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Papers for Wednesday, Oct 08 2025

Papers with local authors

Jiayi Sun, Yu-Hsuan Teng, I-Da Chiang, Adam K. Leroy, Karin Sandstrom, Jakob den Brok, Alberto D. Bolatto, Jeremy Chastenet, Ryan Chown, Annie Hughes, Eric W. Koch, Thomas G. Williams

this https URL

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Paper 7 — arXiv:2510.05214
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Paper 7 — arXiv:2510.05214

We present radial profiles of surface brightness in UV and IR bands, estimate stellar mass surface density ($\Sigma_\star$) and star formation rate surface density ($\Sigma_\mathrm{SFR}$), and predict the CO-to-H$_2$ conversion factor ($\alpha_\mathrm{CO}$) for over 5,000 local galaxies with stellar mass $M_\star\,{\geq}\,10^{9.3}\rm\,M_\odot$. We build these profiles and measure galaxy half-light radii using GALEX and WISE images from the $z$0MGS program, with special care given to highly inclined galaxies. From the UV and IR surface brightness profiles, we estimate $\Sigma_\star$ and $\Sigma_\mathrm{SFR}$ and use them to predict $\alpha_\mathrm{CO}$ with state-of-the-art empirical prescriptions. We validate our (kpc-scale) $\alpha_\mathrm{CO}$ predictions against observational estimates, finding the best agreement when accounting for CO-dark gas as well as CO emissivity and excitation effects. The CO-dark correction plays a primary role in lower-mass galaxies, whereas CO emissivity and excitation effects become more important in higher-mass and more actively star-forming galaxies, respectively. We compare our estimated $\alpha_\mathrm{CO}$ to observed galaxy-integrated SFR to CO luminosity ratio as a function of $M_\star$. A large compilation of literature data suggests that star-forming galaxies with $M_\star = 10^{9.5{-}11}\,M_\odot$ show strong anti-correlations of SFR/$L^\prime_\mathrm{CO(1{-}0)} \propto M_\star^{-0.29}$ and SFR/$L^\prime_\mathrm{CO(2{-}1)} \propto M_\star^{-0.40}$. The estimated $\alpha_\mathrm{CO}$ trends, when combined with a constant molecular gas depletion time $t_\mathrm{dep}$, can only explain ${\approx}1/3$ of these SFR/$L^\prime_\mathrm{CO}$ trends. This suggests that $t_\mathrm{dep}$ being systematically shorter in lower-mass star-forming galaxies is the main cause of the observed SFR/$L^\prime_\mathrm{CO}$ variations. (Abridged)

The fate of hot Jupiters is thought to be engulfment by their host stars, the outcome of tidal orbital decay. Transit timing has revealed a few systems with apparently shrinking orbital periods, but such signals can be mimicked by light travel-time effects (LTTE) of a distant companion. Combining transit timings with precise radial-velocity data, including new data, we reassessed three reported cases of orbital decay: WASP-4, WASP-12, and Kepler-1658. For WASP-4, the period change is best explained by LTTE due to a 10-Jupiter-mass companion at 4 AU, with no need to invoke orbital decay. For WASP-12, in contrast, the data firmly exclude LTTE and confirm genuine orbital decay. For Kepler-1658, spectroscopic and photometric anomalies reveal the "planet" to be an eclipsing K/M binary bound to the F-type primary, with LTTE explaining the observed period change. Thus, among the known hot Jupiters, only WASP-12 b currently shows compelling evidence for orbital decay.

Fan Zou, Elena Gallo, Anil C. Seth, Edmund Hodges-Kluck, David Ohlson, Tommaso Treu, Vivienne F. Baldassare, W. N. Brandt, Jenny E. Greene, Piero Madau, Dieu D. Nguyen, Richard M. Plotkin, Amy E. Reines, Alberto Sesana, Jong-Hak Woo, Jianfeng Wu
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Paper 16 — arXiv:2510.05252
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Paper 16 — arXiv:2510.05252

The black-hole occupation fraction ($f_\mathrm{occ}$) defines the fraction of galaxies that harbor central massive black holes (MBHs), irrespective of their accretion activity level. While it is widely accepted that $f_\mathrm{occ}$ is nearly 100% in local massive galaxies with stellar masses $M_\star \gtrsim 10^{10}~M_\odot$, it is not yet clear whether MBHs are ubiquitous in less-massive galaxies. In this work, we present new constraints on $f_\mathrm{occ}$ based on over 20 years of Chandra imaging data for 1606 galaxies within 50 Mpc. We employ a Bayesian model to simultaneously constrain $f_\mathrm{occ}$ and the specific accretion-rate distribution function, $p(\lambda)$, where the specific accretion rate is defined as $\lambda=L_\mathrm{X}/M_\star$, and $L_\mathrm{X}$ is the MBH accretion luminosity in the 2-10 keV range. Notably, we find that $p(\lambda)$ peaks around $10^{28}~\mathrm{erg~s^{-1}}~M_\odot^{-1}$; above this value, $p(\lambda)$ decreases with increasing $\lambda$, following a power-law that smoothly connects with the probability distribution of bona-fide active galactic nuclei. We also find that the occupation fraction decreases dramatically with decreasing $M_\star$: in high mass galaxies ($M_\star \approx 10^{11-12}M_\odot$), the occupation fraction is $>93\%$ (a $2\sigma$ lower limit), and then declines to $66_{-7}^{+8}\%$ ($1\sigma$ errors) between $M_\star\approx10^{9-10}M_\odot$, and to $33_{-9}^{+13}\%$ in the dwarf galaxy regime between $M_\star\approx10^{8-9}~M_\odot$. Our results have significant implications for the normalization of the MBH mass function over the mass range most relevant for tidal disruption events, extreme mass ratio inspirals, and MBH merger rates that upcoming facilities are poised to explore.

Huynh Anh N. Le, Jong-Hak Woo, Yongquan Xue, Ashraf Ayubinia, Changseok Kim, Xiaozhi Lin
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Paper 47 — arXiv:2510.05687
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Paper 47 — arXiv:2510.05687

We utilize a large sample of $\sim$113,000 galaxies ($z < 0.3$) from the Sloan Digital Sky Survey with high-quality data to compare star formation rates (SFRs) across multiple diagnostic methods and examine their connection to Active Galactic Nuclei (AGNs) strength, indicated by Eddington ratio. Our sample encompassed star-forming (SF), composite, Seyfert, and LINER galaxies. Our analysis utilizes various SFRs indicators, including observed infrared flux ($\rm SFR_{FIR}$) from AKARI/Herschel ($\sim$4,100 sources), the MPA-JHU catalog ($\rm SFR_{Dn4000}$), the ANN catalog ($\rm SFR_{ANN}$), the GSWLC catalog ($\rm SFR_{SED}$ and $\rm SFR_{MIR}$), as well as \OII\ and \Ha\ emission lines ($\rm SFR_{[OII]}$ and $\rm SFR_{H\alpha}$). Within SF galaxies, SFRs measurements from different tracers exhibited differences, with offsets and scatter below 0.26 dex and 0.29 dex, respectively. Moreover, non-SF galaxies (composite, Seyfert, and LINER) displayed discrepancies among SFR tracers, particularly for LINER galaxies, with offsets below 0.86 dex and a scatter of 0.57 dex. Additionally, our findings revealed robust correlations between SFRs and specific SFRs (sSFRs) with Eddington ratios. Eddington ratio exhibited gradual transitions in the (s)SFRs-stellar mass diagrams. Galaxies with high Eddington ratios displayed high star formation activity, similar to blue SF galaxies. Furthermore, we observed decreasing sSFR trends from SF galaxies to composite, Seyfert, and LINER galaxies. Our results may provide insight into our understanding of (s)SFRs traced by different approaches and their connection to AGN activities.

Brandon Sike, Mateusz Ruszkowski, Oleg Y. Gnedin, Yingtian Chen, Matthias Weber, Timon Thomas, Christoph Pfrommer
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Paper 76 — arXiv:2510.06134
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Paper 76 — arXiv:2510.06134

Star clusters host the massive stars responsible for feedback in star-forming galaxies. Stellar feedback shapes the interstellar medium (ISM), affecting the formation of future star clusters. To self-consistently capture the interplay between feedback and star formation, a model must resolve the parsec-scale star formation sites and the multiphase ISM. Additionally, the dynamical impact of cosmic rays (CRs) on star formation rates (SFRs) must also be considered. We present the first simulations of the formation of an ensemble of star clusters with dynamically-coupled CRs, near-individual star particles, and a feedback-regulated ISM. We analyze tallbox simulations performed using the CRISP model in the moving-mesh code AREPO. We apply varied implementations of CR transport under the theory of self-confinement. We find that CRs simultaneously reduce the SFR, the power law slope of the cluster mass function, and the cluster formation efficiency. Each simulation is compatible with observations, and CR feedback tends to move results along observed star cluster relations. We see only modest changes in cluster radius and velocity dispersions, but significant differences in the virial parameters. Ultimately, the primary impact of CRs is to reduce SFRs. Lower SFRs imply fewer supernovae, and consequently a lower turbulent energy budget for gas. Star clusters formed in a CR-regulated ISM have lower velocity dispersions, and are therefore more bound under self-gravity. The effective clustering of SNe is unchanged by CRs. Through this work, we demonstrate the predictive power of the CRISP feedback model, despite this idealized setup.

Weijian Li, Hong-Yu Chen, Qinjie Lin, Nabeel Rehemtulla, Ved G. Shah, Dennis Wu, Adam A. Miller, Han Liu
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Paper 82 — arXiv:2510.06200
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Paper 82 — arXiv:2510.06200

Time series foundation models (TSFMs) are increasingly being adopted as highly-capable general-purpose time series representation learners. Although their training corpora are vast, they exclude astronomical time series data. Observations of stars produce peta-scale time series with unique challenges including irregular sampling and heteroskedasticity. We introduce StarEmbed, the first public benchmark for rigorous and standardized evaluation of state-of-the-art TSFMs on stellar time series observations (``light curves''). We benchmark on three scientifically-motivated downstream tasks: unsupervised clustering, supervised classification, and out-of-distribution source detection. StarEmbed integrates a catalog of expert-vetted labels with multi-variate light curves from the Zwicky Transient Facility, yielding ~40k hand-labeled light curves spread across seven astrophysical classes. We evaluate the zero-shot representation capabilities of three TSFMs (MOIRAI, Chronos, Chronos-Bolt) and a domain-specific transformer (Astromer) against handcrafted feature extraction, the long-standing baseline in the astrophysics literature. Our results demonstrate that these TSFMs, especially the Chronos models, which are trained on data completely unlike the astronomical observations, can outperform established astrophysics-specific baselines in some tasks and effectively generalize to entirely new data. In particular, TSFMs deliver state-of-the-art performance on our out-of-distribution source detection benchmark. With the first benchmark of TSFMs on astronomical time series data, we test the limits of their generalization and motivate a paradigm shift in time-domain astronomy from using task-specific, fully supervised pipelines toward adopting generic foundation model representations for the analysis of peta-scale datasets from forthcoming observatories.

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Upward emission of artificial light has been investigated by researchers since the commissioning of the Visible/Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) in 2011, with applications ranging from night time light mapping to quantifying socio-economical development. The wide swath of the VIIRS-DNB sensor enables detection of artificial light at multiple angles and was utilized to study emission of artificial light from cities at different angles as well as atmospheric properties. Existing studies of the relationship between the directionality and land surface features are not available for most of the Earth's surface due to the use of space-borne LiDAR as a source of proxy. To solve this problem, we compared the land use data published under the Coordination of Information on the Environment (CORINE) against the fit parameters of radiance of upward artificial light. In general, the quadratic term of the fit, which quantifies how the brightness changes when viewing closer from the horizon at a point on the Earth, is negative when the area is "Continuous urban fabric" or "Sparsely vegetated areas", and vice versa for all other investigated land use classes. However the quadratic term shifts towards negative values for brighter areas. These results indicate that while densely built areas emit more light towards the zenith than sideways, the VIIRS-DNB is unable to distinguish small densely built areas scattered around larger unbuilt areas. Therefore, sensors with higher spatial resolution will be required to resolve the light emission patterns of areas with complicated combinations of land uses.

Wout M. Goesaert, Konrad R. W. Tristram, C. M. Violette Impellizzeri, Alexander P. S. Hygate, Sophie Venselaar, Junzhi Wang, Zhiyu Zhang

Context: Most active galactic nuclei (AGN) are believed to be surrounded by a dusty molecular torus on the parsec scale which is often embedded within a larger circumnuclear disk (CND). AGN are fuelled by the inward transport of material through these structures and can launch multi-phase outflows that influence the host galaxy through AGN feedback. Aims: We use the Circinus Galaxy as a nearby laboratory to investigate the physical mechanisms responsible for feeding the torus and launching a multi-phase outflow in this Seyfert-type AGN, as these mechanisms remain poorly understood. Methods: We analysed observations from the Atacama Large Millimeter/submillimeter Array of the Circinus nucleus at angular resolutions down to 13 mas (0.25 pc). We traced dust and the ionised outflow using 86-665 GHz continuum emission, and studied the morphology and kinematics of the molecular gas. Results: We find that the Circinus CND hosts molecular and dusty spiral arms, two of which connect directly to the torus. We detect inward mass transport along these structures and argue that the non-axisymmetric potential generated by these arms is the mechanism responsible for fuelling the torus. We estimate a feeding rate of 0.3-7.5 M$_{\odot}$yr$^{-1}$, implying that over 88% of the inflowing material is expelled in a multi-phase outflow before reaching the accretion disk. The inferred torus feeding time scale (120 kyr - 2.7 Myr) suggests that variability in AGN activity may be driven by changes in torus feeding. On parsec scales, the ionised outflow is traced by optically thin free-free emission. The outflow is stratified, with a slightly wider opening angle in the molecular phase than in the dusty and ionised components. The ionised outflow is launched or collimated by a warped accretion disk at a radius of r ~ 0.16 pc, and its geometry requires an anisotropic launching mechanism.

Harley Katz, Martin P. Rey, Corentin Cadiou, Oscar Agertz, Jeremy Blaizot, Alex J. Cameron, Nicholas Choustikov, Julien Devriendt, Uliana Hauk, Gareth C. Jones, Taysun Kimm, Isaac Laseter, Sergio Martin-Alvarez, Kosei Matsumoto, Autumn Pearce, Francisco Rodríguez Montero, Joki Rosdahl, Mahsa Sanati, Aayush Saxena, Adrianne Slyz, Richard Stiskalek, Anatole Storck, Oscar Veenema, Wonjae Yee

We present the MEGATRON suite of cosmological radiation hydrodynamics simulations following the formation of Milky Way-mass galaxies from the earliest cosmic epochs when Population III stars form to Cosmic Noon. The suite represents the first set of cosmological simulations that couples a vast non-equilibrium thermochemistry network of primordial species, metals, and molecules to multifrequency, on-the-fly radiation transport, allowing us to directly predict the spectral properties of early galaxies. By initializing the simulations at zero metallicity, resolving haloes well below the atomic cooling threshold, reaching parsec-scale resolution, and modeling a Milky Way-mass environment, we aim to address four key science themes: 1) Star formation at cosmic dawn, 2) Galaxy formation and the interstellar medium in the epoch of reionization, 3) The circumgalactic medium towards cosmic noon, and 4) Reionization in a local volume environment and near-field cosmology. In this introductory work, we present an overview of the physical characteristics of high-redshift MEGATRON galaxies and their environment at $z>8$. We present a library of $>175,000$ simulated galaxy spectra and demonstrate how the diversity of galaxy spectra seen by JWST is naturally reproduced in the context of a $\Lambda$CDM cosmology. This project represents a step towards making more direct comparisons between simulations and observations and will enable future work to both optimize methods for inferring galaxy properties from observations and to elucidate the physics that governs galaxy formation in the early Universe.

Supernova remnants (SNRs) are the aftermath of massive stellar explosions or of a white dwarf in a binary system, representing critical phases in the life cycle of stars and playing an important role in galactic evolution. Physical properties of SNRs such as their shock velocity, density and age are important elements for constraining models for their evolution and understanding the physical processes responsible for their morphological appearance and emission processes. Our study provides, for the first time, a comprehensive statistical analysis of the physical parameters in 64 Galactic SNRs both as a population as well as regions within individual objects. These 64 objects represent the subset of the 310 known Galactic SNRs for which there are published optical data, from which we compiled their physical parameters through an exhaustive literature survey. Through a systematic statistical analysis accounting for uncertainties and/or upper and lower limits in these parameters we obtain distributions of the electron density and shock velocity in the studied SNRs and regions within them. This information is combined with constraints on their age and type. Analysis of electron density and shock velocity distributions for the entire sample of SNRs shows that they are consistent with a log-normal distribution and a skewed log-normal distribution, respectively. Within individual remnants, our study reveals that electron density and shock velocity show larger scatter in younger objects, reflecting the varying conditions of the ambient medium immediately surrounding the explosion epicenter and their impact on SNR evolution. Comparison of the dependence of the shock velocity and density on the supernova age with expectations from theoretical models shows good agreement.

Florian List, Oliver Hahn, Thomas Flöss, Lukas Winkler

The mildly non-linear regime of cosmic structure formation holds much of the information that upcoming large-scale structure surveys aim to exploit, making fast and accurate predictions on these scales essential. We present the $N$-body module of DISCO-DJ (DIfferentiable Simulations for COsmology - Done with Jax), designed to deliver high-fidelity, GPU-accelerated, and differentiable particle-mesh simulations tailored for cosmological inference. Theory-informed time integrators such as the recently introduced BullFrog method allow for accurate predictions already with few time steps (e.g. $6$ steps for per-cent-level accuracy in terms of the present-day power spectrum at $k \approx 0.2 \, h / \mathrm{Mpc}$ using $N = 512^3$ particles, which takes just a few seconds). To control discreteness effects and achieve high accuracy, the code incorporates a suite of advanced techniques, for example a custom non-uniform FFT implementation for force evaluation. Both forward- and reverse-mode differentiation are supported, with memory requirements independent of the number of time steps; in the reverse case, this is achieved through an adjoint formulation. We extensively study the effect of various numerical parameters on the accuracy. As an application of DISCO-DJ, we perform field-level inference by recovering $\sigma_8$ and the initial conditions from a noisy Gadget matter density field. Coupled with our recently introduced Einstein--Boltzmann solver, the DISCO-DJ ecosystem provides a self-consistent, fully differentiable pipeline for modelling the large-scale structure of the universe. The code is available at this https URL.

Michael Zemcov, James J. Bock, Asantha Cooray, Shuji Matsuura, Dae-Hee Lee, Candice Fazar, Richard M. Feder, Grigory Heaton, Ryo Hashimoto, Phillip Korngut, Toshio Matsumoto, Chi H. Nguyen, Kazuma Noda, Won-Kee Park, Kei Sano, Kohji Takimoto, Toshiaki Arai, Seung-Cheol Bang, Priyadarshini Bangale, Masaki Furutani, Viktor Hristov, Yuya Kawano, Arisa Kida, Tomoya Kojima, Alicia Lanz, Chika Matsumi, Dale Mercado, Shunsuke Nakagawa, Tomoya Nakagawa, Shuta Nakahata, Ryo Ohta, Dorin Patru, Mai Shirahata, Hiroko Suzuki, Aoi Takahashi, Momoko Tamai, Serena Tramm, Kohji Tsumura, Yasuhiro Yamada, Shiang-Yu Wang

The background light produced by emission from all sources over cosmic history is a powerful diagnostic of structure formation and evolution. At near-infrared wavelengths, this extragalactic background light (EBL) is comprised of emission from galaxies stretching all the way back to the first-light objects present during the Epoch of Reionization. The Cosmic Infrared Background Experiment 2 (CIBER-2) is a sounding-rocket experiment designed to measure both the absolute photometric brightness of the EBL over 0.5 - 2.0 microns and perform an intensity mapping measurement of EBL spatial fluctuations in six broad bands over the same wavelength range. CIBER-2 comprises a 28.5 cm, 80K telescope that images several square degrees to three separate cameras. Each camera is equipped with an HAWAII-2RG detector covered by an assembly that combines two broadband filters and a linear-variable filter, which perform the intensity mapping and absolute photometric measurements, respectively. CIBER-2 has flown three times: an engineering flight in 2021; a terminated launch in 2023; and a successful science flight in 2024. In this paper, we review the science case for the experiment; describe the factors motivating the instrument design; review the optical, mechanical, and electronic implementation of the instrument; present preflight laboratory characterization measurements; and finally assess the instrument's performance in flight.

We present a novel implementation for the quadratic maximum likelihood (QML) power spectrum estimator for multiple correlated scalar fields on the sphere. Our estimator supports arbitrary binning in redshift and multipoles $\ell$ and includes cross-correlations of redshift bins. It implements a fully optimal analysis with a pixel-wise covariance model. We implement a number of optimizations which make the estimator and associated covariance matrix computationally tractable for a low-$\ell$ analysis, suitable for example for kSZ velocity reconstruction or primordial non-Gaussianity from scale-dependent bias analyses. We validate our estimator extensively on simulations and compare its features and precision with the common pseudo-$C_\ell$ method, showing significant gains at large scales. We make our code publicly available. In a companion paper, we apply the estimator to kSZ velocity reconstruction using data from ACT and DESI Legacy Survey and construct full set of QML estimators on 40 correlated fields up to $N_{\text{side}}= 32$ in timescale of an hour on a single 24-core CPU requiring $<256\ \mathrm{Gb}$ RAM, demonstrating the performance of the code.

Jack Higginson, Rongmon Bordoloi, Robert A. Simcoe, Jorryt Matthee, Daichi Kashino, Ruari Mackenzie, Ivan Kramarenko, Simon J. Lilly, Anna-Christina Eilers, Rohan P. Naidu, Minghao Yue

We investigate the association between galaxies and neutral OI absorption systems at z~6, which trace metal-enriched gas during the epoch of reionization. We identify 40 galaxies across six quasar fields, residing in 15 overdensities within 300 kpc of the background sightlines. Five OI absorption systems are associated with five of these overdensities, yielding a covering fraction of $0.27^{+0.13}_{-0.10}$ within 300 kpc. The absorption occurs beyond typical virial radii, indicating that the gas traces extended overdensity environments rather than individual galaxy halos, unlike the z~0 CGM which is largely bound to halos. These galaxy-associated absorbers account for $\sim35\%$ of all OI systems seen in blind quasar surveys, implying the remainder arise in lower-mass galaxies below our detection threshold or in dense neutral IGM pockets. The CGM around these galaxies contains $\gtrsim 2\times10^6~M_{\odot}$ of oxygen, comparable to the ISM oxygen mass of the galaxies themselves, suggesting that the surrounding environment holds as much metal mass as the galaxies. All five galaxy-associated systems show significantly higher $\log(N_{\rm CII}/N_{\rm OI})$ ratios than absorbers lacking galaxy associations. Furthermore, relative abundance ratios ([Si/O], [C/O]) reveal that four of the five exhibit enrichment patterns consistent with Population III nucleosynthesis. These rare systems offer a unique window into the role of first-generation stars in shaping the early metal enrichment of galaxies and their environments.

Disk galaxies like the Milky Way are expected to experience gas flows carrying matter toward their centers. This paper investigates the role of these radial gas flows in models of Galactic chemical evolution (GCE). We follow five different parameterizations of the Galactocentric radial velocity, $v_{r,g}$, of the interstellar medium (ISM). Relative to the $v_{r,g}=0$ limit, all models predict stellar metallicity to decline less significantly with age in the outer disk and more significantly in the inner disk. This outcome arises because radial flows cannot remove gas from one region of the Galaxy without placing it elsewhere, leading to opposing effects on enrichment timescales between the inner and outer Galaxy. This prediction is at odds with recent observational constraints, which indicate remarkably minimal decline in metallicity ($\lesssim$$0.1$ dex) between young ($\sim$$0-2$ Gyr) and old populations ($\sim$$8-10$ Gyr) across the \textit{entire} Galactic disk. Radial gas flows cannot be the sole explanation of this result at all Galactocentric radii. Our models reproduce this result at $R\gtrsim6$ kpc if the flow velocity is relatively constant in both radius and time near $v_{r,g}\approx-1$ km/s. In agreement with previous GCE models, all of our flow prescriptions lead to lower metallicities and steeper radial gradients relative to static models. Exploiting this universal outcome, we identify mixing effects and the relative rates of star formation and metal-poor accretion as the processes that establish the ISM metallicity at low redshift. We provide a suite of analytic formulae describing radial metallicity gradient evolution based on this connection.

Martin P. Rey, Harley Katz, Corentin Cadiou, Mahsa Sanati, Oscar Agertz, Jeremy Blaizot, Alex J. Cameron, Nicholas Choustikov, Julien Devriendt, Uliana Hauk, Alexander P. Ji, Gareth C. Jones, Taysun Kimm, Isaac Laseter, Sergio Martin-Alvarez, Kosei Matsumoto, Autumn Pearce, Yves Revaz, Francisco Rodriguez Montero, Joki Rosdahl, Aayush Saxena, Adrianne Slyz, Richard Stiskalek, Anatole Storck, Oscar Veenema, Wonjae Yee

We study the stellar mass-iron metallicity relation of dwarf galaxies in the new high-resolution MEGATRON cosmological radiation-hydrodynamics simulations. These simulations model galaxy formation up to $z\approx8$ in a region that will collapse into a Milky-Way-like galaxy at $z=0$, while self-consistently tracking Population III and II (Pop.~III, Pop.~II) star formation, feedback and chemical enrichment. MEGATRON dwarf galaxies are in excellent agreement with the observed stellar mass-metallicity relation at $z=0$, including an over-abundance of dwarfs along a flat plateau in metallicity ($\langle [\rm{Fe}/\rm{H}] \rangle \approx -2.5$) at low stellar masses ($M_{\star} \leq 10^5 \, \rm{M}_{\odot}$). We tie this feature to the chemical enrichment of dwarf galaxies by Pop.~III pair-instability supernova (PISN) explosions. The strong Lyman-Werner background (LW) from the protogalaxy ensures that PISNe occur in haloes massive enough ($\approx 10^7\, \rm{M}_{\odot}$) to retain their ejecta. We also predict a tail of $\approx 20\%$ of iron-deficient ($\langle [\rm{Fe}/\rm{H}] \rangle \leq - 3$) dwarf galaxies. We show that both plateau and tail (i) are robust to large variations in Pop.~II feedback assumptions, and (ii) survive in bound satellites surrounding the central galaxy at $z=0$.

The increasing use of ML in astronomy introduces important questions about interpretability. Due to their complexity and non-linear nature, it can be challenging to understand their decision-making process. While these models can effectively identify unusual spectra, interpreting the physical nature of the flagged outliers remains a major challenge. We aim to bridge the gap between anomaly detection and physical understanding by combining deep learning with interpretable ML (iML) techniques to identify and explain anomalous galaxy spectra from SDSS data. We present a flexible framework that uses a variational autoencoder to compute multiple anomaly scores, including physically-motivated variants of the mean squared error. We adapt the iML LIME algorithm to spectroscopic data, systematically explore segmentation and perturbation strategies, and compute explanation weights that identify the features most responsible for each detection. To uncover population-level trends, we normalize the LIME weights and apply clustering to the top 1\% most anomalous spectra. Our approach successfully separates instrumental artifacts from physically meaningful outliers and groups anomalous spectra into astrophysically coherent categories. These include dusty, metal-rich starbursts; chemically-enriched H\,II regions with moderate excitation; and extreme emission-line galaxies with low metallicity and hard ionizing spectra. The explanation weights align with established emission-line diagnostics, enabling a physically-grounded taxonomy of spectroscopic anomalies. Our work shows that interpretable anomaly detection provides a scalable, transparent, and physically meaningful approach to exploring large spectroscopic datasets. Our framework opens the door for incorporating interpretability tools into quality control, follow-up targeting, and discovery pipelines in current and future surveys.

P. Tiwari, B. Banerjee, D. Miceli, G. Oganesyan, A. Ierardi, S. Macera, M. Branchesi, L. Nava, S. Mohnani, S. Agarwal, A. Shukla

Gamma-ray Bursts (GRBs) generate powerful relativistic jets that inject a large amount of energy into their surrounding environment, producing blast waves that accelerate particles to high energies. The GRB afterglow radiation provides a powerful means to investigate the microphysics of relativistic shocks and to probe the medium surrounding the progenitor of the burst. In this study, we present a comprehensive multiwavelength analysis of 31 GRBs observed between 2008 and 2024 from the Neil Gehrels Swift Observatory (X-ray Telescope and Burst Alert Telescope) and the Fermi Large Area Telescope, covering photon energies from 0.3 keV to 300 GeV. Our goal is to characterize the broadband spectral properties of GRB afterglows in soft X-rays, hard X-rays, and high-energy gamma rays. We investigate correlations between spectral shape and energy output across different parts of the spectrum. The observed emission is modeled using a forward shock scenario that includes both synchrotron and synchrotron self-Compton (SSC) radiation losses. The results favor an SSC-dominated radiation model in a wind-like medium, consistent with expectations for long-duration GRBs. Crucially, this work provides new benchmarks for the microphysical parameters governing the emission, particularly indicating a notably low magnetic energy fraction, which refines previous estimates. By modeling broadband data, this study offers one of the most detailed SSC analyses in a wind-like environment to date. Notably, our results naturally account for the comparable energy output observed in both the soft X-ray and TeV bands, consistent with the previously detected TeV-GRBs.

Morgan Saidel, Shreyas Vissapragada, Heather Knutson, Ethan Schreyer, Mike Greklek-McKeon, Jonathan Gomez Barrientos, W. Garrett Levine, Carlos Gascón, Morgan MacLeod, Haedam Im, Nick Tusay

Hydrodynamic escape can strip the envelopes of close-in exoplanets, but most observations of atmospheric mass loss to date have been confined to planets orbiting K and M dwarfs. A growing body of detections of atmospheric escape from planets orbiting early-type stars indicates that they may have significantly stronger and more extended outflows than planets orbiting cooler stars. However, it is unclear whether this limited sample of planets is representative of all gas giants orbiting early-type stars. Motivated by this question, we initiated the first dedicated survey of atmospheric escape from gas giants orbiting F stars in order to understand how their distinct radiation environments shape planetary outflows. We observed ten transits of six planets in an ultra-narrowband filter centered on the metastable helium line using Palomar/WIRC. We report strong ($>3\sigma$) detections of atmospheric escape for WASP-12~b and WASP-180~A~b, tentative ($>2\sigma$) detections for WASP-93~b and HAT-P-8~b, and non-detections for WASP-103~b and KELT-7~b. We fit these measurements with a 1D Parker wind model to derive corresponding mass-loss rates, and combine our results with literature measurements to obtain an updated picture of mass loss from planets orbiting early-type stars. Our results indicate that the observed variation in mass-loss rates can be explained by a combination of Roche filling factor and XUV luminosity, and disfavors NUV-driven escape models.

Thales A. Gutcke, Giulia Despali, Stephanie O'Neil, Mark Vogelsberger, Azadeh Fattahi, David B. Sanders

We present a detailed comparison of a Local Group dwarf galaxy analogue evolved in two cosmological models: the standard $\Lambda$CDM and a self-interacting dark matter (SIDM) model with a velocity-dependent cross-section. Both simulations are run with the high-resolution, hydrodynamical LYRA galaxy formation model, allowing us to explore the global and substructure properties of the dwarf in a consistent context. While the overall halo growth, final mass, and subhalo mass functions remain largely unchanged across models, SIDM produces a central dark matter core extending to $\sim$1 kpc, which does not significantly vary with the inclusion of baryons. Baryonic properties, however, differ notably. The SIDM model leads to a 25% reduction in stellar mass and retains more gas within the stellar half-mass radius due to a prolonged quiescent phase in star formation. The stellar distribution is less centrally concentrated, and a population of in-situ star clusters form at late times. Substructure analysis reveals fewer luminous satellites and more stellar-only systems in SIDM, driven in part by tidal stripping that affects the dark matter more than the stars. A subset of satellites undergoes tidal-triggered core collapse after infall, enhancing the diversity of SIDM satellite rotation curves. These differences offer potential observational signatures of SIDM in low-mass galaxies.

J. Michael Shull (1 and 2), Rachel M. Curran (2), Michael W. Topping (3), Jonathan D. Slavin (4) ((1) University of Colorado, (2) University of North Carolina, (3) University of Arizona, (4) Harvard/SAO)

arXiv:2508.03800 (accepted to ApJ) with 2 Appendices, 6 figures, 2 tables (21 pages total)

The dominant sources of photoionizing radiation in the extreme ultraviolet (EUV) incident on the exterior of the local interstellar clouds include two nearby early B-type stars, $\epsilon$ CMa ($124\pm2$ pc) and $\beta$ CMa ($151\pm5$ pc), three hot dwarfs, and the local hot bubble (LHB). Line emission (170-912A) from highly ionized metals (Fe, Ne, Mg) in million-degree LHB plasma may be responsible for the elevated ionization fractions of helium ($n_{\rm HeII}/n_{\rm He} \approx 0.4$) compared to hydrogen ($n_{\rm HII} / n_{\rm H} \approx 0.2$) in the local clouds. We update the stellar parameters and ionizing flux for $\beta$ CMa, after correcting the EUV spectra for intervening HI column density, $N_{\rm HI} = 1.9\pm0.1\times10^{18}~{\rm cm}^{-2}$, and its hotter effective temperature, $T_{\rm eff} \approx 25,000$K vs. 21,000K for $\epsilon$ CMa. These two stars produce a combined H-ionizing photon flux $\Phi_{\rm H} \approx 6800\pm1400$ cm$^{-2}$ s$^{-1}$ at the external surface of the local clouds. The hot bubble could produce comparable fluxes, $\Phi_{\rm H} =$ 2000-9000 cm$^{-2}$ s$^{-1}$, depending on the amount of metal depletion into dust grains that survive sputtering. The radial velocities and proper motions of $\beta$ CMa and $\epsilon$ CMa indicate that both stars passed within $10\pm1$ pc of the Sun $4.4\pm0.1$ Myr ago, with 100-200 times higher local ionizing fluxes. At that time, the local clouds were likely farther from the Sun, owing to their transverse motion. Over the last few Myr, EUV radiation from these two stars left a wake of highly ionized gas in a hot, low-density cavity produced by past supernova explosions in the Sco-Cen OB association and connected with the LHB.

Rocky planet atmospheres form and evolve through interactions between the planet's surface and interior. If a growing rocky planet acquires enough mass prior to the dissipation of the nebular gas disk, it can gravitationally capture a `primary' atmosphere dominated by H2. At the same time, these young, rocky bodies are likely to have partial or global magma oceans as a result of the heat from accretion, core formation and radioactive decay of short-lived major element isotopes. During this magma ocean stage, the dissolution of volatile, life-essential elements, such as hydrogen in the form of water or H2, into the magma is critical in determining the extent to which a rocky planet can maintain these elements over time. However, our ability to quantify the amount of hydrogen dissolved in the magma oceans of rocky planets is limited by the lack of experimental constraints on H-bearing species' solubilities at relevant pressure and temperature conditions, including those expected for the early Earth. Here we experimentally determine the solubility of water in silicate melts of various compositions in the Ca-Mg-Al-Si-Fe-O system at a total pressure of 1 bar and temperatures from 1673-1823 K, synthesized in a H2-CO2 gas-mixing furnace. We use Bayesian parameter estimation to derive a robust water solubility law that includes the effects of melt composition and temperature. Using this solubility law, we estimate that ~100 ppm of hydrogen can dissolve into a 1 MEarth planet with a surface pressure of ~300 bars set by accretion of solar-like nebular gas. For rocky planets in general, ingassing of a primary atmosphere may be an important source and initial storage mechanism for hydrogen-bearing species in a planet's interior, provided it grew to a sufficient mass within the lifetime of the solar nebula.

Unnati Kashyap, Thomas J. Maccarone, Eliot C. Pattie, Mason Ng, Swati Ravi, Alexandra J. Tetarenko, Pau Bosch Cabot, Herman L. Marshall

We report the first polarimetric results of the neutron star (NS) low-mass X-ray binary (LMXB) Z-source GX 17+2 using the Imaging X-ray Polarimetry Explorer (IXPE) and the Very Large Array (VLA). We find that the X-ray source was polarized at PD = 1.9 +/- 0.3 % (1-sigma errors) with a polarization angle of PA = 11 +/- 4 degree (1-sigma errors). Simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR) observations show that the source was in the normal branch (NB) during our IXPE observations. The X-ray spectro-polarimetry results suggest a source geometry comprising an accretion disk component, a Comptonization component, and a reflection component. The VLA radio polarization study shows a PD = 2.2 +/- 0.2 % with a Faraday-corrected intrinsic polarization angle of 1 +/- 5 degree, which is an indication of the jet axis. Thus, we find the estimated X-ray PA from the source is consistent with the radio PA. We discuss the accretion geometry of the Z-source in light of our X-ray spectro-polarimetry and radio findings.

Gamma-ray bursts are flashes of high-energy radiation lasting from a fraction of a second to several hours. Military satellites made the first detections of GRBs in the late 1960s. The $\gamma$-ray emission forms from shocks in a relativistic jet launched from a compact central engine. In addition to the emission of $\gamma$-rays, the interaction of the jet with the surrounding medium yields afterglow emission that can be observed across the electromagnetic spectrum. Redshift measurements from these afterglows place GRBs from the local to the distant Universe. The central engines of GRBs are thought to be either a hyperaccreting black hole or a highly magnetized neutron star (magnetar). There is now strong observational evidence that this central engine is created either in the core collapse of a rapidly rotating massive star or via the merger of two compact objects (neutron stars or a neutron star with a black hole). The combination of stellar scale events with extreme energies and luminosities makes GRBs powerful probes of the extreme physics involved in their production and of other areas of astrophysics and cosmology. These include as the electromagnetic counterparts of gravitational wave sources, the production and acceleration of relativistic jets, the synthesis of heavy elements, the study of the interstellar and intergalactic medium, and the identification of the collapse of early generations of stars.

P. Cataldi, S. Pedrosa, L. J. Pellizza, D. Ceverino, L. A. Bignone

The James Webb Space Telescope has found an unexpected population of high-mass galaxies ($\log (M^\star / {\rm M} _\odot) \gtrsim 10$) with extremely small effective radii ($\sim 100\,\rm pc$) at $z \gtrsim 6$. Also, the existence of an unusual size--mass relation has been claimed. These observations are only partially reproduced by current models, and the physics responsible for the observed relations is still under debate. We expect to unveil the formation channels of the observed compact galaxies. We analyse 7605 snapshots for 169 galaxies of the state-of-the-art cosmological simulation suite FirstLight. We find that galaxies undergo an expansion--compaction--re-expansion process. This process operates in a specific mass range; compaction starts at $\log (M^\star_ {\rm on} / {\rm M}_\odot) \sim 8.5$ and ends at $\log (M^\star_{\rm off} / \mathrm{M}_\odot) \sim 9.5$. In between these masses, the size--mass relation becomes inverted, with a negative slope. The physical mechanism driving this process in our simulations involves a self-reinforced inflow of gas from the outer regions, that triggers a strong, localised starburst at the centre (within $1\, {\rm kpc}$). This contraction continues until conditions favour star formation in a broader area, and the normal inside-out growth pattern resumes. We present evidence for the existence of a universal wet compaction operating at Cosmic Dawn. This mechanism is driven by spherical accretion triggered by the change of the state of the central matter of galaxies, from dark matter- to baryon-dominated. We also propose an analytical expression for the infall process, suitable for use in semi-analytic models. Contrary to low-redshift galaxies, in high-redshift systems compaction ends without gas depletion and star-formation quenching.

Scalar-tensor gravity models are among the prime candidates to explain cosmic acceleration, and compact stars provide unique laboratories for testing such theories. Predictions of scalar-tensor gravity in compact stars can be examined during the evolution of neutron stars. Spontaneous scalarization in relativistic stars is influenced by different properties of stellar matter in various evolution regimes. In the present study, we investigate the scalarization of neutron stars in different stages of the evolvement. For this aim, we apply the isentropic equations of state for the neutron star matter including nucleons, hyperons, and $\Delta$- resonances in neutrino-trapped, neutrino diffusion, and neutrino-transparent stages as well as cold-catalyzed neutron star. Our equations of state are based on the relativistic model within the mean-field approximation. To emphasize the role of scalar-tensor theories in exploring the properties and structure of compact stars, we calculate the structure of neutron stars with hyperons and $\Delta$-resonances in different snapshots of the neutron star evolution in the scalar-tensor gravity. Our calculations confirm that the neutron star scalarization is affected by the hyperons as well as the $\Delta$-resonances. Moreover, the properties of scalarized neutron stars depend on the stage of the star evolution.

Matthew De Furio, Marie Ygouf, Alexandra Greenbaum, Graça Rocha, Michael Meyer, Charles Beichman, Jorge Llop-Sayson, Gael Roudier, Steph Sallum, Jarron Leisenring, Anand Sivaramakrishnan

The James Webb Space Telescope is orders of magnitude more sensitive than any other facility across the near to mid-infrared wavelengths. Many approved programs take advantage of its highly stable point spread function (PSF) to directly detect faint companions using diverse high-contrast imaging (HCI) techniques. However, periodic re-phasing of the Optical Telescope Element (OTE) is required due to slow thermal drifts distorting to the primary mirror backplane along with stochastic tilt events on individual mirror segments. Many programs utilize observations of a reference star to remove the stellar contribution within an image which can typically take half of the total allocated time. We present a high-contrast imaging technique for the NIRISS instrument that uses the measured wavefront error (WFE) from a phase calibration observation (performed roughly every 48 hours) as prior information in a Bayesian analysis with nested sampling. This technique estimates the WFE of a given observation and simultaneously searches for faint companions, without using a reference star. We estimate the wavefront error for both full aperture and aperture masking interferometry (AMI) imaging modes using three low order Zernike coefficients per mirror segment, using the Hexike basis, to generate synthetic PSFs and compare to simulations. We compare our technique to traditional interferometric analysis in realistic NIRISS F430M simulations both relative to the photon noise limit, and through recovering an injected companion with $\Delta$F430M= 8 mag at 0.2''. With future testing, this technique may save significant amounts of observing time given the results of our current implementation on NIRISS simulations.

Micheli T. Moura, Anna Ferré-Mateu, Ana L. Chies-Santos, Cristina Furlanetto, Michael A. Beasley

The properties of massive and compact early-type galaxies provide important constraints on early galaxy formation. Among these, massive relic galaxies, characterized by old stellar populations and minimal late-time accretion, are considered preserved compact galaxies from the high-$z$ Universe. We investigate compact and massive galaxies (CMGs) using the TNG50 cosmological simulation, applying uniform selection criteria matching observational surveys at $z=0$, $z=0.3$, and $z=0.7$, enabling direct comparisons with observed compact galaxies. CMGs are classified according to their stellar mass assembly histories to examine how compactness relates to dynamical properties and chemical enrichment across cosmic time. Our results show that simulated CMGs follow the observed mass-size relation, with the number of objects increasing at higher redshifts, in line with observational trends. Dynamically, while observations suggest relic galaxies are outliers in the stellar mass-velocity dispersion plane, simulated compacts show relatively uniform velocity dispersions across different accretion histories. Observed relics are more metal-rich than other compact galaxies with extended star formation, deviating from the local mass-metallicity relation. In contrast, simulated CMGs are overall more metal-rich than the quiescent population, regardless of accretion history. The deviation from the mass-metallicity relation decreases with redshift. These results suggest that the extreme characteristics of CMGs in TNG50, particularly in metallicity and dynamics, are less pronounced than in observed relics. Nonetheless, these results offer a theoretical framework to assess the properties of such extreme objects from different epochs, highlighting both alignment with and deviations between the models.

Multiwavelength polarimetric observations of blazars reveal complex, energy-dependent polarization behavior, including a decrease in polarization fraction from X-rays to millimeter bands and significant variability in the electric vector position angle (EVPA). These trends challenge simple single-zone synchrotron models and suggest a more intricate, turbulent jet structure with multiple emission zones. We develop a statistical framework to model the observed energy-dependent polarization patterns in blazars, focusing on the behavior captured by IXPE in the X-ray band and RoboPol in the optical. The goal is to statistically characterize multi-zone models in terms of the distributions of cell size and the physical parameters of the electron energy distribution (EED). A Monte Carlo approach, implemented with the JetSeT code, is used to generate synthetic multi-zone synchrotron emission from a spherical region filled with turbulent cells with randomly distributed physical properties. Simulations explore scenarios ranging from identical cells to power-law distributions of cell sizes and EED parameters with variable cutoff and low-energy slopes. The results show that a purely turbulent, multi-zone model can reproduce the observed energy-dependent polarization without requiring correlations between cell size and EED parameters. The polarization degree is primarily determined by the effective, flux-weighted, number of emitting cells, modulated by the dispersion in cell properties, particularly the EED cutoff energy at high frequencies and the low-energy spectral index at low frequencies. With a fractional dispersion in cutoff energy of about 90% and a low-energy spectral index dispersion of ~0.5-1.5, the model reproduces the chromatic mm-to-X-ray polarization trends seen by IXPE and the optical polarization limiting envelope observed in the RoboPol dataset.

M. J. Hamel-Bravo, D. B. Fisher, D. A. Berg, A. J. Cameron, J. Chisholm, G. G. Kacprzak, B. Mazzilli Ciraulo, H. Katz

We present VLT/X-shooter spectroscopy of the extremely metal-poor starburst galaxy SBS 0335-052E, a nearby (D $\sim$54 Mpc) analog of high-redshift systems, probing its outflow up to a distance of $\sim$2.6 kpc. Using direct-method oxygen abundances, we find a complex metallicity profile that generally declines with distance, decreasing by 0.37 dex from the galaxy center out to 2.4 kpc into the outflow. This implies a metal-loading factor roughly an order of magnitude lower than predictions based on the mass-metallicity relation for low-mass galaxies. We also detect extended HeII emission, including a broad, redshifted component beyond 2 kpc, distinct from narrow emission associated with star clusters. No H$\beta$ emission is detected associated with the broad redshifted component, implying extremely high HeII/H$\beta$ ratios (0.7--4.8). Such extreme values, combined with the decreasing metallicity, challenge current models for stellar feedback. The contribution of an intermediate-mass black hole could simultaneously account for the declining metallicity and the unusually extended HeII emission.

In this study, we present a comprehensive observational and modeling study of a geo-effective event with D_ST index of -80 nT observed on 2011 May 28 when a coronal hole was bordering an active region. We analyze HMI and EUV images and found that this event involved two filament eruptions ~8 hours apart from two different active region closed to each other. We produce 3D magnetic field configurations for the active regions that are consistent with the observations and employ numerical models to track the CME/ICME propagation up to 1\,au. From our, magnetic models we found that the nearby coronal hole reduced the stability threshold of the flux ropes, with axial flux values approximately three times lower than in comparable cases without coronal holes. A derivative analysis applied to STEREO coronagraph and OMNI database in situ data revealed no evidence of CME-CME interaction during the early stages of their evolution and identified distinct signatures of two CMEs, along with the interacting flow associated with the nearby coronal hole at 1 au. Moreover, we used hydrodynamic simulations constrained by remote sensing and in situ data to track the different structures in the solar wind. We found a good agreement between data and the models. Additionally, we found that the presence of the coronal hole may have suppressed interactions between CMEs, with the transients subsequently propagating along the solar wind streams emerging from the coronal hole.

Christos G. Tsagas, Leandros Perivolaropoulos, Kerkyra Asvesta

Observations have repeatedly confirmed the presence of large-scale peculiar motions in the universe, commonly referred to as ``bulk flows''. These are vast regions of the observable universe, typically spanning scales of several hundred Mpc, that move coherently with speeds of the order of several hundred km/sec. While there is a general consensus on the direction of these motions, discrepancies persist in their reported sizes and velocities, with some of them exceeding the predictions of the standard $\Lambda$CDM model. The observed large-scale peculiar-velocity fields are believed to have originated as weak peculiar-velocity perturbations soon after equipartition, which have subsequently grown by structure formation and by the increasing inhomogeneity of the post-recombination universe. However, the evolution and the implications of these bulk velocity fields remain poorly understood and they are still a matter of debate. For instance, it remains a challenge for the theoreticians to explain the high velocities measured by several bulk-flow surveys, like those recently reported using the CosmicFlows-4 data. Such extensive and fast velocity fields could have played a non-negligible role during structure formation and they might have also ``contaminated'' our observations. After all, in the history of astronomy, there are examples where relative-motion effects have led us to a serious misinterpretation of reality (shortened abstract due to length limits).

Marissa N. Perry (1), Anthony J. Taylor (1), Oscar A. Chavez Ortiz (1), Steven L. Finkelstein (1), Gene C. K. Leung (2), Micaela B. Bagley (3 and 1), Vital Fernandez (4), Pablo Arrabal Haro (3), Katherine Chworowsky (1), Nikko J. Cleri (5, 6, and 7), Mark Dickinson (8), Richard S. Ellis (9), Jeyhan S. Kartaltepe (10), Anton M. Koekemoer (11), Fabio Pacucci (12 and 13), Casey Papovich (14), Nor Pirzkal (15), Sandro Tacchella (16 and 17) ((1) The University of Texas at Austin, Department of Astronomy, (2) MIT Kavli Institute for Astrophysics and Space Research, (3) Astrophysics Science Division, NASA Goddard Space Flight Center, (4) Michigan Institute for Data Science, University of Michigan, (5) Department of Astronomy and Astrophysics, The Pennsylvania State University, (6) Institute for Computational and Data Sciences, The Pennsylvania State University, (7) Institute for Gravitation and the Cosmos, The Pennsylvania State University, (8) NSF's National Optical-Infrared Astronomy Research Laboratory, (9) University College London, Department of Physics &amp; Astronomy, (10) Laboratory for Multiwavelength Astrophysics, School of Physics &amp; Astronomy, Rochester Institute of Technology, (11) Space Telescope Science Institute, (12) Center for Astrophysics, Harvard &amp; Smithsonian, (13) Black Hole Initiative, Harvard University, (14) George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A&amp;M University, (15) ESA/AURA Space Telescope Science Institute, (16) Kavli Institute for Cosmology, University of Cambridge, (17) Cavendish Laboratory, University of Cambridge)

We present an analysis of bursty star-formation histories (SFHs) of 346 star-forming galaxies at $1\lesssim z<7$, selected from JWST/NIRSpec G395M and PRISM spectroscopy provided by the CEERS and RUBIES surveys. We analyze the correlation of star-formation rate vs. stellar mass (the star-forming main sequence, SFMS) for our sample and find no significant difference between the intrinsic scatter in the H$\alpha$-based SFMS and the UV-continuum-based SFMS. However, the diagnostic power of the SFMS is limited at high redshift and low stellar mass due to observational biases that exclude faint, quenched galaxies. To more directly probe star-formation variability, we examine the dust-corrected H$\alpha$-to-UV ratio, which is assumed to trace deviations a from constant SFH over the past $\sim100$ Myr. In our sample, $73^{+4}_{-4}$% of galaxies exhibit H$\alpha$-to-UV ratios inconsistent with a constant SFH. We do not observe any statistically significant evolution in the H$\alpha$-to-UV ratio with redshift. Additionally, lower-mass galaxies ($7\leq\text{log}(M_*/M_{\odot})<8.5$) are $30 \pm 1$% more likely to lie above this equilibrium range -- indicative of a recent ($\lesssim 100$ Myr) burst of star formation -- compared to higher-mass systems ($8.5\leq\text{log}(M_*/M_{\odot})\leq10.9$). These results suggest that bursty SFHs are more common in low-mass galaxies at $z\sim 1$-$7$ and that this remains relatively stable across $\sim0.8$-$6$ Gyr after the Big Bang.

R. Dastidar, G. Pignata, N. Dukiya, K. Misra, D. A. Howell, M. Singh, C. P. Gutiérrez, C. Pellegrino, A. Kumar, B. Ayala, A. Gangopadhyay, M. Newsome, E. Padilla Gonzalez, K. A. Bostroem, D. Hiramatsu, G. Terreran, C. McCully

We present the analysis of the luminous Type II Supernova (SN) 2021tsz, which exploded in a low-luminosity galaxy. It reached a peak magnitude of -18.88 $\pm$ 0.13 mag in the $r$ band and exhibited an initial rapid decline of 4.05 $\pm$ 0.14 mag (100 d)$^{-1}$ from peak luminosity till $\sim$30 d. The photospheric phase is short, with the SN displaying bluer colours and a weak H$\alpha$ absorption component--features consistent with other luminous, short-photospheric phase Type II SNe. A distinct transition from the photospheric to the radioactive tail phase in the $V$ band--as is common in hydrogen-rich Type II SNe--is not visible in SN 2021tsz, although a modest $\sim$1 mag drop is apparent in the redder filters. Hydrodynamic modelling suggests the luminosity is powered by ejecta-circumstellar material (CSM) interaction during the early phases (<30 days). Interaction with 0.6 M$_\odot$ of dense CSM extending to 3100 R$_\odot$ reproduces the observed luminosity, with an explosion energy of 1.3$\times$10$^{51}$ erg. The modelling indicates a pre-SN mass of 9 M$_\odot$, which includes a hydrogen envelope of 4 M$_\odot$, and a radius of $\sim$1000 R$_\odot$. Spectral energy distribution analysis and strong-line diagnostics reveal that the host galaxy of SN 2021tsz is a low-metallicity, dwarf galaxy. The low-metallicity environment and the derived high mass loss from the hydrodynamical modelling strongly support a binary progenitor system for SN 2021tsz.

Navdeep K. Panesar, Alphonse C. Sterling, Ronald L. Moore, Sanjiv K. Tiwari, David Berghmans, Andrei Zhukov, Marilena Mierla, Cis Verbeeck, Koen Stegen

We present detailed analysis of an active region coronal jet accompanying a minifilament eruption that is fully captured and well-resolved in high spatial resolution 174A coronal images from Solar Orbiters Extreme Ultraviolet Imager (EUI). The active region jet is simultaneously observed by the Interface Region Imaging Spectrograph (IRIS) and the Solar Dynamics Observatory (SDO). An erupting minifilament is rooted at the edge of an active region where mixed-polarity magnetic flux is present. Minority-polarity positive flux merges and cancels with the active regions dominant negative flux at an average rate of 1019 Mx/hr, building a minifilament-holding flux rope and triggering its eruption. The eruption shows a slow rise followed by a fast rise, akin to large-scale filament eruptions. EUI images and Mg II k spectra, displaying simultaneously blueshifts and redshifts at the opposite edges of the spire, indicate counterclockwise untwisting of the jet spire. This jet is the clearest, most comprehensively observed active-region jet with this instrument set, displaying striking similarities with quiet Sun and coronal hole jets. Its magnetic, thermal, and kinetic energies suggest a significant contribution to local coronal heating. We conclude that magnetic flux cancelation builds a minifilament-carrying twisted flux rope and also eventually triggers the flux ropes eruption that makes the coronal jet, in line with our recent results on the buildup and explosion of solar coronal jets in quiet Sun and coronal holes. That is, this active region jet clearly works the same way as the vast majority of quiet Sun and coronal hole jets.

The current cosmological paradigm, $\Lambda$CDM, is characterized its expansive description of the history of the Universe, its deep connections to particle physics and the large amounts of data that support it. Nonetheless, $\Lambda$CDM's critics argue that it has been falsified or must be discarded for various reasons. Critics and boosters alike do agree on one thing: it is the not the final cosmological theory and they are anxious to see it replaced by something better! I review the status of $\Lambda$CDM, provide my views of the path forward, and discuss the role that the ``Hubble tension'' might play.

The potential field source surface (PFSS) method is a widely used magnetic field extrapolation technique in the space weather community. The only free parameter in the PFSS method is the source-surface height ($R_{\rm SS}$), beyond which all field lines are open. Although $R_{\rm SS}$ is known to vary with solar activity, there is no consensus on how to determine it for a given surface magnetic field distribution. In this study, we investigate the nature of $R_{\rm SS}$ using a long-period (2006-2023) data, covering two solar minima and one maximum. We adopt ADAPT-GONG magnetograms and determine $R_{\rm SS}$ by matching the open flux estimated from observations at 1 au with that calculated using the PFSS method. Our analysis reveals that $R_{\rm SS}$ increases slightly after the solar minima and around the solar maximum, and that it can be characterized by both the mean unsigned photospheric magnetic field strength and the dipolarity parameter $f_{\rm dip}$, defined as $f_{\rm dip} = B_{\rm dip}^2/(B_{\rm dip}^2 + B_{\rm quad}^2 + B_{\rm oct}^2)$, with $B_{\rm dip}$, $B_{\rm quad}$, and $B_{\rm oct}$ denoting the magnitudes of dipolar, quadrupolar, and octupolar components of photospheric radial magnetic field, respectively. Our results suggest that $R_{\rm SS}$ does not exhibit a simple monotonic dependence on the solar activity and must be determined by properly considering both surface magnetic field strength and global field structure.

Garima Rajguru, Lea Marcotulli, Marco Ajello, Mattia Di Mauro, Meg Urry

We have utilized the largest sample of $\gamma$-ray selected Fermi flat-spectrum radio quasars (FSRQs) ever used (519 sources) to construct the luminosity function and its evolution through the cosmic history. In addition to spanning large redshift ($0<z\lesssim 4$) and luminosity ranges ($2.9\times10^{43}$ erg s$^{-1}$ - $7.3\times10^{48}$ erg s$^{-1}$), this sample also has a robust calculation of the detection efficiency associated with its observation, making its selection effects and biases well understood. We confirm that the local luminosity function is best explained by a double power law. The evolution of the luminosity function of FSRQs follows a luminosity-dependent density evolution. FSRQs experience positive evolution with their space density growing with increasing redshift up to a maximum redshift, after which the numbers decrease. This peak in redshift occurs at larger redshifts for higher luminosity sources and at lower redshifts for lower luminosity sources. We find an unexpected similarity between the luminosity function of FSRQs and that of BL Lacertae objects at intermediate luminosity. This could be a sign of a strong genetic link between the two blazar sub-classes or that BL Lac samples are contaminated by large amounts of FSRQs with their jets nearly perfectly aligned with our line of sight.

N. Emas, A. Porredon, C. Blake, J. DeRose, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, F. J. Castander, T. Claybaugh, A. Cuceu, A. de la Macorra, A. Dey, B. Dey, P. Doel, S. Ferraro, J. E. Forero-Romero, C. Garcia-Quintero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, S. Heydenreich, K. Honscheid, D. Huterer, M. Ishak, S. Joudaki, R. Joyce, E. Jullo, S. Juneau, R. Kehoe, D. Kirkby, T. Kisner, A. Kremin, A. Krolewski, O. Lahav, M. Landriau, J. U. Lange, L. Le Guillou, A. Leauthaud, M. Manera, R. Miquel, S. Nadathur, W. J. Percival, F. Prada, G. Rossi, R. Ruggeri, E. Sanchez, C. Saulder, A. Semenaite, H. Seo, J. Silber, D. Sprayberry, Z. Sun, G. Tarlé, B. A. Weaver, R. H. Wechsler, R. Zhou

Combined survey analyses of galaxy clustering and weak gravitational lensing (3x2-pt studies) will allow new and accurate tests of the standard cosmological model. However, careful validation is necessary to ensure that these cosmological constraints are not biased by uncertainties associated with the modelling of astrophysical or systematic effects. In this study we validate the combined 3x2-pt analysis of the Dark Energy Spectroscopic Instrument Data Release 1 (DESI-DR1) spectroscopic galaxy clustering and overlapping weak lensing datasets from the Kilo-Degree Survey (KiDS), the Dark Energy Survey (DES), and the Hyper-Suprime-Cam Survey (HSC). By propagating the modelling uncertainties associated with the non-linear matter power spectrum, non-linear galaxy bias and baryon feedback, we design scale cuts to ensure that measurements of the matter density and the amplitude of the matter power spectrum are biased by less than 30% of the statistical error. We also test the internal consistency of the data and weak lensing systematics by performing new measurements of the lensing shear ratio. We demonstrate that the DESI-DR1 shear ratios can be successfully fit by the same model used to describe cosmic shear correlations, and analyse the additional information that can be extracted about the source redshift distributions and intrinsic alignment parameters. This study serves as crucial preparation for the upcoming cosmological parameter analysis of these datasets.

Minchul Kam, Hiroshi Nagai, Motoki Kino, Keiichi Asada, Rüdiger Kneissl, Iván Agudo, Sascha Trippe, Seiji Kameno, Ioannis Myserlis, Ramprasada Rao, Hojin Cho, Richard A. Perley, Bryan J. Butler, Mark Gurwell, Tomoki Matsuoka, Jongho Park, Carolina Casadio, Baltasar Vila Vilaro, Celia Verdugo, Matias Radiszcz, Kurt Plarre, Wanchaloem Khwammai, Diego Álvarez-Ortega, Juan Escudero, Clemens Thum, Garrett Keating

We present the results of multi-frequency monitoring of the radio quasar 3C 286, conducted using three instruments: ALMA at 91.5, 103.5, 233.0, and 343.4 GHz, the IRAM 30-m Telescope at 86 and 229 GHz, and SMA at 225 GHz. The IRAM measurements from 2006 to 2024 show that the total flux of 3C 286 is stable within measurement uncertainties, indicating long-term stability up to 229 GHz, when applying a fixed Kelvin-to-Jansky conversion factor throughout its dataset. ALMA data from 2018 to 2024 exhibit a decrease in flux, which up to 4% could be attributed to an apparent increase in the absolute brightness of Uranus, the primary flux calibrator for ALMA with the ESA4 model. Taken together, these results suggest that the intrinsic total flux of 3C 286 has remained stable up to 229 GHz over the monitoring period. The polarization properties of 3C 286 are stable across all observing frequencies. The electric vector position angle (EVPA) gradually rotates as a function of wavelength squared, which is well described by a single power-law over the full frequency range. We therefore propose using the theoretical EVPA values from this model curve for absolute EVPA calibration between 5 and 343.4 GHz. The Faraday rotation measure increases as a function of frequency up to (3.2+/-1.5)x10^4 rad m^-2, following RM proportional to nu^alpha with alpha = 2.05+/-0.06. This trend is consistent with the core-shift effect expected in a conical jet.

The luminosity distance-redshift ($D_{\rm L}$--$z$) relation derived from Type Ia supernovae (SNe Ia) yields evidence for a nonzero cosmological constant. SNe Ia analyses typically fit to the functional form $D_{\rm L}(z)$ derived theoretically from the homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) metric. Yet, the metric in the epoch relevant to SNe Ia measurements deviates slightly from FLRW due to gravitational clumping of mass into large-scale structures like filaments and voids, whose sizes span many orders of magnitude. The small deviation is modeled typically by scalar perturbations to the FLRW metric. Each line of sight to a SNe Ia passes through a random sequence of structures, so $D_{\rm L}$ differs stochastically from one line of sight to the next. Here, we calculate the $D_{\rm L}$ dispersion in an exact Lemaitre-Tolman-Bondi Swiss-cheese universe with a power-law hole size distribution, as a function of the lower cut-off $R_{\rm min}$ and logarithmic slope $\gamma$. We find that the standard deviation of $D_{\rm L}$ scales as $\sigma_{D_{\rm L}} \propto z^{2.25\pm0.01} (R_{\rm min}/24\pm1\,{\rm Mpc})^{(0.157\pm0.003)\left[\gamma - (1.16\pm0.02)\right]}$ for redshifts in the range $0.5 \lesssim z \lesssim 2.1$. The scaling shows that the $D_{\rm L}$ dispersion is dominated by a few large voids rather than the many small voids.

We analyzed Insight-HXMT data of the black hole X-ray binary MAXI J1348-630 during the type-B QPO phase of its 2019 outburst. Using the Gaussian process method, we applied an additive composite kernel model consisting of an SHO, a DRW, and an additional white noise (AWN) to data from three energy bands: LE (1-10 keV), ME (10-30 keV), and HE (30-150 keV). We find that for the DRW component, correlations on the timescale of $\tau_{\rm DRW}\sim10$ s are absent in the LE band, while they persist in the ME and HE bands over the full duration of the light curves. This energy-dependent behavior may reflect thermal instabilities, with the shorter correlation timescale in the disk compared to the corona. Alternatively, it may reflect variable Comptonizations of seed photons from different disk regions. Inner-disk photons are scattered by a small inner corona, producing soft X-rays. Outer-disk photons interact with an extended, jet-like corona, resulting in harder emission. The QPO is captured by an SHO component with a stable period of $\sim 0.2$ s and a high quality factor of $\sim 10$. The absence of significant evolution with energy or time of the SHO component suggests a connection between the accretion disk and the corona, which may be built by coherent oscillations of disk-corona driven by magnetorotational instability. The AWN components are present in all the three-band data and dominate over the DRW and SHO components. We interpret the AWN as another fast DRW with its $\tau_{\rm DRW} < 0.01$ s. It may trace high-frequency fluctuations that occur in both the inner region of the accretion disk and the corona. Overall, our work reveals a timescale hierarchy in the coupled disk-corona scenario: fast DRW < SHO < disk DRW < corona DRW.

Narendranath Layek, Prantik Nandi, Sachindra Naik, Birendra Chhotaray, Arghajit Jana, Priyadarshee P. Dash, Neeraj Kumari, C. S. Stalin, Srikanth Bandari, S. Muneer

We present a comprehensive long-term multi-wavelength study of the active galactic nucleus (AGN) NGC 3822, based on 17 years (2008 to 2025) of X-ray, ultraviolet (UV), and optical this http URL dataset includes observations from Swift, XMM-Newton, and NuSTAR, the Very Large Telescope, and the Himalayan Chandra Telescope. Our multiwavelength light curve analysis reveals flux variations across X-ray to optical/UV bands, with an increased variability amplitude at shorter wavelengths. X-ray spectral analysis indicates the presence of intrinsic absorption during the 2016 and 2022 observations; however, this absorption disappeared before and after these epochs. The presence and absence of the absorber are attributed to clouds moving in and out of the line of sight. During the long-term monitoring period, the bolometric luminosity of the source varies between ($1.32-17)\times10^{43}$ erg s$^{-1}$. Optical spectroscopic monitoring reveals changing-look (CL) behaviour in NGC~3822, characterized by the appearance and disappearance of broad emission lines (BELs). These CL transitions are associated with changes in the Eddington ratio rather than changes in the obscuration. The BELs appear only when the Eddington ratio is relatively high ($\sim 3.8\times10^{-3}$) and disappear when it drops to a lower value ($\sim 0.9\times10^{-3}$).

Late-stage infall onto protoplanetary disks can produce large scale spiral arms. In this paper we used 3D smoothed particle hydrodynamics and radiative transfer simulations to study the kinematic perturbations induced in disks by infalling material. We found that deviations from Keplerian rotation are predominantly in the radial and vertical velocity components, spatially correlated with spiral arms in the gas surface density. The infall produces observable wiggles in the channel maps, analogous to those produce by the gravitational instability (GI), along with large-scale arcs and filaments. GI induced spiral arms produce radial velocity perturbations that point towards the center of the spiral arm owing to their higher self-gravity. We found a similar signature from infall-induced spiral arms, despite not including self-gravity in our simulation. Our study suggests that recent evidence of GI in the kinematics of the disk around AB Aur may instead be due to the observed infall, without the need for invoking GI.

Shuai Liu, Long Wang, Ataru Tanikawa, Weiwei Wu, Michiko S. Fujii

GW231123 is a binary black hole merger whose primary component lies within or above the pair-instability mass gap, while the secondary component falls within this gap. The standard theory of stellar evolution is significantly challenged by this event. We investigate the formation of candidate progenitors of GW231123 in Population III (Pop3) star clusters. We find that they could form through stellar mergers, binary black hole mergers, and mixed mergers. The mass distribution of these candidate progenitors covers the component masses of GW231123. Their predicted merger rate density spans the range of $0.001{\rm Gpc^{-3}yr^{-1}}-0.26{\rm Gpc^{-3}yr^{-1}}$, encompassing that of GW231123. These findings suggest that GW231123 may originate from Pop3 star clusters. Furthermore, such candidate progenitors are expected to be detectable by future gravitational wave detectors LISA/Taiji/TianQin/DECIGO/CE/ET, which would provide valuable insights into the formation scenarios of events like GW231123.

The intrinsic width and scattering distributions of fast radio bursts (FRBs) inform on their emission mechanism and local environment, and act as a source of detection bias and, hence, an obfuscating factor when performing FRB population and cosmological studies. Here, we utilise a sample of 29 FRBs with measured high-time-resolution properties and known redshift, which were detected using the Australian Square Kilometre Array Pathfinder (ASKAP) by the Commensal Real-time ASKAP Fast Transients Survey (CRAFT), to model these distributions. Using this sample, we estimate the completeness bias of intrinsic width and scattering measurements, and fit the underlying, de-biased distributions in the host rest-frame. We find no evidence for a down-turn towards high values of the intrinsic distributions of either parameter in the 0.01-40 ms range probed by the data. Rather, the intrinsic scattering distribution at 1 GHz is consistent with a log-uniform distribution above 0.04 ms, while the intrinsic width distribution rises as a Gaussian in log-space in the 0.03-0.3 ms range, and is then log-uniform above that. This is inconsistent with previous works, which assumed that these parameters have lognormal distributions. This confirms that FRB observations are currently strongly width- and scattering-limited, and we encourage FRB searches to be extended to higher values of time-width. It also implies a bias in FRB host galaxy studies, although the form of that bias is uncertain. Finally, we find that our updated width and scattering model - when implemented in the zDM code - produces 10% more FRBs at redshift $z=1$ than at $z=0$ when compared to alternative width/scattering models, highlighting that these factors are important to understand when performing FRB population modelling.

Corentin Cadiou, Harley Katz, Martin P. Rey, Oscar Agertz, Jeremy Blaizot, Alex J. Cameron, Nicholas Choustikov, Julien Devriendt, Uliana Hauk, Gareth C. Jones, Taysun Kimm, Isaac Laseter, Sergio Martín Álvarez, Kosei Matsumoto, Camilla T. Nyhagen, Autumn Pearce, Francisco Rodríguez Montero, Joki Rosdahl, Víctor Rufo Pastor, Mahsa Sanati, Aayush Saxena, Adrianne Slyz, Richard Stiskalek, Anatole Storck, Wonjae Yee

We present three cosmological radiation-hydrodynamic zoom simulations of the progenitor of a Milky Way-mass galaxy from the MEGATRON suite. The simulations combine on-the-fly radiative transfer with a detailed non-equilibrium thermochemical network (81 ions and molecules), resolving the cold and warm gas in the circumgalactic medium (CGM) on spatial scales down to 20 pc and on average 200 pc at cosmic noon. Comparing our full non-equilibrium calculation with local radiation to traditional post-processed photoionization equilibrium (PIE) models assuming a uniform UV background (UVB), we find that non-equilibrium physics and local radiation fields fundamentally impact the thermochemistry of the CGM. Recombination lags and local radiation anisotropy shift ions away from their PIE+UVB values and modify covering fractions (for example, HI damped Ly$\alpha$ absorbers differ by up to 40%). In addition, a resolution study with cooling-length refinement allows us to double the resolution in the cold and warm CGM gas, reaching 120 pc on average. When refining on cooling length, the mass of the lightest cold clumps decreases tenfold to $\approx 10^4\,M_\odot$, their boundary layers develop sharper ion stratification, and the warm gas is better resolved, boosting the abundance of warm gas tracers such as CIV and OIII. Together, these results demonstrate that non-equilibrium thermochemistry coupled to radiative transfer, combined with physically motivated resolution criteria, is essential to predict circumgalactic absorption and emission signatures and to guide the design of targeted observations with existing and upcoming facilities.

L. Bruno, A. Botteon, D. Dallacasa, T. Venturi, M. Balboni, N. Biava, M. Brienza, M. Brüggen, G. Brunetti, F. de Gasperin, E. De Rubeis, G. Di Gennaro, F. Gastaldello, A. Ignesti, T. Pasini, K. Rajpurohit, A. Shulevski, K. S. L. Srikanth, R. J. van Weeren, X. Zhang

Complex energy transfer processes in the intracluster medium (ICM) can revive fossil (with spectral ages $\gg100$ Myr) plasma initially generated by radio galaxies. This leads to the re-ignition of faint radio sources with irregular and filamentary morphologies, and ultra-steep ($\alpha \gtrsim 1.5$) synchrotron spectra, which can be more easily detected at low frequencies ($\sim 100$ MHz). These sources offer the opportunity to investigate the microphysics of the ICM and its interplay with radio galaxies, the origin of seed relativistic electrons, the merging history of the host cluster, and the phenomenology of radio filaments. The study of revived sources has so far been hampered by the requirement of sensitive and high-resolution multi-frequency radio data at low frequencies to characterise their spatial properties and provide a proper classification. We aim to perform the analysis of a sample of candidate revived sources identified among nearby ($z\leq0.35$) and low-mass ($M_{500}\leq5\times 10^{14} M_\odot$) \textit{Planck} clusters in the footprint of LoTSS-DR2. By inspecting LoTSS-DR2 images at 144 MHz, we identified 7 targets with patchy and filamentary morphologies, which have been followed-up with the uGMRT at 400 MHz. By combining LOFAR and uGMRT data, we obtained high-resolution images and spectral index maps, which we used to interpret the nature of the sources. All targets show regions with very steep spectra, confirming the effectiveness of our morphology-based selection in identifying fossil plasma. Based on their morphology, spectral properties, and optical associations, we investigated the origin of the targets. We found a variety of promising revived fossil sources, while also showing that apparently intricate structures can be easily misclassified in the absence of high-resolution and multi-band data.

Jorge Sanchez Almeida (1, 2) ((1) Instituto de Astrofisica de Canarias, La Laguna, Tenerife, E-38200, Spain, (2) Departamento de Astrofisica, Universidad de La Laguna, Spain)

It has been proposed that the stellar cores observed in ultra-faint dwarf (UFD) galaxies reflect underlying dark matter (DM) cores that cannot be formed by stellar feedback acting on collisionless cold dark matter (CDM) halos. Assuming this claim is correct, we investigate the constraints that arise if such cores are produced by self-interacting dark matter (SIDM). We derive the range of SIDM cross-sections (sigma/m) required to reproduce the observed core sizes. These can result from halos in either the core-formation phase (low sigma/m) or the core-collapse phase (high sigma/m), yielding a wide allowed range (sim 0.3 -- 200 cm2/g) consistent with values reported in the literature for more massive galaxies. We also construct a simple model relating stellar mass to core radius - two observables likely connected in SIDM. This model reproduces the stellar core sizes and masses in UFDs with sigma/m consistent with those derived above. It also predicts a trend of increasing core radius with stellar mass, in agreement with observations of more massive dwarf galaxies. The model central DM densities match observations when assuming the SIDM profile to originate from an initial CDM halo that follows the mass-concentration relation. Since stellar feedback is insufficient to form cores in these galaxies, UFDs unbiasedly anchor sigma/m at low velocities. If the core-collapse scenario holds (i.e., high sigma/m), UFD halos are thermalized on kpc scales, approximately two orders of magnitude larger than the stellar cores. These large thermalization scales could potentially influence substructure formation in more massive systems.

The abundance patterns of extremely metal-poor stars preserve a fossil record of the Universe's earliest chemical enrichment by the supernova explosions from the evolution of first generation of stars, also referred to as Population III (or Pop III). By applying Bayesian inference to the analysis of abundance patterns of these ancient stars, this study presents a systematic investigation into the properties and explosion mechanism of Pop III stars. We apply NLTE corrections to enhance the reliability of abundance measurements, which significantly reduces the discrepancies in abundances between observations and theoretical yields for odd-Z elements, such as Na and Al. Our Bayesian framework also enables the incorporation of explodability and effectively mitigates biases introduced by varying resolutions across different supernova model grids. In addition to confirming a top-heavy ($\alpha=0.54$) initial mass function for massive Pop III stars, we derive a robust mass--energy relation ($E\propto M^2$) of the first supernovae. These findings demonstrate that stellar abundance analysis provides a powerful and independent approach for probing early supernova physics and the fundamental nature of the first stars.

L. Foffano, C. Arcaro, A. Arbet-Engels, F. D'Ammando, P. Da Vela, J. Jormanainen, D. Linder, S. Menon, E. Prandini, S. Ventura, E. Visentin (for the MAGIC Collaboration)

Extremely high-peaked BL Lac objects (or extreme blazars) are unique extragalactic laboratories where particle acceleration processes are pushed at their physical limits. In these blazars, synchrotron emission peaking above keV energies is reprocessed to very-high-energy (VHE, energies > 100 GeV) gamma rays, often resulting in very hard TeV spectra. Over the past two decades, they have attracted a growing interest from the scientific community, both experimentally and theoretically, as crucial targets for understanding the diversity within the blazar class. On the experimental side, new sources have been detected and characterized, populating the extreme blazars class. Notably, VHE campaigns have revealed evidence of emerging spectral differences in this energy band, suggesting inhomogeneity within this class of sources. Recent studies have also unveiled intriguing differences in the temporal evolution of their spectral emission. On the theoretical side, these spectral differences are challenging the current standard emission and acceleration models for blazars, suggesting the need for more complex theoretical frameworks. In this contribution, we present the latest results from recent MAGIC Collaboration observing campaigns aimed to enlarge the extreme blazars population at VHE and understand the origin of their extreme properties. Furthermore, we will present the results of the most recent observations, discussing analogies and differences with well-known sources such as the archetypal 1ES 0229+200, as well as interpretations of their non-conventional spectral emission.

The identification of $\gamma$-rays from the predominant hadronic-background is a key aspect in their ground-based detection using Imaging Atmospheric Cherenkov Telescopes (IACTs). While current methods are limited in their ability to exploit correlations in complex data, deep learning-based models offer a promising alternative by directly leveraging image-level information. However, several challenges involving the robustness and applicability of such models remain. Designing model architectures with inductive biases relevant for the task can help mitigate the problem. Three such deep learning-based models are proposed, trained, and evaluated on simulated data: (1) a hybrid convolutional and graph neural network model (CNN-GNN) using both image and graph data; (2) an enhanced CNN-GNN variant that incorporates additional reconstructed information within the graph construction; and (3) a graph neural network (GNN) model using image moments serving as a baseline. The new combined convolution and graph-based approach demonstrates improved performance over traditional methods, and the inclusion of reconstructed information offers further potential in generalization capabilities on real observational data.

Collision broadening by molecular hydrogen of sodium and potassium is one of the major broadening mechanisms in the atmospheres of brown dwarf stars and exoplanets at an effective temperature of about 1000K. The accurate computation of line profiles from collision broadening at high density requires use of a Fourier transform of the autocorrelation function inside the model atmosphere code. We strongly warn that use of Lorentzian profiles at a high perturber density neglects radiation during close collisions and may lead to erroneous conclusions.

Recent measurements from the Atacama Cosmology Telescope (ACT), particularly when combined with DESI baryon acoustic oscillation data, have reported a scalar spectral index $n_s$ slightly higher than that inferred by {\it Planck}~2018, suggesting a mild tension with the predictions of standard inflationary attractor models. In this work, we revisit the quantum-corrected Higgs inflation scenario within the framework of a non-minimally coupled scalar field theory. Starting from the one-loop effective action, we incorporate radiative corrections through the anomalous scaling parameter ${\bf A_I}$ and derive analytic expressions for the inflationary observables $n_s$ and $r$ in the Einstein frame. Our analysis demonstrates that quantum corrections naturally shift $n_s$ toward higher values while keeping the tensor-to-scalar ratio $r$ suppressed. For ${\cal N} = 60$, the model predicts $n_s \simeq 0.9743$ and $r \simeq 5.4\times10^{-3}$, in excellent agreement with the latest ACT+DESI (P-ACT-LB) data and fully consistent with the \textit{Planck}~2018 limit $r < 0.036$. The derived constraint $4.36\times10^{-10} < \lambda/\xi^{2} < 10.77\times10^{-10}$ confirms the robustness of the quantum-corrected Higgs framework and indicates that near-future CMB polarization experiments such as CORE, AliCPT, LiteBIRD, and CMB-S4 will be able to probe the predicted parameter space with high precision.

A striking aspect of the radio profiles of many millisecond pulsars (MSPs) is that they consist of components separated from each other by regions lacking in emission. We devise a technique for determining "disjoint" from "contiguous" components and show that 35% of MSPs have disjoint components as opposed to only 3% of the slow pulsar population. We surmise that the pulsars with these disjoint components show evidence for both emission above the polar cap and from the current sheet beyond the light cylinder, co-located with gamma-ray emission. For a sub-class of radio MSPs only the light cylinder emission is being observed. It is our contention that almost all of the current population of gamma-ray MSPs show evidence for co-located radio emission. A simple geometric explanation allows the presence (or not) of light cylinder emission and the relationship (or not) between the gamma-ray and radio profiles to be determined. The light-cylinder components have frequently very high polarization and typically flat position-angle traverses thus helping to explain the difficulties in determining the geometry of MSPs. In cases where the geometry can be determined the values broadly align with expectations. If our picture is correct, the beaming fraction of radio MSPs is higher than previously thought and a mechanism is required to produce coherent radio emission far from the stellar surface. This has implications for our understanding of the populations of radio-loud and radio-quiet rotation-powered millisecond pulsars, and could relate to the timing stability of some of these sources.

Daye Lim, Tom Van Doorsselaere, Nancy Narang, Laura A. Hayes, Emil Kraaikamp, Aadish Joshi, Konstantina Loumou, Cis Verbeeck, David Berghmans, Krzysztof Barczynski

Small scale extreme ultraviolet (EUV) transient brightenings are observationally abundant and critically important to investigate. Determining whether they share the same physical mechanisms as larger scale flares would have significant implications for the coronal heating problem. A recent study has revealed that quasi periodic pulsations (QPPs), a common feature in both solar and stellar flares, may also be present in EUV brightenings in the quiet Sun (QS). We aim to characterise the properties of EUV brightenings and their associated QPPs in both QS and active regions (ARs) using unprecedented 1 s cadence observations from Solar Orbiter/Extreme Ultraviolet Imager (EUI). We applied an automated detection algorithm to analyse statistical properties of EUV brightenings. QPPs were identified using complementary techniques optimised for both stationary and non stationary signals, including a Fourier based method, ensemble empirical mode decomposition, and wavelet analysis. Over 500000 and 300000 brightenings were detected in ARs and QS regions, respectively. Brightenings with lifetimes shorter than 3 s were detected, demonstrating the importance of high temporal resolution. QPP periods span from 5 to over 500 s and show similar distributions between AR and QS. We found a consistent power law scaling, with a weak correlation and a large spread, between QPP period and lifetime in EUV brightenings, solar, and stellar flares. The results support the interpretation that EUV brightenings may represent a small scale manifestation of the same physical mechanisms driving larger solar and stellar flares. Furthermore, the similarity in the statistical properties of EUV brightenings and their associated QPPs between AR and QS regions suggests that the underlying generation mechanisms may not strongly depend on the large scale magnetic environment.

F. Lykou, J. Varga, F. Cruz-Saénz de Miera, P. Ábrahám, Á. Kóspál, B. Lopez, T. Henning, S. Wolf, G. Weigelt, F. Millour, M. Hogerheijde, L. Chen, T. Ratzka, W. Danchi, P. Boley, J.-C. Augereau, P. Priolet

The mid-infrared (MIR) emitting regions of the individual protoplanetary disks in the binary system Z CMa are resolved by MATISSE/VLTI. The observations were obtained during a serendipitous large outburst of the HBe star that lasted more than 100 days, while the FUor companion is presumed to be in quiescence. The size of the MIR-emitting disk region of the more massive HBe star increases toward longer wavelengths from $<14$ mas at 3.5$\mu m$ to $\ll 50$ mas at 11.5$\mu m$ . The lack of substructures in the HBe disk might suggest that it is a continuous disk; however, this could be due to observational constraints. We also note a radial variation of the silicate absorption feature over the disk, where the optical depth increases inwards of $<$40~au radii. This contradicts the scenario of a carved, dusty cocoon surrounding the HBe star. In the case of the less massive FUor companion, the MIR-emitting region is much smaller with an angular size $\leq$15 mas (or else a physical radius $<9$ au) in all bands, suggesting a compact disk. Both disks are aligned within uncertainties, and their orientation agrees with that of the known jets. Furthermore, MATISSE data place the binary's separation at $117.88 \pm 0.73$ mas and a position angle of $139.16^o\,\pm\,0.29^o$ east of north. Our estimates for the orbital elements gave an eccentric orbit ($e\sim0.17$) with a moderate inclination ($i\sim 66$\degr). The derived total mass is $M_{\rm total} = 16.4^{+2.1}_{-2.3}$ M$_\odot$, while the period is approximately 950 years. Our MATISSE imaging of the Herbig disk during outburst indicates a temperature gradient for the disk, while imaging of the FUor companion's disk corroborates previous studies showing that FUor disks are rather compact in the MIR. We cannot infer any misalignment between the MATISSE results and earlier ALMA/JVLA data, nor can we infer any influence from the alleged flyby event.

We report a successful observation of a stellar occultation by asteroid (16583) Oersted, enabling a detailed physical characterization of its shape, spin state, and surface properties. Our goal is to determine the physical parameters of Oersted by combining multi-chord occultation timing, sparse optical photometry, and thermal infrared observations. Such asteroids (size$\sim$20 km) are rarely modeled in this detail due to observational limitations, making Oersted a valuable case study. We applied convex lightcurve inversion to sparse photometric data to derive an initial shape and spin state. This model was then refined and scaled using non-convex shape modeling with the ADAM algorithm, incorporating constraints from the occultation chord profile. Thermophysical modeling based on WISE thermal infrared fluxes was used to determine the asteroid's effective diameter, geometric albedo, and thermal inertia. The non-convex shape model reveals localized surface concavities and provides a size estimate consistent with radiometric measurements. The derived thermal inertia is typical for asteroids of comparable size. This work demonstrates the effectiveness of combining stellar occultations, photometry, and thermal infrared data for asteroid modeling and highlights the valuable contributions of citizen scientists, who played a key role in capturing the occultation and constraining the asteroid's profile.

Stergios Amarantidis, Duncan Farrah, Nick Seymour, Mark Lacy, Iris Breda, Bodo Ziegler, Olmo Piana, Miguel Sánchez-Portal

Accretion rates in radio galaxies are typically estimated from optical and total radio flux measurements, incorporating emission from the core, jets, and lobes. These estimates can be used to investigate the link between observed Active Galactic Nuclei (AGN) emission properties and the underlying accretion physics of their Super-Massive Black Holes (SMBHs). However, while optical and core radio emission trace the ongoing accretion episode, extended jet and lobe structures may result from past AGN activity. Therefore, accretion rates inferred from spatially unresolved radio observations may be systematically overestimated, a bias whose prevalence and extent have yet to be thoroughly explored. In this study, using a sample of 121 local radio-loud galaxies with spatially resolved radio components, we assess this effect by estimating their \textit{Eddington}-scaled accretion rates ($\lambda$) using both the common methodology which considers total radio fluxes and a simple but novel approach that treats core and extended emission as signatures of distinct accretion phases. Our results show that the former method systematically overestimates the $\lambda$ by a factor of $\sim 3$, affecting the accretion mode classification in approximately $11\%$ of sources. This discrepancy appears to correlate with radio size, with the most extended galaxies indicating a transition in accretion disk mode. Such a bias could affect AGN classification in unresolved high-redshift radio surveys. Our results motivate re-examining accretion rate calculations from AGN radio surveys and align with the AGN unification model for radio galaxies, revealing a clearer link between accretion disk physics and optical spectral properties.

The existence of a deficit of brown dwarfs (BDs) in close orbit around main-sequence stars is one of the most intriguing questions in stellar physics. This so-called BD desert may result from the transition between two different dominant formation processes occurring for different mass regimes. While the BD mass derived from radial-velocity measurements helps confirm the nature of the analyzed objects, the BD radius obtained from transits is important to better constrain the BD age, as BDs are believed to contract with age. Such objects with well-constrained parameters, although in small number, are of prime interest for deeper investigations of BD structure and chemical composition. The present document aims at presenting the first results of a search for BD transits among a sample of approximately 3300 host star candidates observed by the Transiting Exoplanet Survey Satellite during Cycle 6.

In this paper we use statistical complexity and information theory metrics to study structure within solar wind time series. We explore this using entropy-complexity and information planes, where the measure for entropy is formed using either permutation entropy or the degree distribution of a horizontal visibility graph (HVG). The entropy is then compared to the Jensen complexity (Jensen-Shannon complexity plane) and Fisher information measure (Fisher-Shannon information plane), formed both from permutations and the HVG approach. Additionally we characterise the solar wind time series by studying the properties of the HVG degree distribution. Four types of solar wind intervals have been analysed, namely fast streams, slow streams, magnetic clouds and sheath regions, all of which have distinct origins and interplanetary characteristics. Our results show that, overall, different metrics give similar results but Fisher-Shannon, which gives a more local measure of complexity, leads to a larger spread of values in the entropy-complexity plane. Magnetic cloud intervals stood out in all approaches, in particular when analysing the magnetic field magnitude. Differences between solar wind types (except for magnetic clouds) were typically more distinct for larger time lags, suggesting universality in fluctuations for small scales. The fluctuations within the solar wind time series were generally found to be stochastic, in agreement with previous studies. The use of information theory tools in the analysis of solar wind time series can help to identify structures and provide insight into their origin and formation.

Maria Chiara de Simone, Manuela Campanelli, Lorenzo Ennoggi, Carlos O. Lousto, Yosef Zlochower (RIT)

We report the first 3D general relativistic magnetohydrodynamic (GRMHD) simulation that captures the full, self-consistent evolution from the late inspiral through merger and subsequent recoil of a supermassive binary black hole (SMBBH) with misaligned spins embedded in an equilibrated circumbinary disk (CBD). Our full numerical simulation follows the final 40 orbits of the inspiral and merger of the binary, following an initial phase of 165 orbits of CBD evolution toward equilibrium. We find that the jets, launched from the minidisks surrounding each black hole, are tilted toward the black hole spin direction close to the individual black holes, but align with the binary's total angular momentum at larger distances. Following the merger, the remnant black hole receives a recoil kick exceeding 1000 km/s. Remarkably, it retains its gravitationally bound CBD as if it were ejected from a galactic nucleus. Furthermore, the jet launched by the recoiling remnant black hole preserves the large-scale orientation established during the late inspiral. We demonstrate that the majority of the luminosity emerges from a region in close proximity to the black hole, suggesting that the accretion disk surrounding the recoiling remnant would remain the most luminous feature postmerger, persisting for long enough to be observable by modern telescopes (hours in the case of LISA sources). These findings introduce a direct, first-principles model for the recoil of supermassive black holes (SMBH) in active galactic nuclei (AGNs), offering a comprehensive theoretical basis to support and elucidate both ongoing and future observational efforts.

We report on the characterization of a coronal mass ejection (CME) observed on 22 October 2003 by the LASCO-C2 and C3 coronagraphs over a time interval of 6 hours. This CME clearly appears as an asymmetric flux-rope in self-similar expansion and in spite of having a single vantage point, this relatively simple morphology and the geometry of the observations allow us to reconstruct its shape and its trajectory. The images are first processed in order to remove most of the background or foreground coronal structures (essentially streamers) which are superimposed on the CME. The analysis is based on forward modeling of an asymmetric structure where the plasma is homogeneously distributed in a thin shell and synthetic images are calculated from Thomson scattering by the electrons. They are best fitted to the images to determine the exact shape of the flux rope, and to track its evolution characterized by a radial propagation in self-similar expansion. The analysis supports the forward propagation (over the backward one) characterized by constant accelerations of 76 and 46 m/sec^2 for the front and rear parts of the CME, respectively. The respective velocities at 20 Rsun reach 2000 and 1100 km/s, and its mass unbiased by projection effects is estimated at 1.7x10^16 g. Altogether, these are quite exceptionally large values among CMEs and imply a very energetic event. No erupting event could be identified at or near the calculated initial location of the CME. It lies 25° west of the active region NOAA 10484, the site of contemporary, violent, and recurrent solar eruptions (the ``Halloween event'') and a putative connection would require a strong deflection over a very short path. Therefore, the origin of this CME remains unclear.

Ian W. Stephens, Simon Coude, Philip C. Myers, Catherine Zucker, James M. Jackson, B-G Andersson, Rowan Smith, Archana Soam, Patricio Sanhueza, Taylor Hogge, Howard A. Smith, Giles Novak, Sarah Sadavoy, Thushara Pillai, Zhi-Yun Li, Leslie W. Looney, Koji Sugitani, Andres E. Guzman, Alyssa Goodman, Takayoshi Kusune, Miaomiao Zhang, Nicole Karnath, Jessy Marin

Stars primarily form in galactic spiral arms within dense, filamentary molecular clouds. The largest and most elongated of these molecular clouds are referred to as ``bones," which are massive, velocity-coherent filaments (lengths ~20 to >100 pc, widths ~1-2 pc) that run approximately parallel and in close proximity to the Galactic plane. While these bones have been generally well characterized, the importance and structure of their magnetic fields (B-fields) remain largely unconstrained. Through the SOFIA Legacy program FIELDMAPS, we mapped the B-fields of 10 bones in the Milky Way. We found that their B-fields are varied, with no single preferred alignment along the entire spine of the bones. At higher column densities, the spines of the bones are more likely to align perpendicularly to the B-fields, although this is not ubiquitous, and the alignment shows no strong correlation with the locations of identified young stellar objects. We estimated the B-field strengths across the bones and found them to be ~30-150 $\mu$G at pc scales. Despite the generally low virial parameters, the B-fields are strong compared to the local gravity, suggesting that B-fields play a significant role in resisting global collapse. Moreover, the B-fields may slow and guide gas flow during dissipation. Recent star formation within the bones may be due to high-density pockets at smaller scales, which could have formed before or simultaneously with the bones.

We develop a three-dimensional kinetic model of the solar transition region and corona in which the plasma above the chromosphere is collisionless and embedded in a uniform magnetic field. Heating occurs intermittently at discrete locations on the chromospheric surface, modeled through a surface coarse-graining procedure that produces non-thermal boundary conditions for the Vlasov equation. The resulting stationary distribution functions generate suprathermal particle populations and naturally lead to a temperature inversion via gravitational filtering, without any local coronal heating. The model reproduces realistic temperature and density profiles with a thin transition region and a hot corona, consistent with solar observations. These results demonstrate that the spatial intermittency of heating at the chromospheric interface is sufficient to account for the formation of the transition region and the high-temperature corona.

The era of real-time cosmology has begun. It is now possible to directly measure the apparent drift of high-redshift astronomical sources across the sky $\textit{in real time}$. This so-called $\textit{position drift}$ provides a valuable probe of the peculiar velocity field and cosmic structure formation by giving direct access to the transverse velocity that is otherwise currently not measurable and must be statistically reconstructed from the density field in a model-dependent way. To fully exploit this new window into the Universe, it is essential to understand how cosmological structures affect position drift measurements. Here we present the first position drift study based on the general relativistic N-body simulation code $\texttt{gevolution}$. We calculate the position drift directly from the past light cone for ten different observers and compare the results to predictions from linear perturbation theory. At linear order, the position drift is directly proportional to the transverse velocity on the sky. This linear approximation reproduces our non-linear simulation results to within about 5%. We calculate power spectra for the position drift, splitting the signal into an E- and B-mode and compare the former to linear expectations, finding good agreement. The B-mode is suppressed on linear scales, but has similar amplitude as the E-mode on non-linear scales. We further demonstrate that light-cone inhomogeneities induce biases in the dipole of the drift, introducing redshift dependence of both the amplitude and direction. Although our analysis is not yet sufficient for a firm conclusion, our results suggest that these effects alone cannot explain the possible redshift-dependent dipole in Gaia DR3 data reported in the literature.

Hot Jupiters are Jupiter-sized exoplanets with close-in orbits, characterized by extreme day-night temperature contrasts due to synchronous rotation. These planets offer unique observational opportunities through transit photometry, transmission spectroscopy, and infrared (IR) phase curve analysis, which reveal information about heat redistribution and atmospheric dynamics. Complementary to common generalized circulation models (GCMs), we introduce a more comprehensive approach using the anelastic fluid equations that fully capture the three-dimensional nature of the emerging non-linear flows. We identify various non-linear flow regimes and analyze the heat distribution when irradiation and thermal advection reach equilibrium. Eastward zonal winds can reach velocities comparable to the planetary rotation (up to several kilometers per second), while slower radial flows, though less prominent, contribute significantly to heat advection and can cause both eastward and westward hotspot shifts. The efficiency of day-to-night heat redistribution and the positioning of brightness maxima are shown to depend strongly on pressure and the interplay of advective and radiative processes. These findings improve our understanding of the diversity observed in the IR phase curves and suggest a non-magnetic mechanism for retrograde hotspot shifts. By extending the scope of traditional GCM models, our work demonstrates the usefulness of anelastic models in capturing the complex, multidimensional dynamics of irradiated exoplanetary atmospheres.

Michele Benaco, Dimitrios Karamitros, Sami Nurmi, Kimmo Tuominen

We investigate scalar-induced stochastic gravitational waves from adiabatic curvature perturbations sourced by a spectator field via the modulated reheating mechanism. We consider a spectator scalar with Higgs-like couplings and inflaton decay via shift symmetric dimension-five operators. The spectator is assumed to be in the Sitter vacuum and it sources blue-tilted, strongly non-Gaussian curvature perturbations which can dominate the spectrum on small scales $k \gg \rm{Mpc}^{-1}$. We find that the setup could generate a gravitational wave signal testable by surveys like BBO and DECIGO but only for large coupling values not expected in low-energy particle physics setups that can be perturbatively extrapolated up to the inflationary scale.

I. Kontogiannis (1 and 2), Y. Zhu (1), K. Barczynski (3), M. Z. Stiefel (1 and 4), H. Collier (1 and 4), J. McKevitt (5 and 6), J.S. Castellanos Durán (7), S. Berdyugina (2 and 8), L.K. Harra (1 and 3) ((1) ETH Zürich, Institute for Particle Physics and Astrophysics, (2) Istituto Ricerche Solari Aldo e Cele Daccò (IRSOL), Faculty of Informatics, Università della Svizzera Italiana, (3) Physikalisch-Meteorologisches Observatorium Davos/World Radiation Center, (4) University of Applied Sciences and Arts Northwestern Switzerland, (5) University College London, Mullard Space Science Laboratory, (6) University of Vienna, Institute of Astrophysics, (7) Max Planck Institute for Solar System Research, (8) Euler Institute, Faculty of Informatics, Università della Svizzera Italiana)

Magnetic flux emergence and decay in the Sun span from days to months. However, their tracking is typically limited to about half a solar rotation when relying on single-vantage-point observations. Combining observations from both the Earth-facing and far side of the Sun, we monitored the magnetic and coronal evolution and characterised the non-potentiality of one of the most complex and eruptive regions of the past two decades, over more than three full solar rotations. We used photospheric magnetograms and EUV filtergrams from the Solar Orbiter and the Solar Dynamics Observatory along with flare detections from the GOES and the STIX instrument on board the Solar Orbiter. All images were deprojected into a common coordinate system and merged into a unified dataset. We tracked the evolution of magnetic flux and EUV emission and computed magnetic field parameters from the line-of-sight magnetograms to quantify the region's non-potentiality. We identified the region's initial emergence and followed its evolution through to its decay. The region developed through successive flux emergence episodes over a period of 20 days, reached its peak complexity one month after the first emergence, and gradually decayed over the subsequent two months. Unlike many complex regions, it consistently maintained high levels of non-potentiality for most of its lifetime, sustaining equally strong flaring activity. The derived time series of non-potentiality parameters, the first of their kind, far exceeded the typical 14-day window imposed by solar rotation and were remarkably consistent, exhibiting strong correlation with the flaring activity of the region. Multi-vantage-point observations can significantly improve our understanding of how magnetic flux emerges, evolves, and drives solar activity, beyond the two-week limit imposed by solar rotation on observations along the Sun-Earth line.

Johanna Müller-Horn, Hans-Walter Rix, Kareem El-Badry, Ben Pennell, Matthew Green, Jiadong Li, Rhys Seeburger

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We present a rigorous identification of candidates for dormant black holes (BHs) and neutron stars (NSs) in binaries using summary statistics from Gaia DR3, rather than full orbital solutions. Although Gaia astrometric orbits have already revealed a small sample of compact object binaries, many systems remain undetected due to stringent quality cuts imposed on the published orbits. Using a forward-modelling framework that simulates Gaia observables, in particular the renormalised unit weight error (ruwe) and radial velocity (RV) scatter, we infer posterior distributions for companion mass and orbital period via MCMC sampling, marginalising over nuisance orbital parameters. We validate our approach by comparing the predicted masses and periods against full orbit solutions from DR3, and by successfully recovering known compact object binaries as promising candidates. The method is best suited for systems with red giant primaries, which have more reliable Gaia RV scatter and a light centroid more likely dominated by one component, compared to main-sequence stars. And they are less likely to be triples with short-period inner binaries, which produce confounding signatures. We apply the method to three million giants and identify 556 systems with best-fit companion masses $\gtrsim 3\,M_\odot$. Recovery simulations suggest our selection method is substantially more sensitive than the DR3 non-single-star catalogue, particularly for binaries with periods below 1 year and above $\sim 6$ years. These candidates represent promising targets for spectroscopic follow-up and Gaia DR4 analysis to confirm the presence of compact objects. Candidate main-sequence stars with massive companions face a larger set of confounding effects. Therefore, we present an analogous catalogue of 279 additional `main sequence' candidates only as an appendix.

Lucas Barrault, Lisa Bugnet, Stéphane Mathis, Joey S.G. Mombarg

Gamma Dor stars are ideal targets for studies of the innermost dynamical properties of stars, due to their rich frequency spectrum of gravito-inertial modes propagating in the radiative envelope. Recent studies found that these modes could couple at the core-to-envelope interface with pure inertial modes in their sub-inertial regime, forming the so-called inertial dip in the period-spacing pattern of these stars. The inertial dip, as formed by core modes, stands out as a unique probe of core properties. We aim in this work to explore the effect of core magnetism on its structure, property of key relevance in modern stellar physics. We describe the outlines of our model and the geometry of the considered field. We give the coupling equation and the variation of the dip shape and location with increasing magnetic contrast between the core and the envelope. We compare our findings to the ones obtained in a hydrodynamical, differentially-rotating case. We show hints at potentially lifting the degeneracy between the signatures of core-to-envelope differential rotation and core magnetic fields. Together, these two cases can be considered as an exploration of different magnetic regimes potentially reached in the core of gamma Dor stars.

Very-high energy (VHE; $>$100 GeV) $\gamma$-ray emission originates via some of the most extreme particle acceleration processes in the universe. Considering beamed active galactic nuclei, i.e., blazars, only a small fraction, mainly high synchrotron peak BL Lacs, have been detected in the VHE band with the ground-based Cherenkov telescopes. We utilized $\sim$16 years of Fermi-Large Area Telescope (LAT) observations in the 0.1$-$2 TeV energy range to systematically search for potential VHE emitters in a sample of high synchrotron peaked ($\nu^{\rm peak}_{\rm syn}>10^{15}$ Hz) BL Lac sources. We identified, for the first time, 92 VHE emitting blazars at $\geq 5\sigma$ confidence level. A significant VHE emission was also detected from 52 objects, which have been previously reported to be a VHE blazar. Comparing with the general blazar population, these VHE emitting blazars are found to be located at low redshifts (mean $z=0.2 \pm 0.1$) and exhibit bright synchrotron emission ($\log F^{\rm peak}_{\rm syn}=-11.2 \pm 0.4$, in erg cm$^{-2}$ s$^{-1}$). We also investigated the coincidence of VHE photon arrivals with the source activity states and found that Fermi-LAT has detected VHE photons during both quiescent and elevated activity epochs. These VHE emitting blazars represent promising targets for current and next-generation ground-based Cherenkov telescopes, and provide valuable laboratories for probing particle acceleration in relativistic jets, testing multi-messenger connections, and constraining extragalactic background light models.

Renyu Luo, Chunhua Zhu, Guoliang Lü, Helei Liu, Sufen Guo, Lei Li, Zhuowen Li

During the late stages of massive stellar evolution, failed supernovae (FSN) may form through core-collapse processes. The traditional evaluation criterion $\xi_{2.5}$ $=$ 0.45, primarily established using non-rotating progenitor models, suffers from significant inaccuracies when applied to rotating pre-supernova systems. The effects of metallicity and rotation on the explodability landscapes of massive stars lack robust quantification. We aim to investigate how rotation and metallicity influence the explodability of massive stars. We investigate how rotation and metallicity affect stellar explodability using MESA simulations with initial rotational velocities of $0$, $300$, and $600~\mathrm{km,s^{-1}}$ at three metallicities ($Z_{\odot}$, $1/10,Z_{\odot}$, $1/50,Z_{\odot}$). Core-collapse phases are simulated with GR1D to determine critical heating efficiencies. Our results yield revised $\xi_{2.5}$ criteria: 0.45 for non-rotating models; 0.48 for $300~\mathrm{km,s^{-1}}$; 0.47 for $600~\mathrm{km,s^{-1}}$ at solar metallicity; and 0.59 for low-metallicity models. Chemically homogeneous evolution in rapidly rotating low-metallicity stars significantly raises the compactness limit for successful explosions and narrows the zero-age main sequence mass range for failed supernovae. Rotation substantially affects the explodability of low-metallicity massive stars, underscoring the importance of incorporating rotational effects in models of core-collapse supernova progenitors.

We model the outcomes of catastrophic disruptions on small, gravity-dominated natural satellites, accounting for the tidal potential of the central body, which is neglected in classical disruption scaling laws. We introduce the concept of $Q^\star_\text{TD}$, the specific energy required to disperse half of the total mass involved in a collision, accounting for the tidal potential of a central body. We derive a simple scaling relation for $Q^\star_\text{TD}$ and demonstrate that for close-in planetary or asteroidal satellites, the tides from the central body can significantly reduce their catastrophic disruption threshold. We show that many satellites in the Solar System are in such a regime, where their disruption threshold should be much lower than that predicted by classical scaling laws which neglect tidal effects. Some notable examples include Mars' Phobos, Jupiter's Metis and Adrastea, Saturn's ring moons, Uranus' Ophelia, and Neptune's Naiad and Thalassa, among others. We argue that traditional impact scaling laws should be modified to account for tides when modeling the formation and evolution of these close-in satellites. Our derivation for $Q^\star_\text{TD}$ can easily be used in existing $N$-body and collisional evolution codes.

A. Circiello, A. McDaniel, M. Di Mauro, C. Karwin, N. Khatiya, M. Ajello, F. Donato, D. Hartmann, A. Strong

We evaluate the contribution to the Isotropic Gamma-Ray Background (IGRB) coming from Radio Galaxies (RGs), the subclass of radio-loud Active Galactic Nuclei (AGN) with the highest misalignment from the line of sight (l.o.s.). Since only a small number of RGs are detected in gamma rays compared to the largest known radio population, the correlation between radio and gamma-ray emission serves as a crucial tool to characterize the gamma-ray properties of these sources. We analyse the population of RGs using two samples. The first sample contains 26 sources individually detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope at gamma rays. The second sample contains 210 RGs for which the gamma-ray emission is not significantly detected by the LAT. We use a stacking analysis to characterize the average properties of the gamma-ray emission of the two samples, separately at first and then combined. We then evaluate the correlation between their gamma-ray emission and the emission from their radio core at 5 GHz, and we use it to determine their contribution to the IGRB. Due to the limited number of RGs detected at the gamma-rays, information on the gamma-ray luminosity function is limited. The correlation between the gamma-ray emission and the emission of the radio core allows us to characterize it starting from the luminosity function of the radio cores, which is modeled with greater accuracy due to the larger number of sources detected at these frequencies. We find that the diffuse emission as extrapolated from the properties of the subthreshold RGs is lower than the one inferred from detected RGs, showing that the contribution of the population of RGs to the IGRB is lower than the previous estimates and it is around the 30% level of the IGRB intensity.

C. J. K. Larkin, C. Hawcroft, J. Mackey, R. R. Lefever, L. Härer, A. A. C. Sander

Feedback from Young Massive Clusters (YMCs) is an important driver of galaxy evolution. In the first few Myr, mechanical feedback is dominated by collective effects of the massive stellar winds in the YMC. The mass-loss rates and terminal wind velocities of these stars change by orders of magnitude over pre-SN timescales as the massive stars evolve, and mass-loss rates of Cool Supergiant (CSG) stars in particular are uncertain by a factor $\sim~20$ or more. In this work we perform a first study of the time evolution of average cluster wind velocity $\bar{V}_{\mathrm{cl}}$ as a function of stellar metallicity $Z$, assuming single star evolution. We also check the validity of assuming Wolf-Rayet stars dominate the feedback effects of a YMC, as often done when interpreting X-ray and $\gamma$-ray observations, and test how sensitive $\bar{V}_{\mathrm{cl}}$ is to current uncertainties in mass-loss rates. We use pySTARBURST99 to calculate integrated properties of YMCs for $Z$ in the range of $0.0004-0.02$, representing a range of environments from IZw18 to the Galactic Centre. We find that $\bar{V}_{\mathrm{cl}}$ drops off rapidly for sub-LMC $Z$, and we recommend a value of $500-1000\,~\textrm{km~s}^{-1}$ be used in this regime. We show accounting only for WR stars can overestimate $\bar{V}_{\mathrm{cl}}$ by $500-2000\,~\textrm{km~s}^{-1}$ at $Z \geq Z_\text{LMC}$. We also find that different RSG mass-loss assumptions can change the inferred $\bar{V}_{\mathrm{cl}}$ by $\sim1000\,~\textrm{km~s}^{-1}$, highlighting the need for improved observational constraints for RSGs in YMCs.

Alexander Reeves, Simone Ferraro, Andrina Nicola, Alexandre Refregier

We perform a multiprobe analysis combining cosmic microwave background (CMB) data from Planck and the Atacama Cosmology Telescope (ACT), ACT CMB lensing, and large-scale structure (LSS) measurements from the Dark Energy Spectroscopic Instrument (DESI), including DESI Legacy Imaging Survey (LS) galaxies and baryon acoustic oscillations (BAOs). We present the first $5\times2$pt analysis of ACT DR6 lensing, DESI LS, and Planck ISW. Within $\Lambda$CDM, this yields $S_8 = \sigma_8(\Omega_m/0.3)^{0.5} = 0.819 \pm 0.016$, in good agreement with primary CMB inferences and provides a sound-horizon-free Hubble constant constraint of $H_0 = 70.0 \pm 4.4$ km s$^{-1}$ Mpc$^{-1}$. Then, combining with CMB primary and BAO, we reconfirm a CMB-BAO discrepancy in the $\Omega_m$-$\frac{D_v}{r_d}$ plane, which is heightened when combining BAO with the $5\times2$pt data vector. We explore two dark-energy extensions that may reconcile this: an early-time modification, early dark energy (EDE), and late-time dynamical dark energy (DDE) parameterized by $w_0w_a$. For CMB primary+BAO+$5\times2$pt, we find a $3.3\sigma$ preference for DDE over $\Lambda$CDM, while EDE is modestly favoured at $2.3\sigma$. The models address different shortcomings of $\Lambda$CDM: DDE relaxes the neutrino mass bound ($M_\nu<0.17$eV vs. $<0.050$eV under $\Lambda$CDM), making it compatible with neutrino oscillation measurements, while EDE raises the Hubble constant to $H_0=70.5\pm1.2\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$, easing the discrepancy with SH0ES. However, neither model resolves both issues simultaneously. Our analysis indicates that both DDE and EDE remain viable extensions of $\Lambda$CDM within current uncertainties and demonstrates the capacity of combined probes to place increasingly stringent constraints on cosmological parameters.

The formation of gullies on Mars has often been attributed to the melting of (sub)surface water ice. However, melting-based hypotheses generally overlook key processes: (1) sublimation cooling by latent heat absorption, (2) the non-stability of ice where melting conditions can be reached, and (3) the particular microclimates of gullied slopes. Using state-of-the-art climate simulations, we reassess ice melting scenarios over the past four million years (obliquity $\le$35\textdegree)), beyond the estimated period of gully formation. We find that surface melting is impossible anywhere due to sublimation cooling, while (quasi-) stable subsurface ice is typically too deep to reach melting temperatures. We propose an alternative mechanism in which seasonal CO$_2$ frost sublimation destabilizes the regolith and brings the underlying water ice close to the surface, allowing rapid heating. Even under these optimal conditions, melting requires unrealistic assumptions. The only remaining possibility is solar absorption in dusty ice, though its occurrence remains uncertain.

Parity-odd four-point correlation functions, or trispectra, of cosmic matter density fields provide a unique probe of fundamental symmetries in cosmology. Trispectra of primordial matter density fluctuations produced in the early universe are modified by the subsequent nonlinear structure formation. In this paper, we compute the nonlinear evolution of the parity-odd matter trispectrum to one-loop order, i.e., to third order in density fluctuations, within the framework of effective field theory of the large-scale structure of the universe. By analyzing the different terms in the perturbation series, we demonstrate the structure of infrared divergence cancellations, as required by the equivalence principle. We also derive the forms of the counterterms required to renormalize the ultraviolet divergences. Adopting a specific model for a primordial parity-odd trispectrum, we numerically compute the leading-order effects of nonlinear gravitational evolution and study its impact on baryonic acoustic oscillations within the signal. These calculations are essential for comparing the observed trispectra of nonlinear cosmic density fields with theoretical expectations.

Baria Khan, Samuel A. Daza Rodriguez, Els Peeters, Alexander G. G. M. Tielens, Takashi Onaka, Jan Cami, Bethany Schefter, Christiaan Boersma, Felipe Alarcón, Olivier Berné, Amélie Canin, Ryan Chown, Emmanuel Dartois, Javier R. Goicoechea, Emilie Habart, Olga Kannavou, Alexandros Maragkoudakis, Amit Pathak, Alessandra Ricca, Gaël Rouillé, Dinalva A. Sales, Ilane Schroetter, Ameek Sidhu, Boris Trahin, Dries Van De Putte, Yong Zhang, Henning Zettergren

Infrared emission from polycyclic aromatic hydrocarbons (PAHs) play a major role in determining the charge balance of their host environments that include photo-dissociation regions (PDRs) in galaxies, planetary nebulae, and rims of molecular clouds. We aim to investigate the distribution and sizes of charged PAHs across the key zones of the Orion Bar PDR. We employ JWST MIRI-MRS observations of the Orion Bar from the Early Release Science program ''PDRs4All'' and synthetic images in the JWST MIRI filters. We investigate the spatial morphology of the AIBs at 6.2, 7.7, 8.6, and 11.0 $\mu$m that commonly trace PAH cations, and the neutral PAH-tracing 11.2 $\mu$m AIB, their (relative) correlations, and the relationship with existing empirical prescriptions for AIBs. The 6.2. 7.7, 8.6, 11.0, and 11.2 $\mu$m AIBs are similar in spatial morphology, on larger scales. Analyzing three-feature intensity correlations, two distinct groups emerge: the 8.6 and 11.0 $\mu$m vs. the 6.2 and 7.7 $\mu$m AIBs. We attribute these correlations to PAH size. The 6.2 and 7.7 $\mu$m AIBs trace cationic, medium-sized PAHs. Quantum chemical calculations reveal that the 8.6 $\mu$m AIB is carried by large, compact, cationic PAHs, and the 11.0 $\mu$m AIB's correlation to it implies, so is this band. The 6.2/8.6 and 7.7/8.6 PAH band ratios thus probe PAH size. We conclude that the 6.2/11.2 AIB ratio is the most reliable proxy for charged PAHs, within the cohort. We outline JWST MIRI imaging prescriptions that serve as effective tracers of the PAH ionization fraction as traced. This study showcases the efficacy of the 6-9 $\mu$m AIBs to probe the charge state and size distribution of the emitting PAHs, offering insights into the physical conditions of their host environments. JWST MIRI photometry offers a viable alternative to IFU spectroscopy for characterizing this emission in extended objects.

Jacob Lustig-Yaeger, Kristin S. Sotzen, Kevin B. Stevenson, Shang-Min Tsai, Ryan C. Challener, Jayesh Goyal, Nikole K. Lewis, Dana R. Louie, L. C. Mayorga, Daniel Valentine, Hannah R. Wakeford, Lili Alderson, Natalie H. Allen, Thomas J. Fauchez, Ana Glidden, Amélie Gressier, Sarah M. Hörst, Jingcheng Huang, Zifan Lin, Avi M. Mandell, Elijah Mullens, Sarah Peacock, Edward W. Schwieterman, Jeff A. Valenti, C. Matt Mountain, Marshall Perrin, Roeland P. van der Marel

Theoretical studies have suggested using planetary infrared excess (PIE) to detect and characterize the thermal emission of transiting and non-transiting exoplanets, however the PIE technique requires empirical validation. Here we apply the PIE technique to a combination of JWST NIRSpec G395H transit and eclipse measurements of WASP-17b, a hot Jupiter orbiting an F-type star, obtained consecutively (0.5 phase or 1.8 days apart) as part of the JWST-TST program to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS). Using the in-eclipse measured stellar spectrum to circumvent the need for ultra-precise stellar models, we extract the first JWST nightside emission spectrum of WASP-17b using only transit and eclipse data thereby performing a controlled test of the PIE technique. From the WASP-17b nightside spectrum, we measure a nightside equilibrium temperature of $1005 \pm 256$ K and find tentative evidence for nightside SO2 absorption ($\ln B = 1.45$, $2.3\sigma$). In context with the dayside, the temperature of the nightside is consistent with (1) previous eclipse mapping findings that suggest relatively inefficient day-night heat transport, and (2) a non-zero bond albedo of $0.42^{+0.06}_{-0.10}$. SO2 on the nightside, if confirmed, would represent the first direct evidence for transport-induced chemistry, matching previous model predictions, and opening a new door into the 3D nature of giant exoplanets. Our results suggest that PIE is feasible with JWST/NIRSpec for two epochs separated in time by significantly less than the rotation period of the host star.

The origin of ultra-high-energy cosmic rays remains one of the central open questions in astroparticle physics. Recent measurements reveal anisotropies in arrival directions, a rigidity-dependent composition dominated by intermediate-mass nuclei, and striking hemispheric differences in the energy spectra. Here we show that rare transients in nearby galaxies can naturally account for these features. In our fiducial neutron-star merger model, the cosmic ray flux above $25$ EeV is dominated by ten nearby galaxies within $8\,$Mpc. This accounts for the observed hotspots: seven of the ten brightest galaxies coincide with reported excess regions, a chance probability of $p\simeq0.003$. Nearby transients also explain the spectral excess of TA over Auger; link their angular sizes to extragalactic magnetic fields at $\sim$1 nG; explain the dominance of individual species over narrow energy ranges; and the rigidity-aligned succession of isotopes.

Priscilla Muheki, Mirjana Pović, Somaya Saad, Salma Sylla Mbaye, in collaboration with Vanessa McBride, Naomi Asabre Frimpong, Meryem Guennoun, African Science Stars team

In preparation for the International Astronomical Union (IAU) General Assembly (GA) 2024, the first GA held in Africa, the African Network of Women in Astronomy (AfNWA) embarked on a visionary project: the creation of an inspiring storytelling book that showcases the remarkable journeys of professional female astronomers in Africa. This book is not merely a collection of biographies; it is a tapestry of resilience, passion, and scientific excellence woven through the lives of women who have ventured into the cosmos from the African continent. The primary aim of this book is twofold. Firstly, it seeks to bring greater visibility to women astronomers in Africa, highlighting their groundbreaking research and the personal stories that have shaped their careers. By shining a light on their achievements and awards, we hope to acknowledge their contributions to the field of astronomy and underscore the importance of diversity in science. Secondly, this book aspires to inspire and empower the next generation of scientists, particularly young women and girls across Africa. Through the personal narratives and professional achievements of these trailblazing astronomers and students in astronomy, we aim to spark curiosity, foster a love for science, and demonstrate that the sky is not the limit but just the beginning for those who dare to dream. As you delve into the stories within these pages, you will encounter a rich array of experiences and insights that reflect the unique challenges and triumphs women face in astronomy. From overcoming societal barriers to making groundbreaking discoveries, these women have carved paths that others can follow, proving that with determination and passion, the stars are within reach for everyone.

Yunjia Bao, Dhong Yeon Cheong, Nicholas L. Rodd, Joey Takach, Lian-Tao Wang, Kevin Zhou

Is the usual treatment of axion dark matter as a classical field reliable? We show that the answer is subtle: the axion field could well be in a quantum state that has no complete classical description, but realistic detectors cannot tell the difference. To see this, we solve a fully quantum model of axion detection using quantum optics techniques. We show that intrinsically quantum effects are washed out by mode averaging or small amounts of noise, and significantly suppressed by the weakness of the axion coupling. Our work exemplifies that there should always be a classical analog for axion dark matter effects, extends to other wave (ultralight) dark-matter candidates, and gives a general method to compute the effects of exotic dark-matter states.

Normal particles carry a microscopic arrow of causality. Lee-Wick ghosts carry the reversed arrow, mediating characteristic collider signals in flat space: opposite-sign scattering amplitudes that violate positivity bounds; acausality on time scales set by their negative decay rate. During inflation, the corresponding cosmo-collider ghost signals are: opposite-sign non-Gaussianities; Boltzmann-unsuppressed local oscillatory signals without their non-local counterparts; IR-enhanced bi-spectrum and power spectrum, depending on the dimension of the interaction operator, which decreases if the ghost decay rate is comparable to the Hubble rate.

A common challenge in the natural sciences is to disentangle distinct, unknown sources from observations. Examples of this source separation task include deblending galaxies in a crowded field, distinguishing the activity of individual neurons from overlapping signals, and separating seismic events from an ambient background. Traditional analyses often rely on simplified source models that fail to accurately reproduce the data. Recent advances have shown that diffusion models can directly learn complex prior distributions from noisy, incomplete data. In this work, we show that diffusion models can solve the source separation problem without explicit assumptions about the source. Our method relies only on multiple views, or the property that different sets of observations contain different linear transformations of the unknown sources. We show that our method succeeds even when no source is individually observed and the observations are noisy, incomplete, and vary in resolution. The learned diffusion models enable us to sample from the source priors, evaluate the probability of candidate sources, and draw from the joint posterior of the source distribution given an observation. We demonstrate the effectiveness of our method on a range of synthetic problems as well as real-world galaxy observations.

Solar Proton Events (SPEs) cause significant radiation hazards to satellites, astronauts, and technological systems. Accurate forecasting of their proton flux time profiles is crucial for early warnings and mitigation. This paper explores deep learning sequence-to-sequence (seq2seq) models based on Long Short-Term Memory networks to predict 24-hour proton flux profiles following SPE onsets. We used a dataset of 40 well-connected SPEs (1997-2017) observed by NOAA GOES, each associated with a >=M-class western-hemisphere solar flare and undisturbed proton flux profiles. Using 4-fold stratified cross-validation, we evaluate seq2seq model configurations (varying hidden units and embedding dimensions) under multiple forecasting scenarios: (i) proton-only input vs. combined proton+X-ray input, (ii) original flux data vs. trend-smoothed data, and (iii) autoregressive vs. one-shot forecasting. Our major results are as follows: First, one-shot forecasting consistently yields lower error than autoregressive prediction, avoiding the error accumulation seen in iterative approaches. Second, on the original data, proton-only models outperform proton+X-ray models. However, with trend-smoothed data, this gap narrows or reverses in proton+X-ray models. Third, trend-smoothing significantly enhances the performance of proton+X-ray models by mitigating fluctuations in the X-ray channel. Fourth, while models trained on trendsmoothed data perform best on average, the best-performing model was trained on original data, suggesting that architectural choices can sometimes outweigh the benefits of data preprocessing.

Binary neutron star mergers are unique probes of matter at extreme density and standard candles of cosmic expansion. The only such event observed in both gravitational waves and electromagnetic radiation, GW170817, revealed the origin of heavy elements, constrained the neutron star equation of state, and provided an independent measurement of the Hubble constant. Current detectors such as LIGO, Virgo, and KAGRA capture only the final minutes of inspiral, offering limited advance warning and coarse sky localization. In this study, we present a comprehensive analysis of binary neutron star signals for lunar-based gravitational-wave observatories (LILA, LGWA, GLOC) envisioned within NASA's Artemis and Commercial Lunar Payload Services programs, and compare their performance with current and next-generation Earth-based facilities. For GW170817-like sources, we find that lunar detectors can forecast mergers weeks to months in advance and localize them to areas as small as 0.01 deg$^{2}$, far beyond the reach of terrestrial detectors. We further show that lunar observatories would detect on the order of 100 well-localized mergers annually, enabling coordinated multi-messenger follow-up. When combined in a multi-band LIGO+Moon network, sky-localization areas shrink to just a few arcsec$^{2}$, comparable to the field of view of the James Webb Space Telescope at high zoom. Multi-band parameter estimation also delivers dramatic gains: neutron star mass-ratio uncertainties can be measured with $\sim0.1\%$ precision, spin constraints to 0.001$\%$ with luminosity distance errors to 1$\%$ level, enabling precision measurements of the equation of state and the cosmic expansion rate. Our results demonstrate that lunar gravitational-wave observatories would revolutionize multi-messenger astrophysics with binary neutron stars and open a unique discovery landscape in the Artemis era.

Nuclear symmetry energy $E_{\mathrm{sym}}(\rho)$ encoding the cost to make nuclear matter more neutron rich has been the most uncertain component of the EOS of dense neutron-rich nucleonic matter. It affects significantly the radii, tidal deformations, cooling rates and frequencies of various oscillation modes of isolated neutron stars as well as the strain amplitude and frequencies of gravitational waves from their mergers, besides its many effects on structures of nuclei as well as the dynamics and observables of their collisions. Siemens (1970s) observed that $E_{\mathrm{sym}}(\rho)$ scales as $(\rho/\rho_0)^{2/3}$ near the saturation density $\rho_0$ of nuclear matter, since both the kinetic part and the potential contribution (quadratic in momentum) exhibit this dependence. The scaling holds if: (1) the nucleon isoscalar potential is quadratic in momentum, and (2) the isovector interaction is weakly density dependent. After examining many empirical evidences and understanding theoretical findings in the literature we conclude that: (1) Siemens' $\rho^{2/3}$ scaling is robust and serves as a valuable benchmark for both nuclear theories and experiments up to $2\rho_0$ but breaks down at higher densities, (2) Experimental and theoretical findings about $E_{\mathrm{sym}}(\rho)$ up to $2\rho_0$ are broadly consistent, but uncertainties remain large for its curvature $K_{\mathrm{sym}}$ and higher-order parameters, (3) Above $2\rho_0$, uncertainties grow due to poorly constrained spin-isospin dependent tensor and three-body forces as well as the resulting nucleon short-range correlations. Looking forward, combining multimessengers from both observations of neutron stars and terrestrial heavy-ion reaction experiments is the most promising path to finally constraining precisely the high-density $E_{\mathrm{sym}}(\rho)$ and the EOS of supradense neutron-rich matter.

Magnification of total image fluxes is typically considered a defining feature of gravitational microlensing. In contrast, I will show that nonminimal couplings to gravity can generate regions of negative gravitational potential curvature, giving rise to the distinctive possibility of demagnification. Such events, appearing as flux troughs in microlensing light curves, provide a direct probe of dark matter structures and, crucially, offer a means to disentangle nonminimal couplings to gravity from other astrophysical and cosmological models.

S.P. Maydanyuk (1 and 2), Ju-Jun Xie (1, 3 and 4), V.S. Vasilevsky (5), K.A. Shaulskyi (2) ((1) Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences, Huizhou 516000, China, (2) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, 03680, Ukraine, (3) Heavy Ion Science and Technology Key Laboratory, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China, (4) School of Nuclear Sciences and Technology, University of Chinese Academy of Sciences, Beijing 101408, China, (5) Bogolyubov Institute for Theoretical Physics, Metrolohichna str., 14b, Kyiv, 03143, Ukraine)

Purpose To investigate synthesis of nuclei in pycnonuclear reactions in dense medium of neutron stars on the basis of understanding, how the compound nucleus is formed during collision of two nuclei. To implement microscopic formulation of nuclear interactions and fusion in pycnonuclear reactions in dense medium. Methods (1) Nuclei synthesis in pycnonuclear reaction in dense medium of neutron star is investigated in the folding approximation of the cluster model. (2) Formation of compound nucleus in dense medium is studied with the method of Multiple Internal Reflections. Results (1) Wave functions of resonance states of \isotope[24]{Mg} are determined by interaction of two \isotope[12]{C} nuclei. (2) Clear maxima of probability of formation of compound nucleus in dense stellar medium are established at first time. (3) Difference between quasibound energies for potential of Woods-Saxon type and folding potentials with the shell-model approximation for wave functions is essential. (4) Formation of the compound nucleus is much more probable in the quasibound states than in states of zero-point vibrations. (5) Only the first quasibound energies for $\isotope[12]{C} + \isotope[12]{C}$ are smaller than the barrier maximums. At these energies compound nuclear system has barrier which prevents its decay going through tunneling phenomenon. This is the new excited nucleus \isotope[24]{Mg} synthesised in the neutron star. \item[Conclusions] Cluster approach with folding potential provides significant modification of picture of formation of compound nucleus, previously obtained concerning the potential of Woods-Saxon type. The highest precision is provided by the folding potential, created by semi-realistic nucleon-nucleon potential and shell-model description of the internal structure of interacting $p$-shell nuclei.

This ongoing work focuses on the development of a methodology for generating a multi-source mapping of astronomical observation facilities. To compare two entities, we compute scores with adaptable criteria and Natural Language Processing (NLP) techniques (Bag-of-Words approaches, sequential approaches, and surface approaches) to map entities extracted from eight semantic artifacts, including Wikidata and astronomy-oriented resources. We utilize every property available, such as labels, definitions, descriptions, external identifiers, and more domain-specific properties, such as the observation wavebands, spacecraft launch dates, funding agencies, etc. Finally, we use a Large Language Model (LLM) to accept or reject a mapping suggestion and provide a justification, ensuring the plausibility and FAIRness of the validated synonym pairs. The resulting mapping is composed of multi-source synonym sets providing only one standardized label per entity. Those mappings will be used to feed our Name Resolver API and will be integrated into the International Virtual Observatory Alliance (IVOA) Vocabularies and the OntoPortal-Astro platform.

We use Legendre polynomials (previously discussed in this context by Pitrou and Cusin [1]) to model signals in pulsar timing arrays (PTA). These replace the (Fourier mode) basis of trigonometric functions normally used for data analysis. The Legendre basis makes it simpler to incorporate pulsar modeling effects, which remove constant-, linear-, and quadratic-in-time terms from pulsar timing residuals. In the Legendre basis, this zeroes the amplitudes of the the first three Legendre polynomials. We use this basis to construct an optimal quadratic cross-correlation estimator $\widehat{\mu}$ of the Hellings and Downs (HD) correlation and compute its variance $\sigma^2_{\widehat{\mu}}$ in the way described by Allen and Romano [2]. Remarkably, if the gravitational-wave background (GWB) and pulsar noise power spectra are (sums of) power laws in frequency, then in this basis one obtains analytic closed forms for many quantities of interest.

The ${}^{\mathsf{12}}\mathsf{C}(\mathsf{p},\gamma)$ reaction cross section is currently under investigation in the low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA). It is being studied using different types of solid targets, and employing two complementary detection techniques: HPGe spectroscopy and activation counting. To reduce systematic uncertainties, targets have been accurately characterized and their degradation under the intense beam of the LUNA-400 accelerator monitored. We present the experimental techniques and the corresponding analyses used to extract the reaction cross section.

Tanmoy Kumar, N. P. S. Mithun, Subhendra Mohanty, Sourov Roy, B. S. Bharath Saiguhan, Santosh Vadawale

Axions and axion-like particles (ALPs) have gained immense attention in searches for beyond Standard Model (BSM) physics. Experiments searching for axions leverage their predicted couplings to Standard Model (SM) particles to look for observable signals. Though weak, these couplings allow axions to be produced abundantly in the interiors of stars such as the Sun. Once created, axions can escape the Sun and while passing through the solar atmosphere, oscillate into photons in the magnetic field producing x-rays. For the first time, we used data from the observation of soft x-rays from the quiet Sun during the 2019-20 solar minimum by the solar x-ray monitor (XSM), onboard India's Chandrayaan-2 lunar exploration mission, to constrain the coupling of axions to photons ($g_{a \gamma \gamma}$). Using the latest models of the solar atmosphere to calculate the magnetic field and plasma frequency, we constrain $g_{a \gamma \gamma} \lesssim (0.47\,-\,2.2) \times 10^{-10}$ GeV$^{-1}$ at 95% confidence level for axion masses $m_a \lesssim 5 \times 10^{-4}$eV.

J. Schueler, H. M. Araújo, S. N. Balashov, J. E. Borg, C. Brew, F. M. Brunbauer, C. Cazzaniga, A. Cottle, D. Edgeman, C. D. Frost, F. Garcia, D. Hunt, M. Kastriotou, P. Knights, H. Kraus, A. Lindote, M. Lisowska, D. Loomba, E. Lopez Asamar, P. A. Majewski, T. Marley, C. McCabe, L. Millins, R. Nandakumar, T. Neep, F. Neves, K. Nikolopoulos, E. Oliveri, A. Roy, T. J. Sumner, E. Tilly, W. Thompson, M. A. Vogiatzi

The separation of overlapping objects presents a significant challenge in scientific imaging. While deep learning segmentation-regression algorithms can predict pixel-wise intensities, they typically treat all regions equally rather than prioritizing overlap regions where attribution is most ambiguous. Recent advances in instance segmentation show that weighting regions of pixel overlap in training can improve segmentation boundary predictions in regions of overlap, but this idea has not yet been extended to segmentation regression. We address this with Overlap-Aware Segmentation of ImageS (OASIS): a new segmentation-regression framework with a weighted loss function designed to prioritize regions of object-overlap during training, enabling extraction of pixel intensities and topological features from heavily obscured objects. We demonstrate OASIS in the context of the MIGDAL experiment, which aims to directly image the Migdal effect--a rare process where electron emission is induced by nuclear scattering--in a low-pressure optical time projection chamber. This setting poses an extreme test case, as the target for reconstruction is a faint electron recoil track which is often heavily-buried within the orders-of-magnitude brighter nuclear recoil track. Compared to unweighted training, OASIS improves median intensity reconstruction errors from -32% to -14% for low-energy electron tracks (4-5 keV) and improves topological intersection-over-union scores from 0.828 to 0.855. These performance gains demonstrate OASIS's ability to recover obscured signals in overlap-dominated regions. The framework provides a generalizable methodology for scientific imaging where pixels represent physical quantities and overlap obscures features of interest. All code is openly available to facilitate cross-domain adoption.

From catalogs of gravitational-wave transients, the population-level properties of their sources and the formation channels of merging compact binaries can be constrained. However, astrophysical conclusions can be biased by misspecification or misestimation of the population likelihood. Despite detection thresholds on the false-alarm rate (FAR) or signal-to-noise ratio (SNR), the current catalog is likely contaminated by noise transients. Further, computing the population likelihood becomes less accurate as the catalog grows. Current methods to address these challenges often scale poorly with the number of events and potentially become infeasible for future catalogs. Here, we evaluate a simple remedy: increasing the significance threshold for including events in population analyses. To determine the efficacy of this approach, we analyze simulated catalogs of up to 1600 gravitational-wave signals from black-hole mergers using full Bayesian parameter estimation with current detector sensitivities. We show that the growth in statistical uncertainty about the black-hole population, as we analyze fewer events but with higher SNR, depends on the source parameters of interest. When the SNR threshold is raised from 11 to 15 -- reducing our catalog size by two--thirds -- we find that statistical uncertainties on the mass distribution only grow by a few 10% and constraints on the spin distribution are essentially unchanged; meanwhile, uncertainties on the high-redshift cosmic merger rate more than double. Simultaneously, numerical uncertainty in the estimate of the population likelihood more than halves, allowing us to ensure unbiased inference without additional computational expense. Our results demonstrate that focusing on higher-significance events is an effective way to facilitate robust astrophysical inference with growing gravitational-wave catalogs.