Papers for Thursday, Jul 17 2025

The Earth possesses many environmental extremes that mimic conditions on extraterrestrial worlds. The stratosphere at 30-40 km altitude closely resembles the surface of Mars in terms of pressure, temperature, and radiation levels (UV, proton, and Galactic cosmic rays). While microbial life in the troposphere is well documented, the true upper limit of Earth's biosphere remains unclear. The stratosphere offers a promising environment to explore microbial survival in such extreme conditions. Despite its significance to astrobiology, this region remains largely unexplored due to difficulties in access and avoiding contamination. To address this, we have developed SAMPLE (Stratospheric Altitude Microbiology Probe for Life Existence), a balloon-borne payload designed to collect dust samples from the stratosphere and return them in conditions suitable for lab analysis. The entire system is novel and designed in-house, with weight- and stress-optimized components. The main payload includes three pre-sterilized sampling trays and a controller that determines altitude and governs tray operation. One tray will remain closed during flight (airborne control) and another on the ground (cleanroom control) to monitor contamination. Additional systems include environmental sensors, GPS trackers, cameras, and a Flight Termination Unit (FTU) to end the mission once sampling is complete. A parachute ensures the safe recovery of the payload. Upon retrieving the payload, the sampling trays (including controls) will be sent to a suitable laboratory where the samples will be examined for the presence and nature of collected material.

This white paper highlights the work that is needed to anticipate the challenges and societal impacts of a possible technosignature detection. We recommend practical steps to strengthen NASA's astrobiology agenda, guided by the existing interdisciplinary framework of the SETI PostDetection Hub (est. 2022) at the University of St Andrews (Elliot et al. 2023), which emphasizes comprehensive preparedness across science, society, governance, and communication. NASA can significantly enhance readiness by supporting deep interdisciplinary integration, funding SETI post-detection research infrastructure, and cultivating international collaboration. We outline six key dimensions of readiness-directed evidence-based research: cross-divisional methodologies, humanities and social sciences integration, communication, strategic foresight, and development of resilient global infrastructures.

K2-18b closely orbits a nearby M3 dwarf within its habitable zone, where this planet could be either a super-Earth or a mini-Neptune. Recent studies using transit spectroscopy suggest that it is Hycean in nature, but this classification is currently controversial. We use the N-body integrator rebound and its extension library reboundx to investigate the possibility of exomoons around K2-18b. Due to tidal interactions that induce outward migration, we find that any moons would be extremely unlikely. If formed, their lifetimes would be relatively short, not exceeding 10 Myr assuming Earth-like or Neptune-like tidal parameters for K2-18b. Recent studies estimate the stellar (and system) lifetime as 3 Gyr, which is significantly longer than the tidal migration timescale. We show that exomoons are unlikely to survive around K2-18b due to rapid tidal-driven migration, casting doubt on moon-based habitability scenarios for short-period M-dwarf planets in general.

We present a detailed kinematic study of a sample of 32 massive ($9.5\leqslant\log(M_*/{\rm M_{\odot}})\leqslant10.9$) main-sequence star-forming galaxies (MS SFGs) at $4<z<6$ from the ALMA-CRISTAL program. The data consist of deep (up to 15hr observing time per target), high-resolution ($\sim1$kpc) ALMA observations of the [CII]158$\mu$m line emission. This data set enables the first systematic kpc-scale characterisation of the kinematics nature of typical massive SFGs at these epochs. We find that $\sim50\%$ of the sample are disk-like, with a number of galaxies located in systems of multiple components. Kinematic modelling reveals these main sequence disks exhibit high-velocity dispersions ($\sigma_0$), with a median disk velocity dispersion of $\sim70{\rm kms^{-1}}$ and $V_{\rm rot}/\sigma_0\sim2$, and consistent with dominant gravity driving. The elevated disk dispersions are in line with the predicted evolution based on Toomre theory and the extrapolated trends from $z\sim0$-$2.5$ MS star-forming disks. The inferred dark matter (DM) mass fraction within the effective radius $f_{\rm DM}(<R_{\rm e})$ for the disk systems decreases with the central baryonic mass surface density, and is consistent with the trend reported by kinematic studies at $z\lesssim3$; roughly half the disks have $f_{\rm DM}(<R_{\rm e})\lesssim30\%$. The CRISTAL sample of massive MS SFGs provides a reference of the kinematics of a representative population and extends the view onto typical galaxies beyond previous kpc-scale studies at $z\lesssim3$.

The chemical abundance patterns of near-pristine objects provide important constraints on the properties of the first generations of stars in the Universe. We present the chemical abundances of five very metal-poor ([M/H]<-2.5) sub damped Lyman alpha systems (subDLAs) covering the redshift range $3.6<z<4.3$, identified with the XQ-100 survey. We find that the subDLAs in our sample show consistent chemical abundance patterns (in particular [C/O], [Al/O], and [Fe/O]) with those of very metal-poor DLAs. Based on Voigt profile fitting, the chemical abundance ratios [C/O], [Al/O], and [Si/O] of individual velocity components in at least three of the subDLAs shows some intrinsic scatter. In order to verify these chemical inhomogeneities in absorption components, we present a novel method for computing ionization corrections (ICs) on a component-by-component basis and show that ICs alone cannot explain the variations in [C/O], [Al/O], and [Si/O] between components of the same absorber at ~2 sigma significance. Comparing the observed abundance ratios to the simulated core-collapse supernovae yields of early stellar populations, we find that all individual components of the subDLAs appears to be enriched by progenitor masses of <30 M_sol. The observed inhomogeneities between components can be reproduced by differences in the progenitor mass or supernova explosion energy. As such, the observed chemical inhomogeneities between components can be explained by poorly mixed gas from different nucleosynthetic events.

Emission and absorption line features are important diagnostics for the physics underlying extragalactic astronomy. The interpretation of observed signatures involves comparing against forward modeled spectra from galaxy formation simulations as well as more simplified geometries, while including the complex scattering radiative transfer (RT) of resonant emission lines. Here, we present thor, a modern C++ radiative transfer code focused initially on resonant emission lines. thor is a high-performance, distributed memory MPI-parallel, multi-target code, running on CPUs, GPUs and other accelerators, yielding large $\sim 10-50\rm{x}$ speed-ups compared to previous CPU-only codes. We support multiple grid-based and gridless data structures, enabling comparisons across different hydrodynamical codes as well as toy model geometries. We demonstrate its science capabilities with a number of example use cases across scales: (i) Lyman-alpha RT on simple shell-like gas distributions; (ii) Lyman-alpha RT applied to a high-resolution, high-redshift $z \sim 6$ cosmological hydrodynamical galaxy formation simulation; (iii) Lyman-alpha and Magnesium-II halos, i.e. scattering and emission from the circumgalactic medium of $z \simeq 1-2$ galaxies drawn from cosmological magnetohydrodynamical simulations; (iv) the large-scale cosmic web in gas emission, a $6144^3$ volume-element RT scaling calculation; and (v) synthetic absorption spectra of the Lyman-alpha forest. Extensive verification and benchmarking validates our approach and its computational efficiency.

High-redshift active galactic nuclei (AGN) have long been recognized as key probes of early black hole growth and galaxy evolution. However, modeling this population remains difficult due to the wide range of luminosities and black hole masses involved, and the high computational costs of capturing the hydrodynamic response of gas and evolving radiation fields on-the-fly. In this study, we present a new suite of simulations based on the IllustrisTNG galaxy formation framework, enhanced with on-the-fly radiative transfer, to examine AGN at high redshift (z > 5) in a protocluster environment extracted from the MillenniumTNG simulation. We focus on the co-evolution of black holes and their host galaxies, as well as the radiative impact on surrounding intergalactic gas. The model predicts that black holes form in overdense regions and lie below the local black hole-stellar mass relation, with stellar mass assembly preceding significant black hole accretion. Ionizing photons are primarily produced by stars, which shape the morphology of ionized regions and drive reionization. Given the restrictive black hole growth in the original IllustrisTNG model, we reduce the radiative efficiency from 0.2 to 0.1, resulting in higher accretion rates for massive black holes, more bursty growth, and earlier AGN-driven quenching. However, the resulting AGN remain significantly fainter than observed high-redshift quasars. As such, to incorporate this missing population, we introduce a quasar boosted model, in which we artificially boost the AGN luminosity. This results in strong effects on the surrounding gas, most notably a proximity effect, and large contributions to He ionization.

Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3mm have recently revealed surprising complexity in the circumstellar environment of DFK 52, a red supergiant (RSG) located in the Stephenson 2 massive open cluster. We provide an initial characterisation of the star's mass-loss properties by studying its circumstellar emission in continuum, $^{12}$CO, $^{13}$CO, and SiO rotational lines. We find that DFK 52 is surrounded by an extremely large outflow (up to 50,000 au in radius) that shows complex morphologies in both its molecular and dust emission. The size of the circumstellar medium is unprecedented, even when compared with other known extreme RSGs, and its lower luminosity indicates that its mass ejection mechanism may be unique among this population. The molecular emission can be partially reproduced by a two-component model consisting of a fast (27 km/s) detached equatorial component with $M{\sim}0.05$ $M_{\odot}$ and a slow (10 km/s) spherical envelope with $\dot{M}\sim3\times10^{-6}$ $M_{\odot}$ yr$^{-1}$. This suggests that DFK 52 underwent a dramatic mass-loss event $\sim$4000 years ago, but has since transitioned into having a slower more symmetric mass loss. We conservatively estimate a total mass of $0.1-1$ $M_{\odot}$ in the complex extended regions of the outflow. The uncertain nature of the dramatic mass loss warrants extensive follow-up of this likely supernova progenitor.

The 21-cm forest, comprising narrow absorption features imprinted on the radio spectra of high-redshift radio-loud quasars by intervening neutral hydrogen, offers a uniquely sensitive probe of the thermal state of the neutral intergalactic medium (IGM) during the epoch of reionization. Although over 30 such quasars are now known at $z > 5.5$, the signal remains elusive in practice, owing to instrumental noise, the intrinsic weakness of the absorption features, and the limited brightness of available background sources. Recent studies have focused on the one-dimensional transmission power spectrum as a statistical observable, but this approach also demands high signal-to-noise ratios. Here, we present a systematic comparison of five inference pipelines for recovering IGM parameters from mock 21-cm forest spectra at $z = 6$, incorporating realistic instrumental noise and telescope characteristics. We show that likelihood-free inference based on machine learning substantially outperforms traditional Bayesian methods. In particular, our most effective method dispenses with the power spectrum entirely: we use a convolutional U-Net to extract a latent-space encoding of the input spectrum and perform parameter regression using XGBoost. This approach yields accurate constraints on the IGM neutral fraction and X-ray heating efficiency even with a single 50-hour uGMRT sightline, which is an orders-of-magnitude improvement in integration time relative to existing techniques. We publicly release our code, training data, and models. Beyond the 21-cm forest, these results underscore the promise of hybrid deep learning and gradient-boosted inference techniques for extracting physical information from low-SNR data across astrophysics.

The detection of planets in protoplanetary disks has proven to be extremely challenging. In contrast, rings and gaps, usually attributed to planet-disk interactions, have been found in virtually every large protoplanetary (Class II) disk observed at 0.9-1.3 mm with sufficient spatial resolution (5 au). The nearby disk around MP Mus (PDS 66) stands as an exception to this rule, and its advanced age (7-10 Myr) is particularly difficult to reconcile with its apparent lack of substructures. Despite the disk's smooth appearance, Gaia data of MP Mus show a significant proper motion anomaly, signalling the presence of a companion. Here we present ALMA 3 mm observations of the system with comparable high spatial resolution to previous 1.3 mm data. The new observations pierce deeper into the disk midplane and reveal an inner cavity (<3 au) and a ring at 10 au. The disk structure inferred from ALMA observations narrows down the properties of the companion to a gas giant orbiting at 1-3 au, and hydrodynamic simulations further confirm that such a planet can produce the observed cavity. These independent pieces of evidence constitute an indirect but compelling detection of an exoplanet within a protoplanetary disk using Gaia astrometry. MP Mus is the first system in which undetected substructures are revealed thanks to the lower optical depths at longer wavelengths, suggesting that rings and gaps are even more abundant than what is currently believed.

We present the first results from the COS-EDGES survey, targeting the kinematic connection between the ISM and multi-phase circumgalactic medium (CGM) in nine isolated, edge-on galaxies at z~0.2, each probed along its major axis by a background quasar at impact parameters of 13-38kpc. Using VLT/UVES and HST/COS quasar spectra, we analyse MgI, MgII, HI, CII, CIII, and OVI absorption relative to galaxy rotation curves from Keck/LRIS and Magellan/MagE spectra. We find that at lower $D/R_{vir}$ ($D/R_{vir}\leq 0.2$), over 80% of absorption in all ions lies on the side of systemic velocity matching disk rotation, and the optical-depth-weighted median velocity ($v_{abs}$) is consistent with the peak rotation speed. At higher $D/R_{vir}$ ($D/R_{vir} > 0.2$), the kinematics diverge by ionisation state: For low ionisation gas, the amount of co-rotating absorption remains >80%, yet $v_{abs}$ drops to 60% of the galaxy rotation speed. For high ionisation gas (OVI), only 60% of the absorption is consistent with co-rotation and $v_{abs}$ drops to 20% of the rotation speed. Furthermore, the velocity widths, corresponding to 50% of the total optical depth ($\Delta v_{50}$) for low ionisation gas is 1.8 times larger in the inner halo than at larger radii, while for CIII and OVI $\Delta v_{50}$ remains unchanged with distance. These results suggest a radially dependent CGM kinematic structure: the inner halo hosts cool, dynamically broad gas tightly coupled to disk rotation, whereas beyond 0.2$R_{vir}$, particularly traced by OVI and HI, the CGM shows weaker rotational alignment and lower velocity dispersion. Therefore, low-ionisation gas likely traces extended co-rotating gas, inflows and/or recycled accretion, while high-ionisation gas reflects a mixture of co-rotating, lagging, discrete collisionally ionised structures, indicating a kinematic stratification of the multi-phase CGM. [Abridged]

The Earth's atmospheric turbulence degrades the precision of ground-based astrometry. Here we discuss these limitations and propose that, with proper treatment of systematics and by leveraging the many epochs available from the Korean Microlensing Telescope Network (KMTNet), seeing-limited observations can reach sub-milliarcsecond precision. Such observations may be instrumental for the detection of Galactic black holes via microlensing. We present our methodology and pipeline for precise astrometric measurements using seeing-limited observations. The method is a variant of Gaia's Astrometric Global Iterative Solution (AGIS) that include several detrending steps. Tests on 6,500 images of the same field, obtained by KMTNet with typical seeing condition of 1 arcsecond and pixel scale of 0.4 arcsecond, suggest that we can achieve, at the bright end (mag <17), relative proper motion precision of 0.1-0.2 mas/yr, over a baseline of approximately five years, using data from the Cerro Tololo Inter-American Observatory (CTIO) site. The precision is estimated using bootstrap simulations and further validated by comparing results from two independent KMTNet telescopes.

Astrophysical plasmas in relativistic spacetimes, such as black hole accretion flows, are often weakly collisional and require kinetic modeling to capture non-local transport and particle acceleration. However, the extreme scale separation between microscopic and macroscopic processes limits the feasibility of fully kinetic simulations. A covariant guiding center formalism has recently been derived to address this challenge in curved spacetimes. We present a new hybrid numerical algorithm based on this formalism, which evolves the trajectories of charged particles over macroscopic timescales in GRMHD backgrounds. To address numerical instabilities in the equations of motion, we develop a semi-implicit integrator that ensures stable evolution in strong-field environments. We apply our method to GRMHD simulations of black hole accretion flows, demonstrating its accuracy and efficiency across a range of physical conditions.

Binaries of two white dwarfs (WDs) are an important class of astrophysical objects that are theorized to lead to Type Ia supernovae and are also used to gain insight into complex processes involved in stellar binary evolution. We report the discovery of SDSS~J090618.44+022311.6, a rare post-common envelope binary of a hydrogen atmospheric DA WD and a DQ WD which shows carbon absorption features, and is only the fourth such binary known. We combine the available spectroscopic, photometric, and radial velocity data to provide a self-consistent model for the binary and discuss its history as a binary DA+DQ. The system has a period of 31.17 hours with masses of 0.42 M$_{\odot}$ for DA WD and 0.49 M$_{\odot}$ for DQ WD. The corresponding cooling ages point to an Algol type of evolution with the lower mass star evolving into a DA WD first and later the massive DQ WD is formed. The system has a merger timescale of 450 Gyrs and will lead to the formation of a massive WD. With this, the number of known DA+DQ WD binaries has increased to four, and we find that their stellar properties all lie in the same range. Detailed study of more such systems is vital to understand common processes involved in the formation of this rare class of binaries and give insights towards the broader picture of WD spectral evolution.

Extra-tidal features around globular clusters (GCs) are tracers of their disruption, stellar stream formation, and their host's gravitational potential. However, these features remain challenging to detect due to their low surface brightness. We conduct a systematic search for such features around 19 GCs in the DECam Local Volume Exploration (DELVE) survey Data Release 2, discovering a new extra-tidal envelope around NGC 5897 and find tentative evidence for an extended envelope surrounding NGC 7492. Through a combination of dynamical modeling and analyzing synthetic stellar populations, we demonstrate these envelopes may have formed through tidal disruption. We use these models to explore the detectability of these features in the upcoming Legacy Survey of Space and Time (LSST), finding that while LSST's deeper photometry will enhance detection significance, additional methods for foreground removal like proper motions or metallicities may be important for robust stream detection. Our results both add to the sample of globular clusters with extra-tidal features and provide insights on interpreting similar features in current and upcoming data.

Protoplanetary discs around Very Low Mass Stars (VLMS) show hydrocarbon-rich MIR spectra indicative of C/O>1 in their inner discs, in contrast to discs around higher-mass hosts which mostly show O-bearing species. One scenario proposed to elevate C/O in VLMS inner discs is the advection of O-depleted gas from the outer disc. However, if CO gas remains abundant, C/O can be at most ~1. We test if chemical transformation of CO into other species allows this transport scenario to produce C/O significantly above 1. We track the evolving inner disc C/H and O/H with a 1D disc evolution code. We model the transport of molecules in gas and ice and add conversions of species to represent key reaction pathways at the midplane. We explore the role of disc mass, size, ionization rate, and substructures. The inner disc C/O increases over time due to sequential delivery where O-rich species (e.g. H2O) give way to C-rich species (e.g. CH4). To reach C/O>1, separating C and O is key, hence the liberation of C from gaseous CO by He+ is critical. Ionization drives this chemistry and needs rates >~10^-17 s^-1 for VLMSs for sufficient chemical evolution within a disc lifetime. However, <~10^-17 s^-1 is needed to ensure that C/O stays <1 for the first few Myr in T Tauri discs. While C/O is usually higher for VLMS than T Tauri stars due to faster sequential delivery, C/O significantly above 1 is only produced by combining gas-phase CO destruction with gas advection and radial drift. Sufficient O depletion and hydrocarbon production around VLMSs can then be achieved but may imply higher ionization rates than T Tauris. Observations of older discs may distinguish whether higher ionization rates are indeed needed or faster physical evolution timescales alone are sufficient. CH3OH ice photodissociation at a dust trap between the CH3OH and CH4 snowlines may also liberate C as CH4 gas that can enrich the inner disc.

The detection of gravitational waves (GW) by the LIGO-Virgo-KAGRA (LVK) network has opened up a new era in astrophysics. The identification of the electromagnetic counterparts of GW sources is crucial for multi-messenger astronomy, one way of which is to use galaxy catalogues to guide optical follow-up observations. In this paper, we test the utility of galaxy-targeted approach with mass prioritised galaxy ranking for the ongoing LIGO O4 run. We have used the simulated results for the expected LIGO O4 events and the NED-LVS galaxy catalogue and based our study for small field of view telescopes, specifically the GROWTH-India Telescope (GIT). With the increase in sensitivity of LIGO/Virgo in the ongoing observing run O4, the expected number of total detections have gone up but most of these are also now poorly localised. We show that a larger volume covered in the same field-of-view (FoV) on the sky results in a large increase in the total number of galaxies in each FoV. A significant top-heaviness is observed in the mass-ranked list of galaxies, which still number to a few thousand in most cases. At larger distances, such high numbers of deep follow-up observations are infeasible in most cases rendering galaxy catalogues useful in limited cases, but these are still useful at lower distances where LVK detectors are currently sensitive and where galaxy completeness is higher. We also explore the effect of mass-filling to account for galaxy catalogue incompleteness at large distances. If mass-filled probabilities are considered as the metric for ranking and coverage, we find that the conventional 2D probability search performs better than a 3D galaxy catalogue (without mass-filling) based search at distances larger than 300 Mpc (upto which NED-LVS is ~70% complete), and using 3D mass times probability in each tile performs better for nearby events.

Since 2014, the Pierre Auger Observatory has exploited a dedicated trigger and its very high time resolution to study ELVES and harvest record samples of multiple ELVES using the Fluorescence Detector (FD). In 2017, after extending the readout of trace lengths to 0.9 ms, we started observing other types of light transients from the base of the ionosphere, such as HALOS, which deserved further investigation. In December 2023 and April 2024, we installed two additional cameras (TLECAMs), which allow us to perform simultaneous detection of these transients with higher space resolution and longer integration times. Here, we present our first simultaneous observations of SPRITES and ELVES by both TLECAMs and FD. Furthermore, we describe the Python algorithm based on DBSCAN to automatically detect SPRITES in the videos recorded by our TLECAMs and acquire data efficiently without needing the FD trigger.

We present the results of a search for scandium K$_\alpha$ X-ray fluorescence resulting from $^{44}$Ti electron capture decay in four young supernova remnants. We analyzed archival XMM-Newton data from Tycho's SNR, Kepler's SNR, Cassiopeia A, and SN 1987A. We fit the X-ray spectra in regions of interest with up to four components, thermal and power-law, as needed to fit the spectrum, and add a gaussian to test for extra Sc emission. While all require the line with modest confidence, none represent definitive detections on their own, and all are consistent with previous gamma-ray detections or limits on the $^{44}$Ti mass.

We investigate the chemical evolution of N/O using a sample of 45 local star-forming galaxies (SFGs) from the CLASSY survey. This sample spans a wide range of galaxy properties, with robust determinations of nitrogen and oxygen abundances via the direct-$T_{\rm e}$ method. We explore how N/O relates to density structure, stellar mass, star formation rate (SFR), stellar age, compactness, and gas kinematics. In addition, we compare our results with those of galaxies at $z =2-10$ where N/O ratios were derived from optical or UV nitrogen lines, aiming to identify chemical enrichment pathways across cosmic time. Our analysis shows that the N/O-O/H relation in CLASSY galaxies aligns with the trends seen in local galaxies and extragalactic HII regions, and that galaxies at $z = 2-6$ exhibit similar N/O values, indicating no significant redshift evolution in N/O. We identify a significant correlation between electron density $n_{\rm e}$([S II]) and N/O, suggesting that density structure contributes to the scatter in the N/O-O/H relation. The CLASSY galaxies with high SFRs or compact star formation show elevated N/O, though no strong correlation with stellar mass is found. We also find that high-velocity outflows (v$_{out}$ > 350 km/s) and low mass-loading factors are linked to elevated N/O, indicating that feedback plays a significant role. These results highlight the importance of density, star formation, and feedback from young stellar populations in shaping N/O enrichment and provide key insights for interpreting high-$z$ galaxies observed with JWST.

Quasar sightline observations reveal that low-ionization-state gas corotates with the galaxy disk and often at sub-centrifugal velocities, suggesting that the gas is spiraling towards the galaxy disk. However, while observations ubiquitously detect O VI absorption around low-redshift, $\sim L^*$ star-forming galaxies, the relationship between O VI and the galaxy disk, especially the kinematics, is not well-established. This work focuses on the O VI kinematics and its comparison with that of the low ions and galactic disk rotation. We present observations of 18 pairs of quasars and $z\approx0.2$ star-forming galaxies. All quasar sightlines intersect the circumgalactic medium (CGM) within 45$^\circ$ from the galaxy major axes. We show that while individual O VI velocity components do not correlate with disk rotation, the bulk of O VI gas in individual sightlines rarely counter-rotates. We then match O VI velocity components with those of low ions by minimizing the difference of their velocity centroids. The O VI velocity components with successful low-ion matches are typically found at small sightline impact parameters and are more likely to corotate with the disk. We suggest that the low-ion-matched O VI velocity components trace the gas co-spatial with the low ions near the extended disk plane in the inner CGM, whereas those without low-ion matches represent the gas at large 3D radii. While the gas at large radii is theoretically expected to kinematically correlate with the disk angular momentum, this correlation is expected to be weaker due to the higher turbulent to mean rotation velocity ration at large radii, consistent with our results.

We have previously studied several elements in 58 selected bulge spheroid stars, based on spectral lines in the H-band. We now derive the abundances of the less-studied elements phosphorus (P; Z=15), sulphur (S; Z=16), and potassium (K; Z=19). The abundances of P, S, and K in 58 bulge spheroid stars are compared both with the results of a previous analysis of the data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), and with a few available studies of these elements. We derive the individual abundances through spectral synthesis, using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project. We provide recommendations for the best lines to be used for the studied elements among those in the H-band. We also compare the present results, together with literature data, with chemical-evolution models. Finally, the neutrino-process was taken into account for the suitable fit to the odd-Z elements P and K. We confirm that the H-band has useful lines for the derivation of the elements P, S, and K in moderately metal-poor stars. The abundances, plotted together with literature results from high-resolution spectroscopy, indicate that: moderately enhanced phosphorus stars are found, reminiscent results obtained for thick disk and halo stars of metallicity [Fe/H]~-1.0. Therefore, for the first time, we identify this effect to occur in the old stars from the bulge spheroid. Sulphur is an alpha-element and behaves as such. Potassium and sulphur both exhibit some star-to-star scatter, but fit within the expectations from chemical evolution models.

The exoALMA program gave an unprecedented view of the complex kinematics of protoplanetary disks, revealing diverse structures that remain poorly understood. We show that moderate disk warps ($\sim 0.5-2^\circ$) can naturally explain many of the observed large-scale velocity features with azimuthal wavenumber $m = 1$. Using a simple model, we interpret line-of-sight velocity variations as changes in the projected Keplerian rotation caused by warping of the disk. While not a unique explanation, this interpretation aligns with growing observational evidence that warps are common. We demonstrate that such warps can also produce spiral structures in scattered light and CO brightness temperature, with $\sim 10$ K variations in MWC 758. Within the exoALMA sample, warp properties correlate with stellar accretion rates, suggesting a link between the inner disc and outer disc kinematics. If warps cause large-scale kinematic structure, this has far reaching implications for turbulence, angular momentum transport, and planet formation.

(abridged) We consider a secular orbital evolution of a supermassive binary black hole (SBBH) with unequal masses $M_p$ and $M_s < M_p$ in a central part of a non-spherical nuclear star cluster (NSC). When the mass of NSC inside the orbit is smaller than $M_{s}$ dynamical friction becomes inefficient. The subsequent orbital evolution of SBBH is largely governed by perturbing tidal potential of NSC arising from its non-sphericity. When the perturbing potential is mainly determined by quadrupole harmonics with azimuthal number $|m|=2$ the secular dynamics of the SBBH does not conserve any components of the angular momentum and can lead to the formation of highly eccentric orbits. Such orbits can experience an efficient circularization due to emission of gravitational waves (GW). In this Paper we consider this situation in some detail. We study analytically and numerically the orbital evolution taking into account the important effect of Einstein apsidal precession and estimate the largest possible value of $e$, which can be obtained. We then estimate a possibility of fast orbital circularization through emission of gravitation waves on a highly eccentric orbit, with circularization timescale of the order of the orbital period. We find that our mechanism could result in such events on a time scale of the order of or smaller than a few Gyr. It is stressed that for particular values of the model parameters such events may sometimes be distinguished from the ones expected in more standard scenarios, since in our case the eccentricity may remain substantial all the way down to the final merger. It is also noted that our results can be applied to other astrophysical settings, e.g. to study the orbital evolution of a binary star or a proto planetary system inside a massive deformed gas cloud.

Modern digital sky surveys have been acquiring images of billions of galaxies. While these images often provide sufficient details to analyze the shape of the galaxies, accurate analysis of such high volumes of images requires effective automation. Current solutions often rely on machine learning annotation of the galaxy images based on a set of pre-defined classes. Here we introduce a new approach to galaxy image analysis that is based on generative AI. The method simplifies the galaxy images and automatically converts them into a ``skeletonized" form. The simplified images allow accurate measurements of the galaxy shapes and analysis that is not limited to a certain pre-defined set of classes. We demonstrate the method by applying it to galaxy images acquired by the DESI Legacy Survey. The code and data are publicly available. The method was applied to 125,000 DESI Legacy Survey images, and the catalog of the simplified images is publicly available.

Context: Tidal disruption and engulfment events around main-sequence stars, such as the luminous red nova ZTF SLRN-2020 (a candidate planetary-engulfment event), reveal the destruction of close-in giant planets. While current observations focus on stellar accretion and inner dust emission, the fate of the volatile-rich material expelled during disruption remains poorly understood. Aims: We investigate whether the H/He-rich gas expelled from the disrupted planet's envelope and atmosphere can escape the inner system and be gravitationally captured by an outer low-mass planet (a volatile-enriched planet, or VEP), potentially forming a transient atmosphere and producing detectable volatile contamination. Methods: We model the outward diffusion of gas from a tidally stripped giant using two-dimensional hydrodynamical simulations with FARGO3D, complemented by analytical estimates of volatile observability and atmospheric escape. We assess the efficiency of gas capture by outer planets and the survival timescales of the resulting secondary atmospheres under high-energy stellar irradiation. Results: Our simulations show that volatile-rich gas can form a VEP. The resulting envelopes can contain between 1e-10 and 1e-6 Earth masses, up to the mass of Earth's atmosphere, for Earth-like planets, yielding transit depths of tens to several hundred ppm. Such signatures may persist for 1 to 100 million years, depending on planetary mass, orbit, and stellar activity. Conclusions: This scenario offers a viable pathway to form volatile-rich atmospheres in evolved low-mass planets. When accompanied by dynamical signatures such as eccentric orbits, these chemical anomalies may trace past planetary disruption. This framework may help interpret the atmospheric and orbital properties of systems like TOI-421b and WASP-107b, shedding new light on the late-stage evolution of planetary systems.

Understanding the granulation background signal is of vital importance when interpreting the asteroseismic diagnostics of solar-like oscillators. Various descriptions exist in the literature for modelling the surface manifestation of convection, the choice of which affects our interpretations. We aim to evaluate the performance of and preference for various granulation background models for a suite of 3D hydrodynamical simulations of convection across the HR diagram, thereby expanding the number of simulations and coverage of parameter space for which such studies have been made. We take a statistical approach by considering the granulation in power density spectra of 3D simulations, where no biases or systematics of observational origin are present. To properly contrast the performance of the models, we develop a Bayesian nested sampling framework for model inference and comparison. This framework was extended to real stellar data using KIC 8006161 (Doris) and the Sun. We find that multi-component models are consistently preferred over a single-component model, with each tested multi-component model demonstrating merit in specific cases. This occurs for simulations with no magnetic activity, thus ruling out stellar faculae as the sole source of the second granulation component. Like a previous study, we find that a hybrid model with a single overall amplitude and two characteristic frequencies performs well for numerous simulations. Additionally, a tentative third granulation component beyond the value of $\nu_\mathrm{max}$ is seen for some simulations, but its potential presence in observations requires further efforts. Studying the granulation signatures in these simulations paves the way to studying stars with accurate granulation models. This deeper understanding of the granulation signal may lead to complementary methods to existing algorithms for determining stellar parameters.

High-resolution spectroscopy (HRS) plays a crucial role in characterizing exoplanet atmospheres, revealing detailed information about their chemical composition, temperatures, and dynamics. However, inaccuracies in orbital parameters can affect the result of HRS analyses. In this paper, we simulated HRS observations of an exoplanet's transit to model the effects of an offset in transit midpoint or eccentricity on the resulting spectra. We derived analytical equations to relate an offset in transit midpoint or eccentricity to shifted velocities, and compared it with velocities measured from simulated HRS observations. Additionally, we compared velocity shifts in the spectrum of the ultra-hot Jupiter WASP-76b using previously reported and newly measured transit times. We found that transit midpoint offsets on the order of minutes, combined with eccentricity offsets of approximately $0.1$, lead to significant shifts in velocities, yielding measurements on the order of several kilometers per second. Thus, such uncertainties could conflate derived wind measurements.

We explore the use of Swin Transformer V2, a pre-trained vision Transformer, for photometric classification in a multi-survey setting by leveraging light curves from the Zwicky Transient Facility (ZTF) and the Asteroid Terrestrial-impact Last Alert System (ATLAS). We evaluate different strategies for integrating data from these surveys and find that a multi-survey architecture which processes them jointly achieves the best performance. These results highlight the importance of modeling survey-specific characteristics and cross-survey interactions, and provide guidance for building scalable classifiers for future time-domain astronomy.

On July 1st 2025 the third interstellar object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered, with an eccentricity of $e=6.15 \pm 0.01$ and perihelion of $q=1.357\pm0.001$ au. We report our initial visible to near-infrared (420-1000 nm) spectrophotometry of 3I/ATLAS using both the Palomar 200 inch telescope and Apache Point Observatory. We measure 3I/ATLAS to have a red spectral slope of 19 %/100 nm in the 420-700 nm range, and a more neutral 6 %/100 nm slope over 700-1000 nm. We detect no notable emission features such as from C$_2$.

We present a view of the stellar halo in the inner-central regions of the Milky Way (R <~ 10 kpc) mapped by RR Lyrae stars. The combined BRAVA-RR/APOGEE RR Lyrae catalog is used to obtain a sample of 281 RR Lyrae stars located in the bulge region of the Galaxy, but with orbits indicating they belong to the inner-central halo. The RR Lyrae stars in the halo are more metal-poor than the bulge RR Lyrae stars and have pulsation properties more consistent with an accreted population. We use the Milky Way-like zoom-in cosmological simulation Auriga to compare the properties of the RR Lyrae stars to those expected from the "Gaia-Enceladus-Sausage" (GES) merger. The integrals of motions and eccentricities of the RR Lyrae stars are consistent with a small fraction of 6-9 +- 2 % of the inner-central halo RR Lyrae population having originated from GES. This fraction, lower than what is seen in the solar neighborhood, is consistent with trends seen in the Auriga simulation, where a GES-like merger would have a decreasing fraction of GES stars at small Galactocentric radii compared to other accreted populations. Very few of the Auriga inner Galaxy GES-18 particles have properties consistent with belonging to a bulge population with (z_max < 1.1 kpc), indicating that no (or very few) RR Lyrae stars with bulge orbits should have originated from GES.

We present the Dispersion Leverage Coronagraph (DLC), a novel variation of the Achromatic Interfero Coronagraph (AIC) that is designed for optical systems featuring large, dispersive primary objective gratings. DLC was originally designed for the Diffractive Interfero Coronagraph Exoplanet Resolver (DICER), a notional 20m class infrared space telescope utilizing the enhanced one-dimensional angular resolution of large diffraction gratings in order to discover and characterize near-Earth exoplanets. Here we develop the theoretical foundation for DLC, and apply it to DICER as an example use case. We derive important properties of the DLC system including focal plane transmission maps, stellar leakage, residual optical path difference tolerance, and pointing error/jitter considerations. Ultimately, we found that DLC effectively nulls an on-axis target across the entire spectrum in the focal plane, allowing for 2D/lambda diffraction-limited imaging. It requires asymmetrical fine-guidance tolerances on pointing error/jitter. We work through a benchmark DICER design, explaining the need for a second disperser to reduce background from Zodiacal light, and showing that it could plausibly find and characterize approximately 4 nearby, habitable exoplanets around Sun-like stars in a seven year mission; about 30% of the habitable exoplanets within 8 pc were found in our simulation. The DLC may be useful for any application requiring extremely high resolution, close-companion spectroscopy.

We calibrate the Tully-Fisher relation (TFR) with data from the DESI Peculiar Velocity (PV) Survey taken during the Survey Validation (SV) period of the DESI galaxy redshift survey. Placing spectroscopic fibers on the centers and major axes of spatially-extended spiral galaxies identified in the 2020 Siena Galaxy Atlas using the DESI Legacy Surveys, we measure the rotational velocities at 0.33R26 for 1163 (1136 + 27 dwarf) spiral galaxies observed during SV. Using 41 spiral galaxies observed in the Coma Cluster, we find a slope for the TFR of -7.96+/-0.13 AB mag in the r-band, with a scatter about the TFR of 1.07+/-0.02 AB mag. We calibrate the zero-point of the TFR using galaxies with independent distances measured using type Ia supernovae via the cosmological distance ladder. From the SN Ia distances, we measure a zero-point of -19.34(+0.30,-0.29) AB mag in the r-band. We produce a public catalog of the distances to these 1136 spiral galaxies observed during DESI SV as part of the DESI PV Survey with our calibrated TFR. This is, to our knowledge, the first catalog of TFR distances produced with velocities measured at a single point in the disk.

We present SEDONA-GesaRaT, a rapid code for supernova radiative transfer simulation developed based on the Monte-Carlo radiative transfer code SEDONA. We use a set of atomic physics neural networks (APNN), an artificial intelligence (AI) solver for the non-local thermodynamic equilibrium (NLTE) atomic physics level population calculation, which is trained and validated on 119 1-D type Ia supernova (SN Ia) radiative transfer simulation results showing great computation speed and accuracy. SEDONA-GesaRaT has been applied to the 3-D SN Ia explosion model N100 to perform a 3-D NLTE radiative transfer calculation. The spatially resolved linear polarization data cubes of the N100 model are successfully retrieved with a high signal-to-noise ratio using the integral-based technique (IBT). The overall computation cost of a 3-D NLTE spectropolarimetry simulation using SEDONA-GesaRaT is only $\sim$3000 core-hours, while the previous codes could only finish 1-D NLTE simulation, or 3-D local thermodynamic equilibrium (LTE) simulation, with similar computation resources. The excellent computing efficiency allows SEDONA-GesaRaT for future large-scale simulations that systematically study the internal structures of supernovae.

KM3NeT has recently reported the detection of a very high-energy neutrino event, while IceCube has previously set upper limits on the differential neutrino flux above 100 PeV but has yet to observe a neutrino event with an energy comparable to that of the KM3NeT detection. To improve diffuse measurements above 10 PeV, we apply machine learning techniques to enhance atmospheric muon background rejection and directional reconstruction. We utilize a Graph Neural Network (GNN) to perform a classification task that distinguishes neutrinos from high-energy atmospheric muons. The method allows for the rejection of early hits from laterally spread, lower-energy muons in cosmic ray showers without relying on directional reconstruction as a prior. Additionally, a Transformer-based Neural Network is implemented for directional reconstruction. Unlike previous likelihood-based rapid reconstruction algorithms that assume a single muon track, this method makes no prior assumptions about event topology of the particle inside the detector. We demonstrate improved background rejection and reconstruction performance using machine learning techniques. Applications to the development of future Extremely High Energy (EHE) selections are also discussed.

We present the discovery of two intersecting radio shells, likely radio relics, surrounding a compact galaxy group dominated by a massive elliptical galaxy. The shells present as partial, edge-brightened rings with diameters of about 240" (720 kpc) each and resemble a pair of odd radio circles. The central galaxy, WISEA J184105.19-654753.8, which shows signs of interactions, is radio bright, has a stellar mass of 3.1 x 10^11 Msun (for a redshift of zphot = 0.18) and is located in the intersect region. The double radio shell system, which we refer to as ORC J1841-6547 (also known as ORC 6), was detected in 944 MHz radio continuum images obtained with Phased Array Feeds on the Australian Square Kilometre Array Pathfinder (ASKAP). The more prominent, north-western shell may be associated with an X-ray detection, while the weaker, south-eastern shell has no counterpart at non-radio wavelength. We propose outwards moving shocks from galaxy mergers driving into the intragroup medium, re-energising relic radio lobes, as a possible formation scenario for the observed radio shells. We conclude that at least some ORCs are shock-energised relics in the outskirts of galaxy groups, which originate during the merger evolution of the brightest group galaxy.

Follow-up of gravitational-wave events by wide-field surveys is a crucial tool for the discovery of electromagnetic counterparts to gravitational wave sources, such as kilonovae. Machine learning tools can play an important role in aiding search efforts. We have developed a public tool to predict kilonova light curves using simulated low-latency alert data from the International Gravitational Wave Network during observing runs 4 (O4) and 5 (O5). It uses a bidirectional long-short-term memory (LSTM) model to forecast kilonova light curves from binary neutron star and neutron star-black hole mergers in the Zwicky Transient Facility (ZTF) and Rubin Observatory's Legacy Survey of Space and Time filters. The model achieves a test mean squared error (MSE) of 0.19 for ZTF filters and 0.22 for Rubin filters, calculated by averaging the squared error over all time steps, filters, and light curves in the test set. We verify the performance of the model against merger events followed-up by the ZTF partnership during O4a and O4b. We also analyze the effect of incorporating skymaps and constraints on physical features such as ejecta mass through a hybrid convolutional neural network and LSTM model. Using ejecta mass, the performance of the model improves to an MSE of 0.1. However, using full skymap information results in slightly lower model performance. Our models are publicly available and can help to add important information to help plan follow-up of candidate events discovered by current and next-generation public surveys.

The discovery of $N_{\rm pp} = 40$ Jupiter-mass binary objects (JuMBOs) alongside $N_{\rm p} = 500$ free-floating Jupiter-mass objects (JMOs) in the Trapezium cluster's central portion raises questions about their origin \cite{2023arXiv231001231P}. \citet{2024NatAs...8..756W} argue that the rate at which two planets orbiting the same star are stripped by a close encounter can explain about half the observed JuMBOs in the Trapezium cluster. Although, their cross-section calculations agree with our own \citep{2024ScPA....3....1P}, one cannot extrapolate their results into clustered environments because it ignores the dissociation of JuMBOs due to subsequent encounters in the clustered environment. The inability of forming JuMBOs via the proposed scenario either calls for another formation mechanism, or the observed JuMBOs require thorough confirmation.

Coronal mass ejections (CMEs), powerful solar eruptions with massive plasma ejected into the interplanetary space, are caused by the release of the magnetic free enengy stored in coronal electric currents. Photospheric current helicity, defined as the integral of the product of vertical electric current density and vertical magnetic field ($H_c=\int j_zB_z\ dS$), serves as a key parameter in understanding the eruptions. Using a 3D magnetohydrodynamic model, we identify a current helicity reversal pattern associated with the eruption: a pre-eruption decrease and a post-eruption increase. This helicity reversal is attributed to the redistribution of electric currents: before the eruption, currents concentrate toward the polarity inversion line (PIL); after the eruption they move away from the PIL, consistent with the flare ribbon separation, which is caused by the upward progression reconnection site. To validate this pattern, we conducted an observational analysis of 50 $\geq$M5.0 eruptive flares. The results reveal that 58\% of cases exhibited a pre-eruption decrease and 92\% showed the post-eruption increase in current helicity. Detailed analysis of two cases with this reversal suggests that they share the same current redistribution pattern, consistent with the mechanism identified in the simulations. Moreover, the pre-eruption decrease could be observed clearly even in the long-term evolution of the two cases. Current helicity can serve as an indicator of when electric currents are built up for the subsequent eruption, and it has the potential to predict CMEs to some extent.

The $\sim 60\,000$ solar-mass (\MSun) star-cluster R136 (NGC~2070) in the Tarantula Nebula in the Large Magellanic Cloud is the host of at least 55 massive stars ($M \apgt 10$\,\MSun) which move away from the cluster at projected velocities $\gteq 27.5$\,km/s \cite{2024Natur.634..809S}. The origin of the high velocities of such runaway stars have been debated since the 1960s, resulting either from dynamical ejections \citep{1961BAN....15..265B,1961BAN....15..291B} or from supernova explosions \citep{1983ApJ...267..322H}. Due to the Gaia satellite's outstanding precision, we can now retrace the most recently ejected binary star, Mel 34, back to the center of R136 and reconstruct the events that 52\,000 years ago let to its removal from R136, i.e., we establish its dynamical interaction and ejection history. We find that this ejection requires the participation of 5 stars in a strong interaction between a triple composed of the tight massive binary Mel~39 orbited by the star VFTS~590, and the binary star Mel~34. The participation of 5 stars is unexpected because runaway stars were not expected to result from triple interactions \cite{2011Sci...334.1380F}. The deterministic nature of the Newtonian dynamics in the scattering enables us to reconstruct the encounter that ejected Mel~34. We then predict that Mel~39 is a binary star with an 80\,\Msun\, companion star that orbits within $\sim 1^\circ$ in the same plane as Mel~34, and escapes the cluster with a velocity of $\sim 64$\,km/s. The five stars will undergo supernova explosions in the coming 5\,Myr at a distance of $\sim 180$\,pc to $\sim 332$\,pc from their birth location (R\,136). The resulting black hole binaries, however, are not expected to merge within a Hubble time.

The transport of energetic particles in a spatially varying magnetic field is described by the focused transport equation. In the past two versions of this equation were investigated. The more commonly used standard form described a pitch-angle isotropization process but does not conserve the norm. In the current paper we consider the focused transport equation in conservative form also called modified focused transport equation. This equation conserves the norm but does not describe pitch-angle isotropization. We use the previously developed subspace method to solve the focused transport equation analytically and numerically. For a pure analytical treatment we employ the two-dimensional subspace approximation. Furthermore, we consider a higher dimensionality for which one needs to evaluate occurring matrix exponentials numerically. This type of semi-numerical approach is much faster than traditional solvers and, therefore, it is very useful.

We report the discovery of a large-scale structure containing multiple overdensities at $z= 4.54 \pm 0.03$ in the COSMOS field, with the most prominent one likely infalling towards the recently identified Taralay protocluster. We use combined wide-band and narrow-band optical photometry to identify Ly$\alpha$ emitters (LAEs) within a 21 cMpc radius from the submm source J1000+0234, at $z= 4.54$, to identify typical star-forming galaxies that may trace an underlying structure. Our approach selects line emitters as narrow-band excess objects and we use the COSMOS2020 photometric redshift catalog to eliminate potential low-redshift interlopers whose line emission (e.g. [OIII] at $z\sim 0.3$) might be responsible for the observed excess in the narrow band. In comparison with the LAE density in the field, our results point to a mean LAE number overdensity of $\bar\delta = 3$ spanning a region of $27 \times 20 \times 36$ cMpc$^3$, probably evolving into a moderate-mass cluster ($3 - 10 \times 10^{14} \, M_\odot$) at $z\sim 0$. This work supports the idea that submm sources, although offset from the major overdensity peaks, serve as traces of moderately massive, potentially infalling structures.

Gravitational waves (GWs) have provided a new lens through which to view the universe beyond traditional electromagnetic methods. The upcoming space-based gravitational wave mission, Laser Interferometer Space Antenna (LISA), will give us the first glimpse of the sky in mHz gravitational waves, a waveband that contains a rich variety of sources including massive binary black hole (MBBH) mergers. In this work, we investigate the spatial distribution of MBBH mergers versus the galaxy distribution to determine how well LISA could be used as a unique and independent probe of large-scale structure. We compare the two-point correlation function (2pt CF) of MBBH mergers to that of galaxies within the cosmological hydrodynamic simulation IllustrisTNG. Our results show that MBBH mergers exhibit stronger clustering than galaxies at scales less than 10 Mpc $h^{-1}$, particularly at higher redshifts, and that the bias is relatively constant as a function of separation. These findings imply that the spatial distribution of MBBH mergers detectable by LISA could inform the observed galaxy distribution. In addition, this implies that searches for a cosmological background in LISA data could use a prior derived from large-scale structure observations to subtract the MBBH foreground.

The turnover scale of the power spectrum is related to the size of the particle horizon at the matter-radiation equality, which can be used as a standard ruler to constrain cosmological parameters. In this work, we apply a model-independent method to mock datasets to forecast constraints on the turnover scale below a redshift of 0.5, investigating for the first time with a multi-tracer approach. We find that combining the galaxy density with peculiar velocity does not improve the turnover scale constraints for current or currently planned surveys because either the cosmological volume or the effective number density of peculiar velocities is too low. However, we demonstrate that when combining the galaxy power spectrum from 4HS with the HI power spectrum from SKA1-B2, the constraints on the turnover scale improve by $\sim30\%$ compared to using only a single tracer. We demonstrate for the first time that combining DESI, 4HS, and an SKA Phase 1 Band 2 survey could achieve a $\sim5\%$ level constraint on the turnover scale and a $\sim90\%$ probability of detecting the turnover below a redshift of 0.5. Lastly, we also demonstrate that combining the DESI BGS redshift sample with the LRG, ELG, and QSO samples could break the degeneracy between $r_H$ and $\Omega_m$ and improve their constraints by $\sim25\%$ and $\sim45\%$, respectively, compared to only using the high redshift samples. The constraints on the particle horizon at the matter-radiation equality $r_H$ and the matter density $\Omega_m$ could then further improve by $\sim20\%$ and $\sim30\%$, respectively, when combining the full set of DESI redshift tracers with 4HS and SKA1-B2.

Far-infrared (FIR) and mid-infrared (MIR) fine-structure lines (FSLs) provide key diagnostics of physical conditions in the interstellar medium (ISM). Building on empirical relations established in our previous work, we use photoionization models to systematically investigate the emission from both ionized and neutral gas phases in a coherent structure. By applying power-law fits to model parameters, we quantitatively capture how key FIR FSL ratios scale with physical properties such as density, radiation field strength and hardness, and elemental abundances. Our analysis confirms the primary dependencies behind most observed empirical trends and establishes certain FIR FSL ratios as tracers of physical parameters, while revealing that parameter marginalization-particularly in density and the O/H-$U$-$Q_1/Q_0$ relation-plays a crucial role in shaping tight correlations seen in galaxies. We also identify persistent challenges, including degeneracies between ionization parameter and radiation field hardness, uncertainties in neutral gas density, and difficulties in modeling dusty H II regions. We outline the fundamental observational and theoretical limitations of current FIR FSL diagnostics, and highlight prospects for advancing the field through comprehensive, multi-wavelength studies of diverse galaxy populations.

Totally eclipsing contact binaries provide a unique opportunity to accurately determine mass ratios through photometric methods alone, eliminating the need for spectroscopic data. Studying low mass ratio (LMR) contact binaries is crucial for advancing our understanding of binary star evolution and the formation of rare optical transients known as red novae. We identified 143 totally eclipsing contact binaries from the Transiting Exoplanet Survey Satellite. These high-precision light curves reveal a distinct O'Connell effect, which we interpret by introducing a cool spot on the primary star. Training a neural network model that includes cool spot parameters can generate a high-precision light curve 2 orders of magnitude faster than Phoebe. Utilizing the neural network (NNnol3) model combined with the Markov Chain Monte Carlo algorithm, we rapidly derived the fundamental parameters of these systems. By leveraging the relationship between orbital period and semimajor axis using the Random Sample Consensus algorithm, we estimated their absolute parameters. Our analysis identified 96 targets with mass ratios below 0.25, all of which were not listed in any previous catalog, thus signifying the discovery of new LMR system candidates. Assuming all 143 binary systems are affected by a third light during parameter estimation, we train a neural network (NNl3) model considering the third light. Then we calculate the residuals between the mass ratio ql3 (considering the third light) and qnol3 (neglecting it). For these residuals, the 25th percentile (Q1) is 0.012, the median (Q2) is 0.026, and the 75th percentile (Q3) is 0.05.

Generative machine learning models have been demonstrated to be able to learn low dimensional representations of data that preserve information required for downstream tasks. In this work, we demonstrate that flow matching based generative models can learn compact, semantically rich latent representations of field level cold dark matter (CDM) simulation data without supervision. Our model, CosmoFlow, learns representations 32x smaller than the raw field data, usable for field level reconstruction, synthetic data generation, and parameter inference. Our model also learns interpretable representations, in which different latent channels correspond to features at different cosmological scales.

Core-collapse supernovae (CCSNe) may contribute a significant amount of dust in the early universe. Freshly formed coolant molecules (e.g., CO) and warm dust can be found in CCSNe as early as ~100 d after the explosion, allowing the study of their evolution with time series observations. In the Type II SN 2023ixf, we aim to investigate the temporal evolution of the temperature, velocity, and mass of CO and compare them with other CCSNe, exploring their implications for the dust formation in CCSNe. From observations of velocity profiles of lines of other species (e.g., H and He), we also aim to characterize and understand the interaction of the SN ejecta with pre-existing circumstellar material (CSM). We present a time series of 16 near-infrared spectra of SN 2023ixf from 9 to 307 d, taken with multiple instruments: Gemini/GNIRS, Keck/NIRES, IRTF/SpeX, and MMT/MMIRS. The early (t<70 d) spectra indicate interaction between the expanding ejecta and nearby CSM. At t<20 d, intermediate-width line profiles corresponding to the ejecta-wind interaction are superposed on evolving broad P Cygni profiles. We find intermediate-width and narrow lines in the spectra until t<70 d, which suggest continued CSM interaction. We also observe and discuss high-velocity absorption features in H$\alpha$ and H$\beta$ line profiles formed by CSM interaction. The spectra contain CO first overtone emission between 199 and 307~d after the explosion. We model the CO emission and find the CO to have a higher velocity (3000-3500 km/s) than that in Type II-pec SN 1987A (1800 - 2000 km/s) during similar phases (t=199-307 d) and a comparable CO temperature to SN 1987A. A flattened continuum at wavelengths greater than 1.5 $\mu$m accompanies the CO emission, indicating the presence of warm dust forming in the ejecta. The warm dust masses are estimated to be in the range of 1.0-2.3$\times$10$^{-5} M_{\odot}$.

Magnetic reconnection is a process that converts magnetic energy into plasma energy by changing the magnetic field line topology. The outstanding question is why the reconnection rate is $\mathcal{O}(0.01 - 0.1)$ in many astrophysical phenomena, for example solar flares and terrestrial substorms. Previous studies have shown two ideas of Hall reconnection and plasmoid instability. However, there is no consensus on which process is the reason for the fast reconnection. In this paper, we discuss the formation of secondary plasmoids in \rewrite{2D antiparallel collisionless reconnection} using 2.5-dimensional particle-in-cell simulations and discuss whether plasmoid-mediated reconnection occur in collisionless systems by comparing with plasmoid instability in resistive MHD simulations. We find that in collisionless systems secondary plasmoids can indeed form. However, the mass ratio has a strong effect on the formation of secondary plasmoids, and it indicates that secondary plasmoids do not emerge using realistic ion-electron mass ratio ($m_i/m_e = 1836$). Furthermore, we find that there is no enhancement of the reconnection rate due to the secondary plasmoid in the collisionless system, as discussed in the plasmoid-mediated reconnection. Although our simulation $\mathcal{O}(100\lambda_i)$ box is not large enough to discuss astrophysical phenomena such as solar flares, it can reflect a relatively small plasma system such as the Earth's magnetotail.

The dense material in a compact star from a supernova remnant is beyond terrestrial experimentation, so phenomenological modeling is used to match astrophysical observations. This is crucial due to the complex sensitivity of compact star features to dense matter properties. Despite modeling flexibility, certain universal relationships among compact star features hold true, regardless of the matter model. Our study examines these universal relationships, focusing on the moment of inertia, tidal Love number, and quadrupole moment, as well as correlations between non-radial oscillation frequencies and star compactness. We consider baryonic stars with cores of heavier baryons. Our findings show that baryonic stars with cores of heavier baryons follow the universal relations, and the f-mode oscillation frequency's universality relative to tidal deformability is notable, with an error margin under 1$\%$.

The recent detection of the neutrino event KM3-230213A ($\sim$~220 PeV) by the KM3NeT/ARCA telescope, the most energetic ever observed, could represent the long-awaited evidence for a cosmogenic origin, arising from the interaction of an ultra-high-energy cosmic ray with background photons. Its secure confirmation would mark a major advance in high-energy astrophysics. We perform a self-consistent multimessenger transport calculation of protons and their secondary $\gamma$-rays and neutrinos from cosmologically evolving sources, confronting predictions with data from the Pierre Auger Observatory, IceCube, KM3NeT, and the Fermi-LAT isotropic $\gamma$-ray background. A steep sub-ankle proton component saturates the diffuse $\gamma$-ray background and is disfavoured, whereas a hard proton spectrum extending beyond $10^{20}$~eV with evolution $\propto (1+z)^3$ reproduces KM3-230213A without violating any limits. This scenario requires a proton fraction $\lesssim 10$\% at $3\times 10^{19}$~eV and excludes faster-evolving sources. Joint UHE-neutrino and $\gamma$-ray observations thus sharpen constraints on extragalactic cosmic-ray sources and set targets for AugerPrime and next-generation neutrino telescopes.

In this Letter, taking advantage of microwave data from the Expanded Owens Valley Solar Array and extreme-ultraviolet (EUV) data from the Atmospheric Imaging Assembly, we present the first microwave imaging spectroscopy diagnosis for the slow-rise precursor of a major coronal mass ejection (CME) on 2022 March 30. The EUV images reveal that the CME progenitor, appearing as a hot channel above the polarity inversion line, experiences a slow rise and heating before the eruption. The microwave emissions are found to mainly distribute along the hot channel, with high-frequency sources located at the ends of the hot channel and along precursor bright loops underneath the hot channel. The microwave spectroscopic analysis suggests that microwave emissions in the precursor phase are dominated by thermal emission, largely different from the main phase when a significant non-thermal component is present. These results support the scenario that the precursor reconnection, seeming to be moderate compared with the flare reconnection during the main phase, drives the build-up, heating, and slow rise of CME progenitors toward the explosive eruption.

In this work we study a robust, $K_s$-band complete, spectroscopically-confirmed sample of 104 unobscured (Type-1) quasars within the COSMOS and XMM-LSS fields of the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey, at 0.60 < $z$ < 3.41. The quasars are selected via $gJK_s$ colour-space and, with 1.3-GHz flux-densities reaching rms ~ 3.0$\mu$Jy beam$^{-1}$, we find a radio-loudness fraction of 5 per cent. Thanks to the deep, multiwavelength datasets that are available over these fields, the properties of radio-loud and radio-quiet quasars can be studied in a statistically-robust way, with the emphasis of this work being on the active-galactic-nuclei (AGN)-related and star-formation-related contributions to the total radio emission. We employ multiple star-formation-rate estimates for the analysis so that our results can be compared more-easily with others in the literature, and find that the fraction of sources that have their radio emission dominated by the AGN crucially depends on the SFR estimate that is derived from the radio luminosity. When redshift dependence is not taken into account, a larger fraction of sources is classed as having their radio emission dominated by the AGN. When redshift dependence $is$ considered, a larger fraction of our sample is tentatively classed as 'starbursts'. We also find that the fraction of (possible) starbursts increases with redshift, and provide multiple suggestions for this trend.

Spectroscopic studies of massive and luminous O-type stellar atmospheres and winds have primarily been done by using 1D, spherically symmetric and stationary models. Both observations and modern theoretical models show that such stars have highly structured and variable atmospheres and winds. We present first spectral synthesis based on 3D time-dependent unified RHD model atmospheres with winds for O stars. We first carried out time-dependent, 3D simulations of unified atmospheres with winds. We then used 3D radiative transfer to compute surface brightness maps for the optical continuum as well as integrated flux profiles for select diagnostic lines. To derive occupation numbers and source functions, an aNLTE method was used, as well as scattering source functions. Our continuum intensity maps of a prototypical early O star reveal a highly variable and time-dependent surface, characterised by local emergent radiation temperature variations. Our averaged synthetic line profiles of optical absorption lines have large widths, without applying any macro- or microturbulence. From the simulations we find correspondingly large velocity dispersions in the photospheric layers. Additionally, the absorption line EWs are larger than for comparable 1D models. First results using scattering source functions further demonstrate that characteristic features like the softening of the blue edge of strong ultra-violet wind lines are qualitatively well-reproduced by our models. Our 3D simulations clearly predict a highly structured and strongly variable O star surface. First line profile results further suggest that several observed features are naturally reproduced by our models without the need to introduce ad-hoc spectral fitting parameters. We also discuss how using 3D rather than 1D simulations as a basis for future studies may affect the derivation of fundamental stellar parameters.

The spatial diffusion of energetic particles in a magnetic field composed of a large-scale background and a small-scale turbulent component should be expected to be anisotropic. While such anisotropic diffusion has been known for quite a while in first-principle plasma physics and while it is required for an understanding of the transport of cosmic rays in the heliosphere or close to supernova remnants, only in recent years it has also become of particular interest for the modeling of Galactic cosmic ray (GCR) transport in the Milky Way in the context of their residence time and their (local) energy spectra. Also, the large-scale spatial distribution of GCRs is shaped by an anisotropic diffusion in the Galactic magnetic field, which should directly affect both the diffuse gamma-ray and the neutrino emission. We solve the anisotropic diffusive transport of GCRs in the Milky Way using the publicly available transport code CRPropa. The anisotropy of the diffusion is characterized by the ratio between the diffusion coefficient perpendicular and parallel to the local magnetic field $\epsilon = D_\perp / D_\parallel$, where we test different values reaching from nearly parallel transport ($\epsilon = 10^{-3}$) to more isotropic diffusion ($\epsilon = 10^{-1}$). From the three dimensional distribution of GCRs in the Milky Way we calculate the all-sky gamma-ray emission, using the line-of-sight integration framework HERMES. Finally, we demonstrate the impact of the anisotropy in the diffusion on the spatial distribution of the gamma-ray flux and its spectral energy distribution. It shows strong influences by the anisotropy of the diffusion and the magnetic field geometry.

Compact object systems exhibit Quasi-Periodic Oscillations (QPOs) as revealed by peaked features in their power density spectra. It has been known that stochastic variations in the accretion disc will propagate to the corona after a time delay and that the hard X-rays from the corona impinge back on the disc, giving reflection spectral features. Here, we show that the combination of these two effects makes a simple radiative feedback system between the corona and the disc, which naturally produces the observed QPOs whose primary frequency corresponds to the inverse of the time delay. The analytical form of the expected power spectra can be statistically compared with the observed ones. Hence, for the first time, a physical model is used to describe and fit the AstroSat observed power spectra of the black hole systems MAXI J1535-571 and GRS 1915+105, including the QPO, its harmonics, as well as the broadband components.

We present a statistical analysis of the 175 SPARC galactic rotation curves to test the hypothesis of whether the Keplerian velocity tapering at large radii ($v(r)\propto 1/\sqrt{r}$) of the Navarro-Frenk-White (NFW) halo model agrees with observational data. The null hypothesis is Rubin's flat-rotation curve, $v(r)=\text{constant}$ -such as can be obtained from a spherical, isothermal-like density profile, or alternatively with a very prolate halo-. To decide whether we adopt the null (Rubin behaviour) or alternative (NFW behaviour) hypothesis, we evaluate the derivative in each galaxy of $v(r)$ with its last data points. We conclude that the data is presently compatible with the null hypothesis -no taper off, no decline of $v(r)$ is seen.

The Lyman-$\alpha$ forest of high redshift quasars is a powerful probe of the late stages of the Epoch of Reionization (EoR), particularly through the presence of Gunn-Peterson troughs. These troughs span a broad range of lengths (up to $\sim 100$ Mpc), suggesting large-scale coherent structures in the intergalactic medium. We aim to gain insight into the presence, extent, and magnitude of correlations in the Lyman-$\alpha$ forest at $5<z<6.1$, and to quantify the scales over which correlations are significant to inform on the necessary volume for simulating the EoR. Using the extended XQR-30 dataset and accounting for the relevant systematics, we compute the flux correlation matrix and perform an MCMC analysis to quantify the extent and strength of the correlation. To interpret our results, we compare to $1.5^3,\mathrm{Gpc}^3$ lightcones of Lyman-$\alpha$ transmission fluxes from several reionization scenarios, including a fiducial box employing SCRIPT. We detect strong correlations at $z > 5.3$, extending at least tens of Mpc and strongly increasing with redshift. Our results suggest a redshift-dependent correlation length, from $L \leq 26.53\, (68.47)$ Mpc at 1-$\sigma$ (2-$\sigma$) limit at $z = 5.0$ to $L = 252.72^{+272.61}_{-41.61}$ Mpc at $z = 6.1$. In contrast, all simulation models predict shorter correlation lengths ($< 60$ Mpc) and a slower redshift evolution. The presence and redshift-dependence of correlations in the Lyman-$\alpha$ forest on $>200$ Mpc scales at $z=6$ indicates that cosmological simulations should be larger than this scale to adequately sample the Lyman-$\alpha$ forest. Despite implementing a fluctuating UVB and numerous neutral islands at $z<6$, our fiducial SCRIPT-based simulation fails to reproduce the large-scale correlations. It may be that those ingredients are necessary, but not sufficient, to understanding the unfolding of the EoR.

The dark siren method exploits the complementarity between gravitational-wave binary coalescence signals and galaxy catalogs originating from the same regions of space. However, all galaxy catalogs are incomplete, i.e. they only include a subset of all galaxies, typically being biased towards the bright end of the luminosity distribution. This sub-selection systematically affects the dark siren inference of the Hubble constant $H_0$, so a completeness relation has to be introduced that accounts for the missing objects. In the literature it is standard to assume that the missing galaxies are uniformly distributed across the sky and that the galaxy magnitude distribution is known. In this work we develop a novel method which improves upon these assumptions and reconstructs the underlying true galaxy field, respecting the spatial correlation of galaxies on large scales. In our method the true magnitude distribution of galaxies is inferred alongside the spatial galaxy distribution. Our method results in an improved three-dimensional prior in redshift and sky position for the host galaxy of a GW event, which is expected to make the resulting $H_0$ posterior more robust. Building on our previous work, we make a number of improvements, and validate our method on simulated data based on the Millennium simulation.

The phenomenon of magnetic braking is one of the significant physical effects of the magnetic field in rotating molecular clouds. The physical characteristics of the core can affect on the core rotation rate. and one of the important parameter is the core density structure. According to observation, by regarding the power-law density distribution, $r^{-p}$, for molecular cloud cores, using smoothed particle hydrodynamics simulation, the results show that the increasing of density steepness (i.e., larger $p$) leads to the intensity of the toroidal components of the magnetic field and as a result larger $B_{\phi}$-components lead to more transfer of angular momentum to the outward. Thus, results show that the magnetic braking being stronger with increasing density slope in non-uniform molecular core. For example, the rotation of the system can approximately decrease by fifty percent from $p=0.2$ to $p=1.8$ for a non-uniform system.

At this early stage of its passage through our Solar System, 3I/ATLAS, the recently discovered interstellar interloper, has displayed various anomalous characteristics, determined from photometric and astrometric observations. As largely a pedagogical exercise, in this paper we present additional analysis into the astrodynamics of 3I/ATLAS, and hypothesize that this object could be technological, and possibly hostile as would be expected from the 'Dark Forest' resolution to the 'Fermi Paradox'. We show that 3I/ATLAS approaches surprisingly close to Venus, Mars and Jupiter, with a probability of $\lesssim 0.005$\%. Furthermore the low retrograde tilt of 3I/ATLAS's orbital plane to the ecliptic offers various benefits to an Extra-terrestrial Intelligence (ETI), since it allows the object access to our planet with relative impunity. The eclipse by the Sun from Earth of 3I/ATLAS at perihelion, would allow it to conduct a clandestine reverse Solar Oberth Manoeuvre, an optimal high-thrust strategy for interstellar spacecraft to brake and stay bound to the Sun. An optimal intercept of Earth would entail an arrival in late November/early December of 2025, and also, a non-gravitational acceleration of $\sim{5.9} \times 10^{-5}$ au day$^{-2}$, normalized at 1 au from the Sun, would indicate an intent to intercept the planet Jupiter, not far off its path, and a strategy to rendezvous with it after perihelion.

Understanding how well future cosmological experiments can reconstruct the mechanism that generated primordial inhomogeneities is key to assessing the extent to which cosmology can inform fundamental physics. In this work, we apply a quantum metrology tool - the quantum Fisher information - to the squeezed quantum state describing cosmological perturbations at the end of inflation. This quantifies the ultimate precision achievable in parameter estimation, assuming ideal access to early-universe information. By comparing the quantum Fisher information to its classical counterpart - derived from measurements of the curvature perturbation power spectrum alone (homodyne measurement) - we evaluate how close current observations come to this quantum limit. Focusing on the tensor-to-scalar ratio as a case study, we find that the gap between classical and quantum Fisher information grows exponentially with the number of e-folds a mode spends outside the horizon. This suggests the existence of a highly efficient (but presently inaccessible) optimal measurement. Conversely, we show that accessing the decaying mode of inflationary perturbations is a necessary (but not sufficient) condition for exponentially improving the inference of the tensor-to-scalar ratio.

Interstellar Objects are comets and asteroids that formed around other stars but were ejected before they could accrete into exoplanets. They therefore represent a rare opportunity to compare the building blocks of planets in the Solar System to those in other stellar systems. The third Interstellar Object, 3I/ATLAS, is the newest, brightest, potentially largest, and fastest member of this population. We report observations of 3I/ATLAS taken on 2025 July 3 and 4 with the NASA Infrared Telescope Facility just days after its discovery. In r'-band imaging with 'Opihi, we see no obvious lightcurve variability and derive a g'-i' color of 1.06+/-0.11 which is consistent in spectral slope to recent work by D.Z. Seligman et al. (2025) and C. Opitom (2025). We obtained the first near-infrared (NIR) reflectance spectrum of 3I/ATLAS with SpeX. The visible color and NIR spectrum show a linear, red visible slope, a somewhat less red slope between 0.7 and 1.1 $\mu{m}$, and a neutral or slightly blue slope at longer wavelengths. Challenges in modeling the reflectivity of 3I may indicate that this comet has a complex grain size distribution, grain compositions unlike Solar system comets, or both. Like 2I/Borisov, there are no obvious signatures of water ice in the coma of 3I/ATLAS. Observations closer to perihelion will help elucidate whether 3I has less water than anticipated or whether the Interstellar Objects might retain and release their ices somewhat differently than Solar System comets do.

Cold brown dwarf atmospheres are good training grounds for analyzing temperate giant planets. WISEP J173835.52+273258.9 (WISE 1738) is an isolated Y0 brown dwarf with a temperature between 350-400 K, at the T-Y transition. While its near-infrared spectrum has been studied, bulk properties and chemistry remain uncertain. We analyze new JWST MIRI medium-resolution spectra (5-18 micron), combined with near-infrared spectra (0.98-2.2 micron) from HST/WFC3 and Gemini/GNIRS, to better constrain WISE 1738's atmosphere and physical parameters. We use Neural Posterior Estimation (NPE) with a cloud-free petitRADTRANS model and evaluate results using posterior checks, coverage, and L-C2ST diagnostics. Our retrieval confirms previous constraints on H2O, CH4, and NH3, and for the first time constrains CO, CO2, and 15NH3. We find evidence of disequilibrium chemistry through CO and CO2 abundances not expected under equilibrium. Estimated properties are temperature 402 (+12,-9) K, log g 4.43 (+0.26,-0.34) cm/s2, mass 13 (+11,-7) M_Jup, radius 1.14 (+0.03,-0.03) R_Jup, and bolometric luminosity -6.52 (+0.05,-0.04) log L/L_sun. Evolutionary models suggest an age between 1 and 4 Gyr, consistent with a 6-hour rotation. We place an upper bound on 15NH3, implying a 3-sigma lower limit on the 14N/15N ratio of 275. We also derive a C/O ratio of 1.35 (+0.39,-0.31) and metallicity of 0.34 (+0.12,-0.11), without accounting for oxygen sequestration.

The elastic properties of the neutron star crust are thought to play a crucial role in various phenomena of neutron stars (glitches, oscillations, gravitational wave emission) and should be described quantitatively to model these phenomena. The fundamental problem of this description is associated with the polycrystalline nature of the crust: similar to terrestrial materials, the elastic moduli, strictly speaking, depend on the shape and orientation of crystallites, but for the crust, they are unknown. As a result, some assumptions are generally required to predict the elastic properties or constrain their possible range. In this paper, we follow the commonly believed assumption that the crust is (locally) isotropic, which allows us to describe elastic properties by two (effective) parameters: bulk and shear moduli. The bulk modulus is well determined by the Voigt-Reuss bounds, and we constrain the shear modulus by applying, for the first time in astrophysics of compact stars, the variational Hashin-Shtrikman approach, based on the additional assumption that there are no correlations in the orientation of crystallites. We analyse the Hashin-Shtrikman bounds for the one-component crust taking into account the electron screening and the motion of the nuclei, and for two-component static crystals. In particular, we demonstrate that within applied assumptions the effective shear modulus should be lower than the Voigt estimate, typically applied in the astrophysical literature.

Context. Dust is a fundamental component of the interstellar medium (ISM) and plays a critical role in galaxy evolution. Dust grains influence the ISM by cooling the gas, altering its chemistry, and absorbing stellar radiation, re-emitting it at longer wavelengths in the far-infrared (FIR) and sub-millimeter regimes. The cold dust component, which dominates the dust mass, is primarily heated by stellar radiation, including both young, massive stars and the diffuse emission from older stars. Understanding dust heating is essential to trace the connection between stellar populations and their environments. Aims. We aim to identify the dominant heating mechanisms of the cold dust in typical nearby spiral galaxies and explore the contributions of young and evolved stars to dust heating. Methods. Using 18 large, face-on spiral galaxies from the DustPedia project, we apply two complementary approaches: (1) correlation analysis between dust temperature (T_dust), SFR surface density (Sigma_SFR), and stellar mass surface density (Sigma_Mstar); and (2) study of the relationship between T_dust and dust mass surface density (Sigma_dust). Results. T_dust peaks at ~24 K in galaxy centers and drops to ~15 K at large radii. Galaxies with and without AGNs show similar T_dust profiles. For ~72% of the sample, both methods agree on the dominant heating source. Overall, we find that both young and evolved stars contribute to dust heating, with their relative roles varying between galaxies.

We present the first application of marked angular power spectra to weak lensing data, using maps from the Subaru Hyper Suprime-Cam Year 1 (HSC-Y1) survey. Marked convergence fields, constructed by weighting the convergence field with non-linear functions of its smoothed version, are designed to encode higher-order information while remaining computationally tractable. Using simulations tailored to the HSC-Y1 data, we test three mark functions that up- or down-weight different density environments. Our results show that combining multiple types of marked auto- and cross-spectra improves constraints on the clustering amplitude parameter $S_8\equiv\sigma_8\sqrt{\Omega_{\rm m}/0.3}$ by $\approx$43\% compared to standard two-point power spectra. When applied to the HSC-Y1 data, this translates into a constraint on $S_8 = 0.807\pm 0.024$. We assess the sensitivity of the marked power spectra to systematics, including baryonic effects, intrinsic alignment, photometric redshifts, and multiplicative shear bias. These results demonstrate the promise of marked statistics as a practical and powerful tool for extracting non-Gaussian information from weak lensing surveys.

In order to develop a consistent quantum theory of gravity, we must understand the nature of spacetime at the Planck scale. In particular if it exhibits quantum fluctuations, they may cause propagating particles to evolve in an apparently non-unitary manner. Neutrinos, which interact only via the weak force and gravity, maintain quantum coherence while propagating over large distances. Thus, neutrino oscillations serve as a precise interferometer to search for Planck-scale fluctuations of spacetime. The IceCube Neutrino Observatory is the world's largest neutrino telescope, located in the Antarctic icecap. We search the data on atmospheric neutrinos detected by IceCube in the energy range 0.5-100 TeV to test for neutrino decoherence. In this contribution, we present the sensitivity of the analysis, which shows significant improvement compared to previous IceCube results as a result of improved reconstruction and a larger sample of events.

The transport of chemical elements in stellar interiors is one of the greatest sources of uncertainties of solar and stellar modelling. The Sun, with its exquisite spectroscopic, helioseismic and neutrino observations, offers a prime environment to test the prescriptions used for both microscopic and macroscopic transport processes. We study in detail the impact of various formalisms for atomic diffusion on helioseismic constraints in both CLES (Scuflaire et al., 2008a) and Cesam2k2 (Morel and Lebreton 2008; Marques et al. 2013; Deal et al. 2018) models and compare both codes in detail. Moreover, due to the inability of standard models using microscopic diffusion to reproduce light element depletion in the Sun (Li, Be), another efficient process must be included to reproduce these constraints (rotation-induced: Eggenberger et al. 2022, overshooting -- or penetrative convection -- below the convective envelope: Thévenin et al. 2017, or ad hoc turbulence: Lebreton and Maeder 1987; Richer, Michaud, and Turcotte 2000). However, introducing such an extra mixing leads to issues with the CNO neutrino fluxes (see Buldgen et al. 2023), which seem to be systematically lower than the Borexino observations (Appel et al., 2022. Another key aspect to consider when reconciling models with neutrino fluxes is the impact of electronic screening (Mussack and Däppen, 2011).

Distinguishing the component spectra of double-line spectroscopic binaries (SB2s) and extracting their stellar parameters is a complex and computationally intensive task that usually requires observations spanning several epochs that represent various orbital phases. This poses an especially significant challenge for large surveys such as Gaia or LAMOST, where the number of available spectra per target is often not enough for a proper spectral disentangling. We present a new approach for characterizing SB2 components from single-exposure spectroscopic observations. The proposed tool uses deep neural networks to extract the stellar parameters of the individual component spectra that comprise the single exposure, without explicitly disentangling them or extracting their radial velocities. The neural networks were trained, tested, and validated using simulated data resembling Gaia RVS spectra, which will be made available to the community in the coming Gaia data releases. We expect our tool to be useful in their analysis.

We present a search for short-duration gravitational-wave transients in data from the first eight months of Advanced LIGO-Virgo-KAGRA's fourth observing run, denoted O4a. We use four analyses which are sensitive to a wide range of potential signals lasting up to a few seconds in the 16-4096 Hz band. Excluding binary black hole merger candidates that were already identified by low-latency analyses, we find no statistically significant evidence for other gravitational-wave transients. We measure the sensitivity of the search for representative signals, including sine-Gaussians, Gaussian pulses, and white-noise bursts with different frequencies and durations, adopting a false alarm rate of 1 per 100 years as detection threshold. Depending on signal type, we find improvements over previous searches by factors of 2 to 10 in terms of sensitivity to strain amplitude and of 90% confidence upper limit on the rate density of sources. We also evaluate a variety of core-collapse supernova models and find that, for some models, the search could have detected gravitational waves from stellar core-collapse throughout the Milky Way. Finally, we consider neutron star f-modes associated with pulsar glitches and find that, assuming a source similar to the Vela Pulsar, the search could have detected a gravitational-wave signal from a glitch with fractional frequency change as small as $\sim 2$ to $6 \times 10^{-5}$ depending on the neutron star mass.

We derive constraints on the neutrino mass using a variety of recent cosmological datasets, including DESI BAO, the full-shape analysis of the DESI matter power spectrum and the one-dimensional power spectrum of the Lyman-$\alpha$ forest (P1D) from eBOSS quasars as well as the cosmic microwave background (CMB). The constraints are obtained in the frequentist formalism by constructing profile likelihoods and applying the Feldman-Cousins prescription to compute confidence intervals. This method avoids potential prior and volume effects that may arise in a comparable Bayesian analysis. Parabolic fits to the profiles allow one to distinguish changes in the upper limits from variations in the constraining power $\sigma$ of the different data combinations. We find that all profiles in the $\Lambda$CDM model are cut off by the $\sum m_\nu \geq 0$ bound, meaning that the corresponding parabolas reach their minimum in the unphysical sector. The most stringent 95% C.L. upper limit is obtained by the combination of DESI DR2 BAO, Planck PR4 and CMB lensing at 53 meV, below the minimum of 59 meV set by the normal ordering. Extending $\Lambda$CDM to non-zero curvature and $w_0w_\mathrm{a}$CDM relaxes the constraints past 59 meV again, but only $w_0w_\mathrm{a}$CDM exhibits profiles with a minimum at a positive value. Using a combination of DESI DR1 full-shape, BBN and eBOSS Lyman-$\alpha$ P1D, we successfully constrain the neutrino mass independently of the CMB. This combination yields $\sum m_\nu \leq 285$ meV (95% C.L.). The addition of DESI full-shape or Lyman-$\alpha$ P1D to CMB and DESI BAO results in small but noticeable improvement of the constraining power of the data. Lyman-$\alpha$ free-streaming measurements especially improve the constraint. Since they are based on eBOSS data, this sets a promising precedent for upcoming DESI data.

The Galactic fast radio burst (FRB) FRB 200428 was associated with a short X-ray burst (XRB) from the magnetar SGR J1935+2154 during one of its active phases. This FRB-associated XRB exhibits distinct properties compared to other typical XRBs, including a significantly higher cutoff energy and a steeper power-law index. Its recovered X-ray light curve shows a multiple-peak structure, with the time of arrival offset from that of the FRB. These unique features imply a special physical link between the FRB and X-ray emissions. In 2022 October, a similar FRB-XRB association was detected from the same source. In this paper, we propose a model in which the observed spectral and temporal features of the associated XRBs can be attributed to the inverse Compton scattering (ICS) of FRB photons by an extreme pair flow around the light cylinder, with a bulk Lorentz factor of $\Gamma\sim10$ and a power-law distribution in the comoving frame, characterized by a typical Lorentz factor $\gamma^\prime_\mathrm{m}\sim5\times 10^4$. This extreme pair flow could originate from the compression of a transient pulse of $\sim10^{40}-10^{41}\mathrm{erg\,s^{-1}}$ and the acceleration through magnetic reconnection in the current sheet during magnetar activity. The Doppler-boosted ICS spectra and the arrival time shifts in such a scenario can well explain the observed features of the FRB 200428-associated XRB and can also account for another associated event in 2022.

The scalar spectral index $n_s$ is a powerful test of inflationary models. The tightest constraint on $n_s$ to date derives from the combination of cosmic microwave background (CMB) data with baryon acoustic oscillation (BAO) data. The resulting $n_s$ constraint is shifted significantly upward relative to the constraint from CMB alone, with the consequence that previously preferred inflationary models are seemingly disfavored by $\gtrsim 2 \sigma$. Here we show that this shift in $n_s$ is the combined effect of a degeneracy between $n_s$ and BAO parameters exhibited by CMB data and the tension between CMB datasets and DESI BAO data under the assumption of the standard cosmological model. Given the crucial role of $n_s$ in discriminating between inflationary models, we urge caution in interpreting CMB+BAO constraints on $n_s$ until the BAO-CMB tension is resolved.

The Generalized SU(2) Proca (GSU2P) theory has recently garnered attention for its potential to describe key phases of cosmic evolution, including primordial inflation and late-time accelerated expansion. However, its full cosmological implications remain unexplored. In this work, we perform a comprehensive analysis of the dynamical properties of the GSU2P theory in a flat, homogeneous, and isotropic spacetime, through a dynamical-system approach. Our analysis reveals the presence of three pairs of fixed points, one of them corresponding to de-Sitter expansion which may represent either a stable or unstable phase in the evolution of the universe. These points, nonetheless, give rise to an indeterminate or infinite Hubble parameter, which renders them cosmologically unviable. Additionally, we find two key pseudostationary states: the ``attractor lines'', along which the system exhibits constant-roll dynamics, and the ``central zone'', characterized by oscillatory radiation-like behaviour of the field. The dynamics within the central zone could represent a graceful exit from the primordial inflationary phase to a radiation dominated phase, or a state of the dark energy component prior to the late-time cosmic acceleration. However, within the central zone, the dynamics of the vector field leads to recurrent instances of a nonphysical expansion rate. The absence of a limit cycle in the central zone further exacerbates the issue, as the system may follow unbounded phase-space trajectories, and the expansion rate becomes complex once it escapes the region. Collectively, these challenges undermine the viability of the GSU2P theory as a cosmological model for cosmic acceleration.

KM3NeT has recently reported an event where a muon of energy $120^{+110}_{-60}$ PeV was observed at its ARCA detector, which can stem from a very high-energy neutrino interaction in the vicinity of the detector. Besides revolutionizing our understanding of high-energy neutrino sources, this event can serve as a valuable probe for studying Beyond the Standard Model (BSM) interactions of neutrinos. In this work, we study the dark matter (DM)-neutrino interaction by assuming the neutrino for the event KM3-230213A is originated from a blazar. The flux of such neutrinos, traveling through DM distributed across astrophysical and cosmological scales, can get attenuated due to DM interactions. The detection of such event by KM3NeT allows us to place constraints on the interaction cross section at highest-ever neutrino energy. We derive both conservative constraints-neglecting flux attenuation from the host halo-and optimistic ones by including host halo contributions. Our results show that the energy-independent constraints are weaker than previous bounds. For energy-dependent case, the extreme energy of the event allows us to set some of the strongest limits on scattering cross sections. In future, more such neutrino events with well-understood origin will be essential in constraining or potentially discovering DM-neutrino interactions.

In the 1960s and 1970s a series of observations and theoretical developments highlighted the presence of several anomalies which could, in principle, be explained by postulating one of the following two working hypotheses: (i) the existence of dark matter, or (ii) the modification of standard gravitational dynamics in low accelerations. In the years that followed, the dark matter hypothesis as an explanation for dark matter phenomenology attracted far more attention compared to the hypothesis of modified gravity, and the latter is largely regarded today as a non-viable alternative. The present article takes an integrated history and philosophy of science approach in order to identify the reasons why the scientific community mainly pursued the dark matter hypothesis in the years that followed, as opposed to modified gravity. A plausible answer is given in terms of three epistemic criteria for the pursuitworthiness of a hypothesis: (a) its problem-solving potential, (b) its compatibility with established theories and the feasibility of incorporation, and (c) its independent testability. A further comparison between the problem of dark matter and the problem of dark energy is also presented, explaining why in the latter case the situation is different, and modified gravity is still considered a viable possibility.

The dark matter may consist of multiple species that interact differently. We show that a species that is cosmologically subdominant but highly collisional can pile up and become dominant in deep gravitational wells, such as those of white dwarfs and neutron stars.

We propose a novel cogenesis mechanism by utilising the two-body decay of heavy vector-like fermions to dark matter (DM) $\chi$ and right chiral part of light Dirac neutrino $\nu_R$ via the electromagnetic dipole operator. This leads to generation of asymmetry in dark fermion $\chi$ as well as $\nu_R$ with the latter getting transferred to left-handed lepton doublets via Yukawa interactions with a neutrinophilic Higgs doublet. While lepton asymmetry is converted into baryon asymmetry of the Universe via electroweak sphalerons, the dark fermion asymmetry results in asymmetric dark matter. Since CP asymmetries in lepton and dark sector are equal and opposite due to net lepton number conservation, DM mass is restricted to a fixed value $\sim \mathcal{O}(1)$ GeV. Long-lived nature of DM keeps indirect detection prospects at gamma-ray telescopes alive while thermalised light Dirac neutrinos lead to observable dark radiation at cosmic microwave background (CMB) experiments. Heavy vector-like fermions can be probed at terrestrial experiments via their electromagnetic dipole interactions.

Event time series are sequences of discrete events occurring at irregular time intervals, each associated with a domain-specific observational modality. They are common in domains such as high-energy astrophysics, computational social science, cybersecurity, finance, healthcare, neuroscience, and seismology. Their unstructured and irregular structure poses significant challenges for extracting meaningful patterns and identifying salient phenomena using conventional techniques. We propose novel two- and three-dimensional tensor representations for event time series, coupled with sparse autoencoders that learn physically meaningful latent representations. These embeddings support a variety of downstream tasks, including anomaly detection, similarity-based retrieval, semantic clustering, and unsupervised classification. We demonstrate our approach on a real-world dataset from X-ray astronomy, showing that these representations successfully capture temporal and spectral signatures and isolate diverse classes of X-ray transients. Our framework offers a flexible, scalable, and generalizable solution for analyzing complex, irregular event time series across scientific and industrial domains.

With laboratory experiments we investigate the ejecta of low-velocity (~m/s) impacts into multi-scale granular media and compare them against ejecta from impacts into mono-scale media. Impacts are into a 50 cm diameter galvanized washtub filled with fine sand that has larger diameter gravel buried below the surface is filmed with two high-speed cameras. The resulting ejecta curtain consists mainly of fine sand, and has a complex asymmetric structure that depends on the location and interaction of the ejecta with the larger gravel grains mixed into the sand. To characterize the highly heterogeneous ejecta curtain we combine three analysis techniques: Particle tracking measures the ejecta velocities and ejecta angles best in low density regions, while particle image velocimetry (PIV) elucidates average motion in dense regions, and histogram of oriented gradients (HOG) which captures directions of motion against a patterned background. We find significant asymmetries in the multi-scale ejecta's velocity distributions and ejection angles compared to the symmetry seen in the ejecta from impacts into mono-scale media. Our experiments show that larger grains under the surface impede and direct ejecta along preferential paths during the impact process.

We investigate the matter current couplings with the scalar degrees of freedom originated from the torsion in Einstein-Cartan (EC) gravity. It has been shown in previous studies that the presence of the operators consisting of torsion components up to dimension four can naturally induce a (pseudo-)scalar degree of freedom, the scalaron. In this work, we consider the couplings between torsion and matter currents in this framework, and show that they can lead to couplings between these currents and the scalaron in the equivalent metric theory. We consider both gauge-invariant and gauge-dependent currents, showing general results and several concrete examples. These results are useful for the discussion of particle production processes after inflation in the EC framework, such as reheating and baryogenesis, and show the connection to the QCD $\theta$ term.

We present the public release of the low-frequency atlas of continuous gravitational waves, covering signals with frequencies from 20 Hz to 200 Hz and frequency derivatives from -5e-11 to 5e-11 Hz/s. Compared to the previous atlas releases, this version demonstrates significant improvements in sensitivity and sky resolution. In the most sensitive region even the worst-case upper limits on gravitational wave strain are below 1e-25. The atlas data is being released ahead of the completion of the full follow-up analysis.

The standard $\Lambda$CDM model, based on the highly symmetric FLRW geometry, has successfully explained a wide range of cosmological observations. However, it faces unresolved issues, including CMB anomalies, the nature of dark matter, and the matter-antimatter asymmetry. These challenges highlight the limitations of the standard framework and raise questions about the validity of the assumed isotropic background geometry. A natural direction is to explore more general cosmological models that relax this assumption, potentially offering new insights into these problems. In this work, we examine a geometric approach to investigating the matter-antimatter asymmetry, grounded not in physics beyond the Standard Model, but in the structure of spacetime itself. While related questions have been raised previously in specific contexts, here we focus on the Bianchi IX cosmological model, motivated by its relevance to early-universe dynamics through the BKL conjecture and its potential role in generating angular momentum via global rotation. We study the Dirac spinor field in this background and derive the corresponding Dirac equation. Our goal is to investigate how spatial anisotropies and rotation can induce spectral asymmetries between particles and antiparticles. This paper lays the groundwork for a follow-up study analyzing specific solutions and their physical implications on matter-antimatter asymmetry.

We consider the hypothetical possibility that non-stationary glitch features in the noise of ground-based gravitational-wave detectors could be produced by small dark matter clumps that pass through the earth in the vicinity of gravitational-wave detectors. We first derive the gravitational-wave strain that would be generated by the passage of such a dark matter clump. We find that the strain is primarily sourced by the Newtonian gravitational acceleration of the mirrors toward the clump and by the Shapiro time delay of the photons in the laser beams as they pass through the gravitational potential created by the dark matter clump. We also find that the Newtonian acceleration effect dominates the gravitational-wave strain for both ground and space-based interferometers. We then compare our dark matter clump, gravitational-wave strain model to 84 Koi-Fish glitches detected during the second observing run of the LIGO/Virgo/KAGRA collaboration through a Markov Chain Monte Carlo Bayesian analysis. We find that all glitches but 9 can be confidently rejected as having originated from dark matter clumps. For the remaining glitches, the dark matter hypothesis cannot be excluded, and the maximum \textit{a posteriori} parameters yield minimum densities of about $10^{-7} {\rm{g}}/{\rm{cm}}^3$, within the model. These results allow us to place the first direct upper limits with gravitational-wave detectors on the local over-density of dark matter in the form of clumps in the local neighborhood of Earth, namely $\rho_{{\rm DM} \, {\rm clumps}} \lesssim 10^{-15} {\rm{g}}/{\rm{cm}}^{-3}$.

We explore the interplay of the post-inflationary QCD axion and a light scalar field for the axion domain wall decay and dark matter (DM). The scalar field possesses a nonzero vacuum expectation value (VEV) during inflation, so that its interaction with the axion effectively serves as an explicit Peccei-Quinn (PQ) violating term. At a temperature below the PQ phase transition, the effective PQ violating interaction generates the axion potential which generally contains multiple degenerate vacua leading to the formation of the axion string-domain wall networks. The following QCD phase transition provides another contribution to the axion potential making domain walls decay before they dominate the Universe. Later, the scalar field starts to relax to the minimum of its potential with a vanishing VEV, turning off the effective PQ violating interaction so that the axion potential is aligned with the QCD vacuum. We keep track of the evolution of the axion-scalar system and discuss the production of the axion DM through the domain wall decay and the (trapped) misalignment. We find that the string-wall network in some cases can decay due to its structural instability, rather than the volume pressure, and the correct axion DM abundance is realized with the decay constant larger than that of the conventional post-inflationary QCD axion without fine tuning.

Heavy neutral leptons (HNLs) are well-motivated new physics candidates. The mixing of sub-GeV HNLs with active neutrinos is severely constrained by cosmology. In particular, the success of Big Bang Nucleosynthesis (BBN) requires the HNL lifetime to be shorter than about 0.02 sec if they were in thermal equilibrium, thus excluding a wide range of mixing angles accessible to terrestrial experiments. In order to justify the laboratory searches in this cosmologically-forbidden region, it is often argued that adding new dark sector decay modes of HNLs can evade the stringent BBN constraint. Here we rule out this possibility and show that, contrary to the naive expectation, HNLs with significant dark decay modes actually lead to stronger cosmological bounds. This is mainly because of the increase in the extra radiation energy density in the Universe around the BBN epoch, which causes observable effects in the primordial helium fraction and $\Delta N_{\rm eff}$. Our result has major implications for laboratory searches of HNLs.

Cosmic strings are predicted in various extensions of the Standard Model, including grand unified theories. Depending on the symmetry-breaking pattern, they can be either topologically stable or metastable. Intriguingly, metastable strings have been proposed as a possible origin of the gravitational wave (GW) background observed by recent pulsar timing array experiments. When metastable strings decay, they fragment into segments with monopoles and antimonopoles attached at their endpoints. The monopole and antimonopole are strongly pulled by the string tension. Violent oscillations of these segments have been considered as a potential GW source, in addition to contributions from string loops. We show that, in realistic situations, the monopoles frequently collide with thermal fluctuations on the string segments, which act as a resistance and prevent the oscillation. As a result, we find that the contribution from string segments to the GW background is negligible.