Papers for Tuesday, Sep 09 2025

This paper is a response to recent claims that a population of primordial black holes in the Galactic halo has been ruled out by the OGLE collaboration. This claim was based on the latest results from the OGLE microlensing survey towards the Large Magellanic Cloud which failed to detect even the number of events expected from known stellar populations. In particular, their results are completely inconsistent with the results of the MACHO survey which detected a population of compact bodies in the Galactic halo which could not be accounted for by any known stellar population. The discrepancy between the results of these two groups has a long history, and includes problems such as different choice of photometric passbands, quality of light curves, microlensing event selection, detection efficiency, self lensing and halo models. In this paper it is demonstrated that these issues not only account for the discrepancy between the OGLE and MACHO results, but imply that the OGLE observations can put no meaningful constraints on a population of primordial black holes in the Galactic halo.

This chapter introduces the reader to the solar interior, in particular the convection zone. The first section explores the solar cycle and the dynamo models that have been studied to explain this cycle. The second section explores helioseismology observations and analysis of the solar interior, and reviews the fundamental knowledge that has been gained from these studies. The third and final section reviews observations and theory of magnetic fields emerging from the convection zone into the solar corona.

The Hydrogen-alpha (Ha) emission line in galaxies is a powerful tracer of their recent star formation activity. With the advent of JWST, we are now able to routinely observe Ha in galaxies at high redshifts (z > 3) and thus measure their star-formation rates (SFRs). However, using "classical" SFR(Ha) calibrations to derive the SFRs leads to biased results because high-redshift galaxies are commonly characterized by low metallicities and bursty star-formation histories, affecting the conversion factor between the Ha luminosity and the SFR. In this work, we develop a set of new SFR(Ha) calibrations that allow us to predict the SFRs of Ha-emitters at z > 3 with minimal error. We use the SPHINX cosmological simulations to select a sample of star-forming galaxies representative of the Ha-emitter population observed with JWST. We then derive linear corrections to the classical SFR(Ha) calibrations, taking into account variations in the physical properties (e.g., stellar metallicities) among individual galaxies. We obtain two new SFR(Ha) calibrations that, compared to the classical calibrations, reduce the root mean squared error (RMSE) in the predicted SFRs by $\Delta$RMSE $\approx$ 0.04 dex and $\Delta$RMSE $\approx$ 0.06 dex, respectively. Using the recent JWST NIRCam/grism observations of Ha-emitters at z ~ 6, we show that the new calibrations affect the high-redshift galaxy population statistics: (i) the estimated cosmic star-formation density decreases by $\Delta\rho$(SFR) $\approx$ 12%, and (ii) the observed slope of the star-formation main sequence increases by $\Delta$ $\partial$log SFR / $\partial$log M* = 0.08 $\pm$ 0.02.

Multiwavelength analyses of astrophysical transients are essential for understanding the physics of these events. To make such analyses more efficient and effective, we present the Open mulTiwavelength Transient Event Repository (OTTER), a publicly available catalog of published transient event metadata and photometry. Unlike previous efforts, our data schema is optimized for the storage of multiwavelength photometric datasets spanning the entire electromagnetic spectrum. Open source software, including an application programming interface (API) and web application, are available for viewing, accessing, and analyzing the dataset. For the initial release of OTTER, we present the largest ever photometric archive of tidal disruption events (TDEs), including $\gtrsim 80,000$ observations of 232 TDEs spanning from radio to X-ray wavelengths. We demonstrate the power of this infrastructure through four example analyses of the TDE population. We plan to maintain this dataset as more TDEs are discovered in the future and encourage other users to contribute by uploading newly published data via our web application. The infrastructure was built with the goal of archiving additional transient data (supernovae, gamma-ray bursts, fast blue optical transients, fast radio bursts, etc.) in the future. The web application is available at this https URL and the API documentation is available at this https URL.

The forthcoming GRAVITY+ instrument promises to usher in an era of "industrial-scale" mass measurements of isolated black holes (BHs), with the potential to assemble a sample of many tens of BHs via interferometric microlensing over several years. A key challenge will be selecting interferometric follow-up targets from an order-of-magnitude larger pool of ongoing microlensing events when using traditional selection based on event timescale alone. Gould (2023) proposed a criterion optimized for BH selection using space-based microlens parallax measurements enabled by a satellite. We adapt it to work with microlens parallax constraints obtainable from ground-based data only. Using Galactic simulations, we show that our selection criterion is highly efficient, expecting to detect about a dozen BHs per year with GRAVITY+ from following up ~35 selected events.

The TRAPPIST-1 system offers one of the best opportunities to characterize temperate terrestrial planets beyond our own solar system. Within the TRAPPIST-1 system, planet e stands out as highly likely to sustain surface liquid water if it possesses an atmosphere. Recently, we reported the first JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e, revealing significant stellar contamination, which varied between the four visits. Here, we assess the range of planetary atmospheres consistent with our transmission spectrum. We explore a wide range of atmospheric scenarios via a hierarchy of forward modeling and retrievals. We do not obtain strong evidence for or against an atmosphere. Our results weakly disfavor CO$_2$-rich atmospheres for pressures corresponding to the surface of Venus and Mars and the cloud tops of Venus at 2$\sigma$. We exclude H$_2$-rich atmospheres containing CO$_2$ and CH$_4$ in agreement with past work, but find that higher mean molecular weight, N$_2$-rich atmospheres with trace CO$_2$ and CH$_4$ are permitted by the data. Both a bare rock and N$_2$-rich atmospheric scenario provide adequate fits to the data, but do not fully explain all features, which may be due to either uncorrected stellar contamination or atmospheric signals. Ongoing JWST observations of TRAPPIST-1 e, exploiting consecutive transits with TRAPPIST-1 b, will offer stronger constraints via a more effective stellar contamination correction. The present work is part of the JWST Telescope Scientist Team (JWST-TST) Guaranteed Time Observations, which is performing a Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).

TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and that resides in the habitable zone of its star -- located at a distance from its star such that it might, with the right atmosphere, sustain liquid water on its surface. Here, we present a set of 4 JWST/NIRSpec PRISM transmission spectra of TRAPPIST-1 e obtained from mid to late 2023. Our transmission spectra exhibit similar levels of stellar contamination as observed in prior works for other planets in the TRAPPIST-1 system (Lim et al, 2023; Radica et al., 2024), but over a wider wavelength range, showcasing the challenge of characterizing the TRAPPIST-1 planets even at relatively long wavelengths (3-5 um). While we show that current stellar modeling frameworks are unable to explain the stellar contamination features in our spectra, we demonstrate that we can marginalize over those features instead using Gaussian Processes, which enables us to perform novel exoplanet atmospheric inferences with our transmission spectra. In particular, we are able to rule out cloudy, primary H$_2$-dominated ($\gtrsim$ 80$\%$ by volume) atmospheres at better than a 3$\sigma$ level. Constraints on possible secondary atmospheres on TRAPPIST-1 e are presented in a companion paper (Glidden et al., 2025). Our work showcases how JWST is breaking ground into the precisions needed to constrain the atmospheric composition of habitable-zone rocky exoplanets.

GW231123, the most massive binary black hole (BBH) merger detected by LIGO/Virgo/KAGRA, highlights the need to understand the origins of massive, high-spin stellar black holes (BHs). Dense star clusters provide natural environments for forming such systems, beyond the limits of standard massive star evolution to core collapse. While repeated BBH mergers can grow BHs through dynamical interactions (the so-called "hierarchical merger" channel), most star clusters with masses $\lesssim 10^6\,M_\odot$ have escape speeds too low to retain higher-generation BHs, limiting growth into or beyond the mass gap. In contrast, BH--star collisions with subsequent accretion of the collision debris can grow and retain BHs irrespective of the cluster escape speed. Using $N$-body (Cluster Monte Carlo) simulations, we study BH growth and spin evolution through this process and we find that accretion can drive BH masses up to at least $\sim200\,M_\odot$, with spins set by the details of the growth history. BHs up to about $150\,M_\odot$ can reach dimensionless spins $\chi \gtrsim 0.7$ via single coherent episodes, while more massive BHs form through multiple stochastic accretion events and eventually spin down to $\chi \lesssim 0.4$. These BHs later form binaries through dynamical encounters, producing BBH mergers that contribute up to $\sim10\%$ of all detectable events, comparable to predictions for the hierarchical channel. However, the two pathways predict distinct signatures: hierarchical mergers yield more unequal mass ratios, whereas accretion-grown BHs preferentially form near-equal-mass binaries. The accretion-driven channel allows dense clusters with low escape speeds, such as globular clusters, to produce highly spinning BBHs with both components in or above the mass gap, providing a natural formation pathway to GW231123-like systems.

Strong gravitational lensing is a powerful cosmological probe, providing a direct tool to unveil the properties of dark matter (DM) on sub-galactic scales. In particular, flux-ratio anomalies in quadruply imaged quasars ("quads") can reveal the presence of dark substructure, such that population-level statistics can be used to constrain the particle nature of DM. Current methods, however, rely on globally parametrized models ("macromodels") of the lens mass distribution, which impose rigid physical assumptions on the deflection field. Given the high stakes, it is important to develop complementary methods that do not require the assumption of a macromodel. One promising avenue consists of modeling the resolved emission from the quasar host galaxy (lensed arcs) using a local lensing formalism like the Curved Arc Basis (CAB) description. In this paper, we test the ability of CAB models to predict flux ratios from mock imaging data. We find that CAB model-predicted flux ratios accurately reproduce the expected values, with a typical precision of $\sim 3-5\%$. While a macromodel-based approach yields smaller uncertainties, as expected, the CAB method permits a more flexible, local description of the deflection field, thus being more robust to angular structure in the main deflector mass profile, in particular avoiding false-positive detections of flux-ratio anomalies that can arise with overly simplistic parametrizations. On the other hand, by injecting individual DM halos near quasar images, we demonstrate that CAB models do not absorb the local lensing perturbations from DM substructure, and can therefore distinguish flux-ratio anomalies caused by DM substructure from other sources of small-scale perturbation. We conclude that CAB models can be used to infer DM properties from flux-ratio anomaly statistics with minimal assumptions, complementing the traditional macromodel based approach.

Ultra-violet (UV) radiation from accreting black holes ionizes the intergalactic gas around early quasars, carving out highly ionized bubbles in their surroundings. Any changes in a quasar's luminosity are therefore predicted to produce outward-propagating ionization gradients, affecting the Lyman-$\alpha$ (Ly$\alpha$) absorption opacity near the quasar's systemic redshift. This "proximity effect" is well-documented in rest-UV quasar spectra but only provides a one-dimensional probe along our line-of-sight. Here we present deep spectroscopic observations with the James Webb Space Telescope (JWST) of galaxies in the background of a super-luminous quasar at $z_{\rm QSO}\approx6.3$, which reveal the quasar's "light echo" with Ly$\alpha$ tomography in the transverse direction. This transverse proximity effect is detected for the first time towards multiple galaxy sightlines, allowing us to map the extent and geometry of the quasar's ionization cone. We obtain constraints on the orientation and inclination of the cone, as well as an upper limit on the obscured solid angle fraction of $f_{\rm obsc}<91\%$. Additionally, we find a timescale of the quasar's UV radiation of $t_{\rm QSO}=10^{5.6^{+0.1}_{-0.3}}$ years, which is significantly shorter than would be required to build up the central supermassive black hole (SMBH) with conventional growth models, but is consistent with independent measurements of the quasars' duty cycle. Our inferred obscured fraction disfavors a scenario where short quasar lifetimes can be explained exclusively by geometric obscuration, and instead supports the idea that radiatively inefficient accretion or growth in initially heavily enshrouded cocoons plays a pivotal role in early SMBH growth. Our results pave the way for novel studies of quasars' ionizing geometries and radiative histories at early cosmic times.

Analytical templates for the covariance matrix of the 4-Point Correlation Function (4PCF) have been developed in the past assuming a Gaussian Random Field (GRF). In this work, we present the first non-Gaussian calculation of the 4PCF covariance, incorporating 1-loop corrections using the second-order density contrast. Furthermore, we introduce a non-trivial galaxy bias scheme at second order. To simplify the calculation, we decompose the covariance into five distinct structures, and then exploit the isotropic basis functions of Cahn & Slepian (2023). This approach reduces the complexity of the high-dimensional integrals naively involved, enabling the angular parts to be performed and leaving us with low-dimensional radial integrals. This analytical template will provide a more accurate characterization of the statistical errors on the 4PCF, improving both the parity-odd and parity-even analyses. This is the first paper in a two-part series.

Analytical templates for the 4-Point Correlation Function (4PCF) covariance matrix have been developed in the past assuming a Gaussian Random Field (GRF). In this work, we present the second part of the beyond GRF calculation of the 4PCF covariance, incorporating 1-loop corrections stemming from the third-order density contrast. Furthermore, we introduce a non-trivial galaxy biasing scheme at third order. To simplify the calculation, we decompose the covariance into three distinct structures and leverage the isotropic basis of Cahn & Slepian (2023). This approach reduces the complexity of the high-dimensional integrals that would be naively involved, enabling the angular parts to be performed and leaving us with low-dimensional radial integrals. This analytical template will provide a more accurate characterization of the statistical errors on the 4PCF, improving our ability to probe both its parity-even and parity-odd modes. This is the second and final paper in a two-part series.

JWST has revealed a previously unknown population of low-luminosity active galactic nuclei (AGN) in the early Universe. These JWST-AGN at high redshifts are characterised by a set of peculiar properties, including unusually weak X-ray emission. Here we investigate the apparent lack of X-ray emission in the framework of the ``AGN radiative dusty feedback'' scenario based on the effective Eddington limit for dust. We analyse how the boundary in the $N_\mathrm{H} - \lambda$ plane, defined by the column density versus the Eddington ratio, is modified as a function of the dusty gas parameters (metallicity, dust grain size and composition). Low metallicity gas with little dust content tends to survive against radiation pressure, and likely accumulates in the nuclear region. We suggest that such dust-poor gas can provide long-lived absorption and may lead to heavy X-ray obscuration, as observed in early JWST-AGN. The blowout vs. stalling condition of the obscuring clouds indicates that higher metallicities are required to eject heavier column densities, while large columns of gas can stall in low metallicity environments. Therefore the metallicity may play a key role in the AGN radiative dusty feedback scenario. We discuss how other peculiar properties of JWST-AGN --such as Balmer absorption features and weak radio emission-- may be naturally interpreted within the same physical framework.

Accretion onto neutron stars (NSs) in X-ray pulsars (XRPs) results in intense X-ray emission, and under specific conditions, high-energy nuclear interactions that produce gamma-ray photons at discrete energies. These interactions are enabled by the high free-fall velocities of accreting nuclei near the NS surface and give rise to characteristic gamma-ray lines, notably at 2.2 MeV, 5.5 MeV, and 67.5 MeV. We investigate the production mechanisms of these lines and estimate the resulting gamma-ray luminosities, accounting for the suppression effects of radiative deceleration in bright XRPs and the creation of electron-positron pairs in strong magnetic fields. The resulting annihilation of these pairs leads to a secondary emission line at $\sim 511$ keV. We also discuss the possibility that non-stationary pair creation in the polar cap region could drive coherent radio emission, though its detectability in accreting systems remains uncertain. Using a numerical framework incorporating general relativistic light bending and magnetic absorption, we compute the escape fraction of photons and distinguish between actual and apparent gamma-ray luminosities. Our results identify the parameter space - defined by magnetic field strength, accretion luminosity, and NS compactness - where these gamma-ray signatures may be observable by upcoming MeV gamma-ray missions. In particular, we highlight the diagnostic potential of detecting gravitationally redshifted gamma-ray lines and annihilation features for probing the mass-radius relation and magnetospheric structure of NSs.

We present a follow-up study focused on cluster-scale diffuse radio emissions in 115 galaxy clusters in the Southern sky, using full-resolution (7.8") and tapered low-resolution (15") images from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS). In this MGCLS follow-up paper, we update and quantitatively characterise the presence of diffuse radio emission and provide detailed catalogue information on its radio properties at 1.28 GHz. As the MGCLS sample is heterogeneous and was initially used as a test bed to reveal the scientific potential of MeerKAT, the reported numbers are subject to this special case. More than half ($\sim$54%; 62/115) of the observed MGCLS clusters present diffuse cluster radio emission, with the total number of diffuse radio sources or candidates detected being 103. Including candidates, we find that radio relics are the most frequently detected diffuse sources in MGCLS at 53% (55/103), followed by halos at 32% (33/103) and mini-halos at 10% (11/103), with only 3% (3/103) being Phoenixes. The sizes of the diffuse radio structures and candidates range from 55 kpc to over 2 Mpc, with $P_{1.28GHz}$ radio power ranging from $10^{22}$ W Hz$^{-1}$ to greater than $10^{25}$ W Hz$^{-1}$. In-band radio spectral index estimates reveal revived radio plasma emissions that exhibit steep radio spectral indices down to $\alpha^{1656}_{908} \sim -3.5$. Mini-halos and their respective candidates are detected mainly in low-mass ($M_{500}$ $\leq$ 5$\times10^{14}$ M$_\odot$) and low-power ($P_{1.4GHz}$ $\leq$ $10^{23}$ W Hz$^{-1}$) systems. We suggest the presence of a statistically significant correlation between the 1.4 GHz radio power and the cluster mass for mini-halo (and candidate) systems.

The rotation periods of Ap stars range over five to six orders of magnitude. The origin of their differentiation remains unknown. We carry out a systematic study of the longest period Ap stars to gain insight into their properties. We analyse newly obtained spectra of a sample of super-slowly rotating Ap (ssrAp) star candidates identified by a TESS photometric survey to confirm that their projected equatorial velocity v sin i is consistent with (very) long rotation periods, to obtain a first determination of their magnetic fields, and to test their binarity. The value of v sin i in 16 of the 18 studied stars is low enough for them to have moderately to extremely long rotation periods. All stars but one are definitely magnetic; for five of them, the magnetic field was detected for the first time. Five new stars with resolved magnetically split lines were discovered. Five stars that were not previously known to be spectroscopic binaries show radial velocity variations; in one of them, lines from both components are observed.

The JWST has enabled the discovery of Active Galactic Nuclei at high redshifts. The intrinsic UV spectrum of GN-z11 at redshift z = 10.6 has a spectral slope compatible with a standard accretion disc. By fitting a disc model to its spectrum, we find that the mass of the black hole must be above 1.6e7 Msun in order that it lies below the Eddington limit. We define this mass as the Eddington mass of the black hole. We note that the spectral shape is consistent with that of accreting stellar mass black holes sources in their soft state, for which no variability is expected. Mom-z14 is a more distant object at z = 14.44 and has a similar UV slope. Disc model-fitting gives a similar result but lower mass accretion rate. We also examine 3 further high redshift objects: GS z14-1, GHZ2 and GS-z11-1 at z = 13.86, 12.34 and 11.28, again obtaining similar results. If sub-Eddington accretion discs are indeed the origin of much of the UV emission from these objects, then the existence of massive black holes less than 440 and 290 Myr after the Big Bang point either to exceptional black hole seeds or to primordial black holes. The observed spread of UV spectral slopes in high redshift objects suggests that our approach may be relevant to about half of that population.

We present measurements, analyses and results for the seventeen strongly carbon-chain depleted comets in Lowell Observatory's narrowband photometry database. The majority of comets exhibit a very similar, i.e. typical, composition in optical wavelengths, though the existence of anomalous comets with lower abundances of carbon-chain molecules relative to CN has long been known. M. F. A'Hearn et al. (1995) identified an entire class of these carbon-chain depleted comets, and the most recent full analysis of our database reveals there are varying degrees of carbon-chain depletion. Here we focus on the most depleted comets, the strongly carbon-chain depleted class, which is the largest non-typical compositional class to emerge from our taxonomic analyses. All comets in this class are strongly depleted in both C2 and C3 with respect to OH and CN, with depletions for these ratios being 3-27x below the mean abundance ratios for comets with typical composition. Several comets in this class additionally exhibit depletion in NH, with the largest depletions being 11x below mean typical values. A number of these comets exhibit asymmetry in production rates as a function of time and heliocentric distance, and one exhibits evidence of small secular changes. Almost all of the strongly depleted comets are Jupiter-family comets, indicating a Kuiper belt origin for this compositional class. Multiple lines of evidence from our full database indicate this composition is due to primordial conditions when and where these comets were formed and is not due to thermal heating after their arrival in the inner solar system.

JWST has provided critical mid-infrared data for cold brown dwarfs. It has also provided low-resolution near-infrared spectra, and for faint sources these are the first spectra at these wavelengths. We use these data and other literature sources to synthesize near-infrared photometry on the MKO system for 19 T and Y dwarfs, on the Euclid system for 44 T and Y dwarfs, and on the Roman system for 48 T and Y dwarfs. We also synthesize Euclid I_E magnitudes for 15 T and Y dwarfs. Using the Beiler et al. 2024 observational effective temperatures (T_eff), together with ATMO 2020++ model colors, we show that the absolute 4.6um magnitude can be used as a proxy for T_eff. We present a polynomial fit to the M_W2:T_eff relationship for cool dwarfs with 250 < T_eff K < 1000. We select five Y dwarfs with 275 < T_eff K < 400 which have a range in near- to mid-infrared colors. Comparison of the JWST spectral energy distribution to ATMO 2020++ models indicate that Y dwarfs which are bluer in J - W2 are lower gravity or more metal-rich than their redder counterparts, with stronger CO and CO_2 absorption at 4.2 < lambda um < 4.9. The near-infrared color diagrams show significant scatter, with complex dependencies on T_eff, metallicity and gravity. In order to disentangle these effects, opacity sources for cool model atmospheres need to be more complete at lambda < 1um.

We examine velocity-dependent dark matter annihilation in subhalos using a sample of six Milky Way-like galaxies from the Aurgia simulation suite. We quantify the enhancement in the annihilation rate in subhalos when including the contribution from particles in the smooth component of the halo that overlap with the subhalos. The enhancement in the annihilation rate scales with the smooth component of the host halo dark matter density, and is evident for subhalos over the resolvable mass range. Maximal enhancement factors are ~ 48 for p-wave models, and ~ 37,000 for d-wave models. For p and d-wave annihilation models, ~ 13 and ~ 6 subhalos, respectively, across all six host halos have emission from dark matter annihilation in their direction that is above the foreground emission from the smooth dark matter component, and would therefore be resolvable as sources. Such subhalos with the most significant enhancement factors tend to be on the lower end of the mass range and located closer to the center of the host galaxy. We provide a prescription to calculate the enhancement for subhalos as a function of distance from the Galactic center, and use this to examine the impact on dark matter limits from a couple of example dwarf spheroidals. We show that, including the enhancement factors, limits from individual dwarf spheroidals are at a cross section scale that may approach those derived from the Galactic center.

We present analyses of six microlensing events: KMT-2023-BLG-0548, KMT-2023-BLG-0830, KMT-2023-BLG-0949, KMT-2024-BLG-1281, KMT-2024-BLG-2059, and KMT-2024-BLG-2242. These were identified in KMTNet data from the 2023 -- 2024 seasons, selected for exhibiting anomalies shorter than one day -- potential signatures of low-mass planetary companions. Detailed modeling of the light curves reveals that the anomalies in all six events are caused by planetary companions to the lenses. The brief durations of the anomalies are attributed to various factors: a low planet-to-host mass ratio (KMT-2024-BLG-2059, KMT-2024-BLG-2242), a wide planet-host separation (KMT-2023-BLG-0548), small and elongated caustics restricting the source's interaction region (KMT-2023-BLG-0830, KMT-2024-BLG-1281), and a partial caustic crossing (KMT-2023-BLG-0949). { For KMT-2023-BLG-0548, the Bayesian posterior distribution of the lens mass shows two distinct peaks: a low-mass solution indicating a sub-Jovian planet orbiting an M dwarf in the Galactic disk, and a high-mass solution suggesting a super-Jovian planet around a K-type dwarf in the bulge. KMT-2023-BLG-0830 hosts a Neptune-mass planet orbiting an M dwarf in the Galactic bulge. KMT-2023-BLG-0949 involves a super-Jovian planet orbiting a $\sim 0.5~M_\odot$ host located at $\sim 6$ kpc. KMT-2024-BLG-2059Lb is a super-Earth with a mass about seven times that of Earth, orbiting an early M dwarf of $\sim 0.5~M_\odot$. KMT-2024-BLG-1281L hosts a planet slightly more massive than Neptune, orbiting an M dwarf of $\sim 0.3~M_\odot$. The short timescale and small angular Einstein radius of KMT-2024-BLG-2242 suggest a $\sim 0.07~M_\odot$ primary, likely a brown dwarf, with a Uranus/Neptune-mass planet.

The Cherenkov Telescope Array Observatory (CTAO) will greatly improve upon sensitivities in the field of very-high-energy gamma-ray astrophysics. The CTAO northern site (CTAO-North, La Palma, Spain) currently hosts LST-1 with the remaining three large-sized telescopes (LSTs) expected in mid-2026 and one medium-sized telescope (MST) expected in mid-2027. The CTAO southern site (CTAO-South, Paranal, Chile) expects the delivery of five small-sized telescopes (SSTs) and two MSTs in early 2026 with on-site construction beginning in mid-2026. The dual-mirrored Schwarzschild-Couder Telescope (SCT) is a candidate MST for CTAO-South and is capable of observations in the energy range of 100 GeV to 10 TeV, the core of CTAO's 20 GeV to 300 TeV energy range. Inaugurated in January 2019, the prototype SCT (pSCT) located at the Fred Lawrence Whipple Observatory in southern Arizona observed gamma-ray emission from the Crab Nebula at a significance of 8.6 sigma in 2020. The pSCT utilizes a novel dual-mirror optics design and a densely packed focal plane of silicon photomultipliers (SiPMs). An upgrade of the pSCT camera is underway to fully instrument the camera with 11,328 pixels and an 8-degree diameter FoV. In addition, upgraded electronics will lower the front-end electronics noise, allowing for a lower trigger threshold and improved event reconstruction and background rejection. This work will present the status of the upgrade of the pSCT and discuss the future of the SCT.

The Pierre Auger and Telescope Array joint Working Group on the UHECR energy spectrum was established in 2012 to analyze energy scale uncertainties in both experiments and to in vestigate their systematic differences, particularly in the spectral shape of the flux measurements. Previous studies have indeed shown that, within systematic uncertainties, the energy s pectra measured by the two observatories are consistent below~$10\,\mathrm{EeV}$. However, at higher energies, a significant difference remains. In this work, we re-examine this discrepan cy in greater detail and explore its possible origins. We consider systematic and statistical uncertainties, including the conversion from directly measured observables to energy and the calculation of exposures. We present an updated energy scale comparison between the two experiments and updated flux measurements in the common declination band.

Dusty stellar sources, including young stellar objects (YSOs) and evolved stars such as oxygen- and carbon-rich AGBs (OAGBs, CAGBs), red supergiants (RSGs), and post-AGB stars (PAGBs), play a key role in the chemical enrichment of galaxies. Photometric surveys in the Magellanic Clouds have cataloged many such objects, but their classifications are often uncertain due to overlaps between populations. We trained machine learning models on spectroscopically labeled data from the SAGE project and applied them to photometric catalogs. The spectroscopic model achieves about 89\% accuracy. Applied to photometric labels, nearly all OAGBs are correctly identified, and YSOs have a 95\% confirmation rate. In contrast, 16\% of CAGBs are reclassified as OAGBs, only 8\% of RSGs retain their labels, and fewer than half of PAGBs are confirmed. Photometry is thus reliable for abundant populations with distinct signatures, but spectroscopic confirmation remains essential for rare or overlapping stellar classes.

The nature of dark matter remains a central question in cosmology, with fuzzy dark matter (FDM) models offering a compelling alternative to the cold dark matter (CDM) paradigm. We explore FDM scenarios by performing 21-cm simulations across a parameter space with \texorpdfstring{$f_{\rm FDM} \in [0.02, 0.10]$}{f_FDM in [0.02, 0.10]} and \texorpdfstring{$m_{\rm FDM} \in [10^{-24}, 10^{-21}]\,\mathrm{eV}$}{m_FDM in [10^-24, 10^-21] eV}, obtaining global neutral hydrogen fractions (\texorpdfstring{$x_{\rm HI}$}{x_HI}) for each model. Observational \texorpdfstring{$x_{\rm HI}$}{x_HI} data and associated uncertainties from JWST are incorporated by estimating full probability density functions (PDFs) for both \texorpdfstring{$x_{\rm HI}$}{x_HI} and redshift \texorpdfstring{$z$}{z} using Bayesian inference with the No-U-Turn Sampler (NUTS), yielding non-Gaussian multivariate uncertainty distributions. A hybrid machine learning framework is then trained on these observational PDFs to learn both central values and correlated uncertainties in \texorpdfstring{$x_{\rm HI}$}{x_HI} and \texorpdfstring{$z$}{z}, iteratively refining its parameters in each training epoch through direct incorporation of the multivariate PDFs derived from observational constraints. We then compare the simulation outputs to the machine-learned observational trends to identify the most consistent models. Our results indicate that FDM models with \texorpdfstring{$m_{\rm FDM} \simeq 10^{-22}\,\mathrm{eV}$}{m_FDM approx 10^-22 eV} and \texorpdfstring{$f_{\rm FDM} \simeq 0.04$}{f_FDM approx 0.04} best match current data, while lighter masses are strongly constrained. By integrating simulations and machine learning in an uncertainty-aware framework, this work explores the physics of the early Universe and guides future studies of 21-cm cosmology and reionization.

We present calibrated ATLAS photometry of the interstellar comet 3I/ATLAS (C/2025 N1) from 28 March through 29 Aug 2025, obtained with the five-site, robotic ATLAS network in the c (420-650~nm), o (560-820~nm), and Teide w (420-720~nm) bands. Stacked difference images yield reliable light curves measured in four fixed apertures that capture the evolving coma. We observe 3I/ATLAS transitioning in color from red (c-o)~0.7 before MJD 60860 to near-solar (c-o)~0.3 after MJD 60870, coincident with the appearance of a prominent anti-solar tail. The absolute magnitude curve H(t) shows a slope break near MJD 60890 at r~3.3 au from -0.035 to -0.014 mag/day, or in terms of coma cross section as a function of heliocentric distance, r^{-3.9} to r^{-1.2}. We interpret the evolution as a shift from dust lifted from a reddened surface to production of small, optically bright icy grains and changing coma optical depth. We release the aperture photometry with geometry and uncertainties to enable cross-instrument synthesis of 3I/ATLAS activity and color evolution.

Most X-ray pulsars in high-mass X-ray binary (HMXB) systems exhibit both global and local trends of spin acceleration (spin-up) and deceleration (spin-down). Moreover, decades-long monitored objects display even more general spin-up trends in their spin evolution and simultaneously demonstrate a decrease in the orbital period, so-called orbital decay. Although obvious, this general behavior leaves the open question of the energy source and the mechanism of angular momentum transfer that ensures the neutron star's spin acceleration. We hypothesize that the observed spin acceleration of X-ray pulsars in HMXB (RLO and sgXRB) systems results from orbital angular momentum transfer via tidal interactions with their massive companions. To study these phenomena, we sample five well-studied objects with the longest observational history of their spin periods from the population of known Galactic persistent X-ray pulsars in HMXB systems. We obtain the spin frequency change from the observational data and estimate energy losses for orbital decay and pulsars' spin acceleration. We propose a new term of super-global spin-up trends, and show that their observable values do not exceed theoretical upper limits predicted within the scenario of orbital decay due to the tidal interaction between the neutron star and its massive companion.

Primordial black holes (PBHs) formed from the collapse of density fluctuations provide a unique window into the physics of the early Universe. Their evaporation through Hawking radiation around the epoch of Big Bang nucleosynthesis (BBN) can leave measurable imprints on the primordial light-element abundances. In this work, we analyze in detail the effects of PBHs evaporating before BBN, with various intermediate steps understood analytically, and obtain the BBN constraint on PBHs within a transparent and reproducible framework. We find that, to produce observable effects on BBN, the PBH mass must exceed $10^{9}$ g, a threshold higher than that reported in some earlier studies. Slightly above $10^{9}$ g, the BBN sensitivity rapidly increases with the mass and then decreases, with the turning point occurring at $2\times10^{9}$ g. For PBHs in the mass range $[10^{9},\ 10^{10}]$ g, current measurements of BBN observables set an upper bound on the initial mass fraction parameter $\beta$ ranging from $10^{-17}$ to $10^{-19}$. To facilitate future improvements, we make our code publicly available, enabling straightforward incorporation of updated nuclear reaction rates, particle-physics inputs, and cosmological data.

Solar eruptive events are complex phenomena, which most often include coronal mass ejections (CME), CME-driven compressive and shock waves, flares, and filament eruptions. CMEs are large eruptions of magnetized plasma from the Sun's outer atmosphere or corona, that propagate outward into the interplanetary space. Over the last several decades a large amount of remote solar eruption observational data has become available from ground-based and space-borne instruments. This has recently required the development of software approaches for automated characterisation of eruptive features. Most solar feature detection and tracking algorithms currently in use have restricted applicability and complicated processing chains, while complexity in engineering machine learning (ML) training sets limit the use of data-driven approaches for tracking or solar eruptive related phenomena. Recently, we introduced Wavetrack - a general algorithmic method for smart characterization and tracking of solar eruptive features. The method, based on a-trous wavelet decomposition, intensity rankings and a set of filtering techniques, allows to simplify and automate image processing and feature tracking. Previously, we applied the method successfully to several types of remote solar observations. Here we present the natural evolution of this approach. We discuss various aspects of applying Machine Learning (ML) techniques towards segmentation of high-dynamic range heliophysics observations. We trained Convolutional Neural Network (CNN) image segmentation models using feature masks obtained from the Wavetrack code. We present results from pre-trained models for segmentation of solar eruptive features and demonstrate their performance on a set of CME events based on SDO/AIA instrument data.

Short gamma-ray bursts (SGRBs), occasionally followed by a long and spectrally soft extended emission, are associated with compact object mergers (COMs). Yet, a few recent long GRBs (LGRBs) show compelling evidence for a COM origin, in contrast with the massive-star core-collapse origin of most LGRBs. While possible COM indicators were found, such as the minimum variability timescale (MVT), a detailed and unique characterisation of their gamma-ray prompt emission that may help identify and explain their deceptively long profile is yet to be found. Here we report the discovery of a set of distinctive properties that rule the temporal and spectral evolution of GRB 230307A, a LGRB with evidence for a COM origin. Specifically, the sequence of pulses that make up its profile is characterised by an exponential evolution of (i) flux intensities, (ii) waiting times between adjacent pulses, (iii) pulse durations, and (iv) spectral peak energy. Analogous patterns are observed in the prompt emission of other long COM candidates. The observed evolution of gamma-ray pulses would imply that a relativistic jet is colliding with more slowly expanding material. This contrasts with the standard internal shock model for typical LGRBs, in which dissipation occurs at random locations within the jet itself. We tentatively propose a few simple toy models that may explain these properties and are able to reproduce the overall time profile.

We investigated the evolution of the physical properties of the brightest galaxies in clusters and their protohalos from $z = 4$ to $z = 0$. Galaxy clusters and groups are identified using a halo-based group finder applied to the COSMOS2020 galaxy catalog. We construct evolution chains from low redshift clusters to higher redshift groups via the abundance matching method. The region of protohalos corresponding to clusters is defined on the basis of a characteristic radius. Our analysis encompasses a wide range of physical properties, including stellar mass, luminosity, star formation rate (SFR), specific star formation rate (sSFR), color ($g - r$), and stellar age. The evolution trends of the most massive galaxies (MMGs) in higher redshift groups and their corresponding protohalos are generally consistent. The stellar mass of MMGs shows an increasing trend across the entire redshift range. By considering the stellar mass growth as in-situ and ex-situ components, we find that in-situ star formation is efficient at $z \sim 2$, while ex-situ accretion becomes the primary growth channel at later times. At $z \gtrsim 2$, MMGs undergo an intense star formation phase of approximately $10^{2}\ \rm M_{\odot}yr^{-1}$, but are generally quenched at lower redshifts. Stellar age analysis suggests that most stars in MMGs formed at $z > 2$. Our results present a coherent picture of MMG evolution across cosmic epochs, which is broadly consistent with the current theoretical framework of galaxy formation and evolution. Moreover, our work provides an intriguing way to trace galaxy evolution through the construction of cluster evolutionary chains in observations.

The correlation between solar Extreme Ultra-Violet (EUV) radiation above 8.8 eV and the release of sodium from the lunar surface via photon-stimulated desorption (PSD) is investigated. We use simultaneous measurements of EUV photon flux and Na optical spectral line flux ($F_{Na}$) from the lunar exosphere. Data were acquired with the high-resolution (R$\sim$72000) Echelle Spectrograph on the 2.34-m Vainu Bappu Telescope during the lunar first quarter (January-March 2024), observing $Na\,I$ D2 and D1 flux at altitudes below $\sim590\,km$ from the surface. Simultaneous EUV and FUV measurements were acquired from the GOES-R Series Extreme Ultraviolet Sensor (EUVS), while NUV data were obtained from the Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) aboard the ISS. We correlated $F_{Na}$ with EUV photon flux from EUVS across six bands spanning $256-1405\,\text{Å}$ (48.5-8.8 eV) and NUV (2000-4000 $\text{Å}$) from TSIS-1. A non-linear rise in lunar exospheric sodium with increasing EUV and FUV fluxes was observed, contrasting with previous linear PSD models. The EUV radiation above 10 eV drives sodium release, with 256-304 $\text{Å}$ wavelengths as dominant contributors. Additionally, the NUV flux and $F_{Na}$ are positively correlated, indicating the role of sodium release. The zenith column density averages $3.3\times10^{9}$ atoms cm$^{-2}$, with Characteristic temperatures averaging at $\sim$6700K and scale heights of $\sim$1500 km. Elevated temperatures and sodium densities during solar activity suggest enhanced Na release during flares. These results emphasize the need for a revised PSD model above 8.8 eV and improved constraints on the PSD cross-section.

Mars exploration requires precise and reliable terrain models to ensure safe rover navigation across its unpredictable and often hazardous landscapes. Stereoscopic vision serves a critical role in the rover's perception, allowing scene reconstruction by generating precise depth maps through stereo matching. State-of-the-art Martian planetary exploration uses traditional local block-matching, aggregates cost over square windows, and refines disparities via smoothness constraints. However, this method often struggles with low-texture images, occlusion, and repetitive patterns because it considers only limited neighbouring pixels and lacks a wider understanding of scene context. This paper uses Semi-Global Matching (SGM) with superpixel-based refinement to mitigate the inherent block artefacts and recover lost details. The approach balances the efficiency and accuracy of SGM and adds context-aware segmentation to support more coherent depth inference. The proposed method has been evaluated in three datasets with successful results: In a Mars analogue, the terrain maps obtained show improved structural consistency, particularly in sloped or occlusion-prone regions. Large gaps behind rocks, which are common in raw disparity outputs, are reduced, and surface details like small rocks and edges are captured more accurately. Another two datasets, evaluated to test the method's general robustness and adaptability, show more precise disparity maps and more consistent terrain models, better suited for the demands of autonomous navigation on Mars, and competitive accuracy across both non-occluded and full-image error metrics. This paper outlines the entire terrain modelling process, from finding corresponding features to generating the final 2D navigation maps, offering a complete pipeline suitable for integration in future planetary exploration missions.

Aims. The aim of this work is to determine the maximum ages that can be unambiguously established for $\delta$ Sct stars using seismic observables, and, by extension, the oldest open clusters that can be dated using this type of star. Methods. I estimate the large frequency separation using various techniques applied to two samples of $\delta$ Sct located near the red edge of the instability strip. One sample consists of 18 targets observed by the Kepler mission, and the other comprises 17 targets observed by TESS. I employ a grid of stellar models representative of typical $\delta$ Sct parameters, incorporating mass, metallicity, and rotation as independent variables, and compute the first eight radial modes for each model. Using the observed spectroscopic temperature, and the estimated large separation, I estimate the age of each star by fitting a weighted probability density function to the age distribution of the models that best match the seismic constraints. Results. To evaluate the performance of the fitting method, it was applied to a synthetic population of 20 $\delta$ Sct stars with varying metallicities and ages, generated by randomly selecting models. The analysis indicates that $\delta$ Sct stars older than 1 Gyr, but still prior to reaching the terminal-age main sequence, can in principle be reliably age-dated. Nevertheless, when the method is applied to the observational sample, only three out of the 35 stars considered marginally exceed an estimated age of 1 Gyr. Conclusions. From these results, I can say that open clusters older than approximately 1 Gyr cannot be reliably dated using astero-seismology of $\delta$ Sct stars with 1D models, at least not without a more complete treatment of convection and a non-linear treatment of rotation.

Understanding the nature of dark matter (DM) particles remains a pivotal challenge in modern cosmology. Current cosmological research on these phenomena primarily utilizes cosmic microwave background (CMB) observations and other late-time probes, which predominantly focus on large scales. We introduce a novel probe, the 21 cm forest signal, which can be used to investigate DM properties on small scales during the epoch of reionization, thereby addressing the gap left by other cosmological probes. Annihilation and decay of DM particles, as well as Hawking radiation from PBHs, can heat the intergalactic medium (IGM). This heating suppresses the amplitude of the 21 cm forest 1D power spectrum. Therefore, the 1D power spectrum provides an effective method for constraining DM properties. However, astrophysical heating processes in the early universe can also affect the 21 cm forest 1D power spectrum. In this work, we assess the potential of using the SKA to observe the 21 cm forest 1D power spectrum for constraining DM properties, under the assumption that astrophysical heating can be constrained reliably by other independent probes. Under low astrophysical heating conditions, the 1D power spectrum could constrain the DM annihilation cross section and decay lifetime to $\langle\sigma v\rangle \sim {10^{-31}}\,{\rm cm^{3}\,s^{-1}}$ and $\tau \sim {10^{30}}\,{\rm s}$ for ${10}\,{\rm GeV}$ DM particles, and probe PBHs with masses $\sim {10^{15}}\,{\rm\,g}$ at abundances $f_{\mathrm{PBH}} \simeq 10^{-13}$. These constraints represent improvements of 5-6 orders of magnitude over current limits. Furthermore, the 21 cm forest 1D power spectrum has the potential to exceed existing bounds on sub-GeV DM and to probe PBHs with masses above $10^{18}\,{\rm g}$, which are otherwise inaccessible by conventional cosmological probes.

Although asteroseismology is regarded as the most powerful tool for probing stellar interiors, seismic modelling remains dependent on global stellar parameters. Stellar clusters offer direct measurements of these parameters by fitting a CMD, making the application of asteroseismology in clusters a valuable approach to advancing stellar physics modelling. We aimed to develop seismic modelling for gravity-mode pulsators in the open cluster NGC 2516 to determine stellar ages. We computed 1D stellar models using MESA, incorporating rotation-induced transport processes. Exponential overshooting was included, as well as rotationally induced mixing in the radiative envelope. Grids of evolutionary models were computed covering isochrone-derived mass ranges. The models were evolved up to 300 Myr because of the cluster's young age (~100Myr). By fitting the frequencies of identified modes of four gravity-mode member pulsators simultaneously, we measure the seismic age of the cluster NGC 2516 as 132+-8Myr. This high-precision seismic age estimate deviates by 1sigma from the isochronal age derived from public MIST isochrones for rotating stars. Our findings show that seismic modelling strongly constrains core overshooting, but because the period spacing patterns are smooth, it provides weak constraints on mixing in the radiative envelopes. The two most massive gravity-mode pulsators have MIST masses ~2.0M_sun while their seismic masses are 1.75M_sun. We constructed new asteroseismology-calibrated isochrones using input physics identical to that of our seismic model grid. While this resolves the age discrepancy, the mass discrepancy is only partially addressed. The remaining small yet persisting mass discrepancy implies a mismatch between the physics in core to surface environments of 1D stellar models and the seismic observables probing those areas of fast-rotating stars.

Multi-wavelength studies of their circumstellar environments around LBVs are essential to quantify their feedback at Galactic scales. Dominant emission mechanisms at millimetre wavelengths are, however, still poorly understood. Stellar winds, circumstellar dust, and ionised gas have not been explored together in the case of LBVs. We aim to study the millimetre continuum emission of Galactic LBVs to disclose the presence of these components, to describe their morphology and to measure their relevance in the mass and energy injection to the interstellar medium. We have used the NIKA2 continuum camera at the IRAM 30-m radio telescope to observe and analyse 1.15 and 2 mm continuum from the LBVs HD168607, HD168625, MN87, MN101, and G79.29+0.46. We used Virtual Observatory to complement our observations with archival data from optical, infrared, mm- and cm-wavelengths. With this information, we have built complete SEDs for the five sources, covering six decades of the electromagnetic spectrum. All targets except MN87 were detected at both wavelengths, with features including compact sources, extended nebular emission, shells, and unrelated background structures. Spectral indices of compact sources are consistent with thermal emission from stellar winds. We modelled the SEDs and successfully reproduced the emission from stellar photospheres, circumstellar dust, thermal stellar winds and enshrouding HII regions. Our models, in agreement with previous literature results, reveal the presence of unresolved hot dust very close to the stars and provide the first estimates for the fundamental parameters of MN101. This pilot study highlights the great potential of millimetre continuum studies of LBVs and possibly other evolved massive stars. The mm spectral window bridges the far-IR and radio regimes and can disclose the relative contribution of dust and free-free emission in this kind of sources.

The impact of galaxy formation processes on the matter power spectrum is uncertain and may bias cosmological parameters inferred by large-scale structure surveys. Fast Radio Bursts (FRBs), through their dispersion measures (DMs) encoding the integrated column density of baryons, offer a unique window into the distribution of gas. In this work, we investigate the constraining power of a 3x2-point correlation statistic of FRB DMs and galaxies. We present the correlation formalism, derive covariance matrices and forecast signal-to-noise ratios and Fisher parameter constraints. Assuming host galaxy DM variance of 90 pc cm$^{-3}$, for $10^4$ ($10^5$) FRBs across 35% of the sky, the angular DM power spectrum is noise dominated at multipoles $\ell \gtrsim 20$ ($\ell \gtrsim 100$), which implies that the analysis can be conducted using arcmin-scale localizations, where the redshift distribution of the FRB population can be modeled through the FRB luminosity function or FRB position cross-correlations with galaxies. We show that while $10^4$ ($10^5$) FRB DM correlations can constrain cosmological parameters at 40-70% (30-40%) level, this is a factor of 2-3 (1.5-2) weaker than the precision attainable with galaxy clustering alone due to shot noise from the limited FRB number density, variance of the field and host DMs. On the contrary, feedback-sensitive scales are not accessible in galaxy surveys. We demonstrate that combining FRB DMs and galaxies auto- and cross-correlations in a 3x2-point analysis breaks feedback-cosmology degeneracies, yielding 10-18% (7-13%) precision on cosmological parameters and 3% (2%) constraints on feedback using $10^4$ ($10^5$) FRBs. This work positions the 3x2-point statistic of FRB DMs and galaxies as a promising multi-probe strategy, bridging the gap between constraining astrophysical feedback models and precise measurement of cosmological parameters.

I present a preliminary orbit for the satellite of dwarf planet (136472) Makemake, based on archival Hubble Space Telescope images taken on 13 days between April 2015 and February 2019. The satellite was detected on twelve of them. A best-fit circular orbit has a period of $18.023 \pm 0.017$ d, a semi-major axis of $22250 \pm 780$ km, and an inclination of $83.7^{\circ} \pm 1.0^{\circ}$ relative to the line of sight. That orbit is nearly edge-on, raising the possibility of ongoing or imminent mutual events between Makemake and its satellite.

In the presence of significant measurement uncertainties, the events which appear to be the most extreme are very likely to be those exhibiting the greatest statistical fluctuations. It is therefore particularly important to exercise care when interpreting such events and to use the entire observed population for context. Here, I attempt to pedagogically illustrate this using the example of the most massive binary black hole so far detected in gravitational-wave data, GW231123. I argue that its total mass may be significantly lower than $238^{+28}_{-49}$ solar masses as reported by Abac et al. (2025a). The maximum total binary black hole mass from an analysis of the entire detected population may well be less than 140 solar masses, but the value is very sensitive to assumptions about the population distribution.

Comet C/2020 V2 (ZTF) is categorized as a dynamically new long-period comet, making its first approach to the inner Solar system. We have observed this comet for around 32 months (from January 2022 to July 2024) at heliocentric distances from 5.41 au (pre-perihelion) to 5.26 au (post-perihelion) through various telescopes, employing photometric (60 epochs) and spectroscopic techniques (5 epochs). Using these observations, we derived the production rates of different molecules such as CN$(0-0)$, C$_2(\Delta \nu=0)$, and C$_3$ and calculated the production rate ratios. The values of the ratios closest to the perihelion are found to be $\log$ (C$_2/$CN) $ = -0.04 \pm 0.03$ and $\log$ (C$_3/$CN) $ = -0.70 \pm 0.04$, which implies a typical carbon composition. The mean photometric broadband colours are found to be $B-V = 0.77\pm0.04$, $V-R = 0.43\pm0.04$, $R-I = 0.42\pm0.06$, and $B-R = 1.19\pm0.04$. The stability of the molecular production rate ratios and mean photometric broadband colours, pre- and post-perihelion, implies a homogeneous composition. The mean reflectivity gradient for $B-V$ colour is $10.90 \pm 3.62$ $\%/1000$ Å; $V-R$ colour is $6.15 \pm 3.51$ $\%/1000$ Å; and for $R-I$ colour is $4.94 \pm 3.56$ $\%/1000$ Å which is similar to the mean value of the dynamically new comets. Additionally, using an asymmetric non-gravitational force model, we report the comet's nuclear radius to be $1.1 \pm 0.1$ km. Our results are expected to provide inputs to the selection of a potential dynamically new comet as a target for the Comet Interceptor mission.

Interstellar objects (ISOs) can become gravitationally bound to the solar system, enabling multiple observations. If these bound ISOs exist, they provide valuable opportunities to generalize models of planetesimal formation, composition, and ejection beyond our solar system. We explore two mechanisms for ISO capture: gravitational braking (primarily with Jupiter) and the Hills mechanism with the Sun. Using N-body simulations, we investigate ISO capture rates, ejection probabilities, and the resulting orbital elements. Our simulations suggest that approximately 10 ISOs may currently be bound to the solar system, with the vast majority captured through gravitational braking by Jupiter. These objects are bound by a Tisserand parameter with respect to Jupiter less than three, tend to have high eccentricities, semi-major axes larger than Jupiter's, and inclinations modestly biased toward the prograde direction. This region is sparsely populated by observed solar system objects. By comparing known solar system objects to the most probable orbital elements of our simulated ISOs, we identify 18 candidate objects in the current solar system population that may be bound ISOs captured by Jupiter. For the Hills mechanism, we find it to be a viable but less common capture pathway, typically producing isotropic inclinations and perihelia less than one au. Based on these characteristics, we identify seven additional candidate objects for ISOs captured through the Hills mechanism.

We reassess the realistic discovery reach of Solar--System experiments for dark energy (DE) and dark matter (DM) and quantify their complementarity to dedicated cosmological probes, such as the Dark Energy Spectroscopic Instrument (DESI) and Euclid mission. In scalar-tensor frameworks with universal conformal coupling $A(\phi)$, screening (chameleon/symmetron, Vainshtein) suppresses fifth forces in deep Solar potentials, consistent with the gravitational-wave speed bound $|c_{\tt T}/c-1|\lesssim 10^{-15}$. We treat Solar--System tests as hypothesis-driven probes: we assemble quantitative guardrails (MICROSCOPE $\eta$, Cassini $\gamma$, LLR $\dot G/G$ and SEP, ephemeris limits on $\rho_{\rm DM}$ and Yukawa $\alpha(\lambda)$, and clock-network searches for ultralight DM), place them alongside current cosmology posteriors, and provide an explicit map from cosmology-level linear response (e.g., $\mu_{\rm lin,0}$) to local residuals using the screening relations (thin--shell and Vainshtein). Guided by systematics-gated criteria, we outline a near-term program -- solar-conjunction Shapiro-delay and Doppler/range tests, sustained millimeter-class LLR, global optical-clock links, refined ephemerides, and spaceborne atom interferometry (AIS) -- with realistic sensitivities $|\gamma-1|\in (2$--$5)\times 10^{-6}$, $\eta_{\rm EEP}\sim10^{-16}$--$10^{-17}$ (AIS/LLR), $|\dot{G}/G|\lesssim (2$--$5)\times 10^{-14}\,\mathrm{yr}^{-1}$, a uniform $\simeq 2\times$ tightening of AU-scale Yukawa/DM-density bounds, and $3$--$10\times$ gains in ultralight-DM couplings from clock networks. Primary discovery potential for late-time dark energy lies with multi-probe cosmology (geometry and growth), while a hypothesis-driven Solar--System program supplies high-leverage falsification and selective discovery windows for dark matter with ultralight mediators or long-range forces.

In this study, we investigate the microstructure properties of four pulsars (PSRs J0953+0755 (B0950+08), J0627+0706, J0826+2637 (B0823+26) and J1946+1805 (B1944+17)) using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), with particular emphasis on identifying microstructure within interpulse (IP). Through the application of autocorrelation function (ACF) analysis and fast Fourier transform (FFT) techniques, we have systematically examined the periodicity of microstructure in these pulsars. Our findings represent the first successful detection of microstructure within IP. Furthermore, we conducted a comprehensive statistical analysis comparing the characteristic timescales ($\tau_{\mu}$) and the characteristic periods $P_{\mu}$ of quasi-periodic microstructure between the main pulse (MP) and IP, and our results indicate that the $\tau_{\mu}$ and $P_{\mu}$ of microstructure across components appear consistent within measurement errors for PSR J0627+0706, but microstructure in IP are relatively smaller than those in MP for PSR J0953+0755. Furthermore, the relationship between $P_{\mu}$ of microstructure and the rotation period in neutron star populations was reconfirmed: $P_{\mu}(\text{ms})=(1.337\pm0.114)\times P(\text{s})^{(1.063\pm0.038)}$.

We perform long-term general-relativistic neutrino-radiation hydrodynamic simulations for core-collapse supernovae (CCSNe) which include the cooling effect induced by the coupling between axion-like particles (ALPs) and photons. We take into account the \kanji{photon} coalescence and the Primakoff effect, and investigate ALPs with the mass of 10\,MeV and the coupling constant $g_{a\gamma}$ of $1.0\times10^{-9}{\rm \,GeV^{-1}}$ to $7.0\times10^{-9}{\rm \,GeV^{-1}}$. It is found that the effects of the ALP cooling emerge in the late phase rather than the early phase and the ALP luminosities are always lower than the neutrino luminosity in our simulations. We estimate the number of neutrino events for Super-Kamiokande assuming a 10\,kpc CCSN. We conclude that signatures of ALPs could be found in the long-term neutrino signals from a nearby CCSN event in the future, even if $g_{a\gamma}$ is below an upper limit based on the conventional energy-loss argument.

The mass ratio q and effective inspiral spin chi_eff of binary black hole mergers in GWTC-4.0 have been reported to display a weakeran ti-correlation compared to GWTC-3, a feature whose origin has been explored by several groups. In this work, within the isolated binary evolution framework, we adopt a recently proposed wind prescription for helium stars to systematically investigate the spin of the second-born black hole and its role in shaping this correlation. Using the stellar and binary evolution code MESA, which includes a recently proposed helium-star wind prescription alongside internal differential rotation and tidal interactions,we find that the recently proposed wind prescription for helium stars is substantially weaker than the standard Dutch wind scheme, particularly at subsolar metallicity. Using this scheme, we perform detailed binary modeling of a helium star with a black hole companion. Our results show that the spin magnitude of the resulting black hole is insensitive to the helium star's evolutionary stage at the onset of tidal interactions or to the companion mass. Instead, wind mass loss plays the dominant role: more massive helium-star progenitors produce lower-spinning black holes. The initial stellar rotation has only a minor effect, especially under strong tidal coupling, consistent with the common assumption of orbital synchronization. Using the derived relation between the mass and spin of the second-born black hole, we find that the properties of most binary black holes in GWTC-4.0-specifically the mass ratio q and effective inspiral spin chi_eff-can be reproduced. We further show that the q-chi_eff correlation is sensitive to the assumed mass function (e.g., Gaussian and uniform distribution), displaying notable deviations from the Power-Law+Peak model.

The multi-scale structure of the solar surface magnetic field is essential for understanding both the Sun's internal dynamo processes and its external magnetic activity. The surface flux transport (SFT) model has been successful in describing the large-scale evolution of the surface field, but its ability to capture observed multi-scale features, quantified by magnetic power spectra, remains uncertain. Here, we evaluate the SFT model by comparing observed and simulated power spectra across a broad range of spatial scales and by analyzing the effects of key transport parameters. We find that the simulations reproduce the observed spectra well at spherical harmonic degrees $l\lesssim60$, but diverge progressively at smaller spatial scales $l\gtrsim60$. This divergence likely arises from the diffusion approximation used to model the random walk of supergranulation. Power at $20 \lesssim l \lesssim 60$ is primarily determined by the magnetic flux sources, while at $l \lesssim 20$, the spectra are more sensitive to transport parameters. The meridional flow profile, including its equatorial gradient, peak latitude, and polar distribution, along with turbulent diffusivity, has distinct impacts on the low-degree modes ($l \leq 5$). In particular, a comparison of the $l$=3 and $l$=5 multipoles strengths suggests that the poleward flow above $\sim\pm60^\circ$ latitudes is very weak. This study presents the first quantitative validation of SFT models using magnetic power spectra and provides new constraints on surface flux transport physics.

Context. Owing to its sensitivity to wide-orbit giant exoplanets, direct imaging is uniquely positioned to shed light on the interplay between proto-planetary disks and stellar hosts. Besides constraining formation models, new detections are natural benchmarks for atmospheric characterization. Aims. The COBREX project performed an extensive reanalysis of archival observations from SPHERE and GPI using advanced post-processing techniques, enhancing detection sensitivity at close separation. Newly found companion candidates are being followed up to confirm new planets. Methods. Following the detection of a companion candidate around the young ($\sim 15$ Myr) binary star HD 143811, we collected a new observation with SPHERE@VLT ($0.95-1.67 {\mu}$m) to confirm the presence of the source and to assess its physical bond to the target. Results. We report the discovery of a new exoplanet orbiting HD 143811 at a projected separation of $0.43" \sim 60$ au. Thanks to a 9-yr-long baseline, we derive a mostly face-on and low eccentricity orbit with a period of $320^{+250}_{-90}$ years. The luminosity of the planet, constrained through H-band spectrum from GPI, H-band photometry from SPHERE/IRDIS and YJ upper limits from SPHERE/IFS, allows us to place strong constraints on the planet's intrinsic temperature ($T_{int} = 1000 \pm 30$K), corresponding to a mass of $6.1^{+0.7}_{-0.9}$ MJup. Conclusions. HD 143811(AB)b is the second planet ever discovered by GPI; it joins the small cohort of circumbinary planets discovered through imaging, becoming a prime target for follow-up formation, dynamical, and characterization studies.

The first HIRES/Keck precision radial velocity (RV) catalog was released in 2017; it was followed by a second release in 2019, which incorporated corrections for small but significant systematic errors. The manifestation of stellar activity accompanied by systematic errors could affect the detection of exoplanets via the RV method. We expanded the HIRES catalog to March 2023 using publicly available spectra. Furthermore, we included the chromospheric emission line Ca II H&K indicator ($R_{\mathrm{HK}}^\prime$), which is among the most prominent tracers of stellar activity. The precision RVs were obtained using an iodine gas absorption cell and corrected for minor systematic errors. $R_{\mathrm{HK}}^\prime$ measurements were derived by rectifying the observed spectra with PHOENIX synthetic spectra models in six narrow bands surrounding the H and K lines, then subtracting the photospheric contribution. We present an updated HIRES/Keck precision RV catalog featuring 78,920 RV measurements for 1,702 stars. High-quality $R_{\mathrm{HK}}^\prime$ measurements are provided for ~ 40% of the HIRES catalog. The updated catalog can help distinguish stellar activity effects from planetary signals in RV time series, thereby corroborating previously detected planetary candidates and aiding in the detection of new ones.

Several Algol-type binaries were detected to be experiencing rapid orbital decay, which is in contradiction with the conservative mass transfer model.} In this work, we investigate whether anomalous magnetic braking (MB) of intermediate-mass Ap/Bp stars, characterized by surface magnetic fields of $\sim10^2 \mathendash 10^4~\rm G$, could drive orbital decay through magnetic wind-field coupling. Using the stellar evolution code {\ttfamily MESA}, we simulate the evolution of several \add{main-sequence binaries containing Ap/Bp stars}, with typical initial parameters \add{of Algol binaries}. Our models indicate that the anomalous MB mechanism could induce orbital decay in long timescales (hundreds of Myr to several Gyr), \add{reproducing several basic Algol parameters such as the effective temperatures and luminosities of donor stars. However, the predicted orbital period decay rates are much lower than those observed in several Algol systems. We analyze the limitations of the anomalous MB model and discuss alternative mechanisms that could account for the long- or short-term orbital period variations observed in Algol systems, including a surrounding circumbinary disk, stellar expansion, the Applegate mechanism, and the light travel-time effect. Long-term observations are still required to distinguish between these mechanisms in the future.

This study proposes a schematic plan for in-situ resource utilization (ISRU) in Martian volcanic terrains. The work investigated the complexity of volcanic terrains and Martian environmental hazards and suggested comprehensive engineering strategies to overcome the odds and establish a successful mining program in Martian volcanic regions. Slope stabilization methods - such as terracing and anchored drilling rigs - with terrain-adaptive rovers capable of autonomous operations on steep unstable slopes has been suggested as feasible solutions to navigate the complex geological terrains of Martian volcanoes. The mid range rover design with a mass of approximately 2.1 t, proposed here for mining operations, incorporates a six-wheel rocker-bogie suspension, anchoring-enabled drilling arm, dust-mitigation solar arrays, and advanced sensing systems for hazard detection and navigation. A comparative analysis regarding choice of roads and rails for building transport infrastructure has also been performed. We have also looked into the energy requirement of the rover to work under extreme environmental conditions of Mars and suggested a combination of solar and nuclear power to account for the huge energy requirements of sustained operations on Mars. The results demonstrate that mission success in these environments depends on integrating mechanical resilience, environmental adaptability, and operational autonomy, enabling sustainable access to resources in one of Mars' most geologically challenging settings.

The origins of radio astronomy and the discovery of the first radio galaxies are described which showed that the radio emission of active galaxies is very diverse in shape and can reach a size of many times their optical extent. In 1974 the first "giant" radio galaxy (GRG) was discovered, several times larger than any previously known one. Since 2012, when about 100 such GRGs larger than 1 Megaparsec (3.3 million light years) had been reported in literature, the author is performing his own search for GRGs and maintains a list of currently nearly 7000 GRGs, with more than half of these found on his own or his students at the Departamento de Astronomía of Universidad de Guanajuato. An analysis of the very largest GRGs does not reveal any single property of these that would explain why they could grow to such large sizes. Recent advances in radio telescopes have led to vast amounts of images rich in GRGs, but due to the complexity of identifying their host galaxies only a fraction of these images can be searched with visual inspection by humans. Currently available machine algorithms and citizen science projects are prone to erroneous identifications and also leave unnoticed a substantial fraction of GRGs, such that supervision of the results by experts is essential to produce reliable results.

POEMMA Balloon with Radio (PBR) is a NASA super-pressure balloon mission building toward the proposed Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) dual satellite mission. In its planned 2027 launch, PBR will study Ultra-High-Energy Cosmic Rays, Neutrinos, and High-Altitude Horizontal Airshowers from 33 km above the Earth. By operating at balloon altitudes, PBR will provide a novel vantage point to study air-shower physics while offering competitive instantaneous exposure to neutrinos from transient astrophysical phenomena. The payload's optical instrument is a 0.95 m$^2$ aperture hybrid Schmidt telescope with a 3.81 m$^2$ segmented mirror focusing light onto a Fluorescence Camera and a bi-focalized Cherenkov Camera. The payload will also feature a Radio Instrument consisting of two sinuous antennas based on the Payload for Ultrahigh Energy Observations (PUEO) low-frequency instrument. A combined gamma ray/x-ray detector and IR cloud camera round out the instrumentation package, meaning PBR will be the first multi-hybrid balloon-borne multi-messenger observatory flown. This extensive instrumentation must be combined into a radio quiet payload that satisfies the scientific needs and can operate in near vacuum at extreme temperatures, all while meeting NASA safety requirements and weighing no more than 3000 lbs (1361 kg). Accomplishing these tasks together will mark a significant step toward establishing technological readiness for the POEMMA satellite mission. We present an overview of PBR's mechanical and optical systems, additionally detailing our strategies to mitigate electromagnetic interference for the radio instrument and prepare for the harsh near-space environment.

The equation of state (EOS) of cold dense matter is a central open problem in nuclear astrophysics. Its inference is hindered by the lack of \textit{ab initio} control above about twice nuclear saturation density, requiring extrapolation. Parametric schemes such as piecewise polytropes (PP) are efficient but restrictive, while nonparametric approaches like Gaussian processes (GP) allow more flexibility at the cost of larger prior volumes. We extend our hybrid EOS framework by replacing the high-density polytropic extension with a GP representation of the squared sound speed, anchored at low densities by the SLy crust EOS and a nuclear meta-model constrained by $\chi$EFT and laboratory data. Using hierarchical Bayesian analysis, we jointly constrain the EOS and neutron star mass distribution with multi-messenger observations, including NICER radii, GW170817 and GW190425 tidal deformabilities, pulsar masses, and neutron skin experiments. We examine four scenarios defined by high-density extrapolation (PP vs.\ GP) and hotspot geometry in the NICER modeling of PSR~J0030$+$0451 (ST+PDT vs.\ PDT-U). GP extrapolations generally yield softer EOS posteriors with broader uncertainties. Hotspot assumptions also play an important role, shifting inferred mass--radius relations. Bayesian evidence strongly favors the ST+PDT geometry over PDT-U under both extrapolations, while GP is mildly preferred over PP. These results underscore the impact of observational modeling and EOS extrapolation on neutron star inferences, and show that a GP-based extension offers a robust way to quantify systematic uncertainties in high-density matter.

We study the nonlinear evolution of the magnetic buoyancy instability in rotating and non-rotating gas layers using numerical solutions of non-ideal, isothermal MHD equations. The unstable magnetic field is either imposed through the boundary conditions or generated by an imposed $\alpha$-effect. In the case of an imposed field, we solve for the deviations from the background state with periodic boundary conditions. We also include cosmic rays as a weightless fluid which exerts a dynamically significant pressure and amplifies magnetic buoyancy, known as the Parker instability. Without rotation, systems with an imposed magnetic field evolve to a state with a very weak magnetic field, very different from the marginally stable eigenfunction, where the gas layer eventually becomes very thin as it is supported by thermal and turbulent pressures alone. However, this does not happen when the $\alpha$-effect maintains the magnetic field. Rotation fundamentally changes the development of the instability. A rotating system develops nonlinear oscillations, and the magnetic field direction changes even with an imposed magnetic field. We demonstrate that the cause is a secondary $\alpha$-effect at large altitudes as the gas flow produced by the instability becomes helical. The secondary $\alpha$-effect has an anomalous sign with the $\alpha$-coefficient being negative in the northern hemisphere, whereas the Coriolis force produces a positive $\alpha$. The mean-field dynamo action outside the original gas layer can also lead to a switch in the magnetic field parity from quadrupolar to dipolar. Altogether, the magnetic buoyancy instability and the mean-field dynamo action become separated as distinct physical effects in a nonlinear rotating system. We show that none of the assumptions used in analytic studies of the Parker instability is corroborated by numerical results.

The Wang-Sheeley-Arge (WSA) model has been the cornerstone of operational solar wind forecasting for nearly two decades, owing to its simplicity and physics-based formalism. However, its performance is strongly dependent on several empirical parameters that are typically fixed or tuned manually, limiting its adaptability across varying solar conditions. In this study, we present a neural enhancement to the WSA framework (referred to as WSA+) that systematically optimizes the empirical parameters of the WSA solar wind speed relation using in-situ observations within a differentiable physics-constrained pipeline. The approach operates in two stages: first, a neural optimizer adjusts WSA parameters independently for each Carrington Rotation to better match the observed solar wind data. Then, a neural network learns to predict these optimized speed maps directly from magnetogram-derived features. This enables generalization of the optimization process and allows inference for new solar conditions without manual tuning. The developed WSA+ preserves the interpretability of the original relation while significantly improving the match with OMNI in-situ data across multiple performance metrics, including correlation and error statistics. It consistently outperforms the traditional WSA relation across both low and high solar activity periods, with average improvements of approximately 40 percent. By integrating data-driven learning with physical constraints, WSA+ offers a robust and adaptable enhancement, with immediate utility as a drop-in replacement in global heliospheric modeling pipelines.

We present a deep learning approach to classify fast radio bursts (FRBs) based purely on morphology as encoded on recorded dynamic spectrum from CHIME/FRB Catalog 2. We implemented transfer learning with a pretrained ConvNext architecture, exploiting its powerful feature extraction ability. ConvNext was adapted to classify dedispersed dynamic spectra (which we treat as images) of the FRBs into one of the two sub-classes, i.e., repeater and non-repeater, based on their various temporal and spectral properties and relation between the sub-pulse structures. Additionally, we also used mathematical model representation of the total intensity data to interpret the deep learning model. Upon fine-tuning the pretrained ConvNext on the FRB spectrograms, we were able to achieve high classification metrics while substantially reducing training time and computing power as compared to training a deep learning model from scratch with random weights and biases without any feature extraction ability. Importantly, our results suggest that the morphological differences between CHIME repeating and non-repeating events persist in Catalog 2 and the deep learning model leveraged these differences for classification. The fine-tuned deep learning model can be used for inference, which enables us to predict whether an FRB's morphology resembles that of repeaters or non-repeaters. Such inferences may become increasingly significant when trained on larger data sets that will exist in the near future.

We measure the absolute proper motions of Andromeda V (And V) and Andromeda VI/Pegasus (And VI) dwarf galaxies, satellites of M31 located near its galactic plane. And VI is located the farthest from M31 among the six satellites with currently measured proper motions. A combination of ACS/WFC and WFPC2 exposures are utilized, spanning a 20-year time baseline. The WFPC2 exposures are processed using a recently developed deep-learning centering procedure as well as the most up-to-date astrometric calibration of the camera. We use on the order of 100 background galaxies per satellite to determine the correction to absolute proper motion. For And V we obtain an absolute proper motion of $(\mu_{\alpha} , \mu_{\delta})_{And\,V} = (26.1\pm21.5, -74.2\pm19.1)~\mu$as yr$^{-1}$. For And VI we obtain an absolute proper motion of $(\mu_{\alpha} , \mu_{\delta})_{And\,VI} = (-1.6\pm12.3, -52.6\pm11.2)~\mu$as yr$^{-1}$. Orbit integrations and analyses are made for these two Andromeda satellites using two estimates of both the mass and proper motion of M31. It is found that And V has an orbit consistent within errors with alignment with M31's disk and counter orbiting it, although this alignment is not well constrained. And VI's orbit is better determined and is very much consistent with co-orbiting with M31's disk. While currently at a distance of ~280 kpc from M31, And VI will remain beyond a distance of ~ 90 kpc from M31, thus experiencing low tidal influence compared to the other M31 satellites with known orbits. Both satellites are determined to be well-bound to M31.

Determining the physical properties of ices across the solar system is essential for understanding the surface dynamics, volatile transport, and climate evolution on ice-covered planetary bodies. Here, we use well-constrained measurements of snow that has metamorphosed into coarse-grained firn and bubbly glacier ice in East Antarctica to test three commonly-used radiative transfer models: delta-Eddington, Hapke, and Shkuratov. Using the measured optical properties, we find that the delta-Eddington model generally shows the least deviation from the measured albedo, followed by the Shkuratov and Hapke models, respectively. But when the models are used to infer the grain radius using the measured albedo, the Shkuratov model provides closer best-fit grain radii (off by average factor 0.9) than delta-Eddington (0.6), and Hapke (1.8). Despite this, the spectral albedos estimated by the Shkuratov and Hapke models using their respective best-fit grain radii deviate more from the measurements than delta-Eddington. This result is caused by the Hapke and Shkuratov models not accounting for: (1) the increased absorption within dense ice, and (2) specular reflection at the surface of firn and ice. Additionally, all three models do not account for the nonsphericity of bubbles within ice. The combination of these factors leads to model errors generally increasing with increasing grain radius. Based on our quantitative comparison, we recommend using the delta-Eddington model for predicting the albedo and inferring the grain radius of ices across the solar system because it generally produces the least error while using realistic physical parameters.

The traditional model which assumed GRBs as originating from a single Black Hole (BH) have been modified by the Binary Driven Hypernova (BdHN) model in which the trigger of the GRB originate from a binary system composed of a 10 solar mass CO core and a 2 solar mass neutron star binary companion. The binary period being as short as minutes to hours. Recent results evidence that the most energetic GRBs may have as precursors a sequence of two types of SN: a pair-SN followed soon after by a more traditional core collapse. All this appear to open the way to two new types of SNe: the Pair-SNe without a remnant and a magnetized-rotating-core collapse leading to the formation of a pulsar. We generalize our previous assumptions, here the possibility of fission of the rapidly rotating CO core is examined. The role of the magnetic field of the CO core are equally examined with the magneto-hydrodynamic associated process, all the way to generate overcritical fields and e+ e- pairs. All this appear to open the way to a new types of SN, much in line with pair-SN models and a significant change from the initial non rotating models. The BdHN are characterized by seven new physics Episodes here all used to formulate the new approach. The substantial modification of each Episode are outlined by a leading order treatment.

Magnetic reconnection is an important driving mechanism of many chromospheric phenomena, e.g., UV bursts and chromospheric jets. Information about magnetic field is indispensable for analyzing chromospheric magnetic reconnection, which is mainly encoded in polarization signals. The purpose of this work is to predict possible Stokes features related to chromospheric reconnection events, from realistic two-dimensional magnetohydrodynamic simulation and Stokes profile synthesis. An emerging magnetic flux sheet is imposed at the bottom boundary of a well-relaxed unipolar atmosphere that spans from the upper convection zone to the corona. The reconnection region is heated to $\sim$7 kK and the outflow velocity reaches up to $\sim$35 km s$^{-1}$. Through Stokes profile synthesis, several Stokes features related to reconnections and plasmoids are reproduced. We found sign reversal features on circular polarization and amplitude reduction features on linear polarization at reconnection sites. Also, we report strong linear and circular polarization signals corresponding to huge ($\sim$300 km) and tiny ($\sim$40 km) plasmoids, respectively. We conclude that both linear and circular polarization signals may reveal the distinctive physical mechanisms in reconnections, and enhance the understanding of magnetic reconnection in observations.

The recent discovery of a third interstellar object (ISO) 3I/ATLAS, following 1I/`Oumuamua and 2I/Borisov, has raised questions about the nature and origin of these enigmatic objects. With the Vera C. Rubin Observatory expected to discover dozens of new ISOs over the next decade, it is timely to use a classification scheme for their nature in the context of the recently proposed Loeb scale. Here, we provide a formalism for ranking ISOs quantitatively on the Loeb Scale in analogy to Sagan's formalism for mapping the Kardashev scale based on the energy output of technological civilizations.

Spectral line surveys of the Taurus Molecular Cloud-1 (TMC-1) have led to the detection of more than 100 new molecular species, making it the most prolific source of interstellar molecular discoveries. These wide-band, high-sensitivity line surveys have been enabled by advances in telescope and receiver technology, particularly at centimeter and millimeter wavelengths. In this work, we present a statistical analysis of the molecular inventory of TMC-1 as probed by the GOTHAM large program survey from 3.9 to 36.4 GHz. To fully unlock the potential of the $\sim$29 GHz spectral bandwidth, we developed an automated pipeline for data reduction and calibration. We applied a Bayesian approach with Markov-Chain Monte Carlo fitting to the calibrated spectra and constrained column densities for 102 molecular species detected in TMC-1, including 75 main isotopic species, 20 carbon-13 substituted species, and seven deuterium-substituted species. This list of the detected gas-phase molecules is populated by unsaturated hydrocarbons, in stark contrast to the oxygen-rich organics found in sublimated ices around protostars. Of note, ten individual aromatic molecules were identified in the GOTHAM observations, contributing 0.011% of the gas-phase carbon budget probed by detected molecules when including CO and 6% when excluding CO. This work provides a reference set of observed gas-phase molecular abundances for interstellar clouds, offering a new benchmark for astrochemical theoretical models.

This paper presents the first structured evaluation of Solar System bodies hypothetically relocated to Earth orbit (1 AU) to assess their potential as alternative habitats. Using comparative criteria, planetary size and gravity, atmospheric retention, volatile accessibility, weather system potential, soil development feasibility, and orbital transfer cost. We find that most bodies are unsuitable. Mercury and the Moon lack volatiles and atmospheres, while gas and ice giants offer no solid surfaces. Venus, despite strong atmospheric retention, remains constrained by extreme greenhouse forcing. Mars emerges as the most viable candidate, balancing accessibility and volatile resources. Titan provides a conditional long-term promise, with a dense atmosphere and rich organics that could transition to a water-based cycle at 1 AU. These findings highlight new pathways for planetary engineering and long-term human survival.

We investigate dynamical constraints on the population of large interstellar objects (ISOs) by combining encounter rate analysis, Eddington inversion, and Liouville mapping. Encounter rate scaling demonstrates that detections of kilometer-scale ISOs require flux enhancements beyond natural Maxwellian expectations. Using Eddington inversion, we show how steep density profiles imply phase-space biases consistent with strong gravitational focusing and we then develop a Liouville mapping formalism that propagates the interstellar velocity distribution inward under conservation of energy and angular momentum, revealing that low-angular momentum anisotropies can reproduce the observed size dependent detection rates. These results provide a self consistent dynamical framework for interpreting the observed population of ISOs and for assessing whether the required anisotropies arise from natural or artificial origins. The main results are framed in the context of the parameters for 3I/ATLAS, but the implications are general and go on to sharpen the distinction between natural dynamical mechanisms and potential artificial origins for ISOs.

The Five-hundred-meter Aperture Spherical Telescope (FAST) is the world's largest single-dish radio telescope, and the search for extraterrestrial intelligence (SETI) is one of its five key science objectives. We conducted a targeted narrowband search toward the TRAPPIST-1 system using FAST. The observations consisted of five independent L-band pointings, each with a 20-minute integration, for a total on-source time of 1.67h. The frequency coverage spanned 1.05--1.45GHz with a spectral resolution of ~7.5Hz. We searched for narrowband drifting signals with Doppler drift rates within +_4Hz/s and a signal-to-noise ratio threshold of S/N>10 in two orthogonal linear polarizations this http URL on the system parameters adopted in this work, we estimate a minimum detectable equivalent isotropic radiated power of 2.04x10^10W, placing one of the most stringent constraints to date on persistent or high-duty-cycle narrowband transmitters in this system. No credible technosignature candidates were identified within the searched parameter space. Nevertheless,TRAPPIST-1 remains a compelling target for future SETI efforts. We plan to extend our search to other signal types, such as periodic or transient transmitters, and to carry out broader surveys of nearby exoplanetary systems with FAST.

We present an automated search method for radio transients on the minute timescale focused on the emerging long period transients (LPTs) in image-plane radio data. The method is tuned for use with the Murchison Widefield Array (MWA) and tested on archival observations from the GaLactic and Extragalactic All-Sky MWA Extended Survey (GLEAM-X) in the 70--300 MHz range. The images are formed from model-subtracted visibilities, before applying three filters to the time series of each pixel in an image, with each filter designed to be sensitive to a different transient behaviour. Due to the nature of radio interferometry and the refraction of the fluctuating ionosphere, the vast majority of candidates at this stage are artefacts which we identify and remove using a set of flagging measures. Of the 336 final candidates, 7 were genuine transients; 1 new LPT, 1 new pulsar, and 5 known pulsars. The performance of the method is analysed by injecting modelled transient pulses into a subset of the observations and applying the method to the result.

Rejection of cloud-contaminated data is a complex and important process at the Pierre Auger Observatory, one which combines information from several sources, including IR cameras, lidars, and satellite imaging. With the deteriorating quality of the IR cameras and challenges in using other sources, we propose a new method. We use continuous detector monitoring measurements to build a large database of night sky background fluxes for each pixel across 27 telescopes. Using this database, we generate the expected background flux and define cloud rejection thresholds. Through a straightforward analysis we construct boolean cloud-contamination masks. We demonstrate some results of the analysis, including comparisons with cloud detected using infra-red observations.

In high-energy astrophysics, interpreting observed spectra hinges on understanding the competition between energy gains and radiative losses. To progress along these lines, we report on particle-in-cell simulations of particle acceleration in relativistic, magnetized turbulent pair plasmas including synchrotron radiative losses. Our key finding is that the particle energy spectrum does not terminate at this maximal energy but extends beyond with a steepened spectrum, up to the synchrotron burn-off limit where particles cool within a gyrotime. For our adopted parameters (magnetization $\sigma \approx 1 $ and amplitude $\delta B/B_0\simeq 1$), the particle distribution follows ${\rm d}n/{\rm d}\gamma\propto \gamma^{-s}$ with $s\simeq 3$ below the predicted maximal energy, then steepens to $s\simeq 4$ above. The particle distribution and the radiated synchrotron spectra display strong variability near the cutoff energy down to timescales well below the largest eddy turn-around time. We substantiate our results by demonstrating that the acceleration rate itself displays a broken powerlaw-like distribution whose maximal value is the gyrofrequency. The highest energy particles are accelerated by a generalized Fermi process in ideal electric fields, driven by a gradient of the $4$--velocity field $u_E$ of the magnetic field lines of relativistic amplitude, $\delta u_E \gtrsim c$, ordered on a scale comparable to the particle gyroradius. We contend that this is a generic feature of relativistic, large-amplitude turbulence. Lastly, we apply our results to the Crab nebula, which exhibits a hierarchy of characteristic Lorentz factors similar to that studied here. We conclude that stochastic acceleration in this environment is a promising mechanism for explaining the highest-energy part of the synchrotron spectral energy distribution, and its variability. [Abridged]

Based on archival Chandra X-ray observation, optical integral-field spectroscopic data and radio interferometric data, we report the discovery of a pair of giant bubbles (with a projected radius ~ 5 kpc) of ionized gas emerging from a highly inclined starburst galaxy NGC 6286, which is undergoing strong tidal interactions with its close neighbor NGC 6285. The bubbles are manifested by extraplanar soft X-ray emission with an X-shaped morphology, which is tightly co-spatial with $\rm H\alpha$ line emission and partially coincident with radio continuum. Low surface brightness diffuse X-ray emission can be traced out to ~ 90 kpc from the galactic center, revealing the presence of an extended hot gaseous halo. X-ray spectral analysis of the bubbles yields a gas temperature of $0.70^{+0.16}_{-0.18}$ keV, a relatively high value among known galactic-scale bubbles in the local universe. An average energy injection rate of ~ $10^{43}$ erg $\rm s^{-1}$ is required to inflate the bubbles within an estimated dynamical age of ~ 6.4 Myr. The multi-wavelength properties of the bubbles can be understood with the conventional superwind scenario, in which disk/halo gas is swept up into an expanding, cooling shell by a hot tenuous wind. The current starburst in NGC 6286 is energetically sufficient to launch the superwind, although we cannot rule out the possibility of a more violent AGN in the recent past as the driving source. Future high-resolution spectroscopic observations will help to shed light on the origin of the superwind and its role as an important galactic feedback process.

Active galactic nuclei (AGN) are known to drive ionized gas into their host galaxies, which may affect the evolution of both the central supermassive black holes and their hosts. In the case of NGC 3516, a nearby Seyfert 1 galaxy, these AGN winds have historically proven difficult to disentangle from galactic rotation. Using long slit spectroscopy at multiple position angles from the Hubble Space Telescope Space Telescope Imaging Spectrograph and the Apache Point Observatory Kitt Peak Ohio State Multi Object Spectrograph, we separate these kinematic components by fitting multiple Gaussians to the H{\alpha}, N II, H{\beta}, and O III emission lines along the slits. We present a biconical outflow model that agrees well with the observed kinematics of the outflowing gas in the narrow-line region (NLR). Our results indicate that the structure of the O III emission is explained by dusty gas spirals in the galactic disk that are illuminated by the ionizing bicone, which is viewed along one edge, resulting in the complex nuclear kinematics. Our view into the bicone edge is consistent with the multiple, deep components of ionized absorption lines seen in UV and X-ray spectra of NGC 3516. The observed turnover in the velocity of the NLR clouds matches that from a simple dynamical model of radiative acceleration by the AGN and gravitational deceleration by the AGN and galaxy, indicating they are the principal forces at work on the gas clouds. Finally, the model launch radii indicate that the outflowing clouds originate primarily from the inner dusty spirals near the AGN.

As we enter the final year of the second extended mission of the Transiting Exoplanet Survey Satellite (TESS), it is time to reflect on what the TESS mission has contributed to the advancement of astronomy. Thousands of papers based on TESS data have already been published, making it a challenge to select the ones we mention or summarise in this review. As the title suggests, this paper focuses on variable stars, that is, phenomena that causes a star's brightness to change. We discuss all the major classes of extrinsic and intrinsic variables, from planetary transits to pulsating stars, excluding only the longest-period ones, which are not well suited for the typical time spans of TESS time-series observations. TESS has provided significant and interesting data and results for all these variable types. We hope that this selection successfully demonstrates the diverse applicability of TESS in variable star research.

Black hole X-ray binaries (BH XRBs) launch powerful relativistic jets during bright outburst phases. The properties of these outflows change dramatically between different spectral/accretion states. Collimated, compact jets are observed during the hard state and are quenched during the soft state, while discrete ejecta are mainly launched during the hard-to-soft state transition. Currently, we still do not understand what triggers the formation and destruction of compact jets or the launch of discrete ejecta. In this context, finding a unique link between the jet evolution and the properties of the X-ray emission, such as its fast variability, would imply a major progress in our understanding of the fundamental mechanisms that drive relativistic outflows in BH XRBs. Here we show that a brief but strong radio re-brightening during a predominantly soft state of the BH XRB MAXI J1348$-$630 was contemporaneous with a significant increase in the X-ray rms variability observed with NICER in 2019. During this phase, the variability displayed significant changes and, at the same time, MAXI J1348$-$630 launched two pairs of relativistic discrete ejecta that we detected with the MeerKAT and ATCA radio-interferometers. We propose that short-lived compact jets were reactivated during this excursion to the hard-intermediate state and were switched off before the ejecta launch, a phenomenology that has been very rarely observed in these systems. Interestingly, with the caveat of gaps in our radio and X-ray coverage, we suggest a tentative correspondence between the launch of ejecta and the drop in X-ray rms variability in this source, while other typical X-ray signatures associated with discrete ejections are not detected. We discuss how these results provide us with insights into the complex and dynamic coupling between the jets and hot corona in BH XRBs.

Pulsar timing arrays (PTAs) seek to detect a nano-Hz stochastic gravitational-wave background (GWB) by searching for the characteristic Hellings and Downs angular pattern of timing residual correlations. So far, the evidence remains below the conventional $5$-$\sigma$ threshold, as assessed using the literature-standard ``optimal cross-correlation detection statistic''. While this quadratic combination of cross-correlated data maximizes the {\em deflection} (signal-to-noise ratio), it does not maximize the detection probability at fixed false-alarm probability (FAP), and therefore is not Neyman-Pearson (NP) optimal for the assumed noise and signal models. The NP-optimal detection statistic is a different quadratic form, but is not used because it also incorporates autocorrelations, making it more susceptible to uncertainties in the modeling of pulsar timing noise. Here, we derive the best compromise: a quadratic detection statistic which is as close as possible to the NP-optimal detection statistic (minimizing the variance of its difference with the NP statistic) subject to the constraint that it only uses cross-correlations, so that it is less affected by pulsar noise modeling errors. We study the performance of this new $\NPMV$ statistic for a simulated PTA whose noise and (putative) signal match those of the NANOGrav 15-year data release: GWB amplitude $A_{\rm gw}=2.1\times 10^{-15}$ and spectral index $\gamma=13/3$. Compared to the literature-standard ``optimal" cross-correlation detection statistic, the $\NPMV$ statistic increases the detection probability by $47\%$ when operating at a $5$-$\sigma$ FAP of $\alpha = 2.9 \times 10^{-7}$.

(Abridged) Rotational H$_2$O spectra as observed with JWST/MIRI provide a good probe of the temperature and column density structure of the inner disk. H$_2$O emission can also be influenced by dynamical processes, such as dust grains drifting inwards and their icy mantles sublimating once they cross the snowlines, thus enriching the inner regions in H$_2$O vapor. Recent work has found that this process may leave an imprint in the H$_2$O spectrum in the form of excess flux in the cold H$_2$O lines. In this work, we aim to test the accuracy of several common retrieval techniques on full 2D thermochemical disk models. Moreover, we investigate the cold H$_2$O emission that has been proposed as a signature of drift, to gain further insights into the underlying radial and vertical distribution of H$_2$O. We present two sets of Dust And LInes (DALI) thermochemical models and run several retrieval techniques to investigate how the retrieved temperature and column density compare to our models. Single-temperature slab retrievals mainly trace the warm ($\sim$500 K) H$_2$O reservoir, whereas a three-component fit is able to better trace the full temperature gradient in the IR emitting region. Retrieved temperatures tend to underestimate the true temperature of the emitting layer due to non-LTE effects. The retrieved column density traces close to the mid-IR dust $\tau=1$ surface. We find that the strength of the cold H$_2$O emission is directly linked to the H$_2$O abundance above the snow surface at large radii (>1 au). This implies that sources with excess cold H$_2$O flux likely have a high H$_2$O abundance in this region ($\gtrsim10^{-5}$), higher than predicted by the chemical network. This discrepancy is most likely caused by the absence of dust transport processes in our models, further strengthening the theory that this emission may be a signature of radial drift and vertical mixing.

The optical spectra of Titan reveal a rich set of absorption features, most of which are likely associated with methane (CH$_4$). Methane is a key molecule in planetary and exoplanetary atmospheres, yet a comprehensive high-resolution linelist at optical wavelengths remains incomplete. This study identified and characterized potential CH$_4$ absorption features in high-resolution optical spectra of Titan, providing essential data for linelist development and improving CH$_4$ detection and characterization. We analyzed Titan spectra from the ESPRESSO spectrograph (R $\approx$ 190,000), identifying intrinsic features and measuring their relative strengths. A conservative detection approach was employed, slightly overestimating solar and telluric contributions to distinguish them from Titan's intrinsic features. To assess the impact of spectral resolution, we compared the ESPRESSO data with Titan UVES data (R $\approx$ 110,000). We identified 6,195 absorption features in the ESPRESSO spectra potentially associated with CH$_4$, of which 5,436 are newly reported. ESPRESSO detected twice as many features as UVES in overlapping regions, highlighting the advantage of higher-resolution data. Most detected lines remained unresolved, so our reported features are primarily blended absorption structures. We estimated the detection limit for feature identification to correspond to a CH$_4$ absorption coefficient of approximately 0.02 km-am$^{-1}$. Comparison of our results with a previous analysis of Titan UVES spectra and with experimental CH$_4$ data at a similar temperature showed good agreement, while some discrepancies were observed when compared with data acquired at a different temperature. We provide a comprehensive list of Titan absorption features with key reliability metrics, along with Titan's intrinsic spectra, to support future studies.

According to the giant impact theory, the Moon formed through accreting the debris disk produced by a collision between Theia and the proto-Earth. The giant impact theory can explain most of the properties of the Earth-Moon system, however, simulations with respect to giant impact between a planetary embryo and the growing proto-Earth show that more than 40 percent of the materials in the circum-terrestrial debris disk produced by the giant impact originates from the impactor. Thus, the giant impact theory has difficulty explaining the Moon's Earth-like isotopic compositions, which is referred to as the lunar isotopic crisis. With the assumption that Theia may have possessed an iron-rich mantle compared with proto-Earth's mantle, here we show that, after the formation of the stratified lunar magma ocean, solidification of the stratified lunar magma ocean would result that the upper solid layer is composed of proto-Earth's mantle and the lower solid layer is made of Theia's mantle, meaning that the Moon's Earth-like isotopic composition is a natural result of the giant impact. The theory proposed here may provide a way of explaining the lunar isotopic crisis.

This work presents measurements of local HII environment metallicities of core-collapse supernovae (SNe) in hosts with redshifts up to z$\sim$0.025. 139 SNe environments were observed at the Isaac Newton Telescope and data of an additional 268 SNe environments were found in archival data of MUSE, MaNGA and PISCO. The project focuses on SNe with clean Type IIP, Type Ib and Type Ic classifications. We present the largest spectroscopic sample to date, evaluating environment metallicities of 79 Type Ib, 66 Type Ic and 93 Type IIP by N2 and O3N2 strong emission line methods. The cumulative distribution functions (CDFs) of the SN environment metallicities show Type Ib and Type Ic SNe tending towards higher metallicity than Type IIP. We test the null hypothesis that Type Ib/Ic/IIP progenitors are drawn from the same parent population. There is no statistically significant difference between progenitors of Type Ib and Type Ic SNe. However, when comparing Ib/Ic with IIP SNe, the tests indicate strong statistical significance (significance level better than 1\%) to reject our null hypothesis suggesting that the samples are not drawn from the same parent population. The significance is even higher (level better 0.1\%) when testing Type IIP vs. the combined Type Ib+Ic sample. These results support a different physical nature of Type IIP and Types Ib/Ic progenitors. It challenges stellar evolution and SNe explosion models to reproduce the distinct CDFs found.

Super-fast rotators (SFRs; P < 2.2 hr) are of great importance in asteroid studies; yet, many reported detections suffer from aliasing caused by an insufficient observation cadence. We present dense CCD photometry for 15 SFRs candidates (14 after excluding 11219 Benbohn, whose published period already exceeds the spin barrier) observed from 2023 Aug 11 to 2024 Aug 11 with the 1.5 m Sierra Nevada and 1.4 m AS Vidojevica telescopes. Our dataset comprises approximately 2,400 calibrated data points, with per-measurement formal errors of 0.02-0.04 mag and total on-target coverage of 2-13 hr per object. We have reliably determined periods for 9 targets. In terms of spin rate, we have confirmed four SFRs with periods of 1.06-1.84 hr and peak-to-peak amplitudes of 0.054-0.685 mag. Three candidates remain ambiguous, while the rest are reclassified, showing the best solutions with periods greater than 2.5 hr. By extrapolating from our confirmation rate (4/14) to the 3.9 percent occurrence rate found in the Light Curve Database (LCDB) yields a central SFR fraction of 1.1 percent, with a one-sigma lower bound of 0.6 percent among kilometre-scale asteroids.

We present a 3D hydrodynamical simulation of the accretion of a gas cloudlet onto the IRAS 04125+2902 binary system, where the 3-Myr primary hosts a transiting planet. We demonstrate that such an accretion event can naturally produce a circumstellar disk that is misaligned with respect to the rest of the system, consistent with the observed misaligned transition disk. In the model, the prescribed orbital plane of the cloudlet is largely retained by the resulting circumstellar disk after undergoing gravitational interactions with the secondary during the initial accretion. After ~4.4 binary orbits, a disk with $R_d=300~\mathrm{AU}$ has formed around the stellar primary made of ~13% of the cloudlet mass, $M_\mathrm{d,p}=2.1\times 10^{-3}~\mathrm{M}_\odot$. The companion also retains some of the cloudlet's mass and forms a disk with $M_\mathrm{d,c}=9.3\times 10^{-5}~\mathrm{M}_\odot$, though only the transition disk around the primary has been observed. Our findings highlight the importance of considering mass inflow onto protoplanetary disk for their evolution.

Transport and mixing of gas species are of particular interest in planetary environments, where interactions among multiple species can occur within confined or porous media. In this work, we present a novel Smoothed Particle Hydrodynamics (SPH) approach for modeling the mixing of binary gas species. The model treats each gas as a separate fluid governed by its own set of Euler equations, coupled through collisional momentum and energy exchange terms derived from a kinetic relaxation model based on the Boltzmann equation. The numerical scheme employs a first-order operator splitting approach combined with a two-step Euler integrator. In this setup, the hydrodynamic evolution is first computed using standard SPH techniques to handle pressure forces. This is followed by a separate correction step that accounts for interspecies collisional exchanges. Such a decoupled treatment enables the use of a larger timestep dictated by hydrodynamics rather than the typically much smaller collisional timescale, enhancing computational efficiency. The model achieves good accuracy in reproducing the equilibration of density and temperature in a range of molecular mass ratios. Its modular structure supports natural extensions to polyatomic mixtures and enables the inclusion of additional physics, such as gas-solid interactions with dust and ice. These features make the method particularly well-suited for applications involving confined, multi-component gas systems, such as those expected during the ESA ExoMars mission.

The most significant excess in the arrival directions of ultra-high-energy cosmic rays with energies $\gtrsim40\,\mathrm{EeV}$ is found in the direction of several interesting source candidates, most prominently the nearby radio galaxy Centaurus A. Naturally, Cen A has been suspected to create the anisotropy - but very different scenarios have been proposed. This includes a subdominant source contribution in combination with isotropic background sources, as well as a scenario where Cen A supplies the whole cosmic-ray flux above the ankle. Recently, it was suggested that the overdensity could instead consist of strongly deflected events from the Sombrero galaxy. Thanks to the recent development of several models of the Galactic magnetic field, it is now possible to test these proposed scenarios explicitly. Leveraging the measured overdensity direction, significance, angular scale, and energy evolution, we place limits on the allowed signal fraction, the possible ejected charge number and the strength of the extragalactic magnetic field between the respective source and Earth. We find that the scenario of a subdominant source in the overdensity region requires the charge number to be $Z\lesssim6$ and the extragalactic magnetic field quantity $B/\mathrm{nG} \sqrt{L_c/\mathrm{nG}}$ to be between $~1$ and $~100$. For the Sombrero galaxy to be the source, the dominant charge number has to be around $Z=6$ with $1\lesssim B/\mathrm{nG} \sqrt{L_c/\mathrm{nG}}\lesssim20$. We find that a scenario where all the flux above $30\,\mathrm{EeV}$ is supplied by Cen A or M83 is possible for $20\lesssim B/\mathrm{nG} \sqrt{L_c/\mathrm{nG}}\lesssim30$ and a mixed composition - explaining both the Centaurus region excess and the distribution of the highest-energy events - however, another contributing source is possibly required in the energy range $<30\,\mathrm{EeV}$.

Gamma-Ray Bursts are among the most powerful and violent events in the Universe. Despite over half a century of observations of these transient sources, many open questions remain about their nature and the physical emission mechanisms at play. Polarization measurements of the GRB prompt gamma-ray emission have long been theorized to be able to answer most of these questions. Early polarization measurements did not allow to draw clear conclusions because of limited significance. With the aim of better characterizing the polarization of these prompt emissions, a compact Gamma-Ray polarimeter called POLAR has been sent to space as part of the Tiangong-2 Chinese space lab for 6 months of operations starting September 2016. The instrument detected 55 GRBs as well as several pulsars. Time-integrated polarization analysis of the 14 brightest detected GRBs has shown that the prompt emission is lowly polarized or fully unpolarized. However, time-resolved analysis depicted strong hints of an evolving polarization angle within single pulses, washing out the polarization degree in time-integrated analyses. Energy-resolved polarization analysis has shown no constraining results due to limited statistics. Hence, a more sensitive $\gamma$-ray polarimeter is required to perform detailed energy and time-resolved polarization analysis of the prompt gamma-ray emission of GRBs. Based on the success of the POLAR mission, a larger-scale instrument, approved for launch to the China Space Station (CSS) in 2027, is currently being developed by a Swiss, Chinese, Polish, and German collaboration. Thanks to its large sensitivity in the 20-800~keV range, POLAR-2 will produce polarization measurements of at least 50 GRBs per year with a precision equal to or higher than the best results published by POLAR, allowing for good quality time and energy resolved analysis.

We present the analysis of the stellar and interstellar medium (ISM) properties of MARTA-4327, a star-forming galaxy at z=2.224 observed by means of deep JWST/NIRSpec spectroscopy in both medium- and high-resolution gratings as part of the "Measuring Abundances at high Redshift with the Te Approach" (MARTA) programme. We report one of the highest-redshift detections of the Wolf-Rayet (WR) blue and red bumps in a non-lensed system. The broad He ii${\lambda}$4686 feature is consistent with a young (${\sim 5-6}$ Myr) burst dominated by WN stars, although both SSP models and empirical templates struggle to reproduce the nitrogen stellar features at ${\approx}$ 4640 A. Based on the relative strength of the available optical stellar features, we disfavor the presence of very massive stars (VMS) in this system. Elemental abundance ratios such as Ne/O, N/O, and Ar/O align with observations of local star-forming galaxies (including WR galaxies), suggesting that any impact of the WR population on the chemical enrichment of the ISM is strongly localized. However, the gas-phase Fe/O ratio appears enhanced compared to local galaxies of similar metallicity, which we interpret as evidence for reduced Fe depletion onto dust grains, possibly linked to localized destruction in WR-driven wind environments. In addition, we detect a broad and blueshifted (~70 km/s) H${\alpha}$ component, revealing the presence of an ionized outflow with a mass loading factor ${\eta \sim 0.2}$. Finally, we report the robust detection of O I${\lambda}$8446 emission (among the first at high redshift), which we interpret as originating from Ly${\beta}$ fluorescence and/or collisional excitation in dense clumps. Overall, MARTA-4327 represents a unique system for studying the role of massive stars in shaping the ISM in galaxies at Cosmic Noon.

The recent detections of the afterglow phase of long gamma-ray bursts (lGRBs) at very high energies (VHE, >100 GeV) mark a significant advance in astrophysics of transient phenomena, offering deeper insights into the acceleration mechanisms, jet structure, and physical processes driving GRB emission. In the multi-messenger landscape, both high-energy neutrino and gravitational wave detections are providing new insights into the physics of extreme cosmic accelerators and highlighting the need for rapid and broadband follow-up observations. The Large-Sized Telescope (LST-1), the first telescope of the LST array, part of the Cherenkov Telescope Array Observatory (CTAO) North site, is particularly well-suited for real-time, rapid follow-up of transients. In this contribution, we present the latest achievements of the transient observational program with LST-1, which is now in advanced commissioning on La Palma, Canary Islands. We outline the observational strategies in place and describe the dynamic handling of events by the transient handler of LST-1 (e.g., its ability to handle poorly localised events, including gravitational waves, GRBs and neutrinos). We present the key results from transient observation campaigns conducted so far, discuss the lessons learned, and outline the promising prospects for the future LST-1+MAGIC combined transient program with fast response, via a Transient Handler.

Radio continuum emission provides a unique opportunity to study star-formation unbiased by dust obscuration. However, if radio observations are to be used to accurately trace star-formation to high redshifts, it is crucial that the physical processes which affect the radio emission from star-forming galaxies are well understood. While inverse Compton (IC) losses from the cosmic microwave background (CMB) are negligible in the local universe, the rapid increase in the strength of the CMB energy density with redshift [$\sim (1+z)^4$] means that this effect becomes increasingly important at $z\gtrsim3$. Using a sample of ~200,000 high-redshift (3 < z < 5) Lyman-break galaxies selected in the rest-frame ultraviolet (UV), we have stacked radio observations from the MIGHTEE survey to estimate their 1.4-GHz flux densities. We find that for a given rest-frame UV magnitude, the 1.4-GHz flux density and luminosity decrease with redshift. We compare these results to the theoretical predicted effect of energy losses due to inverse Compton scattering off the CMB, and find that the observed decrease is consistent with this explanation. We discuss other possible causes for the observed decrease in radio flux density with redshift at a given UV magnitude, such as a top-heavy initial mass function at high redshift or an evolution of the dust properties, but suggest that inverse Compton scattering is the most compelling explanation.

For the first time, we explore dark matter (DM) admixed quarkyonic stars (DAQSs) within a two-fluid formalism, where the normal/visible sector is modeled by a quarkyonic equation of state (EOS) in the Effective Relativistic Mean Field (E-RMF) framework and the DM component is treated as a degenerate fermionic gas with scalar and vector self-interactions. Our analysis begins with the mass-radius (M-R) relation, showing that the inclusion of DM enables stellar configurations to reach the mass range compatible with the GW190814 event. We identify both DM core and DM halo morphologies among the viable EOSs, with core dominated and halo dominated cases exhibiting distinct signatures. By fixing the stellar mass within the GW190814 range, we constrain the possible dark matter fractions and explore the role of different interaction channels. Using the EOSs consistent with these constraints, we further investigate the tidal deformability ($\Lambda$), moment of inertia (MOI), and stellar radius, finding broad agreement with constraints from GW170817, GW190814, and NICER. Finally, we compile the characteristic properties of DAQSs, including EOS type, DM fractions, morphology (core vs halo), and macroscopic observables in a comparative summary. This study provides a unified two-fluid framework to explore dense QCD matter and dark matter in the multi-messenger era, suggesting that the GW190814 secondary object could plausibly be interpreted as either a DM core or a DM halo quarkyonic star.

This study investigates the orbital migration of a planet located near the truncated edge of protoplanetary disks, induced by X-ray photo-evaporation originating from the central star. The combined effects of turbulent viscous accretion and stellar X-ray photo-evaporation give rise to the formation of a cavity in the central few astronomical units in disks. Once the cavity is formed, the outer disk experiences rapid mass loss and the cavity expands inside out. We have conducted 2D hydrodynamical simulations of planet-disk interaction for various planet masses and disk properties. Our simulations demonstrate that planets up to about Neptune masses experience a strong positive corotation torque along the cavity edge that leads to sustained outward migration -- a phenomenon previously termed {\it rebound} migration. Rebound migration is more favorable in disks with moderate stellar photo-evaporation rates of ${\sim}10^{-8} ~ \rm M_{\odot}\,yr^{-1}$. Saturn-mass planets only experience inward migration due to significant gas depletion in their co-orbital regions. In contrast, Jupiter-mass planets are found to undergo modest outward migration as they cause the residual disk to become eccentric. This work presents the first 2D hydrodynamical simulations that confirm the existence and viability of rebound outward migration during the inside-out clearing in protoplanetary disks.

The strong magnetic fields of neutron stars are closely linked to their observed thermal, spectral, and timing properties, such as the distribution of spin periods and their derivatives. To understand the evolution of astrophysical observables over time, it is essential to develop robust theoretical frameworks and numerical models that solve the coupled thermal and magnetic field evolution equations, incorporating detailed microphysical inputs like thermal and electrical conductivities and neutrino emission rates. These efforts are key to uncovering how the strength and geometry of magnetic fields change with age, ultimately shedding light on the diverse phenomenology of neutron stars. In this review, we outline the fundamental theory underlying magneto-thermal evolution models, with an emphasis on numerical methods and a comprehensive set of benchmark tests intended to guide current and future code development. We revisit established results from axisymmetric simulations, highlight recent progress in fully three-dimensional models, and offer a perspective on the anticipated developments in this rapidly evolving field.

We introduce new functionality to treat fractal aggregate aerosol particles within the Virga cloud modeling framework. Previously, the open source cloud modeling code Virga (Batalha et al. 2025), the Python version of EddySed (Ackerman & Marley, 2001), assumed spherical particles to compute particle mass and size distributions throughout the atmosphere. The initial release of Virga also assumed spherical particles to compute Mie scattering properties, which include the single scattering albedo, asymmetry parameter, and optical depth as a function of particle radius and composition. However, extensive evidence from Solar system aerosols, astrophysical disks and dust, and Earth climate studies suggests that non-spherical aggregate particles are common compared to idealized compact spherical particles. Following recent advances in microphysical and opacity modeling, we implement a simple parametrization for dynamical and optical (modified mean field theory) effects of fractal aggregate particles into Virga. We then use this new functionality to perform a case study using basic planetary parameters similar to the well-characterized, aerosol-laden mini-Neptune GJ 1214 b, using KCl clouds made of aggregate particles. We choose KCl to most directly explore comparisons to previous studies. We demonstrate 1) how our method compares to previous fractal aggregate particle treatments and 2) how our new fractal treatment affects theoretical spectra of cloudy atmospheres. Overall, our model is faster and more flexible for a wider range of parameter space than previous studies. We explore the limitations of our modeling set-up and offer guidance for future investigations using our framework.

We analyze the positional and morphological properties of about 3600 unique fast radio burst (FRB) sources reported in the second FRB catalog generated by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find a two-dimensional dependence of FRB detections on sky position, and identify a significant absence of detections in a roughly circular region centered at Galactic coordinates (77.7$^\circ$, 0.9$^\circ$), spanning an area of 216.2 deg$^2$. This detection gap spatially coincides with the Cygnus X region $--$ a plasma-rich star-forming region in the Milky Way. This lack of FRB detections is most likely the result of increased sky temperature and strong multi-path scattering by turbulent ionized plasma, which broadens the FRB signals beyond detectability in the CHIME band. Our simulations yield a mean of 6 expected FRB detections within the gap when accounting for the elevated sky temperature in the direction of the detection gap. We infer that a lower limit of the maximum scattering timescale $\tau_{\rm sc,\, 1\,GHz} \geq 4.13$ ms is sufficient to suppress the observed signal-to-noise ratio of all FRBs. In addition to Cygnus X, a similar suppression is seen in Catalog 2 along other high-emission measure (EM) sightlines ( i.e., EM$\geq$2900 pc cm$^{-6}$), further supporting a broader trend of suppression due to Galactic scattering. Future very long baseline interferometry (VLBI) measurements of scattering disks with CHIME Outriggers could help confirm our interpretation. Our work highlights the substantial impact of the ionized and turbulent Galactic interstellar medium on the detectability of FRBs.

HD~143811~AB is the host star to the directly imaged planet HD~143811~AB~b, which was recently discovered using data from the Gemini Planet Imager and Keck NIRC2. A member of the Sco-Cen star-forming region with an age of $13 \pm 4$ Myr, HD~143811~AB is somewhat rare among hosts of directly imaged planets as it is a close stellar binary, with an $\sim$18 day period. Accurate values for the orbital and stellar parameters of this binary are needed to understand the formation and evolutionary history of the planet in orbit. We utilize archival high-resolution spectroscopy from FEROS on the MPG/ESO 2.2-meter telescope to fit the orbit of the binary, and combine with unresolved photometry to derive the basic stellar properties of the system. From the orbit, we derive precise values of orbital period of $18.59098 \pm 0.00007$ days, and mass ratio of $0.885 \pm 0.003$. When combined with stellar evolutionary models, we find masses of both components of $M_A = 1.30^{+0.03}_{-0.05}$ M$_\odot$ and $M_B = 1.15^{+0.03}_{-0.04}$ M$_\odot$. While the current data are consistent with the planet and stellar orbits being coplanar, the 3D orientations of both systems are currently poorly constrained, with additional observations required to more rigorously test for coplanarity.

We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the Gemini Planet Imager Exoplanet Survey (GPIES) in 2016 and 2019 and is a member of the Sco-Cen star formation region. The companion object is detected $\sim 430$ mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semi-major axis of $64 ^{+32}_{-14}$ au and eccentricity $\sim 0.23$. Spectral analysis of the GPI $H$-band spectrum and NIRC2 \textit{L'} photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-REM exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of $1042^{+178}_{-132}$ K for the planet and translate the derived luminosity of the planet to a mass of $5.6 \pm 1.1~M_\textrm{Jup}$ assuming hot-start evolutionary models. HD 143811 AB b is one of only a few planets to be directly imaged around a binary, and future characterization of this object will shed light on the formation of planets around binary star systems.

In the standard formation models of terrestrial planets in the solar system and close-in super-Earths in non-resonant orbits recently discovered by exoplanet observations, planets are formed by giant impacts of protoplanets or planetary embryos after the dispersal of protoplanetary disk gas in the final stage. This study aims to theoretically clarify a fundamental scaling law for the orbital architecture of planetary systems formed by giant impacts. In the giant impact stage, protoplanets gravitationally scatter and collide with one another to form planets. Using {\em N}-body simulations, we investigate the orbital architecture of planetary systems formed from protoplanet systems by giant impacts. As the orbital architecture parameters, we focus on the mean orbital separation between two adjacent planets and the mean orbital eccentricity of planets in a planetary system. We find that the orbital architecture is determined by the ratio of the two-body surface escape velocity of planets $v_\mathrm{esc}$ to the Keplerian circular velocity $v_\mathrm{K}$, $k$ = The mean orbital separation and eccentricity are about $2 ka$ and $0.3 k$, respectively, where $a$ is the system semimajor axis. With this scaling, the orbital architecture parameters of planetary systems are nearly independent of their total mass and semimajor axis.

The next generation of ground- and space-based observatories will enable direct imaging and characterization of cold, mature planets through thermal emission and, for the first time, reflected light detection. Known RV and astrometrically detected planets provide a known population for detection and characterization observations. However, many of the most promising targets lack orbital parameters of sufficient precision to confidently predict their location on relative to the star for a direct imaging campaign. We have developed \texttt{projecc}, an open source Python package designed to generate sky-plane planet location posteriors from literature orbit solutions. This tool aims to facilitate community preparation for direct imaging observations of known planets. In this work we describe \texttt{projecc} and use it to examine two case study systems relevant to reflected light imaging with ELTs: GJ~876~b, which we find has a well-constrained prediction, and Proxima Centauri b, whose location remains highly uncertain.%, as well as one potential target for \textsl{Roman} CGI, HD~219134~h, which we estimate has a 40\% probability of being in a detectable sky location at any given time. We provide a web app for exploring reflected light planet targets and their orbit solutions, including predictions from literature for 17 additional planets, located at this https URL. We also discuss future upgrades to \texttt{projecc}.

We present a study of core fragmentation in the W51-E and W51-IRS2 protoclusters in the W51 high-mass star-forming region. The identification of core fragmentation is achieved by the spatial correspondence of cores and compact sources which are detected in the short (low resolution) and the long baseline (high resolution) continuum images with the Atacama Large Millimeter/submillimeter Array (ALMA) in Bands 3 (3 mm) and 6 (1.3 mm), respectively. We characterize the compact sources found in the long baseline image, and conclude that the compact sources are pre/protostellar objects (PPOs) that are either prestellar dust cores or dust disks or envelopes around protostars. The observed trend of core fragmentation in W51 is that (i) massive cores host more PPOs, (ii) bright PPOs are preferentially formed in massive cores, (iii) equipartition of flux between PPOs is uncommon. Thermal Jeans masses of parent cores are insufficient to explain the masses of their fragments, and this trend is more prominent at high-mass cores. We also find that unfragmented cores are large, less massive, and less dense than fragmented cores.

JWST/NIRSpec observations of Makemake reveal a chemically complex surface and evidence of gaseous CH$_4$. Our spectral modeling indicates a surface composition consisting of CH$_4$, CH$_3$D, and possibly CH$_3$OH, combined with aggregates of C$_2$H$_2$ and C$_2$H$_6$. The presence of C$_2$H$_4$ is also considered given its expected photochemical origin. Both areal and layered configurations reproduce the observed spectrum, with the latter being preferred. This composition confirms earlier hydrocarbon detections and suggests that CH$_4$ photolysis is either ongoing or occurred recently. The detection of CH$_3$D yields a D/H ratio in CH$_4$ ice of $(3.98 \pm 0.34) \times 10^{-4}$, consistent within $2\sigma$ with previous estimates. We report the first detection of CH$_4$ fluorescence from Makemake, establishing it as only the second trans-Neptunian object$\unicode{x2014}$after Pluto$\unicode{x2014}$with confirmed volatile release. We explore two scenarios consistent with the observed CH$_4$ emission, though neither fully reproduces the data: an expanding coma, yielding production rates of $(0.2\unicode{x2013}1.6) \times 10^{28}$ molecules s$^{-1}$ and a rovibrational temperature of $\sim$35 K, possibly originating from a localized plume, and a gravitationally bound atmosphere, which, if adopted, implies gas kinetic temperatures near 40 K and surface pressures of $\sim$10 pbar$\unicode{x2014}$values consistent with stellar occultation constraints and an atmosphere in equilibrium with surface CH$_4$ ice. Discriminating between these scenarios will require higher spectral resolution and improved signal-to-noise observations. Together, the gas-phase CH$_4$, intermediate D/H ratio between that in water and CH$_4$ in comets, and complex surface composition challenge the traditional view of Makemake as a quiescent, frozen body.

Differentiating between in-situ and accreted populations in the Milky Way halo is a challenging task. Various kinematic spaces are often used to identify distinct accreted populations from the in-situ Milky Way halo. However, this approach has limitations, especially at low orbital energies. To overcome this ambiguity, elemental abundances are typically used to distinguish between the populations. Yet, for many elemental abundance ratios, it remains difficult to make this distinction at low metallicities. Aluminium abundances, on the other hand, have been empirically found to be an effective discriminator, allowing for the separation of accreted and in-situ populations in the Milky Way halo even at low metallicities and low orbital energies. We aim to test the discriminating power of [Al/Fe] using a well-studied sample of high-velocity stars in the solar vicinity with high-quality spectra. With these stars, we explore the [Al/Fe] ability to separate the in-situ from accreted stars and test its limitations. We derived aluminium abundances from the Al I 3944 and 3961 {\rm Å} lines for 45 stars observed in two ESO programmes, along with 11 stars with archival spectra. Aluminium abundances were determined using 1D LTE and 1D NLTE spectral synthesis and line profile fitting. We confirm that the low-$\alpha$ population systematically has lower [Al/Fe] compared to high-$\alpha$ stars. Aluminium abundances, when carefully measured and NLTE effects taken into account, are effective tracers of the chemical history of halo stars. They provide an independent constraint on origin, complementing $\alpha$-element abundances trends, and help us to disentangle subpopulations within the accreted halo, especially in the metal-poor regime.

By using the horizontal visibility algorithm, the TESS light curves of 69 delta Sct stars are mapped to undirected horizontal visibility graphs (HVGs), where the graph nodes represent the light curve points. Then, the morphological characteristics of HVGs, such as the distribution of links between nodes (degree distribution) or the average fraction of triangles around each node (average clustering coefficient) are measured. The average clustering coefficients for HADS and LADS show two different linear correlations with the peak to peak amplitude of the TESS light curves is naturally separating them into two groups, thys, avoiding ad-hoc criteria for the first time. Exponential fits on HVG degree distributions for both HADS and LADS stars give indices suggesting correlated stochastic generating processes for delta Sct light curves. By applying the theoretical expression for the HVGs degree distribution of random time series we can distinguish significant pulsations from the background noise which might become a practical tool in frequency analysis of stars.

Stellar multiple systems play a pivotal role in cluster dynamics and stellar evolution, leading to intense astronomical phenomena like X-ray binaries, gamma-ray bursts, Type Ia supernova, and stellar mergers, which are prime sources of gravitational waves. However, their origin remains poorly understood. Here we report the discovery of a septuple protostellar system embedded in a Keplerian disk within the high-mass star-forming region NGC\,6334IN, with close separations of 181-461 AU. The stability analysis reveals that the disk surrounding the septuple system is dynamically unstable, indicating that the septuple system formed via disk fragmentation. Previous studies have typically found only 2--3 members forming via disk fragmentation in both low- and high-mass star-forming regions. Our findings provide compelling observational evidence that the fragmentation of a gravitationally unstable disk is a viable mechanism for the formation of extreme high-order multiplicity, confirming what was previously only a theoretical concept. The results shed new light on the formation of extreme high-order multiplicity in cluster environments.

Convolutional neural networks have shown their ability to differentiate between self-interacting dark matter (SIDM) and cold dark matter (CDM) on galaxy cluster scales. However, their large parameter counts and ''black-box'' nature make it difficult to assess whether their decisions adhere to physical principles. To address this issue, we have built a Convolutional Kolmogorov-Arnold Network (CKAN) that reduces parameter count and enhances interpretability, and propose a novel analytical framework to understand the network's decision-making process. With this framework, we leverage our network to qualitatively assess the offset between the dark matter distribution center and the galaxy cluster center, as well as the size of heating regions in different models. These findings are consistent with current theoretical predictions and show the reliability and interpretability of our network. By combining network interpretability with unseen test results, we also estimate that for SIDM in galaxy clusters, the minimum cross-section $(\sigma/m)_{\mathrm{th}}$ required to reliably identify its collisional nature falls between $0.1\,\mathrm{cm}^2/\mathrm{g}$ and $0.3\,\mathrm{cm}^2/\mathrm{g}$. Moreover, CKAN maintains robust performance under simulated JWST and Euclid noise, highlighting its promise for application to forthcoming observational surveys.

Solar jets, characterized by small-scale plasma ejections along open magnetic field lines or the legs of large-scale coronal loops, play a crucial role in the dynamics of the solar atmosphere. Although spectral and EUV images have been widely used to analyze the formation and evolution of jets, the detailed 3D structure at the base of the jet has not been studied in detail due to the limitations in the spatial resolution of observations. Solar Orbiter enables us to investigate the structure of solar jets with much higher spatial and temporal resolutions and from a different angle than from Earth. By combining observations made by instruments onboard Solar Orbiter with data from the SDO, we analyzed recurrent solar jets originating in a mixed-polarity region near an active region. Additionally, we employed potential field and magnetohydrostatic extrapolation techniques to determine the magnetic field topology associated with the jets. The jets display dynamic, multi-strand outflows emanating from compact bright kernels above the magnetic inversion line, with apparent speeds exceeding 100 km/s. Magnetic field evolution reveals continuous flux cancellation at the jet footpoints. Throughout the sequence, base flows are confined within quasi-separatrix layers, with the highest velocities and temperatures located near coronal null points. Over four eruptions, the magnetic topology evolves from a simple fan-spine configuration with a single null to a more complex dome-shaped base containing multiple nulls with separatrix curtain, accompanied by a morphological transition from narrow, well-collimated spire to broader, fragmented outflows. These results provide the first direct observational evidence that dynamic changes in null-point geometry modulate jet morphology and energetics via successive reconnection episodes.

In this review, the methodology of large eddy simulations (LES) is introduced and applications in astrophysics are discussed. As theoretical framework, the scale decomposition of the dynamical equations for compressible neutral fluids by means of spatial filtering is explained. For cosmological applications, the filtered equations in co-moving coordinates are formulated. Moreover, the decomposition is extended to magnetohydrodynamics (MHD). While energy is dissipated through numerical diffusivities in implicit large eddy simulations (ILES), explicit subgrid-scale (SGS) models are applied in LES to compute energy dissipation, mixing, and dynamo action due to numerically unresolved turbulent eddies. The most commonly used models in astrophysics are the Smagorinsky model, the hydrodynamical SGS turbulence energy equation model, and the non-linear structural model for both non-relativistic and relativistic MHD. Model validation is carried out a priori by testing correlations between model and data for specific terms or a posteriori by comparing turbulence statistics in LES and ILES. Since most solvers in astrophysical simulation codes have significant numerical diffusion, the additional effect of SGS models is generally small. However, convergence with resolution increases in some cases. A recent example is magnetic field amplification in binary neutron star mergers. For mesh-free codes, it has been shown that explicit modelling of turbulent diffusion of metals has a significant impact. Moreover, SGS models can help to compute the turbulent velocity dispersion consistently and to parameterize sub-resolution processes that are influenced by turbulence, such as the star formation efficiency in galaxy simulations.

This paper reports a Galactic kinematical and dynamical analysis of 1003 main-sequence carbon stars. The sample is drawn from the Sloan Digital Sky Survey, and cross-matched with Gaia DR3 to obtain 6-dimensional positions and velocities using a Bayesian framework. The study provides the first reliable distances for a large sample of dwarf carbon stars, which are then analyzed using both space motions and actions. The results are combined with dynamical equilibrium models for the three primary Galactic components to assign membership, finding that around 60 per cent belong to the halo, and over 30 per cent originate in the thick disc. Therefore, the results indicate dwarf carbon stars are dominated by a metal-poor halo population, and are thus an excellent resource for stellar archaeology. These stars remain on the main sequence and are relatively nearby, but atmospheric modelling is challenged by their cool effective temperatures and strong molecular features. In light of this, efforts should be made to improve C/O >1 atmospheric modelling, as the subset of low-mass dwarf carbon stars may numerically dominate the Galactic population of carbon-enriched, metal-poor stars.

The 21-cm line of neutral hydrogen is a promising probe of the early Universe, yet extracting astrophysical parameters from its power spectrum remains a major challenge. We present a beginner-friendly PyTorch pipeline for Marginal Neural Ratio Estimation (MNRE), a Simulation-Based Inference (SBI) method that bypasses explicit likelihoods. Using 21cmFAST simulations, we show that MNRE can recover key astrophysical parameters such as the ionizing efficiency $\zeta$ and X-ray luminosity $L_X$ directly from power spectra. Our implementation prioritizes transparency and accessibility, offering a practical entry point for new researchers in 21-cm cosmology.

A major barrier to improving the quantum-limited sensitivity of gravitational-wave observatories are the thermal distortions of the test masses which arise at megawatt laser power. Recent advances in a new form of higher-order wavefront correction, in which corrective heating profiles are applied to the test mass surfaces near their edges, have the potential to enable a tenfold reduction of the quantum noise floor of future detectors. However, realizing high levels of quantum noise reduction in practice hinges on identifying measurable error signals to finely control each wavefront actuator, in order to suppress wavefront errors to few-nanometer precision across the full mirror apertures. No direct source of such an error signal exists in LIGO today. We demonstrate that thermally imaging the surface of each test mass can provide these critical error signals. We show that the surface temperature profiles obtained from thermal imaging can be uniquely mapped to a finite element model of the mirror whose complete thermal state is identified, enabling full-aperture wavefront reconstruction and direct error signals for real-time precision wavefront control. This new sensing capability can enable up to a 34% strain sensitivity improvement in LIGO A+ at 95% confidence, increasing the sky-averaged detection range for binary neutron star mergers by 11 Mpc, and will be integral to a next-generation 40-km gravitational-wave observatory in the U.S., Cosmic Explorer.

The kinematics of the Milky Way bulge is known to be complex, reflecting the presence of multiple stellar components with distinct chemical and spatial properties. In particular, the bulge hosts a bar structure exhibiting cylindrical rotation, and a central velocity dispersion peak extending vertically along the Galactic latitude. However, due to severe extinction and crowding, observational constraints near the Galactic plane are sparse, underscoring the need for additional data to improve the completeness and accuracy of existing kinematic maps, and enabling robust comparison with dynamical models. This work aimed to refine the existing analytical models of the Galactic bulge kinematics by improving constraints in the innermost regions. We present updated maps of the mean velocity and velocity dispersion by incorporating new data near the Galactic plane. We combined radial velocity measurements from the GIBS and APOGEE surveys with both previously published and newly acquired MUSE observations. A custom\ -- developed Python\ -- based tool, {\tt PHOTfun}, was used to extract spectra from MUSE datacubes using PSF photometry based on DAOPHOT-II, with an integrated GUI for usability. The method included a dedicated extension, {\tt PHOTcube}, optimized for IFU datacubes. We applied Markov Chain Monte Carlo techniques to identify and correct for foreground contamination and to derive new analytical fits for the velocity and velocity dispersion distributions. Our analysis included nine new MUSE fields located close to the Galactic plane, bringing the total number of mapped fields to 57 including ~23000 individual RV measured. The updated kinematic maps confirm the cylindrical rotation of the bulge and reveal a more boxy morphology in the velocity dispersion distribution, while preserving a well\ -- defined central peak.

The near-infrared helium triplet line is a powerful tool for studying atmospheric escape processes of close-in exoplanets, especially irradiated gas giants. Line profile fitting provides direct insight into the mechanisms driving atmospheric mass loss of close-in, Jupiter-sized planets. We present high-resolution transmission spectroscopy results for the helium triplet line of sixteen gas giants ($R_{\rm p} > 0.5 R_{\rm Jup}$). These observations are part of an extensive helium survey conducted using the Habitable Zone Planet Finder spectrograph on the 10m Hobby-Eberly Telescope. For the first time, we provide constraints on the helium line for HAT-P-12b, HAT-P-17b, HD118203b, TrES-1b, and WASP-156b. Additionally, we are able to confirm previous robust or tentative detections for HD189733b, HD209458b, WASP-52b, WASP-69b, and WASP-76b, and non-detections for HAT-P-3b, WASP-11b, WASP-80b, WASP-127b, and WASP-177\,b. We do not confirm the previous helium narrow-band detection in HAT-P-26b using high-resolution observations. To identify trends within the population of warm, hot, and ultra-hot Jupiters, we combined our results with available helium studies from the literature. As predicted by theory, we find that warm Jupiters with helium detections orbit K-type stars. However, the helium detections in hot Jupiters are found in low-density planets orbiting F-type stars. There are no helium detections in ultra-hot Jupiters. We compiled a list of 46 irradiated gas giants, but more helium studies are needed to increase the sample and improve our understanding of atmospheric mass loss through helium observations.

One of the leading hypotheses for sunquake generation suggests that flare-accelerated particles originating from the reconnection site in the corona travel down to the chromosphere and photosphere, where they deposit energy through collisions and subsequently drive acoustic oscillations. To properly encompass this top-down excitation mechanism, we extend the domain of a semi-spectral 3D acoustic model of the global Sun up to several 10's of Mm above the photosphere, where the transition region and lower corona are resolved. We then use the radially-dependent heating rates derived from the flare radiative hydrodynamic (RADYN) simulations -- extrapolated to a 3D profile -- to realistically excite sunquakes. In addition to the usual sunquake wavefronts, we also observe waves that propagate through the chromosphere and corona in a similar fashion to Moreton-Ramsey waves and large-scale coronal propagating fronts (LCPFs). We examine the dynamics of these waves and discuss how they may be used to constrain models of sunquake excitation.

Galactic diffuse emissions in gamma rays and neutrinos arise from interactions of cosmic rays with the interstellar medium and probe the cosmic-ray intensity away from the Solar system. Model predictions for those are influenced by the properties of cosmic-ray sources, and understanding the impact of cosmic-ray sources on Galactic diffuse emissions is key for interpreting measurements by LHAASO, Tibet AS-gamma, IceCube, and the upcoming SWGO. We consider supernova remnants as prototypical cosmic-ray sources and study the impact of their discreteness on the Galactic diffuse emissions in different source injection and near-source transport models in a stochastic Monte Carlo study. Three lessons exemplify the results of our simulations: First, the distributions of Galactic diffuse emission intensities can be described by a mixture model of stable laws and Gaussian distributions. Second, the maximal deviations caused by discrete sources across the sky depend on energy, reaching typically tens of percent in burst-like and energy-dependent escape scenarios but order unity or larger in a time-dependent diffusion scenario. Third, the additional model uncertainty from source stochasticity is subdominant in burst-like and energy-dependent escape scenarios, but becomes sizeable above some tens of TeV in the time-dependent diffusion scenario, where it can help reconcile model predictions with LHAASO measurements. With increased spatial resolution, especially at energies beyond tens of TeV, measurements of Galactic diffuse emissions can be expected to constrain source models and locate cosmic ray sources.

Context. The mass-metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. The small scatter in this relation has been used to argue against severe tidal mass loss in Local Group satellites. Aims. We aim to show that the observed scatter is consistent with tidal mass loss seen in cosmological hydrodynamical zoom-in simulations, using simulated Milky Way-mass haloes from the Auriga project as an example. Methods. We analyze the stellar masses and mean metallicites for all accreted systems in Auriga. We compute these quantities two ways: considering the total system (bound + lost material) and only considering the bound progenitor. For both cases we fit the mass-metallicity relation and consider properties that drive scatter about these relations. Results. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the bound progenitor, the tidally evolved mass-metallicity relation has similar scatter ($\sim$0.27 dex) as observed for the Milky Way and M31 satellites ($\sim$0.23 dex). Satellites that lie above the relation have experienced substantial mass loss and typically have low metallicity for their total stellar mass. Even satellites that fall exactly on the evolved relation can lose over half of their stellar mass. Only satellites that are substantially below the evolved relation are reliably intact. Conclusions. The small scatter in the observed mass-metallicity relation is compatible with tidal mass loss. Based on their offset from the observed relation, we predict which Milky Way and M31 satellites have experienced substantial mass loss. These predictions will be tested with deep resolved-star observations from upcoming facilities including Rubin LSST, Euclid, and Roman.

The stellar initial mass function (sIMF) describes the distribution of stellar masses formed in a single star formation event in a molecular cloud clump. It is fundamental to astrophysics and cosmology, shaping our understanding of unresolved stellar populations, galactic chemical enrichment and habitable zones, and black hole growth. This White Paper reviews studies on the core mass function, stellar multiplicity, and dynamical processes affecting sIMF determinations, as well as the link between star-forming clumps and the galaxy-wide IMF (gIMF). The evidence gleaned from observed systems for the dependency of the sIMF on the metallicity and density of the clump is portrayed. We examine evidence from gravitational lensing, stellar and gas kinematics, and spectral diagnostics to assess environmental dependencies of the gIMF. Theoretical perspectives provide further insights into the sIMF's variability. Beyond summarizing current knowledge, this work aims to establish a shared framework and define strategies for studying a variable IMF in the era of near-infrared integral-field spectroscopy, 30m-class telescopes and major space-based observatories.

Adaptive binning is a crucial step in the analysis of large astronomical datasets, such as those from integral-field spectroscopy, to ensure a sufficient signal-to-noise ratio (S/N) for reliable model fitting. However, the widely used Voronoi-binning method and its variants suffer from two key limitations: they scale poorly with data size, often as O(N^2), creating a computational bottleneck for modern surveys, and they can produce undesirable non-convex or disconnected bins. I introduce PowerBin, a new algorithm that overcomes these issues. I frame the binning problem within the theory of optimal transport, for which the solution is a Centroidal Power Diagram (CPD), guaranteeing convex bins. Instead of formal CPD solvers, which are unstable with real data, I develop a fast and robust heuristic based on a physical analogy of packed soap bubbles. This method reliably enforces capacity constraints even for non-additive measures like S/N with correlated noise. I also present a new bin-accretion algorithm with O(N log N) complexity, removing the previous bottleneck. The combined PowerBin algorithm scales as O(N log N), making it about two orders of magnitude faster than previous methods on million-pixel datasets. I demonstrate its performance on a range of simulated and real data, showing it produces high-quality, convex tessellations with excellent S/N uniformity. The public Python implementation provides a fast, robust, and scalable tool for the analysis of modern astronomical data.

We present the X-ray quiescent and flaring properties from a unique, 7-day multiwavelength observing campaign on the M1 flare star AU Mic. Combining the XMM-Newton X-ray spectra with the chromospheric line and broadband NUV and optical continuum observations provides a dataset that is one of the most comprehensive to date. We analyze the sample of 38 X-ray flares and study in detail the X-ray flare temperature ($T$) and emission measure (EM) evolutions of three largest flares with the X-ray flare energies of $>10^{33}$ erg. The $T-\mathrm{EM}$ evolution tracks and multi-wavelength emission evolutions of the largest-amplitude Neupert-type flare reveal that the so-called ``Flare H-R diagram" is consistent with thermal coronal flare emission evolution. The two other more gradual and longer duration X-ray flares are interpreted as having larger size scales. None of the 17 H$\alpha$ and H$\beta$ flares show clear blue/red wing asymmetries, including the ones associated with the potential X-ray dimming event previously reported. The above largest-amplitude Neupert flare shows clear symmetric H$\alpha$ and H$\beta$ broadenings with roughly $\pm$400 and $\pm$600 km s$^{-1}$, respectively, which are synchronized with the optical/NUV continuum emission evolution. Radiative hydrodynamic modeling results suggest that electron beam heating parameters that have been used to reproduce M-dwarf flare NUV/optical continuum emissions can reproduce these large broadenings of H$\alpha$ and H$\beta$ lines. These results suggest that these most energetic M-dwarf flares are associated with stronger magnetic field flux densities and larger size scales than solar flares but can be interpreted in terms of the standard flare model.

Context. Understanding the demographics of white dwarf - main sequence (WDMS) binaries is key to uncovering the formation of various stellar exotica and refining the details of binary stellar evolution. Despite several dedicated efforts to identify unresolved WDMS binaries, their population remains incomplete, even within a 100 pc volume-limited sample. Aims. This study aims to identify WDMS binaries hidden within the main sequence of the optical color-magnitude diagram (CMD), improving the completeness of WDMS binaries within a volume-limited sample of 100 pc. Methods. We use NUV-optical CMDs to distinguish unresolved WDMS binaries from the rest of the populations. High-precision astrometric and photometric data from Gaia DR3 and NUV data from GALEX GR6/7 are combined to construct CMDs. Using the binary spectral energy distribution (SED) fitting algorithm within the Virtual Observatory SED Analyzer (VOSA) tool, we estimate stellar parameters such as effective temperature, bolometric luminosity, and radii. The masses of the WD companions are determined using white dwarf evolutionary models. As we use the sources which are detected only in NUV band of GALEX, this study directly complements to majority of the previous studies. Results. We identify 596 WD-MS binary candidates within 100 pc, with 497 newly reported. Our method predominantly identifies binaries with cooler WD companions (median ~7,000 K) compared to previous studies. The WD masses range from ~0.2 and 1.3 M$_\odot$, and most MS companions are of M spectral type.

We select a mass-complete sample of 225 quiescent galaxies at $z>2$ with $M_* > 10^{10}\ \mathrm{M}_\odot$ from PRIMER and JADES photometry spanning a total area of $\simeq320$ sq. arcmin. We restrict our analysis to only area with optical coverage in three $HST$ ACS filters, and provide evidence that this is important for selecting the most complete and clean samples of $z>2$ massive quiescent galaxy candidates. We investigate the contamination in our sample via $JWST$ NIRSpec spectroscopic validation, $Chandra$ X-ray imaging, and ALMA interferometry, calculating a modest total contamination fraction of $12.9_{-3.1}^{+4.0}$ per cent. The removal of $HST$ data increases star-forming galaxy contamination by $\simeq10$ per cent and results in a $\simeq20$ per cent loss of candidates recovered from $HST$+$JWST$ data combined. We calculate massive quiescent galaxy number densities at $2<z<5$, finding values three times larger than pre-$JWST$ estimates, but generally in agreement with more-recent and larger-area $JWST$ studies. In comparison with galaxy evolution simulations, we find that most can now reproduce the observed massive quiescent galaxy number density at $2<z<3$, however they still increasingly fall short at $z>3$, with discrepancies of up to $\simeq 1$ dex. We place 14 of our $z>3$ massive quiescent galaxies on the BPT and WHaN diagrams using medium-resolution spectroscopic data from the EXCELS survey. We find a very high incidence of faint AGN in our sample, at a level of $\simeq50$ per cent, consistent with recent results at cosmic noon. This is interesting in the context of maintenance-mode feedback, which is invoked in many simulations to prevent quenched galaxies from re-igniting star formation. To properly characterise the evolution of early massive quiescent galaxies, greater coverage in optical filters and significantly larger spectroscopic samples will be required.

We investigate how discontinuities in the point spread function (PSF) and image noise affect weak gravitational lensing shear measurements. Our focus is on discontinuities that arise in coadded images, particularly when edges from input images cross the coadd region. Using Metacalibration and Metadetection for shear calibration and a simple weighted mean coaddition, we find no significant biases for typical galaxy populations, typical edge hit rates (a few percent), or coadds with tens to hundreds of input images. Biases exceeding requirements for large lensing surveys occur only in extreme conditions: (a) coadds with just two input images, (b) an image edge crosses the object in about 25% of coadds, (c) PSF size variations greater than 25%, and (d) relatively small galaxies. Even in these extreme cases, accurate shear recovery is achievable by identifying and removing problematic measurements. We use a simple statistic which quantifies the relative variation in PSF size across each object.

High-redshift ($z>2$) blazars, with relativistic jets aligned toward us, probe the most powerful end of the active galactic nuclei (AGN) population. We aim at determining the black hole masses and mass accretion rates of high-$z$ blazars in a common framework that utilizes a Markov Chain Monte Carlo (MCMC) fitting method and the Shakura-Sunayev multi-temperature accretion disk model, accounting also for attenuation due to neutral hydrogen gas in the intergalactic medium (IGM). We compiled a sample of 23 high-redshift blazars from the literature with publicly available infrared-to-ultraviolet photometric data. We performed a Bayesian fit to the spectral energy distribution (SED) of the accretion disk, accounting for upper limits, and determined the black hole masses and mass accretion rates with their uncertainties. We also examined the impact of optical-ultraviolet attenuation due to gas in the IGM. We find that neglecting IGM attenuation in SED fits leads to systematically larger black-hole mass estimates and correspondingly lower Eddington ratios, with the bias becoming more severe at higher redshift. Our MCMC fits yield median black-hole masses in the range $\sim (10^{8}-10^{10})\,M_{\odot}$ and a broad distribution of median Eddington ratios ($\lambda_{\rm Edd}\sim 0.04 - 1$). Comparison with previous literature shows no clear method-dependent systematic offsets, although individual mass estimates can differ by up to a factor of a few. We also demonstrate that assumptions about black-hole spin introduce a systematic degeneracy. This work is to our knowledge the first systematic study to model the accretion-disk emission of a large sample of high-$z$ blazars within a single, consistent statistical framework. Our results emphasize the importance of accounting for IGM attenuation and of using uniform fitting methods when comparing disk-based black hole estimates across samples.

The PRobe far-Infrared Mission for Astrophysics (PRIMA) will deliver the first comprehensive view of the obscured side of star formation and black hole accretion that dominates galaxy growth at cosmic noon. Around 90% of UV/optical photons from young stars and Active Galactic Nuclei (AGN) are absorbed by dust and reradiated in the mid- to far-infrared, where key diagnostic lines trace accretion, star formation, and the physical and chemical conditions of galaxies. PRIMA will conduct blind spectroscopic surveys out to $z \sim 3-4$, enabling an unbiased determination of the co-evolution of star formation and black hole growth with cosmic time. We simulate a 200 arcmin$^2$ blind spectroscopic survey with FIRESS to measure star formation and black hole accretion rates for hundreds of galaxies at cosmic noon. Follow-up observations will provide relative N/O abundances and N/O-independent metallicities from multiple mid-IR lines. In its high-resolution mode, FIRESS will probe feedback processes through P-Cygni profiles, blueshifted OH absorption, and emission-line wings from highly ionised gas. Beyond cosmic noon, PRIMA will pioneer rest-frame mid-IR spectroscopy of galaxies during reionisation. Bright high-ionisation lines will constrain the primary ionising continuum of luminous Lyman-$\alpha$ emitters and low-metallicity AGN, revealing the conditions that shaped the first galaxies and black holes. By bridging the gap between optical and radio facilities, PRIMA will deliver an unobscured, end-to-end view of the processes driving galaxy evolution from the earliest epochs to the peak of activity.

A semi-analytical model for the evolution of galaxies and supermassive black holes (SMBHs) within the $\Lambda$CDM paradigm has been shown to yield stellar mass-BH mass relations that reproduce both the JWST and pre-JWST observations. Either fuzzy or warm dark matter (FDM or WDM) would suppress the formation of the smaller galactic halos that play important roles in the CDM fit to the high-redshift SMBH data. Our analysis of the stellar mass-BH mass relation disfavours FDM fields with masses $< 2.0\times 10^{-20}$ eV and WDM particles with masses $< 7.2$ keV, both at the 95 % confidence level.

The rotational metric provides an exact solution to Einstein's clock-rate problem in curved spacetime, specifically, whether time flows more slowly at the equator of a compact object such as a neutron star than at its poles. It features a curvature singularity, an event horizon, a potentially evolving ergosphere, a rigidly-rotating normal space, and two stationary limit surfaces. Although derived from the Schwarzschild metric through rotational transformations, it includes an additional ergosphere. Given the equivalence of inertia and gravity, this demonstrates how non-inertial transformations, such as rotational transformations, can introduce new spacetime structures into a gravitational system. In particular, the additional physical degrees of freedom carried by rotational transformations are `eaten' by the gravitational system to form an additional ergosphere. Furthermore, the rotational metric effectively models a rigidly-rotating gravitational system and is applicable for describing rotationally-induced gravitational effects in various rotating magnetospheres.

Dynamic targeting (DT) is a spacecraft autonomy concept in which sensor data is acquired and rapidly analyzed and used to drive subsequent observation. We describe the low Earth orbit application of this approach in which lookahead imagery is analyzed to detect clouds, thermal anomalies, or land use cases to drive higher quality near nadir imaging. Use cases for such a capability include: cloud avoidance, storm hunting, search for planetary boundary layer events, plume study, and beyond. The DT concept requires a lookahead sensor or agility to use a primary sensor in such a mode, edge computing to analyze images rapidly onboard, and a primary followup sensor. Additionally, an inter-satellite or low latency communications link can be leveraged for cross platform tasking. We describe implementation in progress to fly DT in early 2025 on the CogniSAT-6 (Ubotica/Open Cosmos) spacecraft that launched in March 2024 on the SpaceX Transporter-10 launch.

Cosmic Explorer (CE) is a proposed next generation gravitational-wave observatory that would be sited in the United States. As of 2025, CE is in its design phase, with plans to begin operations in the 2030s together with the Einstein Telescope in Europe. CE's reference design consists of two widely separated L-shaped detectors, one with 20km arms and one with 40km arms, each based on technology proven by the National Science Foundation's highly successful Laser Interferometer Gravitational Wave Observatory (LIGO). There are unique challenges associated with identifying locations suitable for hosting Cosmic Explorer in the conterminous United States, not least of which is the order of magnitude upscaling of the observatory with respect to the 4km LIGO observatories. Cosmic Explorer's approach to site evaluation integrates physical, social and cultural criteria. Here we present improvements to the Cosmic Explorer Location Search (CELS) code used to identify and assess locations where CE would have low construction costs incurred by the geology, geography and topography of the land. We also report on efforts to integrate astrophysical requirements established by the Cosmic Explorer Science Traceability Matrix into the site evaluation process. National-level results are presented and combined with results from a related National Suitability Analysis to provide a list of locations that are preliminarily promising for a 40km CE.

When a relativistic star rotates slowly and rigidly, centrifugal forces flatten it slightly, thereby catalyzing a small admixture of quadrupolar vibration into its radial modes and a damping of the resulting quasi-radial modes. The damping rate $1/\tau$ of each quasi-radial mode divided by its frequency $\sigma^{(0)}$ is given by ${(1/\tau) / \sigma^{(0)} }= \beta (\sigma^{(0)})^3 \Omega^4 R^8/M \;, $where $\Omega$, $R$ and $M$ are the angular velocity, radius and mass of the star, and $\beta$ is a dimensionless number that depends on the mode, on relativistic corrections, and on the structure of the star, and is typically of order unity for the fundamental quasi-radial mode in the nonrelativistic limit. In this paper we develop equations and an algorithm for computing the emitted waves and the resulting damping factor $\beta$. The rotation is treated to second-order in the angular velocity and the pulsation amplitudes are assumed small and linearized, but no other approximations are made.

The Alpha Optical Model Potential (\aomp \!) is a phenomenological approach used to describe elastic scattering where multiple reaction channels are open. It is one of the most critical inputs for the calculation of thermonuclear reaction rates in explosive stellar environments, but uncertainties within the $\alpha$-OMP lead to imprecise predictions hindering comparisons between calculations and observations. In order to improve the precision of the $\alpha$-OMP, additional nuclear physics data are required. In this paper, a measurement of the $^{86}$Sr($\alpha$, $\alpha$) elastic scattering cross section at multiple energies is reported. A local optical potential is constructed via a fully Bayesian analysis of the elastic scattering data. The resulting uncertainties on the low energy cross sections relevant to nuclear astrophysics are then calculated and shown to be on the order of $50 \%$.

We revisit sterile-neutrino production enabled by nonstandard interactions (NSI) among active neutrinos mediated by new bosons. We focus on vector mediators, including neutrinophilic, gauged $L_\mu\!-\!L_\tau$, and $B\!-\!L$ realizations that modify in-medium dispersion and scattering, thereby altering the active--sterile conversion history. Building on a novel production framework with NSI thermal potentials and collision integrals, we compute nonthermal phase-space distributions across sterile neutrino mixing and NSI parameters and map each point to an equivalent thermal warm dark matter particle mass $m_{\mathrm{th}}$ via linear-theory transfer function fitting with cosmological structure-formation Boltzmann solver. This enables a direct reinterpretation of state-of-the-art structure-formation limits from Milky Way satellites, strong lensing, and the Lyman-$\alpha$ forest. These limits, in conjunction with X-ray decay searches, as well as results from a wide variety of particle physics experiments allow for a more complete examination of these models. We find that these vector-mediated models are ruled out when the full combination of current constraints, listed above, are taken into account. NSI scalar-mediated models and models with low-reheating temperatures remain viable.

Recent advances in neural density estimation have enabled powerful simulation-based inference (SBI) methods that can flexibly approximate Bayesian inference for intractable stochastic models. Although these methods have demonstrated reliable posterior estimation when the simulator accurately represents the underlying data generative process (GDP), recent work has shown that they perform poorly in the presence of model misspecification. This poses a significant problem for their use on real-world problems, due to simulators always misrepresenting the true DGP to a certain degree. In this paper, we introduce robust variational neural posterior estimation (RVNP), a method which addresses the problem of misspecification in amortised SBI by bridging the simulation-to-reality gap using variational inference and error modelling. We test RVNP on multiple benchmark tasks, including using real data from astronomy, and show that it can recover robust posterior inference in a data-driven manner without adopting tunable hyperparameters or priors governing the misspecification.

Theoretical investigation of the dissociative recombination (DR) of NeH+ with low-energy electrons in the regime where the process occurs without direct potential energy curve crossings is presented. The calculations are performed using multichannel quantum defect theory, incorporating non-adiabatic couplings between electronic states. Unlike the previous treatment of the DR of HeH+, where only first-order radial couplings A(R) were considered, our formulation also incorporates the second-order terms B(R), together with a radial density of states \b{eta}{\nu} (R) to describe the transition into the ionization continuum. This development uses a large number of potential energy curves and non-adiabatic couplings of NeH characterized by us previously, enabling a consistent modeling of the DR process. The resulting cross sections show good agreement with the available experimental data and fill a gap in theoretical data below 4.5 eV, where no detailed quantum calculations are currently available.

We find a relation between the ADM mass and a generalized Komar energy in asymptotically-flat spacetime. We do not need to assume the existence of either a Killing or even asymptotically-Killing vector field. Instead, our generalized Komar energy is constructed from the normal evolution vector (the lapse function times the future-directed unit normal to the spacelike hypersurfaces on which the ADM mass is measured). We find equality between the ADM mass and this generalized Komar energy even for dynamical asymptotically-flat spacetimes provided the 3-dimensional Einstein tensor drops off quickly enough at spatial infinity, in particular, whenever ${}^{(3)}G_{ij}=o(r^{-3})$. No additional assumptions are required for equality. As this generalized energy is fully covariant, it may provide a powerful tool for analyzing energy content in dynamical spacetimes containing compact objects.

Using kinetic simulations and theory, we show that nonlinear electromagnetic waves can make even strongly underdense pair plasmas fully reflective. As the wave compresses and accelerates the plasma, weak reflection seeds a periodic train of density spikes that grow rapidly due to mass symmetry. This moving Bragg-like grating increases reflection and momentum transfer, enabling a transition to a regime where the relativistic plasma-vacuum interface sustains complete reflection. Finite temperature raises the full-reflection density threshold, yet the corresponding density can remain underdense.

A compact object illuminated by background radiation produces a dark silhouette. The edge of the silhouette or shadow (alternatively, the apparent boundary or the critical curve) is commonly determined by the presence of the photon sphere (or photon shell in the case of rotating spacetime), corresponding to the maximum of the effective potential for null geodesics. While this statement stands true for Kerr black holes, here we remark that the apparent boundary (as defined by Bardeen) forms under a more general condition. We demonstrate that a shadow forms if the effective potential of null geodesics has a positive finite upper bound and includes a region where photons are trapped or scattered. Our framework extends beyond conventional solutions, including but not limited to naked singularities. Furthermore, we clarify the difference between the apparent boundary of a dark shadow and the bright ring on the screen of a distant observer. These results provide a unified theoretical basis for interpreting observations from the Event Horizon Telescope (EHT) and guiding future efforts towards extreme-resolution observations of compact objects.

In this work we aim to provide a consistent theoretical framework that revives the power-law $F(R)$ gravity inflation framework in the Jordan frame. It is known in the literature that the power-law $F(R)$ gravity inflation of the form $F(R)=R+\beta R^n$ is non-viable and produces a power-law evolution. We demonstrate that the standard approach in power-law $F(R)$ gravity inflation is flawed for many reasons and we introduce a new framework which elevates the role of power-law $F(R)$ gravity inflation, making it viable and compatible with both the Planck and ACT data. In our framework the power-law $F(R)$ gravity inflation is disentangled from a power-law evolution.

Electron acoustic double layers (EADLs) have been investigated in four component unmagnetized dense quantum plasmas consisting of stationary background ions and two electron populations, cold and hot, with the superthermal kappa distributed electrons. Using the quantum hydrodynamic (QHD) model and the reductive perturbation technique, a generalized Korteweg de Vries (KdV) equation was derived, and stationary analytical solutions were obtained. The analysis revealed that superthermal electrons substantially influence the amplitude, width, and polarity of EADLs. Numerical results indicated that decreasing the spectral index kappa or increasing the relative density of kappa electrons to hot electrons intensifies nonlinear effects, producing stronger compressive and rarefactive structures. It is also found that kappa plays a more dominant role than the density ratio in controlling EADL properties in dense astrophysical environments.

We investigate how resonant excitation near exceptional points manifests in Kerr black hole ringdown waveforms and examine its extraction. Using waveforms generated by localized initial data, where quasinormal mode amplitudes are given solely by excitation factors, we establish a controlled benchmark for overtone extraction. Applying an iterative fitting method with mirror modes, we analyze a mild resonance in the $(l,m)=(2,2)$ multipole and a sharp resonance in the $(3,1)$ multipole occurring as part of a sequence of successive resonances. For $(2,2)$, we extract the fundamental mode, the first three overtones, and the fundamental mirror mode with relative errors below $10\%$, and show that residual waveforms exhibit the expected damped sinusoids together with distinctive resonance signatures. For $(3,1)$, we demonstrate that resonances can not only amplify but also reduce QNM excitations, reshaping the overtone hierarchy and rendering the sharp resonance more pronounced in ringdown. Our results clarify the imprint of resonance in Kerr ringdown and highlight both the robustness and limitations of current extraction techniques, providing a foundation for more reliable extraction of higher overtones and for applications to observational data analysis.

We report results of a public data-analysis challenge, hosted on the open data-science platform Kaggle, to detect simulated continuous gravitational-wave signals. These are weak signals from rapidly spinning neutron stars that remain undetected despite extensive searches. The competition dataset consisted of a population of CW signals using both simulated and real LIGO detector data matching the conditions of actual CW searches. The competition attracted more than 1,000 participants to develop realistic CW search algorithms. We describe the top 10 approaches and discuss their applicability as a pre-processing step compared to standard CW-search approaches. For the competition's dataset, we find that top approaches can reduce the computing cost by 1 to 3 orders of magnitude at a 2% dismissal probability. Additionally, the competition drove the development of new GPU-accelerated detection pipelines and extended CW-inspired statistics to other domains. We release the associated dataset, which constitutes the first open standardized benchmark for CW detection, to enable reproducible method comparisons and to encourage further developments toward the first detection of these elusive signals.

This paper explores the sensitivity of the Cherenkov Telescope Array Observatory to dark matter annihilation in the Galactic Center, within the frameworks of Effective Field Theory and Simplified Models. We present sensitivity forecasts, utilizing an up-to-date instrument configuration and incorporating the latest models for Galactic Diffuse Emission. A key aspect of our work is the inclusion of updated dark matter density profiles, J-factors, and velocity dispersion distributions derived from the FIRE-2 cosmological hydrodynamical simulations, which significantly impact the expected indirect detection signals. Furthermore, we update the constraints from direct detection experiments (Xenon1T and LZ) taking into account the astrophysical uncertainties informed by the FIRE-2 simulations, and also investigate limits coming from collider searches (ATLAS and CMS). Our analysis reveals improved constraints on the effective suppression scale ($M_*$) in the Effective Field Theory framework and on the mediator mass ($M_{med}$) in Simplified Models compared to previous studies, highlighting the complementarity of the Cherenkov Telescope Array Observatory with direct and collider searches in probing a wide range of dark matter scenarios. We discuss the implications of these results for various dark matter interaction types, including scalar, pseudoscalar, vector, and axial-vector mediators, and emphasize the importance of considering realistic astrophysical inputs in interpreting dark matter search results across different experimental fronts.

We investigate the linear onset of thermal convection in rotating spherical shells with a focus on the influence of mechanical boundary conditions and thermal driving modes. Using a spectral method, we determine critical Rayleigh numbers, azimuthal wavenumbers, and oscillation frequencies over a wide range of Prandtl numbers and shell aspect ratios at moderate Ekman numbers. We show that the preferred boundary condition for convective onset depends systematically on both aspect ratio and Prandtl number: for sufficiently thick shells or for large $\text{Pr}$, the Ekman boundary layer at the outer boundary becomes destabilising, so that no-slip boundaries yield a lower $\text{Ra}_c$ than stress-free boundaries. Comparing differential and internal heating, we find that internal heating generally raises $\text{Ra}_c$, shifts the onset to larger wavenumbers and frequencies, and relocates the critical column away from the tangent cylinder. Mixed boundary conditions with no-slip on the inner boundary behave similarly to purely stress-free boundaries, confirming the dominant influence of the outer surface. These results demonstrate that boundary conditions and heating mechanisms play a central role in controlling the onset of convection and should be carefully considered in models of planetary and stellar interiors.

We present a new model for two-component scalar dark matter (DM), consisting of two complex scalar fields. In this model, both the DM components are stable due to the remaining $Z_4$ gauge symmetry, which is the remnant of the $U(1)^\prime$ local symmetry. When the resonance condition for DM masses is fulfilled, we show that the elastic co-scattering processes between two components of dark matter ($u$-channel processes) are enhanced due to the Yukawa potential with a small effective mass for the lighter DM mediator, so we can use such co-scattering processes for dark matter to explain the small-scale problems at galaxies. Moreover, there are also semi-annihilation processes that two components of dark matter annihilate into one dark matter particle and a dark photon/Higgs, which are enhanced by the $u$-channel Sommerfeld factor. Focusing on some benchmark models for two-component dark matter satisfying the observed relic density, we obtain the bounds for the dark photon portal couplings from the direct detection for boosted dark matter, which is produced from the semi-annihilation processes at the galactic center.

Recent results from the Atacama Cosmology Telescope (ACT), when combined with Planck and DESI datasets, indicate a scalar spectral index $n_s$ larger than that reported in the Planck 2018 baseline, thereby challenging conventional Starobinsky-type ($\alpha$-attractor) inflationary scenarios at the $2\sigma$ level. In addition, the positive running of the spectral index $\alpha_s$ implied by the data provides strong constraints on these models. In this paper, we explore the possibility that the presence of an additional heavy field during inflation, with a mass of order the Hubble scale and a sizable mixing coupling to the inflaton, can reconcile such inflationary models with the ACT results by increasing both $n_s$ and $\alpha_s$, particularly in the strong-mixing regime. Furthermore, we extend this framework to traditional inflation models such as chaotic inflation and natural inflation, which have already been excluded by Planck alone, and show that they can be revived in certain regions of parameter space. Inflationary observables, including the spectral index $n_s$, the tensor-to-scalar ratio $r$, and the running $\alpha_s$, are computed within the single-field EFT approach, which is applicable even in the presence of a heavy field with large mixing. We also discuss the non-Gaussianity signatures arising from the heavy field, noting that parts of the parameter space are already excluded or can be tested in future observations. Finally, we present concrete model realizations that allow for such a large mixing.

Gravitational lensing of gravitational waves is expected to be observed in current and future detectors. In view of the growing number of detections, computationally light pipelines are needed. Detection pipelines used in past LIGO-Virgo-KAGRA searches for strong lensing require parameter estimation to be performed on the gravitational wave signal or are machine learning based. Removing the need for parameter estimation in classical methods would alleviate the ever growing demand of computational resources in strong lensing searches and would make real-time analysis possible. We present a novel way of identifying strongly lensed gravitational wave signals, based on the null stream of a detector network. We lay out the basis for this detection method and show preliminary results confirming the validity of the formalism. We also discuss the next development steps, including how to make it independent of parameter estimation.

Beta-decay rates of extreme neutron-rich nuclei remain largely unknown experimentally, while they are critical inputs for $r$-process nucleosynthesis. We present first ab initio calculations of total beta-decay half-lives, with a focus on $N=50$ nuclei. Starting from nuclear forces and currents based on chiral effective field theory, we use the in-medium similarity renormalization group to consistently derive valence-space Hamiltonians and weak operators, from which we calculate the nuclear states involved and the Gamow-Teller transition strengths, without phenomenological adjustments. In addition, we explore effects of first-forbidden contributions. Our results show that the inclusion of two-body currents increases the total half-lives, which then show good agreement with the existing experimental data, thereby validating the predictive capability of our approach.

Asymmetric dark matter can be efficiently captured by neutron stars via elastic scattering with nucleons and dark matter self scattering. The accumulated dark matter thermalizes and concentrates in the stellar interior, forming a dark matter core. In this work, we propose a novel framework in which a $\mathbb{Z}_3$ symmetry allows for number-changing self-interactions of the form $3 \rightarrow 2$ within the dark sector. These cannibalistic reactions become increasingly efficient at high dark matter densities, leading to a significant depletion of the dark matter population in the stellar core. This number depletion heats up the neutron star above the standard cooling expectations, yielding observable thermal signatures in relatively old, isolated neutron stars, potentially detectable via James Webb Space Telescope. We show that even in the presence of other heating mechanisms, e.g. dark matter annihilation and kinetic heating, the cannibal heating dominates for certain parameter space. We demonstrate that the cannibal heating can predict detectable heating signatures in old neutron stars, thereby allowing a broader range of viable dark matter masses and couplings to the Standard Model.

When a gravitational wave encounters a massive object along the line of sight, repeated copies of the original signal may be produced due to gravitational lensing. In this paper, we develop a series of new machine-learning based statistical methods to identify promising strong lensing candidates in gravitational wave catalogs. We employ state-of-the-art normalizing flow generative models to perform statistical calculations on the posterior distributions of gravitational wave events that would otherwise be computationally unfeasible. Our lensing identification strategy, developed on two simulated gravitational wave catalogs that test noise realization and event signal variations, selects event pairs with low parameter differences in the optimal detector basis that also have a high information content and favorable likelihood for coincident parameters. We then apply our method to the GWTC-3 catalog and find a single pair still consistent with the lensing hypothesis. This pair has been previously identified through more costly evidence ratio techniques, but rejected on astrophysical grounds, which further validates our technique.

The DAMIC-M experiment will search for sub-GeV dark matter particles with a large array of silicon skipper charge-coupled devices (CCDs) at the Modane Underground Laboratory (LSM) in France. After five years of development, we recently completed the production of 28 CCD modules at the University of Washington, each consisting of four 9-megapixel skipper CCDs. Material screening and background controls were implemented to meet stringent radio-purity targets, while extensive testing was employed to select science-grade CCDs for the modules and confirm their excellent performance after fabrication. Further testing at LSM will select 26 of these modules (${\sim}$350 g active mass) to be installed and operated in the DAMIC-M detector in early 2026.