttt{SCREAM}$ ($\textbf{S}$tream $\textbf{C}$ha$\textbf{R}$acterization with $\textbf{E}$rror $\textbf{A}$ware $\textbf{M}$achine Learning), a weakly-supervised framework to identify member stars of stellar streams. Building on the $\texttt{CATHODE}$ method originally developed for particle physics, $\texttt{SCREAM}$ identifies streams as localized feature-space over-densities, avoiding rigid physical priors like assumed gravitational potentials or strict isochrone filtering. Crucially, $\texttt{SCREAM}$ is the first machine learning (ML) framework in this domain to directly incorporate observational uncertainties into the neural network training objective. Using astrometric and photometric data from Gaia Data Release 3 and the Dark Energy Spectroscopic Instrument (DESI) Legacy imaging survey, we demonstrate our algorithm's performance on the prominent GD-1 stream. Validated against independent labels, $\texttt{SCREAM}$ achieves an F1 score of 0.745, substantially outperforming existing ML methods in both precision and recall. Furthermore, $\texttt{SCREAM}$ recovers the physically expected diffuse "cocoon" of GD-1 and faint main-sequence members that classical physics-based algorithms (e.g., $\texttt{STREAMFINDER}$) miss. Our results highlight the transformative potential of uncertainty-aware, weakly-supervised ML to uncover complex galactic structures. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09425 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09425v1 Announce Type: new Abstract: The Central Molecular Zone of the Milky Way is shaped by the interplay of bar-driven inflows, shocks, and star formation. At Galactic longitude l=1.3, gas inflowing along the near-side dust lane has been proposed to interact with the CMZ boundary and overshoot above the Galactic plane, making this a key site to investigate how large-scale gas dynamics regulates star formation. We aim to investigate the presence of Class I methanol maser emission in this transitional region, testing whether large-scale gas interactions in the CMZ can trigger widespread maser activity via star formation or shocks. We conducted a dedicated search for the 36.2 and 44.1 GHz Class I CH3OH maser lines, along with the 48.4 GHz thermal transition, using the Yebes 40m telescope. We complemented these data with archival data from the Herschel-HiGAL survey and the CHIMPS2 survey to explore links between masers, shocks, and star formation. We detect widespread 36.2 GHz maser emission and two candidate 44.1 GHz masers in a region extending several parsecs. The brightest maser has an isotropic luminosity 0.9x10^-3 L_Sun, placing it among the most luminous Galactic Class I masers. Thermal CH3OH and SiO emission extend over mapped area of 24 pc, with both species showing enhanced fractional abundances. CO position-velocity analysis further shows that the masers are associated with an extended velocity feature at VLSR~100 km/s. We conclude that the observed masers are primarily associated with shock-processed gas in a kinematically complex bar-CMZ interface region. Large-scale gas interactions are likely to play an important role in producing the maser emission, although a subset of the masers may also be linked to shocks driven by local star-formation activity. This region therefore provides a promising Galactic analogue of shock-dominated Class I CH3OH maser environments observed in nuclear regions of barred galaxies. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09413 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09413v1 Announce Type: new Abstract: Decomposing active galactic nucleus (AGN) emission from host-galaxy light is essential for identifying AGN-dominated systems and accurately deriving host-galaxy physical properties. However, estimating AGN contributions from multi-wavelength photometry remains challenging due to inherent parameter degeneracies in spectral energy distribution (SED) fitting. In this work, we establish a unified framework for estimating AGN contribution fractions and host-galaxy properties by combining complementary diagnostics: SED decomposition with two independent fitting codes, CIGALE and GRAHSP, and deep-learning-based imaging decomposition. We apply this framework to galaxies in the COSMOS-Web field using multi-wavelength photometry from the ultraviolet to the far-infrared. We calculate the AGN contribution fraction in the JWST/NIRCam F150W filter and compare the SED-derived estimates with independent AGN fractions obtained from deep-learning image decomposition. Our results reveal significant degeneracies in current SED-fitting approaches based on empirical or theoretical AGN templates and demonstrate that incorporating independent morphological information can help break these degeneracies and improve the reliability of AGN and host-galaxy property estimates. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09352 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09352v1 Announce Type: new Abstract: Context . Extremely metal-poor (EMP) stars are formed from gas clouds enriched by one or a few supernova explosions belonging to the first stellar generation and this very limited number of sources of metal enrichment is suitable to produce peculiar chemical patterns that give birth to stars with anomalous chemical composition. Among the EMP stars, r-II stars are characterised by an over-abundance of the heavy elements with respect to iron. Aims . In the search for apparently young, metal-poor stars, we serendipitously selected TYC 170-1218-1, which turned out to be an EMP star, enhanced in neutron capture elements over iron. Our aim is to obtain a detailed chemical inventory for this exceptional object. Methods . We investigated high-resolution spectra observed with UVES at the VLT telescope and Mike at the Magellan Clay telescope. We derived the abundance of 33 elements using the MyGIsFOS code and an ATLAS 9 model atmosphere. Results . The star is an EMP with [Fe/H] = -3.52. It is enhanced in the $\alpha$ elements, as EMP stars usually are. It is an r-II star with [Eu/Fe] = +1.84 and [Th/Fe] = +1.85. The star is also poor in carbon with respect to iron. The quality of the spectra was insufficient for us to detect uranium. Kinematically the star belongs now to the Galactic halo, but it joined the Milky Way during the Sequoia accretion event. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09325 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09325v1 Announce Type: new Abstract: Optical tidal disruption events (TDEs) exhibit extremely broad emission lines ($\approx 10^3$-$10^4~{\rm km~s^{-1}}$) and are observationally classified into four spectroscopic types: H-dominated, He-dominated, H+He, and featureless. The prevalent H+He class often displays Bowen fluorescence lines (notably \niii~and \oiii), features that are rarely observed in active galactic nuclei and whose origin has remained poorly understood. We present the first unified radiative transfer framework that reproduces all four TDE spectroscopic classes using simulations of optically thick, outflowing envelopes with solar composition. Our models successfully capture both the continuum properties and key spectral features, including strong \ha, \heii~and Bowen emissions. We demonstrate that the spectroscopic diversity of TDEs is primarily governed by the gas ionization state, controlled by the ratio of injected luminosity to envelope mass. As the ionization level decreases, the observed sequence of spectroscopic classes emerges naturally, transitioning from featureless to He-dominated, to Bowen-dominated, and finally to H-dominated spectra. We further show that electron scattering in the optically thick outflow is the dominant mechanism responsible for the extreme line widths, linking line profiles directly to the physical properties of the wind. The model also explains the observed correlations with luminosity, black hole mass, and the relative stability of spectral classifications during TDE evolution. This work establishes a unified physical framework for TDE spectroscopy, providing new insight into the emission mechanisms, energetics, and outflow structure of these transient events, and offering a practical pathway for interpreting and fitting observed spectra. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.09284 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09284v1 Announce Type: new Abstract: Chemical abundances encode the fossil record of galaxy evolution in a complex and diverse way that requires innovative approaches to reconstruct galactic histories. We investigate the power of using phylogenetic methods to disentangle different evolutionary pathways in analytical chemical evolution models. We ran 1024 one-zone chemical evolution models using flexCE. The resulting chemical abundances are combined with those of two fiducial models, mw-fid and dw-fid, and then used both to determine which combinations produce two-branched phylogenetic trees, as well as how purely these trees split the two input models. We used random forests and Shapley analysis to predict which model combinations return well-separated trees and explain which input parameters are most important for this. We also studied the abundance patterns, as well as star formation rates, mass accumulation, and branch lengths. We found that {\eta}, the mass-loading outflow parameter in flexCE, had the largest impact in separating models into separate branches, due to its importance in driving the chemical enrichment rates and total abundances. Star formation rates and mass accumulation had some impact on {\eta}, but no direct relation between these quantities and the abundances was found. We also found that branches connected through the most metal rich tips in our trees, which is opposite to how phylogenetic trees connect in biological systems. Phylogenetic trees help to reconstruct histories when there is information that is inherited between generations, which is the case of the chemical elements in galaxy evolution. Branch topologies can provide information about the rates of evolutionary change of the various populations, and the connection between branches also contains information about their shared history. This work brings us a step further understanding galaxy evolution through cross-disciplinary research. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.08987 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08987v1 Announce Type: new Abstract: The Wisconsin H$\alpha$ Mapper (WHAM) surveyed the entire Galactic sky in H$\alpha$ ($\vert v_{\rm LSR}\vert \lesssim 100\, {\rm km\,s^{-1}}$) to approximately 0.1\,Rayleigh (R), albeit with a 1-degree beam. %The resulting WHAM Sky Survey, along with large area %imaging in [\ion{S}{2}] and [\ion{N}{2}], laid the foundation for Warm Ionized %Medium (WIM) science. \cite{rcm+05} reported ``point sources" which stood out against the Galactic background in space and velocity. Half of the sources are associated with plausible planetary nebulae and OB stars. Reynolds et al (2005) suggested sub dwarfs for one quarter of the sources. Here, we investigate one such source, WPS\,46, for which Reynolds et al (2005) suggested the sub-dwarf PG\,0931+691 to provide the source of ionization. With the Keck Cosmic Web Imager we found numerous nebular emission lines within the vicinity of WPS\,46, but we failed to find H$\alpha$ emission in the arc-minute vicinity of PG\,0931+691. The line ratios (BPT diagram and [\ion{S}{2}]/H$\alpha$) combined with the morphology are more consistent with AGN or LI(N)ER-like ionization than with pure warm ionized medium or \ion{H}{2} region-like photoionization. Separately, we offer compelling reasons to argue that PG\,0931+691 cannot be the source of ionizing power for WPS\,46. We suggest that WPS\,46 is associated with an intermediate velocity complex (IVC) and that H$\alpha$ and nebula emission may arise as a result of a shock. We conclude by outlining a plan of action of using SDSS's Local Volume Mapper along with deep narrow band imagery obtained by amateur astronomers to explore and study the ionized sky on sub-degree scales, in general, and specifically studies of IVC and high-velocity complexes. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.08961 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08961v1 Announce Type: new Abstract: Observations indicate that supermassive black holes (SMBHs) in high-redshift galaxies formed on timescales far shorter than classical growth models allow. One hypothesis suggests intermediate-mass black hole (IMBH) seeds as an efficient growth channel. Using N-body simulations, we demonstrate that in dense stellar-mass black hole (BH) clusters ($\ge 5\times10^9 M_{\odot}/{\rm pc}^3$), runaway gravitational-wave binary BH (BBH) mergers can produce a $\sim 10^3 M_\odot$ IMBH within 10 Myr from the formation of the BH subsystem. This scenario is simple and avoids large uncertainties regarding stellar mergers and evolution in the IMBH formation via very massive stars channel. We find that the runaway GW-merger mechanism relies on hard BBH formation through a chain of exchanged soft BBHs with accumulated hardening, which is far more efficient than three-body scattering. We analyze how IMBH formation depends on cluster density, total mass, initial mass function, and stellar halo potential. We find that due to cluster expansion, the systems forming IMBHs have densities consistent with present-day nuclear star clusters, such as those in the Milky Way and M33. Furthermore, we show that IMBH spin remains low due to repeated mergers, and we estimate the rate of GW190521 and GW231123-like events within the first 100 Myr to be $2.27-247.52$ and $3.23-63.63 $ per Gyr per cluster. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.08782 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08782v1 Announce Type: new Abstract: We investigate UV absorption lines tracing cool gas in eight bright ($-21.9<M_\mathrm{UV}<-20.5$) galaxies at $z=7.2-10.6$ using deep JWST/NIRSpec medium-resolution spectra homogeneously selected from archival data. We identify multiple absorption lines of low-ionization species (LIS) in five galaxies, while the remaining three show only one or no significant detections. The average LIS equivalent widths $\mathrm{EW_{LIS}}$ indicate weaker absorption lines in compact ($r_\mathrm{e}\lesssim 100$ pc) galaxies with high $L_\mathrm{H\beta}/L_\mathrm{UV}$ and $\Sigma_\mathrm{SFR}$, suggestive of absorption-line suppression due to intense star formation or nuclear activity. We simultaneously fit multiple LIS lines, accounting for both covering fraction $C_f$ and column density $N$, and find that the five galaxies follow the local $C_f$-$N$ relation. Through the LIS-line fitting, we derive chemical abundance ratios. The five galaxies have abundance ratios similar to those of damped Ly$\alpha$ (DLA) systems in the [Si/O]-[C/O] and [Fe/Si]-[Al/Si] planes, suggesting that their absorbing gas is similar to that of DLAs. We find that two galaxies at $z\sim 7$ are already highly Fe-enriched, with $\mathrm{[Fe/Si]}\simeq -0.2$, near the solar abundance ratio. While the high Fe enrichment may originate from early Type-Ia supernovae (SNe Ia) or pair-instability supernovae (PISNe), these two galaxies also show $\mathrm{[Al/Si]}\sim0$, with no signature of the strong odd-even effect expected from PISNe, favoring SNe Ia. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.08778 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08778v1 Announce Type: new Abstract: Systematic surveys of filaments have been conducted to study their properties and their relationship to the process of star formation. In this paper, we use synthetic Herschel observations derived from 3D numerical simulations to compute column density maps, then use the \texttt{FILFINDER} algorithm to identify filaments. We obtain a large sample of 8,832 filaments that we further decompose into 110,193 branches. We characterize the physical properties of these filamentary structures and explore their correlations with embedded clumps. Furthermore, we directly compare our synthetic results with an observational catalogue of 32,059 filaments from the Herschel Infrared Galactic Plane Survey (Hi-GAL). Our results show that filaments are central to the star formation process, hosting $94\%$ of clumps from synthetic observations and $93\%$ of stars from our 3D numerical simulation. Filaments that host clumps have higher median column densities ($1.1\times10^{21}\,\rm{cm}^{-2}$) than those without ($3.8\times10^{20}\,\rm{cm}^{-2}$). We find power-law distributions for our synthetic filament masses and lengths, with power-law indexes of $\alpha_{\rm M}=-0.86$ and $\alpha_{\rm L} = -1.71$, respectively. We also find that the relation between the density of filaments and the background density is $N_{\rm{fs}} \propto N_{\rm{bs}}^{0.78}$. The measured properties of the filaments from the 2D synthetic observations are qualitatively consistent with those of the filaments from the Hi-GAL survey. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.08607 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08607v1 Announce Type: new Abstract: We present 0.1" (~ 50 au) resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the HH 46/47 molecular outflow and its envelope-disk system. The 1.3 mm continuum emission reveals a compact central source surrounded by a circumbinary disk with substructures. The companion, identified in optical and infrared observations, is not detected in the millimeter continuum but coincides with a local intensity minimum. Two spur-like features extending from the primary source toward the companion are identified and are likely induced by gravitational perturbations from the companion. The envelope-disk system is traced by C18O, SO, H2CO, and CH3OH. C18O primarily traces the extended envelope, while SO probes the inner envelope, and H2CO and CH3OH trace compact, faster-rotating structures near the centrifugal barrier. The observations are well reproduced by a rotating-infalling envelope transitioning to an inner disk at a radius of ~30 au around a 0.3 Msun protostar. The 12CO emission, together with JWST NIRCam images, reveals multiple shell structures in the outflow. Using C18O and 13CO to correct for optical depth, we derive the spatial distributions of outflow mass, momentum, and kinetic energy, as well as their corresponding rates. A model-independent analysis of a well-defined redshifted shell yields its three-dimensional velocity field, showing that the shell expands radially rather than flowing along its surface. Although a transverse velocity gradient is detected, interpreting it as rotation implies an unphysically large magnetic lever arm, disfavoring a direct disk-wind origin. Instead, the shell kinematics support an entrainment scenario. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.07751 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07751v1 Announce Type: new Abstract: We address two mass-dependent properties among early-type galaxies (ETGs): (1) abundance ratios [N/Fe] and [Na/Fe], and (2) the centrally concentrated "UV upturn" at far-UV (FUV) wavelengths, which is likely produced by extreme horizontal branch stars with supersolar helium abundances. Using new HST/WFC3 observations of one FUV-weak and one FUV-bright ETG, we probe the "MP scenario" by Goudfrooij who posited that the UV upturn and the mass-dependent abundance variations of N and Na within and among ETGs are physically connected and produced by dissolution of metal-rich globular clusters, which represent the only galactic environment where mass-dependent enrichment of He, N, and Na is known to occur (i.e., second-generation stars of the "multiple stellar populations" (MPs) phenomenon). We show that passbands F275W and F390W are uniquely sensitive to correlated changes in $Y$ and [N/Fe] in integrated-light photometry when combined with archival data in F475W and F850LP. While F475W-F850LP is found to decrease with increasing radius in both galaxies, consistent with known metallicity gradients, F275W-F390W increases with increasing radius, as expected if the UV upturn is caused by second-generation stars with supersolar $Y$ and [N/Fe]. Furthermore, the radial gradient in F275W-F390W and the implied fractions of He- and N-enhanced stars are found to be significantly larger in the FUV-bright ETG than in the FUV-weak one, consistent with the predictions of the MP scenario. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.07750 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07750v1 Announce Type: new Abstract: The Euclid Quick Data Release (Q1) is a powerful dataset to study active galactic nuclei (AGN) and their host galaxies. Deriving their physical properties through multi-component spectral energy distribution (SED) fitting is a challenging task for AGN, but it is greatly aided by the Euclid near-infrared photometry. Here we present a new method to quantify the reliability of SED-derived parameters, such as AGN bolometric and monochromatic luminosities, host's stellar mass $M_\star$, star-formation rate (SFR) and specific star-formation rate (sSFR), by using mock SEDs of AGN built by combining observed SEDs of QSOs and galaxies. We apply this methodology to the ${\sim}1$ million Q1 AGN candidates, constructing a catalogue of AGN and host galaxy properties, alongside their respective reliability values. With a reliability threshold at 0.5, we find 88\% of sources with robust stellar masses and 76\% with reliable AGN luminosities. Moreover, through SED fitting we also measure the AGN fraction $f_{\rm AGN}$ of the total mid-infrared flux and we use its lower-limit to select AGN. A $f_{\rm AGN, \, low} > 0.075$ threshold yields 85\% completeness and purity. Comparable to colour-colour AGN selections, this method has the advantage of being less affected by redshift evolution and exploring fainter magnitudes. Additionally, by comparing the AGN and host galaxy parameters across different identification methods, we find that the probed range in stellar mass and AGN luminosity can be quite different. This highlights the importance of combining different approaches and accounting for their selection biases when studying AGN and their role in galaxy evolution. Finally, for the X-ray detected sample, we present the X-ray to mid-IR luminosity relation, and the correlation between stellar mass and bolometric luminosity as a function of redshift, in good agreement with previous results. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.04875 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.04875v2 Announce Type: replace-cross Abstract: Multidimensional Gaussian Process (multi-GP) regression is widely used to disentangle stellar and planetary signals in radial velocities (RVs) by jointly modelling ancillary activity indicators. However, identifying the combination of indicators that best constrains the stellar signal in the RVs is non-trivial, as classical model comparison methods are not directly applicable when multi-GPs involve different time series combinations. In this work, we present an information criterion to compare multi-GP models based on their ability to explain the RV component, $\mathrm{MGIC}_{\rm rv}$. This metric combines the conditional RV likelihood with an effective parameter count that accounts for the regularisation imposed by the multi-GP model on the RV component. We demonstrate that $\mathrm{MGIC}_{\rm rv}$ provides a quantitative and robust framework for multi-GP model comparison, identifying the activity indicators that most effectively constrain the RV signal. Although developed in the context of RV analysis, the proposed criterion is general and applicable to multi-GP problems in which the inference focuses on a specific observable. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.00463 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.00463v2 Announce Type: replace-cross Abstract: This paper examines how future technosignature searches may constrain competing resolutions of the Fermi Paradox, with particular attention to the possibility that technologically capable entities (TCEs) are either intrinsically rare or deliberately concealed. I propose a multi-pronged observational strategy comprising expanded radio and optical SETI, spectroscopic searches for biosignatures and technosignatures in exoplanet atmospheres, astronomical searches for large-scale extraterrestrial engineering, and Solar System searches for extraterrestrial artefacts (SETA). The latter is identified as having a distinctive temporal advantage because it can probe evidence accumulated over Solar System (and perhaps even Galactic) history, rather than requiring temporal overlap with TCEs. In this context, I argue that searches for micron-scale interstellar technological debris (Arkhipov particles) in lunar and planetary regoliths may provide an additional constraint on past Galactic technological activity. Additionally, I briefly argue that this programme of scientific exploration should be considered alongside its geopolitical and governance implications. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2511.11442 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2511.11442v2 Announce Type: replace-cross Abstract: Stably stratified layers are thought to develop at the top of the liquid metallic cores of many terrestrial planets. We consider the case where the thermal gradient is stable but the compositional gradient is unstable, a situation particularly relevant to Mercury. The strong contrast between molecular diffusivities of temperature and composition leads to fingering convection. We investigate this process using hydrodynamical simulations in a rotating spherical shell, systematically varying the stratification strength N relative to the rotation rate $\Omega$. In all regimes, the primary fingering mode forms narrow, elongated structures that shift orientation from the rotation axis to the direction of gravity as $N^2/\Omega^2$ exceeds 10. The fingers remain laminar, with transverse scales proportional to thermal stratification but independent of rotation. Fingering convection also drives secondary large-scale flows across most of the explored parameter space, producing diverse dynamics including zonal flows, hemispherical convection, axisymmetric poloidal bands, finger clusters, and toroidal gyres. In the rapidly-rotating regime, laterally inhomogeneous mixing generates zonal flows in thermo-compositional wind balance; zonal flow direction and amplitude depend on $N^2/\Omega^2$, with amplitude weakening for strong stratification $N^2/\Omega^2>10$. In the intermediate regime ($N^2/\Omega^2\sim 1$), axisymmetric or spiraling poloidal bands emerge within the tangent cylinder, gradually overtaking the primary fingers. For stronger stratification, finger clusters and weak, large-scale density anomalies surrounded by toroidal gyres form in the upper domain. These diverse large-scale flows may interact with the dynamo-generated magnetic field in the deeper core, potentially influencing surface magnetic fields. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.02778 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.02778v2 Announce Type: replace Abstract: I present EXOVEIL, a transit detection system that learns what a star's brightness should look like and flags when reality disagrees. Unlike existing systems that require phase-folded input, EXOVEIL operates on raw flux time series and can detect planets that transit only once.A Transformer world model, trained on 16,499 Kepler light curves with transit-masked self-supervised learning, predicts expected stellar flux. A matched-filter detector with variance weighting extracts transit signals from the prediction residuals. A learned classifier (XGBoost) separates planets from false positives, achieving AUC 0.938 on Kepler DR25. Applied to single-transit injection-recovery, EXOVEIL recovers 32% of transits at 1000 ppm depth a task where all classification-based systems score 0% by construction. A blind search of 3,737 Kepler stars yields 179 new transit-like signals not present in the DR25 TCE catalogue, including 46 monotransit candidates. Applied withoutretraining to 47 confirmed TESS planets in the PLATO LOPS2 field, EXOVEIL achieves 100% recovery, demonstrating zero-shot cross-mission transfer. At PLATO's 25-second cadence, detection reaches 100 ppm -- approaching the Earth-analog regime. I provide the first application of conformal prediction to transit detection (95.9% empirical coverage) and release the system as pip install exoveil with pretrained weights and a candidate catalogue. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2605.26216 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2605.26216v2 Announce Type: replace Abstract: Recent ground-based microlensing surveys suggest that our Galaxy may abound with small free floating planets, potentially up to $\sim$21 such planets per star. We explore the implication of such possibility on the mass budget for planet formation. When the microlensing planets, both bound and free-floating, are taken into account, along with the short-period planets, T Tauri disks have insufficient mass to source the mass of known planets, even if all the solids convert into planetary bodies. Younger Class 0/I disks can help resolve the problem but generally fall short of the required mass when variable planet formation efficiency from pebble or planetesimal accretion is taken into consideration. If the free-floating planet mass function is as bottom-heavy as reported, heavier Class 0/I disks may be necessary. Alternatively, free-floaters may preferentially form in the most massive disks around massive stars consuming the majority of the mass budget, leading to a decrease in the bound planet occurrence rate for higher mass stars, which is observed. Precise constraints on the bottom of planet mass function are necessary: a peaked mass function may eliminate the missing mass problem; by contrast, verifying a bottom-heavy function could spell a crisis in planet formation. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.09296 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09296v1 Announce Type: cross Abstract: Constraining the physical properties of Earth's deep interior, particularly the viscosity of the solid inner core and the density structure of large low-velocity provinces (LLVPs), remains a major challenge in geophysics. Here we develop a unified dynamical framework that combines mantle-inner core gravitational coupling (MICG) with torsional oscillations in the fluid outer core and show that their interaction can produce a distinct and testable geodetic signature. Guided by this prediction, we analyze satellite gravity observations together with independent corrections for surface mass variability. We identify a robust approximately 6-year signal in the Stokes coefficient Delta S22, while no corresponding stationary signal is detected in Delta C22. A signal with the same periodicity is independently detected in length-of-day variations (Delta LOD), and the two signals exhibit a near anti-phase relationship. Interpreting this coupled signature within the proposed framework allows us to constrain the inner core viscosity to approximately 4.6 (+/- 1.8) x 10^16 Pa s and the equatorial relief of the inner core boundary to a semi-axis difference of about 200 +/- 70 m. The inversion further indicates mean density anomalies of +5.5 (+/- 0.6) per mil at the base of LLVPs. These results indicate that satellite gravimetry provides a direct observational window into deep-Earth dynamics and the physical properties of Earth's deep interior. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08971 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08971v1 Announce Type: cross Abstract: The sub-parsec proximity around the Sgr A$^\star$ supermassive black hole (SMBH) in the center of the Milky Way contains an inner cluster of eccentric S-stars with randomly oriented orbits, a midway-disk of clockwise-rotating stars (CWSs), and a surrounding population of off-the-disk stars (ODSs). Despite their diverse kinematic properties, all three-populations appear to be massive (WR/O/B types) and have similarly limited life span $\tau_\star \sim 6-15$ Myr. Several scenarios, including star formation induced by SMBH's close encounters with one or more gas clouds as well as impulsive close scattering by a putative intermediate-mass companion (IMC) of Sgr A$^\star$ possible an intermediate-mass black hole (IMBH), have been proposed to explain piecemeal for the origin and dynamical evolution of S-stars, CWSs, ODSs, as well as hyper-velocity stars in the Galaxy. But, their coexistence and the origin of a recently discovered zone of avoidance in S-stars' eccentricity-peri-centric-distance distribution remain enigmatic. Here, we construct a unified model to comprehensively take into account these stars' interaction with each other, their single natal disk, and an independent IMC. We show their disparate present-day orbits would only be concurrently attainable, within their multi-Myr age, under the combined influence of IMC's secular perturbation and these stars' resonant relaxation in a depleting gaseous-disk environment. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08373 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08373v1 Announce Type: cross Abstract: Technological societies are separated in time, not just space -- that is the lesson of the Drake equation. Might the best way to seek them be to find technosignatures that persist long after their creators? I present work I and my collaborators have done on the idea of passive technosignatures, requiring no upkeep from an active society. These range from microscopic to galactic in scale, including specular reflections from shiny artifacts in the Solar System, lens flares from X-ray binaries, and the survivability of Dyson swarms. I discuss prospects for detecting these technosignatures. In the end, what we may be left with are the end products of collisional cascades: dust. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07788 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07788v1 Announce Type: cross Abstract: The dynamic range available from a sensor is vital to its utility. The limits on the dynamic range that can be obtained from an image sensor are set by the brightest and faintest objects that can be detected. In recent years, CMOS (complementary metal-oxide-semiconductor) image sensors (CIS) have gained high popularity due to their low cost and high availability. However, as with all detectors, the dynamic range is constrained by the sensor's bit depth. Here, we have modified the readout scheme of a commercial CIS120 sensor from Teledyne e2v, to enhance its dynamic range. We have advanced the interleaved row readout method proposed by Wocial et al. by using a more sophisticated approach, which enables us to readout chosen rows much more frequently to avoid saturation and then readout other rows on the sensor once to form the image. Our laboratory tests provide a dynamic range of 134 dB elevated from the sensor's native 12-bit of about 71 dB. We also built a camera housing that enabled first-time operation of interleaved row readout on-sky to observe the bright stars, Vega and Polaris. In complex mode we obtained unsaturated single exposure images of these bright stars, which have magnitudes near zero and detect background stars with Gaia G magnitudes around 15 in a single exposure, with a detection threshold of 5$\sigma$. The achievable dynamic range with this interleaved row readout is limited only by the readout noise and scattering in the camera optics. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07637 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07637v1 Announce Type: cross Abstract: We argue that an airborne proton accelerator is an interesting tool for weather control. Following the findings of the CLOUD experiment at CERN, one expects that a beam of protons, likewise cosmic rays and other aerosols, can enhance the formation of low-altitude clouds, allow for tailor made cooling of overheated areas and induce the precipitation of high-altitude clouds that trap solar radiation reflected from the ground. The proton accelerator can also be used to mitigate droughts, regularise precipitation and avoid that it takes place through large and harmful storms. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.09481 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09481v1 Announce Type: new Abstract: The inner edge of the dead zone (DZIE) in protoplanetary discs is prone to episodic instability caused by the activation of the magneto-rotational instability (MRI) in the weakly turbulent regions. We show how different magnetic field configurations set the inner disc structure and regulate the morphologies of instability cycles. We performed 2D and 3D radiation hydrodynamic simulations of the regions around the DZIE of a Class II disc over a thousand-year timescale. We implemented MRI activation criteria based on ambipolar and Ohmic diffusion coupled to magnetic field strength profiles comprising stellar and disc components. The properties and consequences of the episodic accretion events are highly sensitive to the magnetic field strength. We recover previously reported behaviour by considering relatively strongly magnetised discs. A new burst mode is revealed, in which the midplane MRI activity is restricted to small radii in the presence of weak magnetic fields. In this narrow mode, the pressure bump at the DZIE does not remain static even during quiescence. A distinct dichotomy between the wide and narrow modes is established by the hydrodynamic (in)stability of the ionisation front. Both modes are additionally separated into a reflaring and a non-reflaring version. Our setup does not lead to the classical thermal instability by hydrogen ionisation. In quiescence, the MRI active region shows a layered structure that converges towards the midplane near the star. Our 3D model reveals the breaking of density features produced in the narrow mode, leading to vortices at radii smaller than 0.5 AU. Coupling MRI activity directly to different magnetic field strengths, rather than using simple temperature thresholds, enables a variety of burst modes. Each mode exhibits characteristic accretion burst signatures and has different consequences for planet formation and migration conditions. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.09072 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09072v1 Announce Type: new Abstract: Aims. We expand the planetary census around massive stellar hosts through a long-term campaign of high-precision radial velocity (RV) measurements on evolved stars. Methods. We analyse data acquired with the CORALIE spectrograph covering 15-18 years on HD125136, HD127195, and HD220218. Stellar parameters are derived through different methods for a comprehensive characterization of each star. We then evaluate the presence of planetary signals in the RV time series using the Bayesian inference tool kima. Finally, we design an observing strategy aimed at mitigating the impact of pulsations on evolved stars and test its effectiveness on the low-luminosity red giant HD127195. Results. We detect signals that are accurately modelled by Keplerian curves in the RV data of the three stars: one on HD 125136, two on HD 127195, and one on HD 220218. While the signals on the first two stars seem to be of planetary origin, the signal on the third one shows several signs of stellar activity. We therefore identify a planetary companion around HD125136 with a minimum mass of 2.26 MJup on an 850 d orbit, and on HD127195 we identify a system composed of planets with 0.66 MJup and 0.78 MJup with orbital periods of 535 d and 834 d, respectively. Conclusions. We detect three massive planets around two low-luminosity red giant stars in a region of the parameter space that is poorly populated in both stellar mass and planetary orbital periods. The dedicated observing campaign on HD127195 showcases how stellar pulsations can be efficiently averaged out to below 5 m/s in low-luminosity giant stars. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08996 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08996v1 Announce Type: new Abstract: With the commissioning of the James Webb Space Telescope (JWST), near- and mid-infrared observations are rapidly extending into the wavelength regime where emission from small dust grains in circumplanetary disks (CPDs) is expected to dominate. We aim to systematically investigate how individual physical parameters of CPDs shape their infrared spectra and to improve the robustness of spectral fitting and physical interpretation of current and future observations. Building on our previous parametric CPD models, we employ a parameter-grid approach combined with radiative transfer simulations to explore the dependence of observable spectra on disk structure and dust properties. We identify the physical mechanisms responsible for the main spectral features and parameter degeneracies, and present the global trends emerging from the parameter study. We also demonstrate the applicability of the models by fitting representative observational data. Our results provide a structured theoretical framework for interpreting near- and mid-infrared observations of CPDs with JWST and related facilities. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08859 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08859v1 Announce Type: new Abstract: The frequency dependence of opacity is crucial for determining the thermal structure of protoplanetary disks, which in turn influences disk dynamics and planet formation. Yet many disk models adopt simplified thermodynamics, and common radiation-hydrodynamic approaches often use gray opacities, ignore scattering, and yield inaccurate results in regions with intermediate optical depth. We present a comprehensive framework that models stellar irradiation with frequency-dependent absorption and scattering across all optical depths using the Athena++ finite-volume code, extended with multigroup radiation transport and newly implemented radial rays to more accurately represent the stellar flux. To calibrate this framework, we focus exclusively on hydrostatic disk models, allowing us to isolate radiative effects and evaluate the method without additional dynamical complexity. Because dust opacity increases strongly with frequency, ultraviolet stellar irradiation heats the tenuous disk atmosphere while the optically thick midplane remains cooler. This vertical temperature gradient is captured more accurately when more frequency bands are used or when scattering is included. Our hydrostatic models achieve equilibrium temperatures that differ from Monte Carlo radiative-transfer benchmarks on average by 2--5% with 64 frequency bands and 7--11% with 3 bands. Reducing the number of bands lowers computational cost by at least an order of magnitude while increasing the maximum possible temperature deviation only from 8% to 19%. This calibration demonstrates the accuracy and efficiency of the framework and provides a solid foundation for future self-consistent studies of irradiated protoplanetary disks, including fully dynamical simulations and applications involving chemical processes and time-dependent stellar luminosity. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08180 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08180v1 Announce Type: new Abstract: We present pre-perihelion observations of methanol, carbon monoxide, and hydrogen cyanide in the Oort cloud comet C/2017 K2 (PANSTARRS), performed with the APEX 12-m and Onsala 20-m telescopes from April to July 2022. As the comets heliocentric distance decreased from 3.4 to 2.7 AU, CH3OH line intensities increased substantially (by factors of 1.1-4.0), with the most pronounced enhancement in lines with the upper-level energies Eu > 40K. In contrast, the brightness of the CO and HCN lines remained constant. We estimate the best-fit gas kinetic temperatures Tgas > 100 K and water production rate of Q(H2O)=(3-10)*10(28) 1/s. The derived methanol-to-water abundance ratio approx. 0.01-0.04, depending on the observed period. Our results demonstrate that non-LTE effects are dominant in the coma and must be accounted for to accurately derive molecular production rates. We also report weak non-thermal excitation, including potential maser activity in the CH3OH 8(0)-7(1) line. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.08628 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08628v1 Announce Type: cross Abstract: We investigate the thermal impact of dark matter (DM) capture and annihilation on neutron stars (NSs) in the Galactic Center (GC). Accounting for both kinetic energy deposition and internal annihilation, we systematically evaluate the influence of various DM density profiles, ranging from cored to cuspy distributions, on the late-time thermal evolution of NSs. For NSs older than $\sim 10^7~\mathrm{yr}$, the surface temperature approaches an equilibrium value $T_\mathrm{s}^{\mathrm{eq}} \sim 10^4$--$10^6~\mathrm{K}$, depending on the stellar location and the ambient DM density. In the presence of a density spike, enhanced heating shifts the emission toward ultraviolet (UV) and soft x-ray bands; however, strong interstellar extinction and large hydrogen column densities significantly suppress the observable flux density. We further provide an estimate of the cumulative infrared surface brightness from the NS population in the GC. The predicted flux density from an individual NS remains below $\sim 0.1\,\mathrm{nJy}$, while the integrated emission yields an average surface brightness $I_\nu \lesssim 10^{-9}\,\mathrm{Jy\,arcsec^{-2}}$, corresponding to a signal-to-noise ratio well below current detection thresholds. Our results indicate that thermal signatures from DM-heated NSs in the GC remain below the sensitivity limits of current instruments, although nearby systems with lower extinction may provide more promising targets for detection. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08220 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08220v1 Announce Type: cross Abstract: Gravitational-waves from astrophysical sources are characterized by their extreme faintness, which remains a primary obstacle for both current and next generation detectors. While rotating black holes dressed in superradiant clouds of ultralight bosons are recognized as promising probes of physics beyond the Standard Model, their capacity to actively emit and modulate gravitational radiation remains largely unexamined. Here we demonstrate that these gravitational atoms can function as natural amplifiers of gravitational-waves via a stimulated emission mechanism analogous to astrophysical masers. By formalizing the interaction between the bosonic cloud and an ambient stochastic gravitational-wave background, we establish the rigorous selection rules and threshold conditions that govern this amplification. Our analysis reveals that the emission rate depends critically on the boson mass, potentially yielding an enhancement of several orders of magnitude over spontaneous processes. For representative mass ranges, these amplified signals bridge the sensitivity gap between ground-based interferometers and pulsar timing arrays. These findings suggest that superradiant clouds can effectively boost previously undetectable signals, offering a novel observational frontier for exploring ultralight fields and the Kerr spacetime environment. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08142 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08142v1 Announce Type: cross Abstract: Particle physics models beyond the Standard Model often contain global symmetries to address various unanswered questions. However, a common criticism of theories based on global symmetries is that such symmetries are generally expected to be explicitly violated by gravitational effects at the Planck scale. In the case of a global $U(1)$ symmetry, this explicit breaking can reduce the symmetry to a discrete subgroup of $U(1)$, leading to the formation of cosmic strings attached to multiple domain walls (DWs). These DWs are usually cosmologically problematic, since their slow scaling behavior can eventually dominate the energy density of the Universe, giving rise to the well-known cosmological DW problem, which is strongly constrained by Big Bang Nucleosynthesis. In this letter, we propose a new annihilation mechanism of such DWs in theories with the simplest continuous global symmetry, $U(1)$, in the presence of gravitational effects. The mechanism is as follows: if a fermion coupled to the symmetry-breaking scalar possesses a small bare mass term, radiative corrections can generate a temperature-dependent bias for triggering DW annihilation. As a representative example, we study a majoron framework containing right-handed neutrinos with small bare mass terms, in which a wall-string network can arise once gravitational effects are taken into account. Within this setup, we show that the small bare masses of the right-handed neutrinos provide the origin of the bias responsible for triggering the annihilation of the DW network. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08003 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08003v1 Announce Type: cross Abstract: The smeared null energy condition (SNEC) imposes a semilocal bound on the negative energy accumulated along null geodesics. In eternal inflation, rare stochastic upward fluctuations of the inflaton locally increase the Hubble parameter, creating an apparent tension with the SNEC. Focusing on a canonical single-field model, we investigate whether this quantum-induced self-reproduction violates the SNEC. Using the Fokker-Planck equation, we demonstrate that the ensemble drift of the Hubble parameter is parametrically bounded by slow-roll parameters and semiclassical suppression. Furthermore, a complementary single-trajectory analysis reveals a strong timescale hierarchy, $N_{\rm SNEC} \gg N_{\rm BR}$. This indicates that even for rare upward stochastic excursions, gravitational backreaction invalidates the background spacetime assumption long before the SNEC bound can be mathematically approached. We conclude that while standard stochastic diffusion drives eternal inflation, it does not inherently lead to SNEC violations within the semiclassical slow-roll regime. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07663 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07663v1 Announce Type: cross Abstract: Current observations constrain primordial perturbations to be adiabatic, approximately Gaussian, and nearly-scale invariant. However, a generic mixed state satisfying these constraints has additional unconstrained degrees of freedom, which can be parameterized by the purity of the state and its momentum variance. This allowable parameter space reveals a unified geometric landscape of mixed states, allowing us to map and relate distinct models of decoherence and their respective pointer bases. Crossing the threshold of a regular, positive-definite Glauber-Sudarshan $P$-function requires the environment to actively inject momentum into the system, rather than suppress it. This enhanced momentum variance dynamically sources the decaying mode of the gravitational potential in the radiation era. While the decaying mode vanishes fast enough to preserve the temporal coherence of the Cosmic Microwave Background, its initial amplitude places severe theoretical constraints on decoherence models to avoid gravitational non-linearities. These non-linearity bounds definitively rule out decohered thermal states, while long-wavelength divergences restrict amplitude-diagonal decoherence models to fewer than 70 $e$-folds of inflation. Altogether, we present a unifying framework for evaluating the quantum-to-classical transition of the early universe. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09810 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09810v1 Announce Type: new Abstract: The second data release of the European Pulsar Timing Array (EPTA) collaboration provides evidence for the presence of a gravitational-wave (GW) background. In this work, we explore a potential cosmological interpretation of this signal in terms of inflationary scenarios. We parametrize the tensor power spectrum in terms of the tensor-to-scalar ratio $r$, the tensor spectral index $n_t$, the reheating temperature $T_{\text{rh}}$, and the cut-off frequency $f_{\text{end}}$. We incorporate all relevant observational constraints, including those from the Cosmic Microwave Background, Big Bang Nucleosynthesis, and LIGO-Virgo-KAGRA observations. We demonstrate that imposing these constraints consistently reduces the region of parameter space that provides a viable interpretation of the EPTA signal, to $-11.66 \lesssim \log_{10}r \lesssim -1.45$, $1.32 \lesssim n_t \lesssim 2.47$, $1.78\text{ MeV} \lesssim T_{\text{rh}} \lesssim 28.2\text{ GeV}$, and $75.86\text{ nHz} \lesssim f_{\text{end}} \lesssim 14.45\text{ Hz}$ at the 95% confidence level. This favours the scenario in which the GW spectrum in the EPTA frequency band originates from tensor modes that re-entered the Hubble radius during the radiation-dominated era, allowing for a higher $r$ and a flatter spectrum. However, $T_{\text{rh}}$ must take very low values, which are challenging to explain theoretically. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09804 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09804v1 Announce Type: new Abstract: Evaporating black holes can leave distinct imprints on gravitational wave (GW) backgrounds. We show that black hole populations with finite width mass distributions exhibit a universal late time evolution governed by the evaporation dynamics rather than the details of the initial mass distribution, leading to a characteristic power law suppression of the induced GWs. We demonstrate this for a broad class of mass functions in primordial black hole (PBH) scenarios featuring an early Universe matter-dominated era, and identify the suppression of PBH-induced GWs found for critical collapse distributions as a manifestation of this general phenomenon. Our results establish a direct connection between the asymptotic GW spectrum and the underlying law of black hole evaporation. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09690 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09690v1 Announce Type: new Abstract: Stochastic inflation can be used to study large inflationary perturbations. This paper presents such a study for a quadratic hilltop potential, corresponding to constant-roll inflation. I solve the perturbation distribution using the spectral method, with detailed solutions of the eigenvalues and eigenfunctions of the Fokker-Planck operator. Contrary to previous studies of stochastic constant-roll inflation, the solution allows trajectories that cross the hilltop and get stuck near a reflecting boundary on the other side, tunneling out slowly in a way dictated by the lowest eigensolution. Despite their rarity, these trajectories turn out to dominate the mean first-passage time. For this reason, I argue the mean does not properly describe the inflationary background. Using the median instead, I compute the distribution of the coarse-grained $\Delta N$ distribution and show that its well-known exponential tail first flattens out and then forms a peak near a maximal $\Delta N$ value. I argue similar intricacies arise in primordial black hole models. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09650 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09650v1 Announce Type: new Abstract: We examine the impact of progenitor age-dependent luminosity evolution of Type Ia supernovae on a cosmographic measurement of the deceleration parameter $q_0$. Our recent redshift tomographic analysis showed that locally $q_0$ has a strong dipole anisotropy aligned approximately with the bulk flow, and only a small monopole component remains at distances exceeding a few hundred Mpc. Applying redshift-dependent corrections for progenitor age to the Pantheon+ catalogue, we find that this shifts the monopole component of $q_0$ to positive values (i.e. deceleration), while leaving the local dipole component essentially unchanged. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09491 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09491v1 Announce Type: new Abstract: Dark photons are a gauge boson of a hypothetical dark sector, representing one of the most-studied minimal extensions of the Standard Model, with wide-ranging theoretical and observational implications. Here, we consider scenarios in which an initially unpopulated dark photon sector is populated via resonant photon to dark photon conversions. This process leads to observable spectral distortions in the cosmic microwave background (CMB), that can be used to constrain these models. We extend previous spectral distortion studies of the monopole spectrum to anisotropic spectral distortions, using the newly developed Frequency Hierarchy (FH) framework of CosmoTherm. We illustrate the physics by presenting detailed computations of the photon transfer functions and distortion cross power spectra throughout the dark photon parameter space. We find that the dark photon mass explicitly controls the shape (i.e., multipole-dependence) of the signal power spectra, while the overall amplitude of the signal is determined by the kinetic mixing parameter of the model. Using these results, we place complementary limits on the minimal dark photon model using data from Planck, finding that the constraints are only marginally weaker than those obtained with COBE/FIRAS data for the average (monopole) distortion. In addition, we compute the corrections to the standard temperature field, arguing that conversions at redshifts larger than $2\times 10^6$ may add iso-curvature type perturbations, which could lead to novel constraints in regimes where distortion anisotropies thermalize. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09427 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09427v1 Announce Type: new Abstract: We investigate late-Universe dynamics in which the dark matter component is described by axion particles. The proposed framework departs from the standard $\Lambda$CDM paradigm due to a small fraction of axions driving the system away from thermal equilibrium. We analyze the evolution of the axion energy density using both a kinetic and a classical field approach, yielding an identical macroscopic evolution equation for the dark matter density. The resulting scenario modifies $\Lambda$CDM dynamics in the late Universe (specifically at $z \lesssim 1$), while asymptotically recovering the standard baseline at earlier cosmic epochs. We compare the theoretical predictions of our formulation against a comprehensive suite of late-Universe datasets. Our statistical analysis reveals that when the SH0ES local calibration is included, the collisional axion model becomes significantly favored over $\Lambda$CDM, yielding a best-fit Hubble constant of $H_0 \simeq 73~{\rm km\,s^{-1}\,Mpc^{-1}}$. Ultimately, this cosmological scenario successfully accommodates local distance-ladder measurements while maintaining excellent agreement with Baryon Acoustic Oscillation data from the DESI Collaboration. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.09210 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.09210v1 Announce Type: new Abstract: Ultra-light dark matter fields induce nearly monochromatic signals in gravitational-wave detectors through their coupling to the Standard Model. Their spectral morphology exhibits features caused by sidereal modulation that, for frequencies below $\sim 30~$Hz, enable discrimination between spin-1 and spin-2 ultra-light dark matter signals, provided sufficient signal-to-noise ratio. In the context of LIGO--Virgo--KAGRA search techniques, we show that incorporating these spectral features can improve current excess-power constraints at low frequencies by up to $\sim36\%$. Additionally, we propose an optimised implementation of the cross-correlation statistics within the Band-Sampled-Data framework, enhancing the sensitivity of cross-correlation searches across nearly the entire frequency range, reaching up to $\sim42\%$ at low frequencies and $\sim35\%$ at high frequencies. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08899 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08899v1 Announce Type: new Abstract: Future space-borne gravitational-wave (GW) detectors, such as LISA and DECIGO, are expected to detect a large number of GW events, a fraction of which may be strongly lensed by intervening galaxies or galaxy clusters. In this work, we develop a comprehensive framework to simulate strongly lensed GWs in the context of space-borne detectors. Based on realistic astrophysical models for both the source population and the lens distribution, we construct mock catalogs of lensed GW events, referred to as \textbf{GW-LMC-Space}. Our results show that, for a four-year LISA observation, the expected number of lensed events ranges from $0$ to $131$, depending on the adopted formation model of massive black hole binaries (MBHBs). The corresponding lensing probability for MBHBs can reach up to $\sim 0.3\%$. For DECIGO, we find that the number of lensed events in a one-year observation is expected to lie in the range of $0$--$44$, with a lensing probability of $\sim 0.15\%$ for stellar-mass binary black holes (BBHs), binary neutron stars (BNSs), and neutron star--black hole binaries (NSBHs). We further show that the overlap of lensed signals is a common feature in space-borne detectors, which can significantly affect both the signal-to-noise ratio (SNR) estimation and event identification. These results highlight the importance of accounting for signal overlap in the analysis of strongly lensed GW events in future space-borne GW observations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08593 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08593v1 Announce Type: new Abstract: We present a Bayesian reconstruction of the local density and velocity fields traced by the 2MASS Redshift Survey (2MRS) and test the inferred gravitational flow against independent Cosmicflows-4 (CF4) galaxy-group peculiar velocities. The fiducial reconstruction is the maximum-a-posteriori (MAP) solution of a Zel'dovich-approximation forward model, constrained by the 2MRS redshift-space distribution through an unbinned Poisson point-process likelihood. The model assumes Gaussian initial conditions and includes the 2MRS selection function, the Zone of Avoidance, redshift-space distortions, and a distance-dependent galaxy-bias prescription. Hamiltonian Monte Carlo provides posterior samples and constrained realizations within the same framework. The reconstructed velocity field agrees well with CF4 in object-by-object, density--velocity-correlation, and shell-by-shell reflex-dipole tests. These comparisons are made at the CF4 redshift-space positions and do not require smoothing the observed CF4 velocities to the MAP resolution. We also evolve constrained initial conditions with Gadget-4. The real-space density retains the large-scale Zel'dovich structure while developing additional nonlinear small-scale structure, and the redshift-space distribution develops nonlinear Fingers of God. The results show that the 2MRS field-level reconstruction captures the large-scale gravitational flow of the nearby Universe and provides initial conditions suitable for constrained simulations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08383 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08383v1 Announce Type: new Abstract: Recent DESI BAO observations provide intriguing hints that dark energy may be dynamical in nature. To investigate deviations of the dark energy equation of state (EoS) from $w = -1$, we introduce the $\delta$-CDM framework, a controlled deformation of $\Lambda$CDM in which deviations from a cosmological constant are parametrized by a redshift-dependent function $\delta(z)$, defined through $w_{\rm de}(z) = -1 + \delta(z)$. As an illustrative example, we reconstruct $\delta(z)$ using effective scalar field dynamics of thawing type, encompassing both quintessence and phantom regimes within a unified description. Notably, the reconstructed $\delta(z)$ is independent of the specific scalar field realization, ensuring theoretical robustness. Using Planck CMB-SPA data, DESI DR2 BAO measurements, and the Pantheon+ supernova sample within a Bayesian Markov Chain Monte Carlo analysis, we find that the $\tilde{w}_0\tilde{w}_a$ parametrization is preferred over this thawing-type realization of deviations from $w = -1$. Overall, the $\delta$-CDM framework provides a minimal yet flexible extension of $\Lambda$CDM, capable of capturing late-time dynamical features of dark energy. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08368 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08368v1 Announce Type: new Abstract: Recent analyses of high-redshift Lyman-$\alpha$ forest observations have revealed strong correlations on scales exceeding 200 cMpc at redshift z = 6. Reproducing these large-scale correlations has proven challenging for current large-volume reionization simulations. In this work, we investigate these large-scale correlations using mock spectra generated from the extended SCRIPT semi-numerical reionization model. We find that while the fiducial model ensemble systematically predicts smaller correlation lengths than those inferred from the 67 sightlines in the extended XQR-30 sample, a small fraction of individual mock realizations can naturally reproduce the observed signal. Using a delete-2 jackknife analysis, we demonstrate that the observed large-scale correlation length is disproportionately driven by a rare pair of highly transmissive sightlines associated with high-redshift transmission spikes. By inserting two such highly transmissive sightlines into our mock realizations, the fraction of models consistent with the observed redshift evolution and correlation length increases significantly from 17.5% to 74.1%. Furthermore, we show that spatial fluctuations in the ionizing mean free path remain an essential physical ingredient for reproducing the observed correlation structure. Our results suggest that the unexpectedly large Lyman-$\alpha$ correlations can be reconciled with existing reionization models when accounting for cosmic variance and the outsized statistical impact of rare, highly transmissive sightlines. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.08097 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.08097v1 Announce Type: new Abstract: We present high-resolution X-ray spectroscopic observations of the cool-core galaxy cluster Abell~1795 obtained with XRISM/Resolve. The cluster was observed with two deep pointings: a 225 ks central exposure and a 113 ks northern exposure, extending to a projected radius of 320 kpc from the cluster center. Single-temperature fits reveal a clear radial gradient in the line-of-sight velocity dispersion, decreasing from 114 $\pm$ 11 km/s in the core to 68 $\pm$ 39 km/s at 320 kpc. The bulk velocities in the central regions are very low (22 $\pm$ 12 and 7 $\pm$ 21 km/s), indicating no significant relative motion between the brightest cluster galaxy (BCG) and the intracluster medium (ICM). Given that the central region includes the southward extending cool gas tail, this result disfavors the ``cooling-wake'' scenario and instead supports an AGN-uplift origin. We find that the nonthermal pressure fraction decreases with radius, from $P_{\rm NT}/P_{\rm T}\approx2\%$ in the core to $\sim0.6\%$ at 330 kpc, suggesting that the northern ICM of A1795 is largely quiescent. Two-temperature and split energy-band (2--4 keV and 6--7 keV) fits identify two gas phases within the central $<1.5'$ region, providing strong evidence for multiphase gas in the cluster core. We detect a $\sim14\%$ resonant suppression of the optically thick Fe XXV $w$ line in the center. Additionally, we observe a significant excess in the Fe XXV $y$ line-flux relative to models. Accounting for uncertainties in the atomic data reduces this discrepancy, suggesting that atomic data uncertainties may contribute to the observed residual flux. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07958 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07958v1 Announce Type: new Abstract: An effective Bayesian evidence ranking is performed for the monomial potentials \(V_p(\phi)=\lambda_p\phi^p/p\), with \(p=2,3,4\), in low temperature warm inflation with the dissipative coefficient fixed as \(\Upsilon=C_\phi T^3/\phi^2\). In cold single field slow roll inflation, these branches are strongly constrained by the observational upper bound on the tensor to scalar ratio \(r=\mathcal P_T/\mathcal P_{\mathcal R}\), whereas warm inflation can reduce this tension by enhancing the scalar spectrum. The relevant question is therefore which monomial power is favored once \(A_s\), \(n_s\), \(r_{0.05}\), and the viable parameter volume are considered simultaneously. For each branch, the warm background equations including radiation backreaction are solved, and a broadened compressed likelihood for \((A_s,n_s,r_{0.05})\) is integrated over the prior volume to obtain \(Z_{\rm eff}^{(A_s,n_s,r)}\). For \(N_*=55\), \(\sigma_r=0.005\), and structure conditioned priors covering viable warm branches, the quadratic and cubic potentials are disfavored relative to the quartic branch: $\Delta\ln Z_{\rm eff}(p=2)=-32.18,~ \Delta\ln Z_{\rm eff}(p=3)=-6.99.$ This hierarchy is stable under changes in \(N_*\), prior ranges, random seeds, and the $r$ bound treatment. A representative quartic trajectory gives \(n_s=0.96420\), \(r_{0.05}=0.02663\), \(Q_*=4.68\times10^{-3}\), and \(T_*/H_*=10.67\), corresponding to a weakly dissipative but thermally occupied CMB window. Decomposing the primordial spectrum shows that the quartic preference is driven mainly by Bose Einstein occupation enhancement for \(T_*/H_*>1\), not by strong dissipative friction. Within the low temperature dissipative effective class and compressed likelihood adopted here, the evidence hierarchy is \(p=4>p=3\gg p=2.\) Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07919 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07919v1 Announce Type: new Abstract: We present a broadband spectro-polarimetric analysis of the extragalactic radio source \texttt{RACS\_0900-28\_7036} using SPICE-RACS DR2 observations with the Australian Square Kilometre Array Pathfinder (ASKAP). The source was selected for its large rotation measure (${\rm RM}=345.7\pm0.2~{\rm rad~m^{-2}}$), substantial excess relative to the local foreground ($\Delta {\rm RM}\approx171~{\rm rad~m^{-2}}$), and strong evidence of Faraday complexity ($\sigma_{\rm add}/\delta\sigma_{\rm add}\approx8.6$). Observations span 803--1083~MHz in 36 spectral channels, enabling detailed characterization of Faraday rotation and wavelength-dependent depolarization. One-dimensional $q$-$u$ fitting and Bayesian model selection identify a multi-component model comprising one Burn-slab component and two external Faraday dispersion components (1 Slab + 2 EFD) as the preferred description. The dominant astrophysical component exhibits ${\rm RM}\approx345.5~{\rm rad~m^{-2}}$ with modest Faraday dispersion ($\sigma_{\rm RM}\approx3~{\rm rad~m^{-2}}$), while a secondary broader component at ${\rm RM}\approx131.5~{\rm rad~m^{-2}}$ shows strong depolarization ($\sigma_{\rm RM}\approx19.5~{\rm rad~m^{-2}}$). The fractional polarization spectrum and $q$--$u$ plane evolution further confirm multiple Faraday-active regions along the line of sight. These results demonstrate that ASKAP broadband spectropolarimetry can resolve complex Faraday structures and probe turbulent magnetized environments, providing a framework for systematic depolarization studies across the full SPICE-RACS catalog and enabling statistical investigations of Faraday complexity in diverse extragalactic radio sources. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07854 Tue, 09 Jun 2026 00:00:00 -0400 arXiv:2606.07854v1 Announce Type: new Abstract: The study of the large-scale distribution of galaxies provides essential information for testing the standard cosmological model, namely the $\Lambda$CDM paradigm. This scenario is based upon two foundations: General Relativity as the theory of gravity, and the Cosmological Principle, which states that the Universe is statistically homogeneous and isotropic on large scales -- so that we can measure distances and ages in the Universe assuming the FLRW metric. In this work, we perform a test of the Cosmological Principle by probing the angular homogeneity scale, $\theta_H$, using the state-of-the-art observational data of Luminous Red Galaxies (LRGs) from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). Our analysis is performed exclusively in two dimensions, across narrow redshift ranges inside a larger redshift sample of $0.4 < z < 1.1$, in two different surveyed regions of the sky (North and South Galactic Caps), as we want to minimize a priori dependences on an underlying cosmological model. We obtain that such a scale is indeed identified in all redshift ranges, and that they are consistent with mock simulations assuming the $\Lambda$CDM model. Moreover, our results are in great agreement with previous measurements using Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16 (SDSS-IV eBOSS DR16), as well as between the north and south galactic caps of the DESI DR1 survey. These findings help underpinning statistical isotropy and homogeneity of the Universe as a physically valid hypothesis in light of upcoming stage-IV redshift surveys, hence are consistent with one of the fundamental pillars of the standard cosmological model. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06593 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06593v1 Announce Type: new Abstract: The relative importance of intrinsic colour variability of supernovae type Ia (SN Ia) versus dust-induced reddening remains an open question with important ramifications for understanding their environmental dependence, as well as for the validity of the traditionally employed Tripp linear correction for cosmological inference. We revisit this question in the light of two low-redshift, homogeneous datasets, the ZTF DR2 and Foundation DR1, which we analyse within the framework of the Bayesian hierarchical model Simple-BayeSN. We demonstrate both with simulation and on real data that traditional colour cuts, which remove highly reddened samples, induce a previously unrecognized selection effect, which may have biased previous conclusions on the origin of SN Ia colour variability. Once this is accounted for, we are able to explain the entirety of the colour--magnitude correlation as due to dust effects, with no need for an intrinsic colour correlation. This result is robust with respect to a host galaxy mass split and projected distance from the center of the host. Our findings imply that the traditional linear Tripp correction maintains an empirical validity, even though it should be ascribed to dust rather than intrinsic colour variation. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06599 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06599v1 Announce Type: new Abstract: We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight axion-like component with mass $m =10^{-24.5} \mathrm{eV}$ constitutes a fraction $f \leq 0.3$ of the total dark matter. To enable consistent halo identification in mixed-species scenarios, we develop a grid-based halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass haloes and modifying the HMF in a manner dependent on redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored ($1 \leq z \leq 4$, $f \leq 0.3$). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06900 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06900v1 Announce Type: new Abstract: We develop an inverse-scattering framework to reconstruct the effective inflationary potentials governing scalar and tensor perturbations. By recasting the Mukhanov--Sasaki equation as a Schr\"odinger-like problem on the half-line, we identify the Bunch--Davies initial condition with the asymptotic Jost solution and show that the freeze-out amplitude of the growing mode is encoded in the corresponding Jost function. This allows the scalar and tensor primordial power spectra to be written in terms of $F^{(s)}_{\nu_s-\frac12}(k)$ and $F^{(t)}_{\nu_t-\frac12}(k)$, respectively, and leads to an inverse-scattering expression for the tensor-to-scalar ratio as a ratio of Jost amplitudes. We then test the reconstruction in the large-$k$ regime using the Born approximation, where the Marchenko equation becomes linear. As benchmarks, we consider a smooth quadratic potential and a step potential that transiently violates slow roll and generates localized features in the primordial spectra. The reconstructed effective potentials reproduce the dominant behavior of $z^{\prime\prime}/z$ and $a^{\prime\prime}/a$ for smooth slow-roll evolution, while localized discrepancies arise in the scalar sector when sharp features induce stronger scattering. Our results show that inverse scattering provides a physically transparent method for connecting features in the primordial spectra to the underlying inflationary dynamics, and that the Jost function acts as a sensitive diagnostic of departures from canonical slow-roll evolution. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06963 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06963v1 Announce Type: new Abstract: Fast radio bursts (FRBs) provide a powerful probe of ionized baryons through their dispersion measures (DMs), but the observed signal contains contributions from the intergalactic medium (IGM), circumgalactic (CGM) gas, host galaxies, and source-local environments. In this thesis, I investigate FRB DMs from cosmic-web to source-local scales using cosmological simulations, zoom-in galaxy simulations, and supernova-remnant (SNR) simulations. Using the CROCODILE simulation suite, I study the DM-$z$ relation, baryon distribution, halo contributions, and host-galaxy DMs. AGN feedback redistributes baryons from halo centers into the diffuse CGM/IGM gas, particularly affecting DM contributions from massive foreground halos. From the simulated DM-$z$ relation, I derive diffuse baryon fractions of $f_{\rm diff}=0.865^{+0.101}_{-0.165}$ and $0.856^{+0.101}_{-0.162}$ for the fiducial and NoBH models. Host-galaxy DM contributions range from below 100 pc cm$^{-3}$ in dwarf galaxies to above 1300 pc cm$^{-3}$ in cluster environments. I also model young magnetars embedded in SNRs using one-dimensional hydrodynamical simulations. The dominant time-variable DM component arises from unshocked ejecta, while the shocked region contributes only a minor fraction. Comparisons with FRB 20190520B and FRB 20121102 suggest source-local DM contributions of tens to hundreds of pc cm$^{-3}$. Most models become transparent to GHz radio emission within 70 yr. In contrast, the shocked region dominates the RM contribution and evolution, with the $11\,M_\odot$ single-star model best reproducing the RM evolution of FRB 20121102. These results demonstrate that FRB dispersion measures must be interpreted as multi-component signals spanning a wide range of physical scales, linking the cosmic web, gaseous halos, host galaxies, and compact-object environments Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06969 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06969v1 Announce Type: new Abstract: Fuzzy dark matter (FDM), often realized as an ultralight scalar field, can suppress the growth of small-scale structures and could be strictly tested with Lyman-$\alpha$ forest measurements. In this work, we constrain both pure and mixed FDM models (PFDM and MFDM) using measurements of the one-dimensional (1D) Lyman-$\alpha$ forest flux power spectrum at $z=5.0$, 4.6, and 4.2. We perform cosmological hydrodynamical simulations with modified initial conditions and construct a two-stage neural network emulator for accurate analysis. The first stage predicts the cold dark matter (CDM) 1D flux power spectrum, while the second stage predicts the MFDM effect relative to the CDM baseline. This construction improves the sensitivity to weak FDM effects, enforces the correct CDM limit, and enables robust interpolation across a broad range of FDM masses and fractions. After marginalizing over the intergalactic medium parameters, we obtain the FDM mass $m_{\mathrm{FDM}}>1.9\times10^{-21}~\mathrm{eV}$ at 95\% credible level for the PFDM model. For the MFDM model, we find the FDM fraction of dark matter $f_{\mathrm{FDM}}<0.07$, $0.12$, and $0.65$ at 95\% credible level for $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})=-23.0$, $-22.0$, and $-21.0$, respectively. When $\log_{10}(m_{\mathrm{FDM}}/\mathrm{eV})\gtrsim -20$, the current data do not provide an effective upper limit on $f_{\mathrm{FDM}}$. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07391 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07391v1 Announce Type: new Abstract: Neutrinos enter cosmology in different ways and are constrained by distinct observational probes across different epochs: as a relativistic species at high redshift, as a massive but clustering-suppressing component at low redshift, and as a particle physics observable in laboratory experiments. Low (verging on negative) bounds on neutrino mass from galaxy surveys motivate exploration of models where neutrinos may couple to dark energy, causing their mass to vary over cosmic evolution. If the coupling involves an inverse phase transition (symmetry broken, rather than restored, as neutrinos become nonrelativistic) this can tame instabilities in neutrino growth, appear as a lower neutrino mass in galaxy surveys, and add extra suppression to the matter power spectrum. We find that the late-time decoupling shuts down the fifth force and inhibits the excessive growth of neutrino perturbations, thereby eliminating linear-regime instabilities. The model may potentially address the Hubble tension via an early dark energy component localized around the time of recombination. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06557 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06557v1 Announce Type: cross Abstract: DARK-FLIP I introduced a semi-analytical and Python-based framework for studying a relativistic version of the intermediate-axis instability (IAI) of a coherent non-axisymmetric matter element around rotating black holes dressed by dark matter (DM). In this second paper I test the robustness of that idea. The main question is simple: if the local environment is changed by the DM profile, how does the flip frequency respond? To answer this, I use a controlled effective response model (ERM), not a full accretion or radiative-transfer simulation. The flip frequency is therefore treated as a diagnostic orientation-modulation timescale, not as a direct quasi-periodic oscillation (QPO) model. I vary the DM normalization, profile scale radius, intermediate principal moment of inertia, effective tidal coupling, initial perturbation, and initial orientation. Einasto and regularized cored Navarro--Frenk--White (cored-NFW) profiles are used as the main DM models, while Hernquist is kept as a control benchmark. The analysis includes one-dimensional scans, two-dimensional response maps, profile-contrast maps, time-domain flip simulations, a profile timing-response diagnostic, and a local projected-emissivity proxy. The results show a clear perturbative trend: increasing the enclosed DM normalization decreases the flip frequency relative to Kerr, while more extended profiles weaken the local response. DARK-FLIP II therefore strengthens the interpretation of the flip frequency as a controlled DM-sensitive orientation clock. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06581 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06581v1 Announce Type: cross Abstract: Lecture notes on inflation. The lectures are three double lectures, held for the first time at the Nordita Winter School 2024 - Particle Physics and Cosmology, covering an advanced introduction to the theory of primordial inflation, as well as the linear and non-linear perturbation theory of slow-roll inflation/quasi-de Sitter spacetimes. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06587 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06587v1 Announce Type: cross Abstract: We propose a novel scenario for the onset of the thermal Big Bang. In this framework, the inflaton transfers its energy exclusively into a dark sector, leaving the Standard Model (SM) sector temporarily trapped in a false vacuum. As the Hubble expansion rate rapidly decreases, the SM phase transition eventually completes, and the standard thermal Big Bang era commences upon the thermalization of the highly energetic bubble walls. We demonstrate that the large Lorentz boost of these bubble walls, combined with their Hubble-scale macroscopic size, generates distinctive gravitational-wave signatures from the SM vacuum decay. This stochastic gravitational-wave background provides a powerful new probe of the early Universe's expansion history, with a present-day energy density fraction that can reach $\Omega_{\text{GW}} \sim 3\times10^{-8}$. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07106 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07106v1 Announce Type: cross Abstract: Dark matter (DM) annihilation into neutrinos provides a promising observational channel targeted by current and forthcoming neutrino detectors. However, the detection of such neutrino fluxes alone cannot uniquely determine their astrophysical or cosmological origin, such as the recent observations from Super-Kamiokande that hint at a small excess of electron antineutrino events. We propose that the effective number of neutrino species and the spectral distortion of the cosmic microwave background (CMB) can serve as complementary observables to probe neutrino signatures from DM annihilation. Using a simple model-independent analysis, we determine the detection windows of these cosmic observables that overlap with the experimental sensitivities from the Super-Kamiokande, Jiangmen Underground Neutrino Observatory, Hyper-Kamiokande, and the Deep Underground Neutrino Experiment, showing that joint probes of large DM annihilation to neutrinos with MeV-GeV masses can be achieved by neutrino detectors and CMB experiments. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07298 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07298v1 Announce Type: cross Abstract: The cosmic chronometer (CC) method provides a direct measurement of the expansion history, $H(z)$, from the differential ages of passively evolving galaxies. However, most CC analyses rely on high-quality spectroscopy to select passive galaxies, measure age-sensitive spectral features, and control stellar-population systematics. We build on existing works that use the D4000 spectral break as a proxy for measuring galaxy ages and apply it to a photometry-selected galaxy sample from VIPERS PDR2 in the range $0.5 \le z \le 0.8$. Our goal is to extend the scope of the standard CC framework to photometric surveys. To achieve this, we first select a massive and passive galaxy sample using rest-frame colors and mass. Second, we design a Bayesian framework to infer full galaxy age posteriors in fine redshift bins, using a D4000-age-metallicity grid from stellar population synthesis (SPS) models. We also marginalize over metallicity, using a Gaussian metallicity prior to break the D4000-age-metallicity degeneracy. Subsequently, we derive age-difference posteriors between redshift bins by convolving their age posteriors to propagate the non-Gaussian features correctly. Finally, using the median and errors extracted from the differential age posteriors, we calculate the weighted average $H(z)$ over our selected redshift range. We obtain $H(z=0.65)=93.68\pm28.27\,{\rm (stat.)}\pm10.67\,{\rm (syst.)}\ {\rm km\,s^{-1}\,Mpc^{-1}}$, which is consistent with existing spectroscopic CC measurements and with the Planck $\Lambda$CDM prediction at the same redshift. This result provides a proof of concept for extending direct $H(z)$ measurements from cosmic chronometers to photometric and spectro-photometric surveys, where larger samples can compensate for lower spectral resolution, provided that passive-galaxy selection, metallicity priors, and stellar-population systematics are carefully controlled. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07330 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07330v1 Announce Type: cross Abstract: Searches for gravitational waves (GWs) from isolated supermassive black hole binaries (SMBHBs) in pulsar timing array (PTA) data require simultaneous estimation of signal and noise parameters, so the dimensionality of the fit scales with the number of observed pulsars. This computational difficulty is exacerbated when source evolution from GW emission is included, since retaining both Earth and pulsar terms introduces the unknown pulsar distances. Existing frequentist methods such as the $\mathcal{F}$-statistic, restricted so far to non-evolving sources, effectively, imply a circular analysis, which may lead to biased estimators. We present a Generalized Likelihood Ratio Test (GLRT) and the associated $\mathcal{T}$-statistic that overcomes the aforementioned limitations. The formulation of the GLRT extends earlier work in which the dimensionality of the fitting problem was drastically reduced by semi-analytical maximization of the likelihood over the pulsar phase parameters, followed by efficient global optimization over the remaining parameters using Particle Swarm Optimization. Our simulations demonstrate that for an evolving SMBHB signal with chirp mass $\mathcal{M}=10^{9.2}\,M_\odot$ and signal-to-noise ratio $20$, this detection statistic achieves a $100\%$ detection probability at a false-alarm probability of $0.06$ in a 30-pulsar timing array, which is characterized by a $100~\mathrm{ns}$ root-mean-square white noise residual and pulsar-specific red noise. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07446 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07446v1 Announce Type: cross Abstract: We compute 95% confidence-level upper limits on the dark matter annihilation cross section and decay rate from both total-intensity and polarized synchrotron emission in five extragalactic targets: M31, the Large Magellanic Cloud (LMC), the Draco and Sculptor dwarf spheroidal galaxies, and the Coma cluster. Using Planck maps at 30, 44, and 70 GHz, we solve the diffusion-loss equation for dark-matter-produced electrons and positrons numerically with DRAGON and integrate the resulting synchrotron emission along the line of sight with HERMES, computing both total-intensity and polarized-intensity maps for each target with target-specific magnetic-field, gas, and radiation-field environments. The 30 GHz channel yields the most stringent constraints in all cases, and limits on annihilation or decay into $e^+e^-$ are stronger than those for $b\bar{b}$ due to the harder injected spectrum. For most targets the total-intensity and polarized limits are broadly comparable; the LMC is an exception, where Faraday depolarization in the turbulent disk suppresses the polarized signal relative to total intensity, making total intensity the primary estimator. Our results are robust against the choice of flux estimator and coordinate uncertainty. This work demonstrates that microwave polarimetry provides a complementary and largely independent probe of dark matter synchrotron emission in extragalactic targets. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07467 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07467v1 Announce Type: cross Abstract: During cosmological inflation, inhomogeneities arising from quantum vacuum fluctuations are stretched to become super-Hubble and effectively classical. As many scenarios of the origin involve nonlinearities or a breakdown of perturbativity in the infrared, the limitations of quantum field theory can be addressed using a stochastic description of the dynamics, the so-called stochastic inflation paradigm. However, the stochastic formalism was only recently formulated consistently within full General Relativity and has not yet been extended to more general theories of the early universe, which is the subject of this work. In order to find the stochastic sources for a wide class of fully nonlinear scalar-tensor theories, we apply our gauge-agnostic coarse-graining procedure to the linear equations of the effective field theory of dark energy. Each theory can then be mapped to its own set of stochastic equations of motion by identifying the corresponding coefficients in the EFT. We illustrate this with a few concrete and, in most cases, unprecedented examples, including Gauss-Bonnet, generalized Brans-Dicke, Horndeski, and braiding theories. Finally, we discuss other natural extensions to provide a phenomenologically complete stochastic framework. For example, we showcase the coarse-graining of multifield inflation in full General Relativity and argue for the generality of our procedure and thus its potential applications beyond the realm of inflation. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.07505 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07505v1 Announce Type: cross Abstract: The asteroid-mass class of Primordial Black Holes (PBHs) is one of the candidates for the dark matter in the universe. With a mass between $4 \times 10^{-17} < M_{\rm PBH} < 4 \times 10^{-12}~M_{\odot}$, they could be the major component of dark matter in the cosmic mass budget. The infall of these PBH into a white dwarf could be one triggering mechanism of Type Ia supernovae (SNe Ia). In [Leung et al, ApJ 991, 11 (2025)] (Paper I), we studied the ignition, explosion dynamics, radiative transfer, and post-explosion nucleosynthesis of the PBH-triggered SNe Ia. The diversity of the explosion models can reconcile with the empirical Phillips relation. In this work, we developed the PBH-triggered SN Ia models in various metallicity. We show that models from this channel can explain some recently observed SN Ia light curves and supernova remnants. We further investigate how these supernovae could affect the chemical evolution on the galactic scale by adding the new SN Ia models as a new chemical source. We examine how the observed chemical trends of stars can lead to constraints on the fraction of this explosion channel relative to the canonical binary star channel. Our models suggest that the PBH can be one major SN Ia channel in the early universe. We also include a comparative study to extract the effects of PBH-triggered SN Ia parameters on the actual chemical trends in the galactic chemical evolution model. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2506.14182 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2506.14182v3 Announce Type: replace Abstract: We present a physically motivated dark-energy (DE) model rooted in the topological structure of the Quantum ChromoDynamic (QCD) vacuum. In this framework, DE arises from the difference between the vacuum energy of an expanding FRW universe and Minkowski spacetime, induced by QCD topological sectors. The resulting DE term in the Friedmann equation scales with the Hubble rate, $\rho_{\rm DE}(t)\propto H(t)$, once DE dominates cosmic expansion, i.e. when the Universe is close to the de Sitter regime with $H\approx$ constant. The QCD scale, $\Lambda_{\rm QCD}\sim100~{\rm MeV}$, naturally fixes the DE density and explains why its influence becomes significant only recently. The construction relies solely on the Standard Model of particle physics, introducing no new fields or couplings. The most fundamental change is the possibility of modifying the evolution of the background cosmology in the Friedmann equation. Key predictions include: (a) A present-day equation of state parameter $w_{\rm DE,0}>-1$ that asymptotically approaches the de Sitter limit $w_{\rm DE}=-1$ in the future. (b) A present-day Hubble constant $H_0$ that asymptotically approaches a constant $\overline{H}$ set by $\Lambda_{\rm QCD}$. (b) For $z\ge 0$, $w_{\rm DE}(z)$ may lie above or below $-1$ and can cross this boundary multiple times at different $z$, behavior qualitatively consistent with the recent DESI findings. (c) In our framework, any deviation from $\Lambda$CDM leads to a corresponding deviation of $H(z)$, which can be tested with existing and future cosmological observations. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2507.15575 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2507.15575v2 Announce Type: replace Abstract: We investigate the background cosmological expansion on the onset of cosmological homogeneous matter creation scenario, a dynamical dark matter approach ($w_{\rm dm} \neq 0$), and an alternative approach to both dark energy and modified gravity theories, after the recent DESI DR2-BAO release. We consider that the total matter sector consists of three independently evolving components, namely, radiation, baryons, and dark matter, with the latter being governed by an adiabatic matter creation process, affects the background homogeneously, leads to a modified continuity equation. Though the total stress-energy tensor is conserved the only violation of the conservation law in the dark matter sector is coming from the creation pressure, and under a proper choice of dark-matter particle creation rate one can obtain the present accelerating phase as well as the past thermal history of the Universe. We study two specific matter creation rates. By applying the dynamical-system analysis we show that both Model I and Model II can mimic a $\Lambda$CDM-like behavior. Furthermore, we perform a detailed observational confrontation using a series of latest observational datasets including Cosmic Chronometers (CC), Supernovae Type Ia (SNIa) (Pantheon+, DESY5 and Union3 samples) and DESI Baryon Acoustic Oscillations (BAO) (DR1 and DR2 samples). In both Model I and Model II we find evidence of matter creation at many standard deviations. Finally, applying the AIC and BIC information criteria we find that Model I is statistically equivalent with $\Lambda$CDM scenario, while Model II shows a mixed picture, namely for most datasets $\Lambda$CDM scenario is favoured, however when DESI data are included matter creation Model II is favoured over $\Lambda$CDM paradigm. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2508.09112 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2508.09112v3 Announce Type: replace Abstract: Line intensity mapping (LIM) is an emerging technique for probing the large-scale structure (LSS) in the post-reionisation era. This captures the integrated flux of a particular spectral line emission from multiple sources within a patch of the sky without resolving them. Mapping different galaxy line emissions, such as the HI $21$-cm and CO rotational lines via LIM, can reveal complementary information about the bias with which the line emitters trace the underlying matter distribution and how different astrophysical phenomena affect the clustering pattern of these signals. The stage at which the structures in the "cosmic web" merge to form a single connected structure is known as the percolation transition. Using mock HI $21$-cm and CO($1-0$) LIM signals in the post-reionisation universe, we explore the connectivity of structures through percolation analysis and compare it with the underlying galaxy distribution. We probe the relative contributions of voids, filaments, and sheets to the galaxy density and line intensity maps using a morphological measure known as the local dimension. The CO($1-0$) map exhibits an increased filamentary behaviour and larger contribution from sheets than the $21$-cm map. We attempt to explain such an emission of the CO($1-0$) line from biased environments. The upcoming SKA-Mid will produce tomographic intensity maps of the $21$-cm signal at $z \lesssim 3$ in Band-1. CO maps can be produced at these redshifts in phase 2 of SKA-Mid, where the frequency coverage is expected to increase up to $\sim 50$ GHz. We present forecasts for the recovery of the local dimensions of these line intensity maps contaminated by thermal noise and line interlopers in SKA-Mid surveys. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2511.13866 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2511.13866v3 Announce Type: replace Abstract: The generation of white noise on large scales is a generic property of the dynamics of physical systems described by local non-linear partial differential equations. Non-linearities prevent the small scale dynamics from being erased by smoothing. Unresolved small scale dynamics act as an uncorrelated (white or Poissonian) noise (seemingly stochastic but actually deterministic) contribution to large scale dynamics. This white noise exists even when the dynamics is very nearly linear. In cases where the power spectrum is sub-Poissonian on large scales, this noise will dominate on the largest scale power no matter the amplitude of the inhomogeneities. Such is the case in the standard model of cosmology, where the primordial density power spectrum is expected to have an almost Harrison-Zel'dovich, $P[k]\sim k$, spectrum on a much broader range of scales than can be observed. Even though linear gravitational evolution dominates non-linear corrections by a factor $\sim10^5$, the non-observation of white noise on the Hubble scale precludes the extrapolation of this power law below the comoving $1\,$pc scale. More generally, observation or non-observation of large scale white noise provides a powerful probe of the universe on very small scales in the early early universe. Gravitational radiation, phase transitions, vorticity, and running of the spectral index are all phenomena that can be probed with large scale white noise. Large scale white noise is a non-optional feature of all cosmological models but one which has not heretofore been appreciated. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2512.06584 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2512.06584v2 Announce Type: replace Abstract: We present a new approach for extracting information about cosmic magnetic fields using cross-correlations between extragalactic Faraday rotation measure (RM) catalogs and galaxy surveys. Specifically, we propose measuring the two-point cross-correlation between RM squared, ${\rm RM}^2$, towards background sources and the projected density field of foreground galaxies, $\langle {\rm RM}^2 \times {\rm g} \rangle$, as a function of transverse separation. This statistic is analogous to the ''projected fields'' estimator used for the kinetic Sunyaev-Zel'dovich (kSZ) effect, $\langle {\rm kSZ}^2 \times {\rm g} \rangle$. Our estimator avoids contamination, and is also free from the noise bias that arises when correlating the absolute value of the RMs with galaxies. Moreover, by binning in foreground galaxy redshifts, $\langle {\rm RM}^2 \times {\rm g} \rangle$ enables a tomographic reconstruction of the redshift evolution of large-scale cosmic magnetic fields. We model this statistic using the Illustris-TNG cosmological magnetohydrodynamic simulations and compare with approximate analytic predictions. We show that $\langle {\rm RM}^2 \times {\rm g} \rangle$ can be related to a bispectrum involving two copies of the electron-density--weighted magnetic field strength and one of the galaxy overdensity. In Illustris-TNG, the effective field strength is primarily set by the magnetic field amplitudes within the inner regions of galaxy-hosting dark matter halos. It increases towards low redshift, driven by dynamo amplification and magnetized outflows. Our forecasts suggest that $\langle {\rm RM}^2 \times {\rm g} \rangle$ is detectable at high significance with current galaxy surveys and future RM catalogs from the SKA, offering a tomographic probe of large-scale magnetic fields across cosmic time. Astro/astro-ph.CO_(Cosmology_and_Nongalactic_Astrophysics) https://arxiv.org/abs/2606.06691 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06691v1 Announce Type: new Abstract: Temperate sub-Neptune and terrestrial exoplanets could contain large inventories of water in various phases, such as water-dominated atmospheres or even oceans. Observations have shown that many exoplanets, including water worlds, likely contain photochemically-generated hazes. Haze particles are a key source of organic matter and may impact the evolution or origin of life; their optical properties are imperative for interpreting observations through theoretical atmospheric modeling. Modelers have thus far assumed haze optical properties that may not represent hazes under sub-Neptune and terrestrial atmospheric conditions. Often orbiting close to M-dwarf stars, these planets receive large amounts of radiation, especially during flaring events, which may accelerate atmospheric escape and affect atmospheric compositions. Here, we present optical constants of experimentally-generated sub-Neptune haze analogs before and after UV irradiation across a broad wavelength range (0.5 to 8 {\mu}m). We find that UV-irradiation alters haze optical constants which become generally more absorbing in this wavelength range, which we hypothesize is due to our sample containing more oxygen-rich absorbing bands post irradiation. We use Virga and PICASO to simulate transmission spectra of potentially hazy water-dominated planets GJ 1214b and LHS 1140b, accounting for irradiated haze layers in their atmospheres. For our GJ 1214b CH4-rich haze modeled case, we see a difference in the N-H feature at 2.6 {\mu}m in the resulting transmission spectrum between irradiated and unaltered haze that should be observable within current JWST capabilities. Broadly, we demonstrate the importance of using more representative optical constants, as they have an impact on current and future atmospheric composition interpretations. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.06868 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06868v1 Announce Type: new Abstract: Recent large-scale transit surveys conducted by space telescopes such as Kepler and TESS have revealed a vast number of exoplanets, uncovering the diversity of their population. One of the remarkable findings is the presence of a deficiency region in the period-radius distribution of short-period ( 5.7 days) based on orbital period, each likely reflecting distinct evolutionary pathways. In this study, we used the InfraRed Doppler (IRD) instrument on the Subaru Telescope to determine the mass of the super-Neptune TOI-1883 b, which resides in the ridge region (P ~ 4.51 days) orbiting an M dwarf. We measured a planetary mass of Mp = 13.7 +6.8/-6.5 Earth masses and a mean density of 0.4 +0.3/-0.2 g cm^-3, with 3-sigma upper limits of 34.1 Earth masses, and 5-sigma upper limits of 47.7 Earth masses. These results suggest that TOI-1883 b is likely a low density super-Neptune. We also find that the boundary of the Neptune desert defined by planets orbiting FGK-type stars exhibits a similar distribution for planets around M-type stars. According to the population-based argument of Bourrier et al. (2025), this suggests that TOI-1883 b may have undergone disk-driven migration to reach its current orbit and experienced early atmospheric photoevaporation driven by strong stellar XUV irradiation. The derived planetary mass is comparable to or exceeds the conventional critical core mass. We suggest that the high metallicity of the host star ([Fe/H] = 0.32 +/- 0.18) may have suppressed the onset of runaway gas accretion. Furthermore, TOI-1883 b has a high Transmission Spectroscopy Metric (TSM > 140), making it an excellent target for future atmospheric characterization via transmission spectroscopy. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07144 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07144v1 Announce Type: new Abstract: How much does the wind affect the path of meteorite falls? We finely model the lower ~30 km of the atmosphere using Weather Research and Forecasting open source tools at 1 km spatial resolution. Models initialised at different times give different results, which can be used as a proxy for uncertainty. We find that in most cases the differences on the ground positions are significant: median shift for a 1 kg meteorite is 143 m, doubling to 307 m for a 10 g rock, though these vary by over an order of magnitude between events. The differences wind model choice makes on the ground are significantly larger than the typical uncertainty on meteoroid state vector obtained from bright flight observations of the fireball (<100 m), and should be taken into account when predicting meteorite free-fall path to the ground. Unsurprisingly the cases where we see the largest differences coincide with documented extreme weather events. We also find that high spatial resolution models (1 vs. 3 km) tend to perform better. We have successfully used these models to guide field teams to the location of 12 fallen meteorites after fireball observations. We release as open data 1107 models we have calculated for 302 meteorite fall events and spacecraft re-entries around the world. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07177 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07177v1 Announce Type: new Abstract: Lunar impact flashes provide a direct means of estimating the flux of centimetre-sized meteoroids impacting the lunar surface. However, 25-60 frames per second imaging typical of most monitoring programs limit the ability to resolve the rapid temporal evolution of the impact process, while the integration of Earthshine background restricts the detection of faint flashes. In this work, we present high-speed observations of lunar impact flashes captured at 200 and 250 FPS using the Zadko Telescope in Western Australia. We resolve the light curves of four confirmed events, revealing complex morphologies, some of which are not well modelled by simple exponential decays. One event was simultaneously detected by a second observer using a 50 FPS system, revealing a significantly faster brightness drop in the high-speed data that cannot be explained by spectral differences alone, indicating temporal integration of the vapour plume and subsequent ejecta. Our data also indicates that the initial flash intensity (representing the vapour plume) exhibits significantly less variance across events than the total luminous energy. Furthermore, we found no statistical correlation between the initial luminous energy and the total integrated energy of the flashes in this data, suggesting that the physical mechanism driving the initial vapour expansion may be physically decoupled from the longer-duration glow driven by the cooling ejecta. High temporal resolution combined with high sensitivity are therefore essential for accurately characterising the physical properties of the impactor and distinguishing the initial vapour plume from the subsequent incandescent cooling phase, although a significantly larger dataset is required to definitively constrain these mechanisms. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07484 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07484v1 Announce Type: new Abstract: Magnetic field generation in giant planets and rapidly rotating stars produces a diverse range of field geometries, from large-scale dipole-dominated configurations to complex, small-scale multipolar structures. Earlier dynamo studies have suggested that multipolar solutions tend to arise when rotational effects become less dominant. We investigate the strength of non-dipolar magnetic fields generated in systems dominated by rotation. 40 three-dimensional, spherical-shell dynamo simulations were carried out using the MagIC code, primarily made up of bistable pairs - simulations with the same control parameters that can settle in both a dipolar and non-dipolar steady-state regime. We use this suite of models to test how their magnetic field strength scales with heat flux and velocity. Our dynamo simulations produce magnetic fields with morphologies that fall on the two distinct branches, dipolar or non-dipolar, yet have very similar convective velocities. The strength of the dipole component differs by an order of magnitude between the two regimes, when scaled as a function of driving power. However, their non-dipolar magnetic field strengths are very similar. We conclude that when attempting to predict the magnetic field strength of rapidly rotating planets and stars, one cannot assume that it will have a dipole-dominated geometry. In particular, the amplitude of the dipole component is expected to be an order of magnitude smaller in the non-dipolar regime. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07497 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07497v1 Announce Type: new Abstract: Ultra-hot Jupiters (UHJs; $T_{\rm eq} \gtrsim 2000$ K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b ($T_{\rm eq} \approx 2600$ K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR$>$4) signals from H$_2$O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of $\approx$0.2 dex, retrieving a solar atmospheric metallicity ([M/H]$_\odot$ $= 0.07^{+0.17}_{-0.13}$ $\approx 1.2\times$ solar), a C/O ratio (C/O $= 0.65^{+0.08}_{-0.08}$) consistent with solar value (C/O $=$ 0.59), an enhanced refractory abundance ([R/H]$_\odot$ $= 0.40^{+0.23}_{-0.17} \approx 2.5\times$ solar; $\approx 3.8\times$ stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V]$_\odot$ $= 0.36^{+0.11}_{-0.09}$ $\approx 2.3\times$ solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H$_2$O or H$_2$O-CO snowlines (at 68$\%$ confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68$\%$ confidence). The Mg/Fe is also found to be consistent with stellar value at 95$\%$ confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.07511 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.07511v1 Announce Type: new Abstract: Despite their large abundance, it is still unknown whether and under what conditions rocky planets around M dwarf stars can host atmospheres. This open question motivated the on-going Rocky Worlds DDT survey focused on searching for atmospheres on relatively low-temperature rocky exoplanets by systematically probing for the presence of day-night heat redistribution and CO2 absorption through JWST/MIRI 15 $\mu$m eclipse observations. Here we present the analysis of the first full data set from this survey, consisting of four observations of the warm Earth-size exoplanet GJ 3929 b, with a planetary mass of 1.75+0.44-0.45 M$_\oplus$ and instellation flux of 17.3+/-0.7 S$_\oplus$. In our analysis, we include two previously unpublished eclipse observations and find an overall eclipse depth of 118+/-22 ppm and a dayside surface brightness temperature of 641+59-64 K. This is marginally lower than the eclipse depth of 160+26-27 ppm previously reported based on only the first two observations. While the full data set remains consistent with bare rock scenarios, it also leaves more room for thin atmosphere scenarios. Only thick CO2 atmospheres without thermal inversion remain ruled out at greater than 3$\sigma$. We also continue with lessons-learned in robustly analyzing these kind of high-precision JWST/MIRI 15 $\mu$m eclipse observations. Notably, we find that the Frame Normalized Principal Component Analysis (FN-PCA) method appears more robust against the choice of extraction aperture size, which otherwise can have a significant impact on the inferred eclipse depth and scientific conclusions when using a standard polynomial baseline detrending method. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.06576 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06576v1 Announce Type: cross Abstract: In the sciences, regression tasks often require predicting high-dimensional outputs from few training examples. Multi-output Gaussian processes excel in low-data regimes but typically struggle with high-dimensional outputs. Compress-then-predict pipelines such as PCA-GP (principal component analysis plus Gaussian process regression) handle high dimensionality, but rely on bases optimized for reconstruction rather than prediction. To address this gap, we propose a model that represents each output as a linear-Gaussian decoding of a low-dimensional latent state drawn from a Gaussian process prior. By analytically marginalizing the decoder weights, we couple compression and prediction in a single objective that scales to high-dimensional outputs. We refer to this model as Gaussian process latent factor regression (GPLFR). We demonstrate GPLFR by building the first spatially resolved emulator of global climate models for rocky exoplanets. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.06692 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06692v1 Announce Type: cross Abstract: We present a simple, rule-based filter for SETI target selection that flags stars unlikely to host complex life and produces an audit-ready exclusion catalog. Using seven stellar parameters, including age, metallicity, and multiplicity, the model excludes roughly half of a 1.74 million-star Gaia DR3 sample, retaining 777,835 high-priority targets, mainly K dwarfs and quiet M dwarfs. Age and metallicity dominate the rejections. Importantly, using Gaia's age upper bounds instead of point estimates saves 355,086 stars from exclusion. A comparison of empirical and synthetic proxies shows that while the overall exclusion rate is robust, individual target assignments change significantly; for instance, the commonly used RUWE indicator flags 2.7x more binaries than Gaia's own non-single-star flag. Cross-matching with the Breakthrough Listen target list reveals a 56.5% exclusion rate, highlighting the complementary nature of habitability-driven and proximity-driven surveys. The catalog, pipeline, and a generalized community tool are publicly available. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.06884 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06884v1 Announce Type: cross Abstract: Blanets are planetary-mass bodies ($20$--$3000\,\Me$) that may orbit supermassive black holes (SMBHs) in the circumnuclear disks of active galactic nuclei (AGN). We examine tidal disruption events produced by blanet--SMBH encounters, from the test-particle limit to massive planetary bodies in Kerr spacetime. Using the geodesic deviation equation and the Kerr tidal tensor, we derive disruption criteria, tidal radii, and Hills masses for planetary-mass objects, and show that blanet TDEs can remain observable for SMBHs up to $\sim10^{10}\,\Msun$, well above the stellar Hills mass of $\sim10^8\,\Msun$. The fallback rate retains the usual $t^{-5/3}$ form, but the peak timescales are shorter -- from hours to months -- with lower peak accretion rates and multi-wavelength signatures that differ from those of stellar TDEs. We also examine orbital stability, including Keplerian precession, Lense--Thirring nodal precession, migration in the circumnuclear disk, and the Kozai--Lidov resonance, and identify the region where blanets can survive before disruption. We derive relativistic corrections to the tidal radius, spin-dependent disruption thresholds, and the effect of Kerr spin on the disruption geometry. We also discuss gravitational-wave emission from blanet debris EMRIs and the prospects for LISA detection, which may help in interpreting unusual TDE-like transients in AGN environments. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2604.06064 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2604.06064v2 Announce Type: replace Abstract: Observations of periodic stellar activity near the transit phase of a close-in exoplanet provide evidence of star-planet magnetic interactions (SPMI), similar to the magnetic coupling between Jupiter and its moons. Comparing the power associated with SPMI signals to analytical theories offers a way to constrain exoplanetary magnetic fields, but models based on moon-magnetosphere analogs often underpredict observed energy fluxes. Unlike moons, many close-in exoplanets are extended, highly irradiated gas giants undergoing significant photoevaporation. However, it is not known how atmospheric escape influences the star-planet magnetic coupling. Here, we present three-dimensional radiation magneto-hydrodynamic simulations that simultaneously model planetary evaporation and SPMI in a hot Jupiter planet embedded in a magnetised stellar wind. Our simulations reveal the formation of magnetic structures known as Alfv\'en wings, which transport magnetic energy away from the planet. When the dayside mass-loss rate $\dot{M}_d$ of the planet lies below a threshold $\dot{M}_0$ defined by pressure balance between the planetary and stellar winds ($\dot{M}_d \leq \dot{M}_0$), the maximal power delivered to the star matches predictions from the Alfv\'en wing model. For higher escape rates, the planetary outflow opens additional magnetic flux, and the SPMI power increases proportionally with $(\dot{M}_d / \dot{M}_0)^{1/2}$. Applying this scaling law to the HD18973 system, we find that a $50$ G planet could reproduce the observed power if $\dot{M}_d \sim 5 \times 10^{11}$ g/s. Although this signal likely represents only a fraction of the total power, additional mechanisms could amplify the energy budget. These results show that photoevaporating exoplanets in sub-Alfv\'enic orbits constitute promising targets for SPMI observations. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.04278 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.04278v2 Announce Type: replace Abstract: Global infrasound monitoring provides a persistent means of detecting energetic bolide atmospheric entries, complementing optical observations and extending coverage over remote regions. We present a global assessment of the physical factors governing bolide infrasound detectability by correlating 623 bolide events reported by the Center for Near-Earth Object Studies between 2007 and 2025 with waveform data from the International Monitoring System. We identify 311 events with confirmed infrasound detections, corresponding to a detection rate of approximately 50%, substantially higher than inferred from earlier surveys, reflecting both the maturation of the global infrasound network and advances in automated, multi-frequency array processing. Analysis of flight parameters shows that infrasound detectability is selective rather than uniform across the bolide population. Detected events are preferentially associated with steeper entry angles and lower-altitude energy deposition, while shallow, high-altitude trajectories are less consistently observed. Very high-energy events remain detectable regardless of geometry, but for the more common lower-energy regime, observability depends on specific combinations of entry parameters and propagation conditions. This geometric dependence persists across comparable energy ranges and atmospheric conditions, indicating that entry angle exerts a primary control on detectability, with energy and propagation acting as secondary modulating factors. These results provide new physical constraints on bolide-atmosphere interactions and improve interpretation of global infrasound observations for planetary defense and atmospheric-entry studies. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2605.06648 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2605.06648v2 Announce Type: replace-cross Abstract: By aiming to find and characterise dozens of habitable exoplanets through the technique of nulling interferometry, the LIFE space mission will produce transformational science. One of the key parameters for such an interferometric mission is the nulling baseline length - the distance between nulled apertures, which past studies have assumed to be 10-100m. Advances in planet occurrence statistics and simulation tools allow us now to revisit this key assumption with significantly more detail, particularly with the intention to reduce the range of baselines considered due to mission implementation concerns. We utilise the LIFEsim mission simulator along with revised mathematical tools to identify whether the range of baselines could be reduced without significantly affecting planet yield and fringe tracking performance. Along the way, we also determine a new astrophysically motivated technique for choosing which baselines are optimal for a given science target. We find that indeed, LIFE could utilise a considerably shorter range of baselines, such as 25-80m, or even discrete baselines without much (<10%) loss of performance. Nevertheless, careful trade-offs between performance and implementation simplification must be made, especially considering any spectral weighting that may be required by the scientific goals, and the potential loss of target-specific baseline optimisation. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2605.23770 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2605.23770v2 Announce Type: replace-cross Abstract: Reachability analysis plays a central role in low-thrust spacecraft trajectory optimization by identifying which target states can be achieved under constraints on time, thrust, and propellant. Classical approaches construct reachable sets by solving many optimal control problems over grids of terminal states, requiring extensive forward simulations with fixed initial conditions. While effective, this approach is computationally expensive and becomes impractical for high-dimensional systems or strongly nonlinear dynamics, such as those encountered in cislunar environments or solar sail missions. This work introduces a dual formulation of the reachability problem. Instead of computing reachable sets directly, we determine, for fixed transfer time and boundary conditions, the maximum allowable initial mass (or, for solar sails, a scalar sail-strength parameter) that permits a successful transfer. A target is reachable if the spacecraft's initial mass does not exceed this threshold. This reformulation reduces reachability assessment to a scalar optimization problem for each target, producing a smooth scalar field that encodes equivalent feasibility information to classical reachable sets. We develop indirect maximum-initial-mass (MIM) formulations for both electric low-thrust and solar-sail dynamics and show how they can serve as efficient reachability oracles. Building on this formulation, we construct data-driven surrogate models to approximate the MIM-based reachability indicator. We investigate fully connected neural networks and demonstrate that residual networks provide the best trade-off between accuracy, training stability, and model complexity. The resulting surrogates enable rapid reachability evaluation while preserving the numerical advantages of the dual formulation, offering a practical tool for preliminary mission design and feasibility assessment. Astro/astro-ph.EP_(Earth_and_Planetary_Astrophysics) https://arxiv.org/abs/2606.06585 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06585v1 Announce Type: new Abstract: The NIRCam medium-bands have proven to be efficient at identifying Emission Line Galaxies (ELGs) with high equivalent width (EW) H$\alpha$ and [OIII]+H$\beta$ emission lines. In this paper we exploit this efficiency to identify a sample of ELGs at $4.9 \lesssim z \lesssim 8.9$ using medium-band imaging from the CANUCS, Technicolor, and JUMPS surveys. We find that the ELGs exhibit a strong correlation between continuum color and emission line strength, such that galaxies with bluer UV/optical continua have stronger H$\alpha$ and [OIII]+H$\beta$ emission lines. We identify 26 galaxies that are outliers from this relation, which we call the Red Emission line Galaxies (REGs), because of their red continuum color and strong emission lines. We classify the REGs into three categories: 1) ''classic'' Little Red Dots (LRDs) selected with common literature criteria, 2) extended REGs, resolved in F444W and consistent with being Dusty Star Forming Galaxies (DSFGs), and 3) compact REGs, unresolved in F444W but not classified as LRDs. The compact REGs fail common LRD selections for several reasons, including faint continuua, contamination from emission lines (very strong [OIII]+H$\beta$), and UV/optical colors that are flatter than those of LRDs. We conclude that the compact REGs are likely LRDs that ''classic'' selection criteria miss, and are therefore missing from existing samples. Our results suggest that medium-band selection can provide more complete samples of these objects. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.06590 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06590v1 Announce Type: new Abstract: The first components of a new meta-survey, the Combined Dense Gas and Excitation Atlas (CODEX) of the Milky Way, are presented here with combined data from five previously published surveys: NANTEN+CHaMP, ThrUMMS, FUGIN, and MWISP. The CODEX is first used to harmonise the combination of parameters used to describe the Galaxy's scale and rotation, including $R_0$ and $\Theta_0$ from recent work, since these are critical components of standard techniques for obtaining kinematic distances. An additional feature is added to these formulae to accommodate local clouds that are otherwise kinematically inconsistent with the Local Standard of Rest. The structure in the combined lV diagram spanning 230 deg of longitude is then analysed, yielding a new Ragged Spiral Arm model that better traces the deprojected (x,y) 12CO structure. The widespread existence of ripples in the molecular layer, first reported in the ThrUMMS data of the Fourth Quadrant (4Q), is confirmed in FUGIN data of the First Quadrant (1Q), averaging amplitudes $\sim$40 and $\sim$23 pc respectively, and wavelength $\sim$4 kpc in both. The (x,y) mass distributions as traced by the molecular line data and the published dust extinction data match well across the 4Q+inner1Q, but poorly across the outer 1Q, probably due to lower sensitivity in the 1Q extinction data. In the 1Q+4Q, however, the two mean-z distributions do not match: the dust ripple amplitude is $\sim$3x smaller than, and opposite in sign to, the gas ripples. This is nevertheless consistent since the dust extinction is insensitive to the densest molecular gas. Astro/astro-ph.GA_(Astrophysics_of_Galaxies) https://arxiv.org/abs/2606.06594 Mon, 08 Jun 2026 00:00:00 -0400 arXiv:2606.06594v1 Announce Type: new Abstract: Several studies have associated globular clusters (GCs) with former Galactic accretion events by comparing their positions in the energy-angular momentum ($E$-$L_z$) plane, an approach further supported by similarities in their age-metallicity relations. However, recent merger simulations suggest that GCs initially associated with the Gaia-Sausage-Enceladus (GSE) disc may have lost their orbital energy and thus may not reliably trace this accretion event. We extend this framework by considering three N-body simulations of the Milky Way-GSE merger with different initial masses, mass ratios, and gas content. In addition to GCs belonging to the GSE disc progenitor, we accounted for GCs in its halo and, in gas-rich models, a population of GCs formed during the Milky Way-GSE merger. We confirm that most GCs originating in the disc have lost a significant part of their orbital energy during repeated passages through the dense disc medium, and we conjecture that associated tidal shocks may have destroyed many of them. In contrast, GCs from the halo and GCs formed during the merger have largely retained their orbital energy, which remains comparable to that of GSE stars even up to 9 Gyr after the completion of the merger. By using a more realistic GC population and GSE modelling, we find that most GCs linked to GSE can be associated with Milky Way accretion events in the $E$-$L_z$ plane, which supports previous observational associations based on a combination of energy-angular momentum and age-metallicity relations. Astro/astro-ph.GA_(Astrophysics_of_Galaxies)