Papers for Thursday, Oct 02 2025

Astronomical image interpretation presents a significant challenge for applying multimodal large language models (MLLMs) to specialized scientific tasks. Existing benchmarks focus on general multimodal capabilities but fail to capture the complexity of astronomical data. To bridge this gap, we introduce AstroMMBench, the first comprehensive benchmark designed to evaluate MLLMs in astronomical image understanding. AstroMMBench comprises 621 multiple-choice questions across six astrophysical subfields, curated and reviewed by 15 domain experts for quality and relevance. We conducted an extensive evaluation of 25 diverse MLLMs, including 22 open-source and 3 closed-source models, using AstroMMBench. The results show that Ovis2-34B achieved the highest overall accuracy (70.5%), demonstrating leading capabilities even compared to strong closed-source models. Performance showed variations across the six astrophysical subfields, proving particularly challenging in domains like cosmology and high-energy astrophysics, while models performed relatively better in others, such as instrumentation and solar astrophysics. These findings underscore the vital role of domain-specific benchmarks like AstroMMBench in critically evaluating MLLM performance and guiding their targeted development for scientific applications. AstroMMBench provides a foundational resource and a dynamic tool to catalyze advancements at the intersection of AI and astronomy.

We explore a much-neglected area of SETI: solar system techno-signatures. As our cursory solar system exploration consolidates into commercial industrialisation, it is crucial that we determine what to look for and where. We first consider the rationale for interstellar self-replicating probes and their implications for the Fermi paradox. Whether for defensive or exploratory reasons, self-replicating probes are a rational strategy for Galactic investigation. We determine that self-replicating probes will systematically explore the Galaxy by tracking resources of sufficient metallicity. We focus on the resource requirements of a self-replicating interstellar probe that may have visited our solar system. After considering asteroid resources, we suggest that evidence of asteroidal processing will be difficult to discern from natural processes given the constraints imposed by self-replication. We further determine that the Moon is an ideal base of manufacturing operations. We suggest that nuclear reactors, such as the Magnox reactor model, can feasibly be constructed from lunar resources which will have left isotopic ratio signatures of Th-232/Nd-144 and/or Th-232/Ba-137. We further suggest that in anticipatory economic trade for resources, a self-replicating probe may have left artefacts buried with asteroidal resources on the Moon. Such gifts would be detectable and accessible only once a threshold of technological sophistication has been achieved. An obvious gift in trade for the resources utilised would be a universal constructor.

This article introduces a new physics-guided Machine Learning framework, with which we solve the generally non-invertible, ill-conditioned problems through an analytical approach and constrain the solution to the approximate inverse with the architecture of Neural Networks. By informing the networks of the underlying physical processes, the method optimizes data usage and enables interpretability of the model while simultaneously allowing estimation of detector properties and the propagation of their corresponding uncertainties. The method is applied in reconstructing Cosmic Microwave Background (CMB) maps observed with the novel interferometric QUBIC experiment aimed at measuring the tensor-to-scalar ratio r.

The shape and orientation of the Milky Way's dark matter halo remain poorly constrained. Observations of the accreted stellar halo show that it is triaxial and tilted with respect to the disc. If this configuration is long-lived, it can be used to place constraints on the shape and orientation of the dark matter halo that can support it close to steady state. We fit equilibrium orbit-superposition (Schwarzschild) models to the stellar halo in a realistic Milky Way potential with a tilted dark matter halo, assuming that the long axes of each halo and the disc normal are coplanar. These models are matched to parametric density fits and velocity anisotropy measurements of Gaia Sausage-Enceladus (GSE) stars at radii $r\in[6,60]$ kpc. The observations are consistent with a (near-)prolate dark matter halo whose density has a short-to-long axis ratio of $q_\mathrm{dm}=0.87_{-0.09}^{+0.05}$. The long axis is inclined at an angle of $\beta_\mathrm{dm}=43_{-8}^{+22}\,^\circ$ to the disc plane, which exceeds the stellar halo tilt by $\approx18^\circ$. Spherical haloes cannot support the observed structure of the GSE in equilibrium. The best-fitting dynamical GSE model has a radius-dependent shape and orientation; between radii of 6 and 60 kpc the tilt increases from $\beta_*(r)\approx10^\circ$ to $\approx35^\circ$. Our model provides a good fit to the observed triaxial structure and dynamics of the GSE. It is therefore an excellent source of realistic initial conditions for simulations of the halo, such as for investigating perturbations from satellites or the Galactic bar.

The calwf3 software for WFC3/UVIS utilizes a reference file to flag pixels that are saturated beyond their full-well depth. Previously, this was accomplished using a constant threshold of 65,500 e$^{-}$ across the entire detector. In this study, we retrieved $\sim$1 million stars from the Mikulski Archive for Space Telescopes (MAST) to determine the flux level at which the Point Spread Function begins to flatten, which occurs as the central pixel saturates. We quantified the saturation limit as a function of position on the detector in 1,024 discrete regions, and interpolated to a pixel-by-pixel saturation map to construct a spatially-variable saturation map reference file that is now implemented in the calwf3 calibration pipeline. We find the saturation varies by 13% across the UVIS detectors, from 63,465 e$^{-}$ to 72,356 e$^{-}$. These values agree well with earlier studies using sparser datasets, with the current analysis leading to improved characterization on small scales. Critically, the revised saturation values are larger than the previous constant threshold over 87% of the UVIS detector, leading to the recovery of usable science pixels near bright sources. This update greatly improves the robustness of saturation flags in the Data Quality arrays of observations obtained with WFC3/UVIS, and users are encouraged to redownload their data from MAST to benefit from the improved flags.

No experimental test precludes the possibility that the dark matter experiences forces beyond general relativity -- in fact, a variety of cosmic microwave background observations suggest greater late-time structure than predicted in the standard $\Lambda$ cold dark matter model. We show that minimal models of scalar-mediated forces between dark matter particles do not enhance the growth of unbiased tracers of structure: weak lensing observables depend on the total density perturbation, for which the enhanced growth of the density contrast in the matter era is cancelled by the more rapid dilution of the background dark matter density. Moreover, the same background-level effects imply that scenarios compatible with CMB temperature and polarization anisotropies in fact suppress structure growth, as fixing the distance to last scattering requires a substantially increased density of dark energy. Though massive mediators undo these effects upon oscillating, they suppress structure even further because their gravitational impact as nonclustering subcomponents of matter outweighs the enhanced clustering strength of dark matter. We support these findings with analytic insight that clarifies the physical impact of dark forces and explains how primary CMB measurements calibrate the model's predictions for low-redshift observables. We discuss implications for neutrino mass limits and other cosmological anomalies, and we also consider how nonminimal extensions of the model might be engineered to enhance structure.

We present the first measurement of the sky-projected orbital obliquity of a benchmark transiting brown dwarf host, HIP 33609, as a part of the Orbital Architectures of Transiting Massive Exoplanets And Low-mass stars (OATMEAL) survey. HIP 33609 b is a highly eccentric, 68 $M_{\rm J}$ brown dwarf orbiting a 10,300 K, A-type star with an orbital period of 39 days. Its host star is a known member of the 150 Myr old MELANGE-6 moving group, making it an excellent laboratory for testing sub-stellar evolutionary models. Using in-transit spectra collected by the Planet Finder Spectrograph (PFS) on the Magellan II Clay 6.5 m telescope, we measured a sky-projected orbital obliquity of $|\lambda|= 12.7 \pm 1.3$°. The mass of the brown dwarf is most consistent with a stellar-like fragmentation formation history followed by a period of migration. Given the high eccentricity ($e=0.557$) but low orbital obliquity of the brown dwarf, we claim that coplanar high eccentricity tidal migration seems to be the most plausible pathway, however, it remains difficult to conclusively rule out other migration mechanisms. The low orbital obliquity for HIP 33609 is consistent with previous measurements of high mass-ratio companions, and bears a striking resemblance to the obliquity distribution of transiting warm Jupiters. We suggest brown dwarfs may follow a dynamically quiescent migration pathway, consistent with them forming in isolated conditions.

We present the first constraints on the electron optical depth to reionization, $\tau_{\mathrm{e}}$, from the Lyman-$\alpha$ forest alone for physically motivated reionization models that match the reionization's end-point, $z_{\rm{end}}$, required by the same astrophysical probe, and for symmetric reionization models with fixed duration, $\Delta z$, commonly adopted in CMB reionization analyses. Compared to traditional estimates from the latter, the Lyman-$\alpha$ forest traces the ionization state of the IGM through its coupling with the thermal state. We find an explicit mapping between the two solving the chemistry and temperature evolution equations for hydrogen and helium. Our results yield $\tau_{\mathrm{e}}$=$0.042^{+0.047}_{-0.02}$ (95% C.L) and $\tau_{\mathrm{e}}$=$0.042^{+0.024}_{-0.015}$ for reionization models with $z_{\rm{end}}$ and $\Delta z$-fixed, respectively, disfavoring a high $\tau_{\mathrm{e}}$=0.09 by 2.57$\sigma$ and 4.31$\sigma$. With mock Lyman-$\alpha$ forest data that mimics the precision of future larger quasar sample datasets, we would potentially obtain tighter $\tau_{\mathrm{e}}$ constraints and exclude such a high $\tau_{\mathrm{e}}$ with a higher significance, paving the way for novel constraints on the epoch of reionization from a large-scale structure probe independent of the CMB.

Ultra-cool T- (T$_{\mathrm{eff}} \approx$ 500 - 1200 K) and Y-dwarfs (T$_{\mathrm{eff}}$ $\lessapprox 500$ K) have historically been found only a few hundred parsecs from the Sun. The sensitivity and wavelength coverage of the NIRCam instrument on board the James Webb Space Telescope offer a unique method for finding low-temperature brown dwarfs in deep extragalactic datasets out to multiple kiloparsecs. Here we report on the selection of a sample of 41 brown dwarf and brown dwarf candidates across the JWST Advanced Deep Extragalactic Survey (JADES) in the GOODS-S and GOODS-N regions. We introduce a new open-source Bayesian tool, the Near-Infrared Fitting for T and Y-dwarfs (\texttt{NIFTY}), to derive effective temperatures, metallicities, and distances from JWST photometry. We find that 31 candidates have fits consistent with T-dwarf temperatures out to 5 - 6 kpc, and 10 candidates have fits consistent with Y-dwarf temperatures out to 1 - 2 kpc. The majority of the sources are best fit with sub-solar metallicity models, consistent with them being subdwarfs in the Milky Way thick disk and halo. We report proper motions for nine brown dwarf candidates (three are newly presented), and calculate the number density of T- and Y-dwarfs as a function of temperature and distance above the Milky Way midplane. We further discuss how Y-dwarfs can serve as contaminants in the search for ultra-high-redshift galaxies. Together, these results demonstrate the power of deep JWST extragalactic imaging to probe the coldest substellar populations far beyond the solar neighborhood, providing new constraints on the Milky Way's structure and brown dwarf demographics.

One of the most puzzling properties of the high-redshift AGN population recently discovered by JWST, including both broad-line and narrow-line sources, is their X-ray weakness. With very few exceptions, and regardless of the optical classification, they are undetected at the limits of the deepest Chandra fields, even when stacking signals from tens of sources in standard observed-frame energy intervals (soft, hard, and full bands). It has been proposed that their elusive nature in the X-ray band is due to heavy absorption by dust-free gas or intrinsic weakness, possibly due to high, super-Eddington accretion. In this work, we perform X-ray stacking in three customized rest-frame energy ranges (1-4, 4-7.25, and 10-30 keV) of a sample of 50 Type 1 and 38 Type 2 AGN identified by JWST in the CDFS and CDFN fields. For the Type 2 sub-sample, we reach a total of about 210 Ms exposure, and we report a significant ($\sim 3\sigma$) detection in the hardest (10-30 keV rest frame) band, along with relatively tight upper limits in the rest frame softer energy bands. The most straightforward interpretation is in terms of heavy obscuration due to gas column densities well within the Compton thick regime ($> 2 \times 10^{24} $cm$^{-2}$) with a large covering factor, approaching 4$\pi$. The same procedure applied to the Type 1 sub-sample returns no evidence for a significant signal in about 140 Ms stacked data in any of the adopted bands, confirming their surprisingly elusive nature in the X-ray band obtained with previous stacking experiments. A brief comparison with the current observations and the implications for the evolution of AGN are discussed.

Very Long Baseline Interferometry (VLBI) provides the highest-resolution radio intensity maps, crucial for detailed studies of compact sources like active galactic nuclei (AGN) and their relativistic jets. Analyzing jet components in these maps traditionally involves manual Gaussian fitting, a time-consuming bottleneck for large datasets. To address this, we present an automated batch-processing tool, based on the Gaussian fitting capabilities of CASA, designed to streamline VLBI jet component characterization (AAP-Imfit). Our algorithm sets a detection limit, performs automatic 2D Gaussian fitting, and removes model artifacts, efficiently extracting component flux densities and positions. This method enables systematic and reproducible analysis, significantly reducing the time required for fitting extensive VLBI datasets. We validated AAP-Imfit by using VLBI observations of the blazars 3C 279 and 3C 454.3, comparing our results with published fits. The close agreement in residual root mean square (RMS) values and model/residual-to-map RMS ratios confirms the accuracy of our automated approach in reproducing original flux distributions. While visual inspection remains important for complex or faint features, this routine significantly accelerates VLBI component fitting, paving the way for large-scale statistical studies of jet dynamics.

Exoplanetary science heavily relies on transit depth ($D$) measurements. Yet, as instrumental precision increases, the uncertainty on $D$ appears to increasingly drift from expectations driven solely by photon-noise. Here we characterize this shortfall (the Transit-Depth Precision Problem, TDPP), by defining an amplification factor, $A$, quantifying the discrepancy between the measured transit-depth uncertainty and the measured baseline scatter on a same time bin size. While in theory $A$ should be $\sim\sqrt{3}$, we find that it can reach values $\gtrsim$10 notably due to correlations between $D$ and the limb-darkening coefficients (LDCs). This means that (1) the performance of transit-based exoplanet studies (e.g., atmospheric studies) can be substantially improved with reliable priors on LDCs and (2) low-fidelity priors on the LDCs can yield substantial biases on $D$--potentially affecting atmospheric studies due to the wavelength-dependence of such biases. For the same reason, biases may emerge on stellar-density and planet-shape/limb-asymmetry measurements. With current photometric precisions, we recommend using a 3$^{\rm rd}$-order polynomial law and a 4$^{\rm th}$-order non-linear law, as they provide an optimal compromise between bias and $A$, while testing the fidelity for each parametrization. While their use combined with existing LDC priors (10-20% uncertainty) currently implies $A\sim10$, we show that targeted improvements to limb-darkening models can bring $A$ down to $\sim2$. Improving stellar models and transit-fitting practices is thus essential to fully exploit transit datasets, and reliably increasing their scientific yield by $5\times$, thereby enabling the same science with up to $25\times$ fewer transits.

Interpreting the spectral energy distributions (SEDs) of astrophysical objects with physically motivated models is computationally expensive. These models require solving coupled differential equations in high-dimensional parameter spaces, making traditional fitting techniques such as Markov Chain Monte Carlo or nested sampling prohibitive. A key example is modeling non-thermal emission from blazar jets - relativistic outflows from supermassive black holes in Active Galactic Nuclei that are among the most powerful emitters in the Universe. To address this challenge, we employ machine learning to accelerate SED evaluations, enabling efficient Bayesian inference. We generate a large sample of lepto-hadronic blazar emission models and train a neural network (NN) to predict the photon spectrum with strongly reduced run time while preserving accuracy. As a proof of concept, we present an NN-based tool for blazar SED modeling, laying the groundwork for future extensions and for providing an open-access resource for the astrophysics community.

Direct-imaging surveys have looked for accreting planets through their accretion tracers such as H alpha but have been less fruitful than expected. However, up to now, hydrogen-line emission at accreting planets has been estimated primarily with extrapolations of stellar-scaling relationships or with theoretical spherically-symmetric computations. To predict the line emission intensity during the formation phase, we wish to follow the consequences of angular momentum conservation of the material accreting onto a gas giant in a protoplanetary disc. We focus on the limiting case that magnetospheric accretion does not occur, which yields a conservative estimate of the line emission and might correspond to certain epochs during formation. We extend but simplify an existing analytical description of the multidimensional gas flow onto an accreting gas giant, the ballistic infall model, and combine this with detailed shock emission models. Applying this to data from a global planet formation model, we confirm that the line-emitting accretion rate is a minuscule fraction of the gas inflow into the Hill sphere. Also, forming planets are mostly fainter than PDS 70 b and c or WISPIT 2 b, with a maximum H alpha line luminosity Lline near 1e-7 Lsol, roughly independent of planet mass. Most surveys have not been sensitive to such faint planets. Other hydrogen lines in the NIR are fainter by 1--2 dex. This implies that accreting planets are fainter than from past estimates, such that the non-detections are not as constraining as thought. Accreting super-Jupiters may well be present, and a deeper look and closer in to the host stars could well reveal many forming planets.

ADARI (Astronomical DAta Reporting Infrastructure) is a system designed for creating graphical reports of astronomical data so that the quality of these products can be assessed. It has been designed from the ground up to be backend-agnostic, meaning the same ADARI code can be sent to a web plotting API, or a code-based plotting API, with no alteration. Quick data inspection is an important feature in data reduction systems. The use cases range from quality control at the telescope, advance quality checks prior to delivering data to the scientists as well as data inspection for users running the pipelines at their home institutes. The goal of ADARI is to deliver the same experience and code for data visualization for all the environments, either running automatically in the Paranal Observatory environment or at the PI premises. ADARI contains a library that can be used to develop the creation of reports as well as a command line tool (genreport) to execute such reports. Most of the time the reports are generated as part of the execution of a data reduction workflow implemented with EDPS, the new ESO system for automatically organising data from ESO instruments and for running the reduction pipelines on them.

Bayes factors have become a popular tool in exoplanet spectroscopy for testing atmosphere models against one another. We show that the commonly used method for converting these values into significance "sigmas" is invalid. The formula is neither justified nor recommended by its original paper, and overestimates the confidence of results. We use simple examples to demonstrate the invalidity and prior sensitivity of this approach. We review the standard Bayesian interpretation of the Bayes factor as an odds ratio and recommend its use in conjunction with the Akaike Information Criterion (AIC) or Bayesian Predictive Information Criterion Simplified (BPICS) in future analyses (Python implementations are included) . As a concrete example, we refit the WASP-39 b NIRSpec transmission spectrum to test for the presence of SO$_2$. The prevalent, incorrect significance calculation gives $3.67\sigma$ whereas the standard Bayesian interpretation yields a null model probability $p(\mathcal{B}|y)=0.0044$. Surveying the exoplanet atmosphere literature, we find widespread use of the erroneous formula. In order to avoid overstating observational results and estimating observation times too low, the community should return to the standard Bayesian interpretation.

We present a new framework for constructing agnostic and yet physical models for planetary interiors and apply it to Uranus and Neptune. Unlike previous research that either impose rigid assumptions or rely on simplified empirical profiles, our approach bridges both paradigms. Starting from randomly generated density profiles, we apply an iterative algorithm that converges toward models that simultaneously satisfy hydrostatic equilibrium, match the observed gravitational moments, and remain thermodynamically and compositionally consistent. The inferred interior models for Uranus and Neptune span a wide range of possible interior structures, in particular encompassing both water-dominated and rock-dominated configurations (rock-to-water mass ratios between 0.04-3.92 for Uranus and 0.20-1.78 for Neptune). All models contain convective regions with ionic water and have temperature-pressure profiles that remain above the demixing curves for hydrogen-helium-water mixtures. This offers both a plausible explanation for the observed non-dipolar magnetic fields and indicates that no hydrogen-helium-water demixing occurs. We find a higher H-He mass fraction in the outermost convection zones for Uranus (0.62-0.73) compared to Neptune (0.25-0.49) and that Uranus' magnetic field is likely generated deeper in the interior compared to Neptune. We infer upper limits of 0.69-0.74 (Uranus) vs. 0.78-0.92 (Neptune) for the outer edges of the dynamo regions in units of normalised radii. Overall, our findings challenge the conventional classification of Uranus and Neptune as "ice giants" and underscore the need for improved observational data or formation constraints to break compositional degeneracy.

The Simons Observatory (SO) is a cosmic microwave background experiment with over 67,000 polarization-sensitive transition-edge sensor (TES) detectors currently installed for use in observations and plans to increase the total detector count to ${\sim}$98,000 detectors with the Advanced SO upgrade. The TES arrays are packaged into Universal Focal-Plane Modules (UFMs), which also contain the multiplexing readout circuit. Within a readout module, a DC/RF routing wafer provides a cold interface between the detectors and the readout multiplexing chips. Each routing wafer hosts twelve bias lines, which contain the ${\sim}$400 ${\mu}{\Omega}$ shunt resistors that are part of the TES bias circuitry. More than 70 routing wafers have been fabricated and tested both at room temperature and 100 mK before integration into UFMs. The lab measurements for all screened wafers have been compiled to show the distribution of measured average shunt resistance Rsh for each bias line, both across bias lines on a single routing wafer and across all routing wafers. The mean average shunt resistance for all wafers was found to be 396 ${\mu}{\Omega}$ with a standard deviation of 16 ${\mu}{\Omega}$, or ${\sim}$4%. For each wafer, we note good uniformity of average Rsh between bias lines, with a slight downward trend with increasing distance from the center of the wafer. The fabrication data collected at room temperature shows agreement with the cryogenic measurements of Rsh distribution.

With the launch and application of next-generation ground- and space-based telescopes, astronomy has entered the era of big data, necessitating more efficient and robust data analysis methods. Most traditional parameter estimation methods are unable to reconcile differences between photometric systems. Ideally, we would like to optimally rely on high-quality observation data provided by, e.g., JWST, for calibrating and improving upcoming wide-field surveys such as the China Space Station Telescope (CSST) and Euclid. To this end, we introduce a new approach (SHAPE, SOM-SED Hybrid Approach for efficient Parameter Estimation) that can bridge different photometric systems and efficiently estimate key galaxy parameters, such as stellar mass ($M_\star$) and star formation rate (SFR), leveraging data from a large and deep JWST/NIRCam and MIRI survey (PRIMER). As a test of the methodology, we focus on galaxies at $z\sim 1.5-2.5$. To mitigate discrepancies between input colors and the training set, we replace the default SOM weights with stacked SEDs from each cell, extending the applicability of our model to other photometric catalogs (e.g., COSMOS2020). By incorporating a SED library (SED Lib), we apply this JWST-calibrated model to the COSMOS2020 catalog. Despite the limited sample size and potential template-related uncertainties, SOM-derived parameters exhibit a good agreement with results from SED-fitting using extended photometry. Under identical photometric constraints from CSST and Euclid bands, our method outperforms traditional SED-fitting techniques in SFR estimation, exhibiting both a reduced bias (-0.01 vs. 0.18) and a smaller $\sigma_{\rm NMAD}$ (0.25 vs. 0.35). With its computational efficiency capable of processing $10^6$ sources per CPU per hour during the estimation phase, this JWST-calibrated estimator holds significant promise for next-generation wide-field surveys.

The rapid appearance of supermassive black holes (SMBHs) at $z\gtrsim7$ requires efficient pathways to form massive black hole seeds. We investigate whether annihilation of weakly interacting massive particles (WIMPs) can alter primordial (Pop III.1) protostellar evolution sufficiently to enable formation of such `heavy'' seeds. Using the one-dimensional Geneva stellar-evolution code (GENEC) with an implemented Gould single-scatter capture module, we compute a grid of protostellar evolution models covering ambient WIMP mass densities $\rho_\chi=10^{12}$-$10^{16}\ \mathrm{GeV\,cm^{-3}}$, WIMP masses $m_\chi=30$-$3000\ \mathrm{GeV}$, spin-dependent cross sections $\sigma_{\rm SD}=10^{-42}$-$10^{-40}\ \mathrm{cm^2}$, and baryonic accretion rates $\dot{M_*}=(1-3)\times10^{-3}\, M_\odot \,{\rm yr}^{-1}$. We find a robust bifurcation of outcomes. For sufficiently high ambient dark matter density ($\rho_\chi\gtrsim5\times10^{14}\ \mathrm{GeV\,cm^{-3}}$) and capture efficiency ($\sigma_{\rm SD}\gtrsim10^{-41}\ \mathrm{cm^2}$) WIMP annihilation supplies enough energy to inflate protostars onto extended, cool (Hayashi-track) configurations that dramatically suppress ionizing feedback and permit uninterrupted growth to $\sim10^{5}\,M_\odot$. Lighter WIMPs and larger $\sigma_{\rm SD}$ favour earlier and stronger annihilation support; heavier WIMPs delay the effect. For our fiducial case, WIMP masses $<$3 TeV are essential for allowing growth to the supermassive regime, otherwise the protostar evolves to the compact, feedback-limited regime that results in `light'' seeds. These results indicate that, under plausible halo conditions, DM annihilation provides a viable channel for forming heavy black hole seeds.

We investigate the cosmological implications of Tsallis entropy in two widely discussed settings: the Cai--Kim thermodynamic derivation of the Friedmann equations and the holographic dark energy (HDE) scenario with the Hubble scale as infrared cutoff. In both cases, the dynamics introduce a nonextensivity parameter $\delta$, with standard $\Lambda$CDM recovered for $\delta=1$. Previous studies have argued that only small deviations from extensivity are observationally allowed, typically constraining $|1 - \delta| \lesssim 10^{-3}$. In this work we go further and present, for the first time, a systematic consistency analysis across the entire expansion history. We show that even mild departures from $\delta=1$ lead to pathological behavior in the effective dark energy sector: its density becomes negative or complex, its equation of state diverges, or alternatively it contributes an unacceptably large early--time fraction that spoils radiation domination and violates BBN and CMB bounds. Our results sharpen and unify earlier hints of tension, providing a clear physical explanation in terms of corrections that grow uncontrollably with expansion rate toward the past. We conclude that, within both the Cai--Kim and HDE frameworks, viable cosmology is realized only in the extensive limit, effectively collapsing the models back to $\Lambda$CDM. More broadly, our findings call attention to the importance of dynamical consistency and cosmological viability tests when assessing nonextensive entropies as possible explanations of the Universe's dynamics.

We present the star formation and dust attenuation properties for a sample of 602 galaxies at redshifts $\rm{3<z<7}$, as part of the JADES survey. Our analysis is based on measurements of the $\rm{H}\alpha/\rm{H}\beta$ Balmer Decrement using medium resolution (R$\sim$1000) spectroscopic observations with the JWST/NIRSpec Micro-Shutter Assembly. Stellar masses and star formation rates (SFRs) are inferred with \texttt{Prospector} using deep multi-band imaging. We utilize the Balmer decrement to measure dust-corrected H$\alpha$-based SFRs, taking into account the subsolar metallicities observed in galaxies at high redshift. We confirm, with our large sample size, that the correlation between the Balmer decrement and stellar mass is already established out to $z\sim7$. We find that the relation between the Balmer decrement and stellar mass does not significantly evolve from the local universe to $z\sim7$. We investigate the UV slope as a function of the Balmer optical depth and find that the best-fit correlation for our high redshift sample is sSFR dependent and significantly different at high redshift when compared to galaxies at $z\approx 0$ and $z \approx 2$. For the highest sSFR galaxies in our sample, there is no significant correlation between the UV slope and Balmer optical depth. This is evidence that the UV slope should be used with great caution to correct for dust in high redshift galaxies.

Currently the asteroid mass window (mass $\sim 10^{17}- 10^{21}$ grams) remains unconstrained for Primordial Black Holes (PBHs) to make up all of the dark matter content of the universe. Given these PBHs have very small masses, their Hawking temperature can be up to hundreds of keV. This study investigates the potential impacts of PBH Hawking radiation on the intergalactic medium from $z\sim 800-25$, namely studying the ionization history, kinetic gas temperature, and ultimately the 21 cm signature. We find that for masses on the low edge of the asteroid mass window, there are up two orders of magnitude increases in the ionization fraction and kinetic gas temperature by redshift 25, and the 21 cm spin temperature can differ from non-PBH cosmology by factors of a few. This analysis results in maximum differential brightness temperatures of +17 mK for our lightest PBH masses of $2.12\times 10^{16}$g. We also show maximal $53$ mK discrepancies in differential brightness temperatures between our PBH and non-PBH cosmologies for our lightest PBH mass, while our heaviest PBH mass of $1.65 \times 10^{17}$g shows only $0.5$ mK variations. We find the Hawking-radiated electrons and positrons are instrumental in driving these IGM modifications. This study shows the necessity for a rigorous treatment of Hawking radiation in PBH cosmological observables from the dark ages through cosmic dawn.

Gamma-ray bursts (GRBs) are cosmic events occurring at large distances beyond our galaxy. They provide a unique opportunity to study electromagnetic patterns not seen elsewhere. When the collimated GRB outflow interacts with the outer layers of a star or the wind generated by a binary neutron star merger, it releases energy, forming a quasi-spherical outflow around it. This broad outflow begins to radiate once it has transferred enough energy to the surrounding medium. We have developed a new analytical model that describes the synchrotron afterglow scenario of the quasi-spherical outflow, including factors such as stratified density, self-absorption regime, and the fraction of electrons accelerated by the shock front. We also successfully describe the multiwavelength observations of a sample of llGRB afterglows (GRB 980425, 031203, 060218, 100316D, 130603B, 150101B and 171205A) that exhibited a late component, analyzed in both stellar wind and constant-density environments. Our analysis shows that a constant-density environment is favored. Additionally, we consider the multiwavelength upper limits of the short bursts reported in the Swift-BAT database.

We explore novel classes of exotic astrophysical sources capable of producing ultra-high-energy gamma rays extending beyond the PeV scale, motivated by quantum gravity scenarios and dark matter phenomenology. These sources include: ultra-spinning black hole vortex-string systems; exotic compact objects such as boson star, axion star and Q-ball. Such Exotica generate powerful magnetic fields through interactions with millicharged dark matter, enabling particle acceleration mechanisms that surpass the energy limits of conventional astrophysical sources like pulsar wind nebulae and supernova remnants. We demonstrate that such exotic PeVatrons could be distributed throughout our Galaxy and may be detectable by current (LHAASO, HAWC) and next-generation (CTA) gamma-ray observatories.

If dark matter is ultra-light and has certain Standard Model interactions, it can change the mass-radius relation of white dwarf stars. The coherence length of ultra-light dark matter imparts spatial correlations in deviations from the canonical mass-radius relation, and thus white dwarfs can be used to reconstruct the coherence length, or equivalently the particle mass, of the dark matter field. We simulate the observability of such spatial correlations accounting for realistic complications like variable hydrogen envelope thickness, dust, binaries, measurement noise, and distance uncertainties in DA white dwarfs. Using a machine learning approach on simulated data, we measure the dark matter field coherence length and find that large deviations from the mass-radius relation ($\sim10\%$ change in radius) are needed to produce an observable signal given realistic noise sources. We apply our spatial correlation measurement routine to the SDSS catalog of 10,207 DA white dwarfs. We detect a positive spatial correlation among white dwarfs at separations corresponding to a coherence length of $300\pm50$ pc, with an average Z-score of 85 for white dwarfs separated by less than this coherence length. We conclude that this signal is due to observational bias. The signal can be explained by an offset between measurements and theory for nearby cool white dwarfs, and the presence of few, low-temperature white dwarfs with noisy measurements at further distances. With future improvements in white dwarf models and measurement techniques, particularly for cool white dwarfs, this method can provide interesting constraints on ultra-light dark matter models.

Ices imprint strong absorption features in the near- and mid-infrared, but until recently they have been studied almost exclusively with spectroscopy toward small samples of bright sources. We show that JWST photometry alone can reveal and quantify interstellar ices and present a new open-source modeling tool, icemodels, to produce synthetic photometry of ices based on laboratory measurements. We provide reference tables indicating which filters are likely to be observably affected by ice absorption. Applying these models to NIRCam data of background stars behind Galactic Center (GC) clouds, and validating against NIRSpec spectra of Galactic disk sources, we find clear signatures of CO, H$_2$O, and CO$_2$ ices and evidence for excess absorption in the F356W filter likely caused by CH-bearing species such as methanol. The ice ratios differ between the Galactic disk and Center, with GC clouds showing a higher H$_2$O fraction. The large ice abundance in CO, H2O, and possibly complex molecules hints that the high complex molecule abundances observed in gas emission in the CMZ are driven by ice-phase chemistry in non-star-forming gas. Accounting for all likely ices, we infer that $>25%$ of the total carbon is frozen into CO ice in the GC, which exceeds the entire solar-neighborhood carbon budget. By assuming the freezeout fraction is the same in GC and disk clouds, we obtain a metallicity measurement indicating that $Z_GC\gtrsim2.5Z_\odot$. These results demonstrate that photometric ice measurements are feasible with JWST and capable of probing the metallicity structure of the cold interstellar medium.

Aims. We aim to confirm and measure the mass of the transiting planet candidate around the K5V star TOI-2093, previously announced by the Transiting Exoplanet Survey Satellite (TESS) project. Methods. We combined photometric data from 32 sectors between 2019 and 2024 with 86 radial velocity measurements obtained with the CARMENES spectrograph over a period of 2.4 years, along with a series of ground-based, broadband photometric monitoring campaigns to characterize the host star and the transiting planet candidate, as well as to search for additional planets in the system. Our data indicate that TOI-2093 is a main-sequence star located at a distance of 83 pc, with solar metallicity, and a rotation period of 43.8 +- 1.8 d. Results. We have confirmed the planetary nature of the TESS transiting planet candidate, named TOI-2093 c, through the detection of its Keplerian signal in the spectroscopic data. We measured a planetary radius of 2.30 +- 0.12 Rearth, a Neptune-like mass of 15.8 +- 3.7 Mearth, and an orbital period of 53.81149 +- 0.00017 d. This makes TOI-2093 c the smallest exoplanet known in the habitable zone of a main-sequence FGK star. Given its size and relatively high density, TOI-2093 c belongs to a class of planets with no analog in the Solar System. In addition, the CARMENES data revealed the presence of a second planet candidate with a minimum mass of 10.6 +- 2.5 Mearth and an orbital period of 12.836 +- 0.021 d. This inner planet, which we designated TOI-2093 b, shows no detectable photometric transit in the TESS light curves. The orbital planes of the two planets are misaligned by more than 1.6 deg despite the near 4:1 mean-motion resonance of their orbital periods.

Small-scale magnetic flux concentrations contribute significantly to the brightness variations of the Sun, yet observing them - particularly their magnetic field - near the solar limb remains challenging. Solar Orbiter offers an unprecedented second vantage point for observing the Sun. When combined with observations from the perspective of Earth, this enables simultaneous dual-viewpoint measurements of these magnetic structures, thereby helping to mitigate observational limitations. Using such a dual-viewpoint geometry, we characterise the brightness contrast of faculae near the limb as a function of both their associated magnetic field strength and the observation angle. We analyse data from Polarimetric and Helioseismic Imager on board Solar Orbiter (SO/PHI), obtained during an observation program conducted in near-quadrature configuration with Earth, in combination with data from the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory (SDO/HMI). The High Resolution Telescope of SO/PHI observed a facular region located near disc centre as seen from its vantage point, while the same region was simultaneously observed near the solar limb by SDO/HMI. We identify faculae and determine their magnetic field strength from the disc-centre observations, and combine these with continuum intensity measurements at the limb to derive dual-viewpoint contrast curves. We then compare these with contrast curves derived from SDO/HMI alone. Using two viewpoints, we consistently find higher facular contrast near the limb than from a single-viewpoint.

We investigate the foreground interstellar medium along the line of sight and intracluster medium of $\omega$ Centauri ($\omega$ Cen) by measuring the equivalent width of Na I D absorptions from MUSE observations. The large line-of-sight velocity difference between $\omega$ Cen and the foreground enables us to separate Na I D absorption contributed from atomic gas in the interstellar and intracluster medium. We find that small-scale substructures in the foreground Na I D distribution correlate with differential reddening derived from photometric methods. Using an empirical Na I D equivalent width-reddening relation, we determine an average reddening of $E(B-V)=0.153\pm0.003$ mag within the half-light radius of $\omega$ Cen. However, the Na I D-inferred differential reddening is significantly larger than photometric estimates. This is likely due to scatter in the Na I D-reddening relation. We find no evidence for intracluster atomic gas from spectra of horizontal branch stars, as there is no significant Na I D absorption at $\omega$ Cen's systemic velocity. Given this non-detection, we place the strongest upper limit to date on the intracluster atomic gas column density in $\omega$ Cen of $\lesssim2.17 \times 10^{18}~\rm{cm^{-2}}$. We also estimate the ionized gas density from pulsar dispersion measure variations, which exceed the atomic gas limit by $\sim$50 times. Nevertheless, the strong correlation between dispersion measure and foreground Na I D suggests that much or all of this ionized gas resides in the foreground. Given ongoing mass loss from bright giant stars, our findings imply that the intracluster gas accumulation timescale is short, and gas removal in the cluster is likely not tied to stripping as $\omega$ Cen passes through the Galactic disk.

We present high-precision TESS photometry of V421 Peg (TIC 301747091), an early F-type eclipsing binary containing a candidate $\gamma$ Dor component. The observed short-cadence data allow the detection of pulsation signals, along with revision of the fundamental properties of the component stars. Detailed binary modeling indicated that the program target is a partially-eclipsing detached system in a circular orbit and that both components are currently in super-synchronous states. The radii of each star were measured with an accuracy of about 1 \%. By periodogram analysis of the outside-eclipse residual lights obtained from the binary star model, we extracted nine significant signals, five of which are likely aliasing frequencies due to sampling artifacts and uncorrected trends in the data used. The other signals of $f_1$, $f_2$, $f_3$, and $f_6$ are considered to be independent pulsations with frequencies ranging from 0.73 day$^{-1}$ to 1.02 day$^{-1}$, corresponding to pulsation constants of 0.63$-$0.88 days. These frequencies, pulsation constants, and position on the H-R diagram reveal that the pulsating signals are $\gamma$ Dor variables arising from the V421 Peg primary component.

Ultra-high-energy cosmic rays (UHECRs) are the most energetic particles ever detected. Cosmic rays that achieve the highest energies are rare, and their flux at Earth is extremely low. As a result, next-generation experiments with large effective areas are required and under development. The Fluorescence detector Array of Single-pixel Telescopes (FAST) is one such project. Although observation time is limited compared with ground particle detectors, it enables direct measurements of $X_\mathrm{max}$, a crucial parameter sensitive to the primary cosmic-ray composition. FAST will achieve large-area coverage by significantly reducing the cost of telescopes. This necessitates a simplified telescope compared to conventional designs. Demonstrating the feasibility of our telescope and observational method is essential. To validate the FAST concept, prototype telescopes have been deployed at the Pierre Auger Observatory and the Telescope Array experiment.

Numerous high-$z$ galaxies have recently been observed with the James Webb Space Telescope (JWST), providing new insights into early galaxy evolution. Their physical properties are typically derived through spectral energy distribution (SED) fitting, but the reliability of this approach for such early systems remains uncertain. Applying {\sc Bagpipes} on simulated SEDs at $z=6$ from the {\sc Sphinx$^{20}$} cosmological simulation, we examine uncertainties in the recovery of stellar masses, star formation rates (SFR$_{10}$), and stellar metallicities from mock JWST/Near-Infrared Camera photometry. Even without dust or emission lines, fitting the intrinsic stellar continuum overestimates the stellar mass by about 60\% on average (and by up to a factor of five for low-mass galaxies with recent starbursts) and underestimates SFR$_{10}$ by a factor of two, owing to inaccurate star formation histories and age-metallicity degeneracies. The addition of dust and nebular emission further amplifies these biases, yielding offsets of approximately +0.3 and -0.4 dex in stellar mass and SFR$_{10}$, respectively, while leaving stellar metallicities largely unconstrained. Incorporating bands free of strong emission lines, such as F410M, helps mitigate stellar mass overestimation by disentangling line emission from older stellar populations. We also find that best-fit or likelihood-weighted estimates are generally more accurate than median posterior values. Although stellar mass functions are reproduced reasonably well, the slope of the star formation main sequence depends sensitively on the adopted fitting model. Overall, these results underscore the importance of careful modelling when interpreting high-$z$ photometry, particularly for galaxies with recent star formation burst and/or strong emission lines, to minimise systematic biases in derived physical properties.

Particle acceleration in relativistic shocks of electron-positron plasmas with proton admixture is investigated through two-dimensional (2D) particle-in-cell (PIC) simulations. The upstream plasma, with a bulk Lorentz factor of $10$ and a magnetization parameter of 0.02, includes a small fraction of protons ($\sim 5\%$ by number). A relativistic perpendicular shock is formed by reflecting the flow off a conducting wall. The shock structure, electromagnetic fields, and particle energy spectra are analyzed. The particle density and the magnetic field have fluctuations. In the far-downstream region of the shock, positrons are accelerated to energies comparable to protons and develop a hard nonthermal component with a spectral index of $\sim 2$ in their energy spectrum, while electrons remain confined to lower energies. This asymmetry is attributed to the polarization properties of proton-driven electromagnetic waves, which favor positron acceleration. The results highlight the importance of plasma composition in shaping particle acceleration and nonthermal emission in relativistic shocks. These findings provide new insights into the microphysics of particle acceleration in astrophysical sources containing relativistic shocks.

We analyze nebular dust attenuation and its correlation with stellar mass ($M_{*}$) and UV spectral slope ($\beta$) in 33 lensed, low-mass star-forming galaxies at $1.4\leq z \leq 2.6$, using Keck/MOSFIRE rest-frame optical spectroscopy. Located behind three massive lensing galaxy clusters Abell 1689, MACS J1149.5+2223, and MACS J0717.5+3745, galaxies in our sample have a median stellar mass of $\log(M_{*}/M_{\odot})=8.3$ and an intrinsic UV absolute magnitude range of $-20.9<M_{UV}<-13$. We measure nebular dust attenuation via Balmer optical depth ($\tau_{B}$) defined as the H$\alpha$/H$\beta$ ratio. We also derive physical properties from Hubble Space Telescope multi-wavelength photometry and construct composite spectra using median stacking in bins of $M_{*}$ and $\beta$. We find that the $\tau_{B}-\beta$ relation for the dwarf galaxies in this study is best represented by SMC dust curve. This is consistent with previous studies of low-metallicity galaxies at similar redshifts, which show a steep attenuation curve similar to the SMC curve, in contrast to high-metallicity and more massive galaxies that exhibit a much shallower dust attenuation curve. We also investigate the relationship between nebular dust attenuation and stellar mass, $E(B-V)_{nebular}-M_{*}$, down to $\log(M_{*}/M_{\odot})\sim 7$. We demonstrate that this relation does not notably evolve with redshift and is consistent with what has been observed for local SDSS galaxies at similar low stellar masses.

We present a detailed depolarization analysis of a radio galaxy ILTJ012215.21+254334.8, utilizing polarimetric data from the LOFAR Two-metre Sky Survey (LoTSS) Data Release 2 (DR2) catalogue. The selected source exhibits a rotation measure (RM) of ~ - 47 rad/m^2 and a projected linear size of 335 kpc at a redshift z ~ 0.05. Depolarization model fitting was performed on LOFAR High Band Antenna data (120 - 168 MHz), with fractional polarization detected at 3.0%. Five depolarization models were tested, and Bayesian qu-fitting revealed that the three-component model (1T+2ED) best describes the data, with a reduced chi-squared value of 2.12 and a logarithmic Bayesian evidence of 1384.82. This model includes a Faraday-thin component at RM ~ - 0.3 rad/m^2 (instrumental leakage) and two external Faraday dispersion astrophysical emission at RM ~ - 47 rad/m^2. The results demonstrate that depolarization in low-frequency radio galaxies requires multi-component modelling and is driven by turbulence and inhomogeneity in the magneto-ionic medium. Our findings highlight the potential of LOFAR polarization studies for probing galactic and intergalactic magnetic fields with high precision.

Dusty, submillimeter-selected galaxies without optical counterparts contribute a non-negligible fraction of the star formation in the early universe. However, such a population is difficult to detect through classical optical/UV-based surveys. We report the serendipitous discovery of such an optically dark galaxy, behind the quadruply-lensed $z=2.56$ quasar, H1413+117, offset to the north by 6\arcsec. From $^{12}$CO $J=4$--3, $J=6$--5, and part of the $J=13$--12 transitions, which all spatially coincide with a compact submillimeter continuum emission, we determine an unambiguous spectroscopic redshift, $z=3.386\pm 0.005$. This galaxy has a molecular mass $M_{\rm mol} \sim 10^{11}$ M$_\odot$ and a black hole mass $M_{\rm BH} \sim 10^{8}$ M$_\odot$, estimated from $^{12}$CO $J=4$--3 and archival {\it Chandra} X-ray data ($L_{\rm 2-10,keV} \sim 4 \times 10^{44}$\,erg\,s$^{-1}$), respectively. We also estimate a total infrared luminosity of $L_{\rm FIR} = (2.8\pm{2.3}) \times 10^{12}$ L$_\odot$ and a stellar mass of $M_* \lesssim 10^{11}$ M$_{\odot}$, from spectral energy distribution fitting. According to these simple mass estimations, this gas-rich and X-ray bright galaxy might be in a transition phase from starburst to quasar offering a unique case for studying galaxy-black hole co-evolution under extremely dusty conditions.

Periodic oscillations at 338 nHz in the Earth frame are observed at high latitudes in direct Doppler velocity measurements. These oscillations correspond to the $m=1$ high-latitude global mode of inertial oscillation. In this study, we investigate the signature of this mode in the photospheric magnetic field using long-term series of line-of-sight magnetograms from the Helioseismic and Magnetic Imager (HMI) and the Global Oscillation Network Group (GONG). Through direct observations and spectral analysis, we detect periodic magnetic field oscillations at high latitudes ($65^\circ$--$70^\circ$) with a frequency of 338 nHz in the Earth frame, matching the known frequency of the $m = 1$ high-latitude inertial mode. The observed line-of-sight magnetic field oscillations are predominantly symmetric across the equator. We find a peak magnetic oscillation amplitude of up to $0.2$~gauss and a distinct spatial pattern, both consistent with simplified model calculations in which the radial component of the magnetic field is advected by the mode's horizontal flow field.

To model the structure and dynamics of the heliosphere well enough for high-quality forecasting, it is essential to accurately estimate the global solar magnetic field used as inner boundary condition in solar wind models. However, our understanding of the photospheric magnetic field topology is inherently constrained by the limitation of systematically observing the Sun from only one vantage point, Earth. To address this challenge, we introduce global magnetic field maps that assimilate far-side active regions derived from helioseismology into solar wind modeling. Through a comparative analysis between the combined surface flux transport and helioseismic Far-side Active Region Model (FARM) magnetic maps and the base surface flux transport model without far-side active regions (SFTM), we assess the feasibility and efficacy of incorporating helio- seismic far-side information in space weather forecasting. We are employing the Wang-Sheeley-Arge Solar Wind (WSA) model for statistical evaluation and leveraging the three-dimensional heliospheric MHD model, EUHFORIA, to analyze a case study. Using the WSA model, we show that including far-side magnetic data improves solar wind forecasts for 2013-2014 by up to 50% in correlation and 3% in Root Mean Square Error and Mean Absolute Error, especially near Earth and STEREO-A. Additionally, our 3D modeling shows significant localized differences in heliospheric structure that can be attributed to the presence or absence of active regions in the magnetic maps used as input boundaries. This highlights the importance of including far-side information to more accurately model and predict space weather effects caused by solar wind, solar transients, and geomagnetic disturbances.

Blazars are active galactic nuclei known for their extreme variability, offering unique opportunities to study jet physics and high-energy emission mechanisms. In 2024, the Flat Spectrum Radio Quasar (FSRQ) OP313 underwent a remarkable flare event, during which the gamma-ray flux observed by the Fermi Large Area Telescope (Fermi/LAT) increased by a factor of 60 over its average value. The flare peak lasted less than two days. Using optical telescopes, we conducted 100-day time-scale observations. Multi-wavelength data revealed that OP313 entered an active state 50 days prior to the flare and remained active for at least 50 days afterward. We propose that this prolonged activity results from variations in electron density within the shock front due to changes in the accretion rate. Concurrently, OP313's spectrum transitioned from an FSRQ-like state to a BL Lac-like state, characterized by a significant increase in the synchrotron peak frequency and the disappearance of broad-line region emission lines. In the post-flare phase, we observed a decoupling between synchrotron radiation and inverse Compton scattering, along with a possible decrease in the magnetic field strength within the shock front.

The discovery of supermassive black holes with masses $\gtrsim 10^9 M_\odot$ at redshifts $z\gtrsim 10$ challenges conventional formation scenarios based on baryonic accretion and mergers within the first few hundred million years. We propose an alternative channel in which ultralight scalar dark matter undergoes dark-to-black conversion via quasi-bound state depletion around black hole seeds. We estimate the accretion rate of the scalar field as a function of the boson mass parameter $\mu$ and the black hole mass $M_{\rm BH}$, and integrate this rate over cosmological timescales. Our results show that once a critical value of $\mu M_{\rm BH}$ is reached, scalar field accretion becomes highly efficient, enabling substantial black hole growth even from relatively small initial seed masses. For boson masses $\mu \sim 10^{-19}-10^{-16}\,\mathrm{eV}$, black hole seeds of $10^2-10^5 M_\odot$ can reach $10^6-10^8 M_\odot$ within $\sim 10^8$ yr. This dark-to-black mechanism provides a natural pathway for the rapid formation of massive black holes in the early universe, offering a potential probe of the microphysical nature of dark matter.

Non-jetted AGN exhibit hard X-ray emission with a power law spectrum above $\sim$2 keV, which is thought to be produced through Comptonization of soft photons by electrons and positrons (pairs) in the vicinity of the black hole. The origin and composition of this plasma source, known as the corona, is a matter open for debate. Our study focuses on the role of relativistic protons accelerated in black-hole magnetospheric current sheets in the neutrino production of AGN coronae. We present a model that has two free parameters, namely the proton plasma magnetization $\sigma_{\rm p}$, which controls the peak energy of the neutrino spectrum, and the Eddington ratio $\lambda_{\rm Edd}$ (defined as the ratio between X-ray luminosity $L_{\rm X}$ and Eddington luminosity $L_{\rm Edd}$), which controls the amount of energy transferred to secondary particles. Furthermore, we combine our coronal model with an AGN population in order to provide a prediction for the diffuse neutrino flux measured on Earth. We compare our results with the observational data by IceCube and we find a satisfactory agreement on both the flux value and the slope of the neutrino distribution when we assume a $\sigma_{\rm p}$ value of $10^5$ for all the sources in our sample.

Gamma-ray bursts (GRBs) are among the most energetic events in the universe, offering insights into stellar collapse, extreme matter behavior, and cosmic evolution. The advent of multi-messenger astronomy, combining electromagnetic, gravitational wave, and neutrino observations, alongside advances in high-energy polarimetry, is revolutionizing GRB research, enabling deeper exploration of their physical mechanisms. This manuscript summarizes how upcoming and proposed space-based missions will tackle key challenges in GRB science, focusing on four areas: (i) identifying high-redshift GRBs to probe the early universe, (ii) enhancing multi-messenger detection and localization, (iii) improving multi-wavelength follow-up of GRB afterglows, and (iv) studying prompt emission polarization to understand jet dynamics and magnetic fields. Highlighting planned missions and their advancements, this work provides a snapshot of current GRB research frontiers, with updates on the evolving status of these missions.

The solar atmosphere is permeated by various types of waves that originate from subsurface convection. As these waves propagate upward, they encounter they encounter a steep decrease in the density of the medium, leading to their steepening into shock waves. These shock waves typically exhibit a characteristic sawtooth pattern in wavelength-time ($\lambda$-t) plots of various chromospheric spectral lines, viz., H$\alpha$, Ca II 8542 Å to name a few. In this study, we investigate the propagation of shock waves in the lower solar atmosphere using coordinated observations from the Swedish 1-meter Solar Telescope (SST), the Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory (SDO). Our analysis reveals that after forming in the chromosphere, these shock waves travel upward through the solar atmosphere, with their signatures detectable not only in the transition region but also in low coronal passbands. These shock waves dissipate their energy into the chromosphere as they propagate. In certain cases, the energy deposited by these waves is comparable to the radiative losses of the chromosphere, highlighting their potential role in chromospheric heating. Our findings reported here provide crucial insights into wave dynamics in the lower solar atmosphere and their contribution to the energy transport process in the chromosphere.

We present a spectroscopic and imaging analysis of the $z_{gal} \approx 1.1334$ ultra-strong MgII absorption system identified in the $VLT$/UVES spectrum of a background quasar located at $\rho \approx 18$ kpc from a star-forming galaxy. Low ionization metal lines like MgI, FeII, and CaII are also detected for this absorber. The HI lines are outside of the wavelength coverage. The MgII has a rest-frame equivalent width of $W_r(2796) =3.185 +/- 0.032 A^{\circ} $, with the absorption spread across $\Delta v \approx 460$ km~s$^{-1}$ in several components. A component-by-component ionization modeling shows several of these components having solar and higher metallicities. The models also predict a total HI column density of $log[N(HI)/cm^{-2}] \approx 22.5$, consistent with ultra-strong MgII absorbers being sub-Damped Lyman Alpha and Damped Lyman Alpha systems. The absorber is well within the virial radius of the nearest galaxy which has a stellar mass $M_* = 4.7 \times 10^{10}$~M$_\odot$, and a star formation rate of $\approx 8.3$~M$_\odot$~yr$^{-1}$. The absorption is along the projected major axis of the galaxy with a velocity spread that is wider than the galaxy's disk rotation. From the kinematic analysis of the absorber and the galaxy, the origin of the absorption can be attributed to a combination of circumgalactic gas structures, some corotating with the disk and the rest at line-of-sight velocities outside of the disk rotation.

The Habitable Zone (HZ) is defined by the possibility of sustaining liquid water on a planetary surface. In the Solar System, the HZ for a conservative climate model extends approximately between the orbits of Earth and Mars. We elaborate on earlier HZ models and apply an analytical climate model of the temperature distribution on tidally-locked planets to extend the HZ. We show that planets orbiting M- and K-dwarf stars may maintain liquid water on their night side, significantly closer to their host star than the inner border of the conservative HZ. We calculate the extended borders of the HZ in the flux-effective temperature diagram. This extension may explain the presence of water vapor and other volatile gases in the transmission spectra of warm Super-Earth-sized exoplanets closely orbiting M dwarfs, recently detected by JWST. We also mention the HZ extension outwards, due to subglacial liquid water in the form of intra-glacial lakes or subglacial melting.

Weak gravitational lensing signals of optically identified clusters are impacted by a selection bias -- halo triaxiality and large-scale structure along the line of sight simultaneously boost the lensing signal and richness (the inferred number of galaxies associated with a cluster). As a result, a cluster sample selected by richness has a mean lensing signal higher than expected from its mean mass, and the inferred mass will be biased high. This selection bias is currently limiting the accuracy of cosmological parameters derived from optical clusters. In this paper, we quantify the bias in mass calibration due to this selection bias. Using two simulations, MiniUchuu and Cardinal, with different galaxy models and cluster finders, we find that the selection bias leads to an overestimation of lensing mass at a 20-50% level, with a larger bias 20-80% for large-scale lensing (>3 Mpc). Even with a conservative projection model, the impact of selection bias significantly outweighs the impact of other currently known cluster lensing systematics. We urge the cluster community to account for this bias in all future optical cluster cosmology analyses, and we discuss strategies for mitigating this bias.

GRB~160821B is the only short GRB detected to date at very high energy (VHE, $\gtrsim 100$ GeV). At a redshift $z=0.161$, it was detected by MAGIC telescopes approximately four hours since the trigger. VHE dataset was complied with the datasets of other wavelengths in between the timescale of 1.7 to 4 hours to construct the broadband spectral energy distribution (SED). In previous studies of GRB~160821B, synchrotron and external Compton (EC) model could explain the VHE emission better than the synchrotron and synchrotron self-Compton (SSC) model. Although, these fits were mostly eyeballing data without any optimisation. Our model includes the combination of synchrotron, SSC, and EC models with Markov Chain Monte Carlo (MCMC) techniques. Our analysis reveals that the EC contribution is negligible in comparison with the SSC and our model explains the VHE data well for the wind medium. We found that GRB~160821B is the least energetic VHE GRB and it occurred in high density wind medium which is quiet unusual for a short GRB. But like other long-duration VHE GRBs, GRB~160821B occurred in a poorly magnetised medium. As there is no statistical study on afterglow modelling of short GRB sample, we compare the inferred properties of GRB~160821B with other VHE GRBs. It stands out distinctively in the $E_{k, \rm iso}$ - $\epsilon_B$ parameter space and lies outside the 3-$\sigma$ region of the correlation. In future, more VHE detections of short GRBs, in the CTA era, will provide crucial insights into the emission sites, radiation mechanisms, and particle acceleration, as well as their connection to long GRBs.

We demonstrate that the extension of the Habitable Zone (HZ) due to the presence of liquid water on the night side of tidally locked planets, modelled in this and earlier works, significantly increases the number of potentially habitable planets. We calculate the occurrence of habitable planets orbiting M-, K-, and G-dwarf stars within the conservative and extended HZ, beyond the inner and outer boundaries of the conservative HZ. Integrating over the phase space in the HZ diagram and normalizing our calculation to relatively recent analyses of the Kepler data, we show that potentially habitable planets may be as much as 50 times more abundant than in the lower estimate, limited to the conservative HZ of G-type stars only. For an intermediate heat transport rate on tidally locked planets, we find that the extended HZ could imply more than one habitable planet per star, and hundreds of habitable planets within 10 pc from Earth.

The atomic hydrogen HI content of galaxies is intimately related to star formation and galaxy evolution through the baryon cycle, which involves processes such as accretion, feedback, outflows, and gas recycling. While probing the HI gas over cosmic time has improved our understanding, direct HI detection is essentially limited to $z \lesssim 0.42$ due to the faintness of the 21cm line. Detections beyond this redshift have made use of the stacking technique to obtain average quantities of galaxy populations. Gravitational lensing by the cluster lenses enhances the HI signal and can extend the redshift limit further. In this work, we describe simulations of HI lensing in cluster lenses. We explore the feasibility of detecting strongly lensed HI emission from background galaxies using known 50 cluster lenses within the uGMRT sky coverage. We demonstrate that certain clusters offer a strong likelihood of HI detection. We also investigate how strong lensing distorts the HI spectral line profile. The shape of the HI signal in these lensing models provides useful information and can be used in optimising signal extraction in blind and targeted HI surveys. We find that blind detection of HI signal from galaxies in the redshift range up to 1.58 requires more than a few hundred hours of observations of individual clusters with the uGMRT. Detection of HI emission in galaxies where strong lensing has been observed in the optical appears to be more promising with potential for a $5\sigma$ detection in $<50$ hours of on-source observations for Abell 370 and in $<75$ hours for Abell 1703 with the uGMRT.

The Hadrosymmetric Twin Higgs (HTH) model provides a natural solution to the little hierarchy problem by incorporating all three generations of quarks in a twin sector. Unlike other Twin Higgs scenarios, such as the Mirror Twin Higgs (MTH), the HTH framework avoids introducing additional light states or radiation and thus remains consistent with stringent bounds on the effective number of relativistic species, $\Delta N_{\rm eff}$. Its particle content and interactions also make it difficult to probe at colliders, highlighting the importance of cosmological tests. In this work, we study the cosmological implications of the HTH model, focusing on the persistent tensions in the Hubble constant ($H_0$) and the matter clustering amplitude ($\sigma_8$). Implementing the HTH sector in a Boltzmann code and confronting it with cosmic microwave background (CMB) data and local $H_0$ measurements, we find that the scenario reduces the Hubble tension from more than $4\sigma$ to about $2.5\sigma$, while also alleviating the $\sigma_8$ discrepancy. These results demonstrate that the HTH framework not only addresses naturalness in particle physics but also offers a viable route to mitigating current cosmological tensions, thereby strengthening the link between fundamental theory and precision cosmology.

We present a comprehensive study of the X-ray binary system XTE~J1550-564, with the primary objective of analyzing the evolution of the black hole's spin parameter. To achieve this objective, we embarked on the necessary step of identifying a plausible progenitor for the system. Using a set of models covering various parameter combinations, we were able to replicate the system's observed characteristics within acceptable error margins, including fundamental parameters such as component masses, orbital period, donor luminosity, and effective temperature. The model results indicate the possibility of diverse evolutionary pathways for the system, highlighting the significant role played by the initial mass of the donor star and the efficiency of mass transfer episodes. While some models are well-aligned with estimates of the mass transfer rate, they all fall short of explaining the black hole's observed moderate spin ($a^* = 0.49$). We also explored alternative magnetic braking prescriptions, finding that only an extreme and fully conservative scenario, based on the convection and rotation boosted prescription, can reproduce the observed spin and only in a marginal way. Our study attempts to shed light on the complex dynamics of black hole X-ray binaries and the challenges of explaining their observed properties with theoretical models.

Context. We present a deep XMM-Newton observation of the massive, edge-on galaxy NGC 5746. The total exposure time of 250 ks provides unprecedented sensitivity to study the diffuse hot gas in the halo, significantly surpassing the depth of previous observations. Aims. While the presence of hot, circumgalactic gas is well tested for starburst galaxies, detections in normal galaxies remain scarce. By studying the diffuse X-ray emission in NGC 5746, we aim to provide new insights into the evolution of star-forming galaxies and their surroundings. Methods. We create X-ray images and surface brightness profiles to quantify the distribution of extraplanar gas in the halo of NGC 5746. In addition, we isolate the diffuse emission component from point source- and background-contamination and study the spectral characteristics of the hot plasma. Results. We detect soft X-ray emission out to 40 kpc from the galactic disc. The gas distribution is reminiscent of a stellar outflow, with two bubbles extending perpendicular to the disc in a biconical shape. The spectral analysis of the halo emission yields a plasma temperature of 0.56 keV, higher than the typical values observed in spiral galaxies (0.2 keV). The disc has an even higher plasma temperature of 0.7 keV, and is dominated by non-thermal emission from unresolved X-ray binaries. The signs of a stellar outflow, bright X-ray emission, and high plasma temperatures indicate that the star-forming activity in NGC 5746 might be higher than previously thought. Conclusions. Our results demonstrate that massive spiral galaxies can host luminous X-ray halos, and support theoretical models that predict their existence. Earlier claims of a lack of hot gas around quiescent spirals might be attributed to the detection thresholds in shallower observations, stressing the need for more, deeper observations of non-starburst galaxies.

We study the inflationary gravitational wave background induced by Abelian gauge fields generated by non-minimal kinetic and axial couplings to the inflaton. We show that the gravitational wave spectrum is scale invariant and derive its amplitude for generic gauge field coupling parameters, within the slow-roll approximation. We constrain the coupling values and the scale of inflation for which the induced gravitational wave background is observable, while ensuring that back-reaction on the inflationary dynamics remains negligible. We find that a sizeable axial coupling can boost this secondary gravitational wave signal above the standard inflationary background. In the course of our analysis, we also show how to analytically match tensor perturbations across an arbitrary number of eras with different equations of state.

The origin of the hard, bright X-ray emission that defines the gamma Cas analog class of Be stars remains an outstanding question in Be star literature. This work explores the possibility that the X-ray flux is produced by accretion onto a white dwarf companion. We use three-dimensional smoothed particle hydrodynamics simulations to model the prototype gamma Cas system assuming a white dwarf companion and investigate the accretion of the circumstellar material by the secondary star. We contrast these results to a model for 59 Cyg, a non-gamma Cas Be star system with a stripped companion. We find that the secondary stars in both systems form disk-like accretion structures with Keplerian characteristics, similar to those seen in the Be decretion disks. We also find that white dwarf accretion can produce X-ray fluxes that are consistent with the observed values for gamma Cas, while the predicted X-ray luminosities are significantly lower for the non-degenerate companion in 59 Cyg. In addition, using the three-dimensional radiative transfer code, HDUST, we find that these models produce H-alpha emission consistent with the observations for both gamma Cas and 59 Cyg, and that the predicted polarization degrees across optical and UV wavelengths are at detectable levels. Finally, we discuss the impact that future UV spectropolarimetry missions could have on our understanding of these systems.

The black hole in the Galactic Center, Sgr A*, is prototypical for ultra-low-fed galactic nuclei. The discovery of a hand-full of gas clumps in the realm of a few Earth masses in its immediate vicinity provides a gas reservoir sufficient to power Sgr A*. In particular, the gas cloud G2 is of interest due to its extreme orbit, on which it passed at a pericenter distance of around 100 AU and notably lost kinetic energy during the fly-by due to the interaction with the black hole accretion flow. 13 years prior to G2, a resembling gas cloud called G1, passed Sgr A* on a similar orbit. The origin of G2 remained a topic of discussion, with models including a central (stellar) source still proposed as alternatives to pure gaseous clouds. Here, we report the orbit of a third gas clump moving again along (almost) the same orbital trace. Since the probability of finding three stars on close orbits is very small, this strongly argues against stellar-based source models. Instead, we show that the gas streamer G1-2-3 plausibly originates from the stellar wind of the massive binary star IRS16SW. This claim is substantiated by the fact that the small differences between the three orbits - the orientations of the orbital ellipses in their common plane as a function of time - are consistent with the orbital motion of IRS 16SW.

More than 60 years have passed since the first formal suggestion to use strongly-lensed supernovae to measure the expansion rate of the Universe through time-delay cosmography. Yet, fewer than 10 such objects have ever been discovered. We consider the merits of a targeted strategy focused on lensed hyperluminous infrared galaxies-- among the most rapidly star-forming galaxies known in the Universe. With star formation rates (SFRs) $\sim {200 - 6000}~\textrm{M}_\odot~\textrm{yr}^{-1}$, the $\sim 30$ objects in the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts (PASSAGES) are excellent candidates for a case study, in particular, and have already led to the discovery of the multiply-imaged SN H0pe. Considering their lens model-corrected SFRs, we estimate their intrinsic supernova rates to be an extraordinary ${1.8 - 65}~\textrm{yr}^{-1}$ (core-collapse) and ${0.2 - 6.4}~\textrm{yr}^{-1}$ (Type Ia). Moreover, these massive starbursts typically have star-forming companions which are unaccounted for in this tally. We demonstrate a strong correlation between Einstein radius and typical time delays, with cluster lenses often exceeding several months (and therefore most favorable for high-precision $H_0$ inferences). A multi-visit monitoring campaign with a sensitive infrared telescope (namely, JWST) is necessary to mitigate dust attenuation. Still, a porous interstellar medium and clumpy star formation in these extreme galaxies might produce favorable conditions for detecting supernovae as transient point sources. Targeted campaigns of known lensed galaxies to discover new lensed supernovae can greatly complement wide-area cadenced surveys. Increasing the sample size helps to realize the potential of supernova time-delay cosmography to elucidate the Hubble tension through a single-step measurement, independent of other $H_0$ techniques.

We present a new implementation of fuzzy dark matter (FDM) dynamical friction within the galpy framework, enabling orbital integrations of globular clusters (GCs) across a broad range of halo-to-GC mass ratios and boson masses. In this alternative DM scenario, dynamical friction is reduced or even suppressed by heating induced by FDM density granules. We further quantify the role of baryons and solitonic cores, natural consequences of FDM in galaxies, on the efficiency of orbital decay and the long-term survival of GCs. The most significant deviations from the cold DM (CDM) paradigm arise in the dwarf-galaxy regime, where FDM dynamical friction can stall the inspiral of GCs over a Hubble time, thereby preventing their sinking into galactic centers and halting the canonical galactic cannibalism of clusters. Importantly, our FDM-only friction model should be regarded as a conservative lower bound, since the inclusion of realistic FDM cores can only strengthen the survival of GCs through core stalling. This stalling mechanism not only preserves in-situ populations that would otherwise be erased in CDM, but also strongly suppresses the mixing of in-situ and ex-situ clusters, yielding a bimodal radial distribution of GCs. Our results show that the demographics of GC systems encode a distinct dynamical signature of FDM in dwarfs. These predictions open a new pathway to constrain the boson mass parameter with upcoming Euclid DR1 observations of extragalactic GCs, while simultaneously offering a natural explanation for the long-standing Fornax timing problem.

We present a sub-grid model for star formation in galaxy simulations, incorporating molecular hydrogen ($\mathrm{H}_2$) production via dust grain condensation and its destruction through star formation and photodissociation. Implemented within the magnetohydrodynamical code AREPO, our model tracks the non-equilibrium mass fractions of molecular, ionised, and atomic hydrogen, as well as a stellar component, by solving a system of differential equations governing mass exchange between these phases. Star formation is treated with a variable rate dependent on the local $\mathrm{H}_2$ abundance, which itself varies in a complex way with key quantities such as gas density and metallicity. Testing the model in a cosmological simulation of a Milky Way-mass galaxy, we obtain a well-defined spiral structure at $z = 0$, including a gas disc twice the size of the stellar one, alongside a realistic star formation history. Our results show a broad range of star formation efficiencies per free-fall time, from as low as $0.001\%$ at high redshift to values between $0.1\%$ and $10\%$ for ages $\gtrsim 3-4 \, \mathrm{Gyr}$. These findings align well with observational estimates and simulations of a turbulent interstellar medium. Notably, our model reproduces a star formation rate versus molecular hydrogen surface densities relation akin to the molecular Kennicutt-Schmidt law. Furthermore, we find that the star formation efficiency varies with density and metallicity, providing an alternative to fixed-efficiency assumptions and enabling comparisons with more detailed star formation models. Comparing different star formation prescriptions, we find that in models that link star formation to $\mathrm{H}_2$, star formation onset is $\sim \! 500 \, \mathrm{Myr}$ later than those relying solely on total or cold gas density.

Radio synchrotron emission originates from both massive star formation and black hole accretion, two processes that drive galaxy evolution. Efficient classification of sources dominated by either process is therefore essential for fully exploiting deep, wide-field extragalactic radio continuum surveys. In this study, we implement, optimize, and compare five widely used supervised machine-learning (ML) algorithms to classify radio sources detected in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE)-COSMOS survey as star-forming galaxies (SFGs) and active galactic nuclei (AGN). Training and test sets are constructed from conventionally classified MIGHTEE-COSMOS sources, and 18 physical parameters of the MIGHTEE-detected sources are evaluated as input features. As anticipated, our feature analyses rank the five parameters used in conventional classification as the most effective: the infrared-radio correlation parameter ($q_\mathrm{IR}$), the optical compactness morphology parameter (class$\_$star), stellar mass, and two combined mid-infrared colors. By optimizing the ML models with these selected features and testing classifiers across various feature combinations, we find that model performance generally improves as additional features are incorporated. Overall, all five algorithms yield an $F1$-score (the harmonic mean of precision and recall) $>90\%$ even when trained on only $20\%$ of the dataset. Among them, the distance-based $k$-nearest neighbors classifier demonstrates the highest accuracy and stability, establishing it as a robust and effective method for classifying SFGs and AGN in upcoming large radio continuum surveys.

Signs of lightning on Venus have long been sought, including by space missions and ground-based telescopes searching for optical flashes, plasma waves, or radio signatures. These efforts have yielded conflicting findings regarding the presence or absence of lightning in Venus's atmosphere. In this study we adopt an indirect approach to constrain the prevalence of lightning on Venus, using the chemical by-products it produces in Venus's atmosphere. Nitric oxide (NO) is a key tracer species of lightning, being exclusively generated by lightning in Venus's lower atmosphere. By calculating the present rate of atmospheric destruction of NO in Venus's atmosphere through photochemical-kinetic modelling, we constrain the lightning power required to sustain the estimated NO abundances on modern Venus. The reported NO constraints require lightning to generate at-least three times the power released on Earth; consistent with either a higher rate of strikes, or greater energy per strike, or a combination of both. Limited detections of optical flashes within the clouds could point to lightning striking deeper in the atmosphere and nearer the surface -- with the result that its optical flashes are obscured by the clouds -- driven by triboelectric charging during volcanic eruptions or wind interactions with surface sediments. Our findings underscore the importance for future missions of confirming lightning on Venus, either by verifying the below-cloud NO abundance, or by detecting another unambiguous lightning signature, to provide the first definitive evidence of lightning on a rocky planet other than Earth.

The AdvCam is a next-generation camera for the Large-Sized Telescopes of the Cherenkov Tele- scope Array Observatory, based on silicon photomultipliers. Its fully digital readout system enables the design of new, sophisticated trigger logic. The Large-Sized Telescopes aim to cover the low-energy range of the cosmic gamma-ray spectrum, with a threshold starting at about 20 GeV, using the existing photomultiplier tube camera. The AdvCam, along with the new trigger logic, as shown by simulations, lowers the detectable energy threshold to 13 GeV. The proposed trigger logic has a multilevel structure. The first level involves fast coincidences among small pixel regions at a rate of approximately 1 GHz, while the second level processes all camera pixels within an approximately 10-nanosecond time window. Different families of machine learning algorithms optimized for FPGAs form the second-level trigger. In this work, we consider two main approaches: Deep Neural Networks and Density-Based Spatial Clustering of Applications with Noise, both running with latencies below 1 microsecond at a 1 MHz rate. This work provides a detailed description of the trigger chain and its performance, as studied through simulation.

Molecules are ubiquitous in space. They are necessary component in the creation of habitable planetary systems and can provide the basic building blocks of life. Solid-state processes are pivotal in the formation of molecules in space and surface diffusion in particular is a key driver of chemistry in extraterrestrial environments, such as the massive clouds in which stars and planets are formed and the icy objects within our Solar System. However, for many atoms and molecules quantitative theoretical and experimental information on diffusion, such as activation barriers, are lacking. This hinders us in unraveling chemical processes in space and determining how the chemical ingredients of planets and life are formed. In this article, an astrochemical perspective on diffusion is provided. Described are the relevant adsorbate-surface systems, the methods to model their chemical processes, and the computational and laboratory techniques to determine diffusion parameters, including the latest developments in the field. While much progress has been made, many astrochemically relevant systems remain unexplored. The complexity of ice surfaces, their temperature-dependent restructuring, and effects at low temperatures create unique challenges that demand innovative experimental approaches and theoretical frameworks. This intersection of astrochemistry and surface science offers fertile ground for physical chemists to apply their expertise. We invite the physical chemistry community to explore these systems, where precise diffusion parameters would dramatically advance our understanding of molecular evolution in space - from interstellar clouds to planetary surfaces - with implications on our understanding on the origins of life and planetary habitability.

Using deep observations across three of the LOFAR Two-metre Sky Survey Deep Fields, this work measures the angular clustering of star forming galaxies (SFGs) and low-excitation radio galaxies (LERGs) to $z$$\lesssim$1.5 for faint sources, $S_{\textrm{144 MHz}}$$\geq$200 $\mu$Jy. We measure the angular auto-correlation of LOFAR sources in redshift bins and their cross-correlation with multi-wavelength sources {to} measure the evolving galaxy bias for SFGs and LERGs. Our work shows the bias of the radio-selected SFGs increases from $b=0.90^{+0.11}_{-0.10}$ at $z \sim 0.2$ to $b = 2.94^{+0.36}_{-0.36}$ at $z \sim 1.2$; faster than the assumed $b(z)$$\propto$$1/D(z)$ models adopted in previous LOFAR cosmology studies (at sensitivities where AGN dominate), but in broad agreement with previous work. We further study the luminosity dependence of bias for SFGs and find little evidence for any luminosity dependence at fixed redshift, although uncertainties remain large for the sample sizes available. The LERG population instead shows a weaker redshift evolution with $b=2.33^{+0.28}_{-0.27}$ at $z \sim 0.7$ to $b=2.65^{+0.57}_{-0.55}$ at $z \sim 1.2$, though it is also consistent with the assumed bias evolution model ($b(z)$$\propto$$1/D(z)$) within the measured uncertainties. For those LERGs which reside in quiescent galaxies (QLERGs), there is weak evidence that they are more biased than the general LERG population and evolve from $b = 2.62^{+0.33}_{-0.33}$ at $z \sim 0.7$ to $b = 3.08^{+0.85}_{-0.84}$ at $z \sim 1.2$. This suggests the halo environment of radio sources may be related to their properties. These measurements can help constrain models for the bias evolution of these source populations, and can help inform multi-tracer analyses.

This paper accompanies Data Release 4 of the JWST Deep Extragalactic Survey (JADES), which presents the full NIRSpec spectroscopy of the survey. We provide spectra of 5190 targets across GOODS-North and GOODS-South (including the Hubble Ultra Deep Field), observed with the low-dispersion (R $\sim$ 30-300) prism and three medium-resolution (R $\sim$ 1000) gratings spanning 0.8 $< \lambda <$ 5.5 microns; 2654 were also observed with the higher-resolution (R $\sim$ 2700) G395H grating. The tiered survey design obtained more than 20 hr exposures for $\sim$ 700 galaxies in the Deep and Ultra Deep tiers, and shallower observations ($\sim$ 1-3 hr per setting) of $>$ 4400 galaxies in the Medium tiers. Targets were selected from photometric redshifts or colours, with priority given to rest-UV-selected galaxies at $z > 5.7$ and F444W-selected galaxies at $1.5 < z < 5.7$. We describe the full target selection and present spectroscopic redshifts and success rates. In total we obtain robust redshifts for 3297 galaxies, including 396 at $z > 5.7$ and 2545 at $1.5 < z < 5.7$. To facilitate uniform analyses, we define 'gold' sub-samples based on UV- and F444W-selection. Using the parent samples and redshift success rates, we construct rest-UV luminosity functions at $6 \lesssim z \lesssim 9$ from the Medium- and Deep-JWST tiers. Our number densities agree well with previous determinations from both photometric and spectroscopic samples, with modest interloper fractions confirming the reliability of photometric UV-bright galaxy selections at these redshifts.

We present the fourth data release of JADES, the JWST Advanced Deep Extragalactic Survey, providing deep spectroscopic observations in the two GOODS fields. A companion paper presents the target selection, spectroscopic redshifts and success rates, and in this paper, we discuss the data reduction and present emission line flux measurements. The spectroscopy in this work consists of medium-depth, deep and ultradeep NIRSpec/MSA spectra of 5,190 targets, covering the spectral range $0.6\text{--}5.5$~\mum and observed with both the low-dispersion prism ($R=30\text{--}300$) and all three medium-resolution gratings ($R=500\text{--}1,500$). We describe the data reduction, analysis and description of the data products included in this data release. In total, we measured 3,297 robust redshifts out of 5,190 targets, spanning a redshift range from $z=0.5$ up to $z=14.2$, including 974 at $z>4$. This data release includes 1-d and 2-d fully reduced spectra with 3 and 5 pixel extractions, with slit-loss corrections and background subtraction optimized for point sources. Furthermore, we provide redshifts and $S/N>5$ emission-line flux catalogues for the prism and grating spectra, as well as new guidelines to use these data products. Lastly, we are launching a new JADES Online Database, designed to enable quick selection and browsing of this data release. Altogether, these data provide the largest statistical sample to date to characterise the properties of galaxy populations across Cosmic time.

Context. Low- and intermediate-mass giants undergo a complex chemical evolution that has yet to be observationally probed. The influence of core helium flash on the chemical composition of stellar atmospheres has been an open question since its theoretical prediction 60 years ago. Aims. Based on high-resolution spectral observations of 44 open star clusters in the Gaia-ESO survey, our aim is to perform the first large-scale homogeneous investigation into the carbon and nitrogen photospheric content of low- and intermediate-mass giant stars in different phases of evolution. Methods. We determined carbon and nitrogen abundances using spectral synthesis of the C2 Swan (1,0) band head at 5135 Å and C2 Swan (0,1) band head at 5635.5 Å, 12C14N bands in the interval 6470 - 6490 Å, and the forbidden [O i] line at 6300.31 Å. Results. We revealed differences in C/N abundance ratios between pre- and post-core-He-flash stars. The lower C/N ratios in core He-burning red clump stars are mainly due to the enhancement of nitrogen abundances. We presented calibrations of the relationship between [C/N] and stellar age for solar metallicity low- and intermediate-mass giants taking into account different evolutionary stages. Conclusions. The C/N abundance ratios in the investigated first-ascent giant stars are slightly less affected by the first dredge-up than predicted by the theoretical models. The rotation-induced extra mixing is not as efficient as theoretically predicted. The core helium flash may trigger additional alterations in carbon and nitrogen abundances that are not yet theoretically modelled. We found that the evolutionary stage of stars must be taken into account when using [C/N] as an age indicator.

Pulsars are spinning neutron stars typically observed as pulses emitted at radio wavelengths. These pulsations exhibit a rotational stability that rival the best atomic clocks, making pulsars one of the most important tools for resolving gravitational phenomena in extreme environments. I will present an overview of the ways in which radio pulsars can be used to test strong-field gravity and observe gravitational radiation, both in the context of historical and ongoing experiments. I will also describe how these measurements can be translated to sought-after quantities like the masses and moments of inertia of neutron stars.

Context. Core-collapse Supernovae of Type II contribute the chemical enrichment of galaxies through explosion. Their role as dust producers in the high-redshift Universe may be of paramount importance. However, the type and amount of dust they synthesise after outburst is still a matter of debate and the formation processes remain unclear. Aims. We aim to identify and understand the chemical processes at play in the dust formation scenario, and derive mass yields for molecules and dust clusters at late post-explosion time. Methods. We revisit existing models by improving on the physics and chemistry of the supernova ejecta. We identify and consider new chemical species and pathways underpinning the formation of dust clusters, and apply a unique exhaustive chemical network to the entire ejecta of a Supernova with a 15 Msun progenitor. We test this new chemistry for various gas conditions in the ejecta, and derive mass yields for molecules and dust clusters. Results. We obtain the molecular component of the ejecta up to 11 years after explosion. The most abundant species are, in order of decreasing masses, O2, CO, SiS, SiO, CO2, SO2, CaS, N2, and CS. We identify molecules that are tracers of high-density clumps. As for dust clusters, we find the composition is dominated by silicates and silica, along with carbon dust, but with modest amounts of alumina. Pure metal clusters and metal sulphide and oxide clusters have negligible masses. High-density gas favours the formation of carbon clusters in the outer ejecta region whereas low temperatures hamper the formation of silicates in the oxygen core. The results are in good agreement with existing astronomical data and recent observations with the James Webb Space Telescope. They highlight the importance of chemistry for the derivation of dust budget from Supernovae.

The Trans-Iron Galactic Element Recorder for the International Space Station (TIGERISS) is under construction and is planned for launch in 2027 and will be attached at the SOX location on the Columbus module on the ISS. TIGERISS will make the first definitive measurements of Ultra-Heavy Galactic Cosmic Rays (UHGCRs; Z >29) on an individual element basis past barium ($^{56}$Ba), through the lanthinides, and to lead ($^{82}$Pb). TIGERISS has a geometry factor of 1.06 m$^2$ sr and is comprised of four planes of single-sided silicon strip detectors (SSDs) arranged in orthogonal X-Y layers with an X-Y pair above and an X-Y pair below two large-area Cherenkov detectors. The top Cherenkov detector is comprised of a mosaic of aerogel radiators (n =1.05) while the bottom Cherenkov detector has an acrylic radiator (n = 1.49). The combination of the Cherenkov velocity measurements with the precise measurements of the ionization and trajectory of the traversing cosmic rays leads to highly accurate charge measurements of $<$ 0.25 c.u. over the entire elemental range of $^5$B through $^{82}$Pb. These TIGERISS measurements are highly sensitive in determining the strength of s-process, r-process, and rp-processes of Galactic nucleosynthesis while providing critical data needed for multi-messenger studies to determine the contributions of extreme phenomena, including supernovae (SN) and Neutron Star Mergers (NSMs), in the production of galactic matter. The science goals of TIGERISS, mission status, instrument design and performance of the TIGERISS SSD subsystem in relation to the measurements and science goals of TIGERISS are discussed in this paper.

The quasar main sequence (QMS), characterized by the Eigenvector 1 (EV1), serves as a unifying framework for classifying type-1 active galactic nuclei (AGNs) based on their diverse spectral properties. Although a fully self-consistent physical interpretation has long been lacking, our physically motivated 2.5D FRADO (Failed Radiatively Accelerated Dusty Outflow) model naturally predicts that the Eddington ratio ($\dot{m}$) is the primary physical driver of the QMS, with black hole mass ($M_{\rm BH}$) and inclination ($i$) acting as secondary contributors. We employed a dense grid of FRADO simulations of the geometry and dynamics of the broad-line region (BLR), covering a representative range of $M_{\rm BH}$ and $\dot{m}$. For each simulation, we computed the full width at half maximum (FWHM) of the H$\beta$ line under different $i$. The resulting FWHM--$\dot{m}$ diagram closely resembles the characteristic trend observed in the EV1 parameter space. This establishes the role of $\dot{m}$ as the true proxy for the Fe II strength parameter ($R_{\rm Fe}$), and vice versa. Our results suggest that $\dot{m}$ can be regarded as the sole underlying physical tracer of $R_{\rm Fe}$ and should therefore scale directly with it. The $M_{\rm BH}$ accounts for the virial mass-related scatter in FWHM, while $i$ acts as a secondary driver modulating $R_{\rm Fe}$ and FWHM for a given $\dot{m}$ and $M_{\rm BH}$.

Data-driven astrophysics currently relies on the detection and characterisation of correlations between objects' properties, which are then used to test physical theories that make predictions for them. This process fails to utilise information in the data that forms a crucial part of the theories' predictions, namely which variables are directly correlated (as opposed to accidentally correlated through others), the directions of these determinations, and the presence or absence of confounders that correlate variables in the dataset but are themselves absent from it. We propose to recover this information through causal discovery, a well-developed methodology for inferring the causal structure of datasets that is however almost entirely unknown to astrophysics. We develop a causal discovery algorithm suitable for astrophysical datasets and illustrate it on $\sim$5$\times10^5$ low-redshift galaxies from the Nasa Sloan Atlas, demonstrating its ability to distinguish physical mechanisms that are degenerate on the basis of correlations alone.

The observation of the redshifted 21-cm signal from the intergalactic medium will probe the epoch of reionization (EoR) with unprecedented detail. Various simulations are being developed and used to predict and understand the nature and morphology of this signal. However, these simulations are computationally very expensive and time-consuming to produce in large numbers. To overcome this problem, an efficient field-level emulator of this signal is required. However, the EoR 21-cm signal is highly non-Gaussian; therefore, capturing the correlations between different scales of this signal, which is directly related to the evolution of the reionization, with the neural network is quite difficult. Here, we introduce CosmoUiT, a UNet integrated vision transformer-based architecture, to overcome these difficulties. CosmoUiT emulates the 3D cubes of 21-cm signal from the EoR, for a given input dark matter density field, halo density field, and reionization parameters. CosmoUiT uses the multi-head self-attention mechanism of the transformer to capture the long-range dependencies and convolutional layers in the UNet to capture the small-scale variations in the target 21-cm field. Furthermore, the training of the emulator is conditioned on the input reionization parameters such that it gives a fast and accurate prediction of the 21-cm field for different sets of input reionization parameters. We evaluate the predictions of our emulator by comparing various statistics (e.g., bubble size distribution, power spectrum) and morphological features of the emulated and simulated maps. We further demonstrate that this vision transformer-based architecture can emulate the entire 3D 21-cm signal cube with high accuracy at both large and small scales.

A number of cosmic shear studies have reported results that are in mild tension with the Planck cosmic microwave measurement. To explore if this can be caused by biases in the shear estimation, we revisit the analysis of data from the Kilo-Degree Survey (KiDS) using an alternative shape measurement pipeline that is more robust to uncertainties in the calibration. To this end, we present an implementation of MetaCalibration, and compare its performance to that of lensfit, which has been used in previous analyses of these data. We find that the multiplicative bias is reduced, especially for the most distant redshifts, as derived from multi-band image simulations designed to match the KiDS data (SURFS-based KiDS-Legacy-Like Simulations: SKiLLS). For all tomographic bins we obtain a multiplicative bias $|m|<0.017$, with negligible additive bias. Importantly, the calibration has a negligible sensitivity to key galaxy properties. The resulting robust shear estimates were used to obtain cosmological parameter constraints. We find that the parameter $S_8\equiv \sigma_8 \sqrt{\Omega_\mathrm{m}/0.3} =0.789_{-0.024}^{+0.020}$ is consistent with the previous KiDS-1000 lensfit constraint of $S_8=0.776^{+0.029 +0.002}_{-0.027-0.003}$ (statistical + systematic errors). Thanks to the higher effective source density, the constraining power is improved by about 28%. The difference in $S_8$ with the Planck value remains at a similar level, 1.8$\sigma$, implying that it is not caused by the shear measurements.

Kilonovae are the scientifically rich, but observationally elusive, optical transient phenomena associated with compact binary mergers. Only a handful of events have been discovered to date, all through multi-wavelength (gamma ray) and multi-messenger (gravitational wave) signals. Given their scarcity, it is important to maximise the discovery possibility of new kilonova events. To this end, we present our follow-up observations of the gravitational-wave signal, S250818k, a plausible binary neutron star merger at a distance of $237 \pm 62$ Mpc. Pan-STARRS tiled 286 and 318 square degrees (32% and 34% of the 90% sky localisation region) within 3 and 7 days of the GW signal, respectively. ATLAS covered 70% of the skymap within 3 days, but with lower sensitivity. These observations uncovered 47 new transients; however, none were deemed to be linked to S250818k. We undertook an expansive follow-up campaign of AT 2025ulz, the purported counterpart to S250818k. The griz-band lightcurve, combined with our redshift measurement ($z = 0.0849 \pm 0.0003$) all indicate that SN 2025ulz is a SN IIb, and thus not the counterpart to S250818k. We rule out the presence of a AT 2017gfo-like kilonova within $\approx 27$% of the distance posterior sampled by our Pan-STARRS pointings ($\approx 9.1$% across the total 90% three-dimensional sky localisation). We demonstrate that early observations are optimal for probing the distance posterior of the three-dimensional gravitational-wave skymap, and that SN 2025ulz was a plausible kilonova candidate for $\lesssim 5$ days, before ultimately being ruled out.

The magnification resulting from strong gravitational lensing is a powerful tool to add new constraints to the cosmic evolution of supernova progenitors by enabling the study of distant supernovae that would otherwise not be observable. iPTF16geu is the most well-observed gravitationally lensed supernova (glSN) to date. At a redshift of $z = 0.409$ and magnified by a factor of $\sim$68, extensive photometric and spectroscopic observations have been obtained. The explosion mechanism producing this rare event and differences compared to lower redshift supernovae however have not been explored in detail. Here we compare observations of iPTF16geu to existing radiative transfer simulations of type Ia supernova explosion models selected from the literature. We find that overall the DDC6 and PDDEL1 models, specific variations of the delayed detonation explosion scenario, produce the closest match to the light curves and many absorption features, but struggle to replicate the observed colours and in particular the rest-frame UV. We also investigate the magnification and reddening values required to improve agreement with the selected models. We find some evidence in favour of a UV flux excess that may be intrinsic to iPTF16geu or due to external factors such as host galaxy subtraction and uncertainties in the reddening law. Upcoming surveys will significantly increase the samples of SNe discovered at high redshifts due to strong gravitational lensing. These glSNe will enable tighter constraints on the explosion physics of type Ia supernovae and how this has evolved throughout the Universe.

The diffuse supernova neutrino background (DSNB) created by stellar core-collapses throughout cosmic history is on the verge of discovery, with SK-Gd showing early deviations from the background expectation and JUNO starting to take data. However, the interpretation of early DSNB data will face significant challenges due to degeneracies between astrophysical parameters and uncertainties in supernova neutrino modeling. We explore how complementary astronomical observations can break these degeneracies and, in this context, we investigate whether early DSNB observations can constrain invisible supernovae, which have no optical emission but are powerful neutrino sources before being swallowed by a forming black hole. Leveraging the differences in the spectra between invisible and visible supernovae, we estimate the sensitivity of 1) detecting the existence of invisible supernovae, and 2) determining the fraction of invisible supernovae. Finally, we discuss how these conclusions depend on the spectral parameters of the black hole-forming component.

Initial states of dense matter with nonzero electron chiral imbalance could potentially give rise to strong magnetic fields through chiral plasma instability. Previous work indicated that unless chiral chemical potential is as large as the electron vector chemical potential, the growth of magnetic fields due to the instability is washed out by chirality flipping rate enabled by electron mass. We re-examine this claim in a broader range of parameters and find that at higher temperatures the hierarchy is reversed supporting a growing magnetic field for an initial electron chiral chemical potential much smaller than the electron vector chemical potential. Further, we identify a qualitatively new effect relevant for magnetized hot and dense medium where chiral magnetic effect (CME) sourced by density fluctuation acts as a powerful source of Joule heating. Remarkably, even modest chiral chemical potentials (keV) in such environment can deposit energy densities set by the QCD scale in a relatively short time of the order of a few milliseconds or seconds. We speculate how this mechanism makes CME-driven Joule heating a potentially critical ingredient in the dynamics of turbulent density fluctuation of supernovae and neutron star mergers.

Surrogate modeling of eccentric binary black hole waveforms has remained challenging. The complicated morphology of these waveforms due to the eccentric orbital timescale variations makes it difficult to construct accurate and efficient surrogate models, especially for waveforms long enough to cover the sensitivity band of the current ground-based gravitational wave detectors. We present a novel and scalable surrogate building technique which makes surrogate modeling of long-duration eccentric binary black hole waveforms both feasible and highly efficient. The technique aims to simplify the harmonic content of the intermediate eccentric surrogate data pieces by modeling them in terms of an angular orbital element called the mean anomaly, instead of time. We show that this novel parameterization yields an order of magnitude fewer surrogate basis functions than using the contemporary parameterization in terms of time. We show that variations in surrogate data-pieces across parameter space become much more regular when expressed in terms of the instantaneous waveform eccentricity and mean anomaly, greatly easing their parameter-space fitting. The methods presented in this work make it feasible to build long-duration eccentric surrogates for the current as well as future third-generation gravitational wave detectors.

Effective field theories offer a powerful method to unify diverse models under a small set of control parameters, allowing systematic expansions around well-established theories. These techniques, developed in particle physics, were designed for experiments where the initial state - the vacuum before a scattering event - is as clean and isolated as possible. Besides colliders, realistic environments are often noisy and dissipative. The recognition of the limitations of traditional EFT techniques has, over the past decade, sparked intense progress at the interface of high-energy physics and condensed matter. These considerations motivate a new approach to gravitation and cosmology, one that models the gravitational sector as evolving in the presence of an unobservable medium. Open Effective Field Theories provide a systematic and controllable field-theoretic framework for modeling dissipation and noise in gravitation and cosmology. These notes aim to introduce this versatile toolkit, enabling model-agnostic assessments of how unknown environments shape our observational probes.

We present ELENA (EvaLuator of tunnElliNg Actions), an open-source Python package designed to compute the full evolution of first-order phase transitions in the early Universe generated by particle physics models, taking into account several refinements that go beyond commonly assumed simplifications. The core of ELENA is based on a vectorized implementation of the tunnelling potential formalism, which allows for a fast computation of the finite-temperature tunnelling action. This, in turn, enables the sampling of the full range of temperatures where two phases coexist and the use of integral expressions that track the complete evolution of the transition, providing a comprehensive picture of it. In addition, ELENA provides all the tools to compute the resulting stochastic gravitational waves spectrum, allowing for the full chain of computations - from the Lagrangian parameter inputs to the final gravitational waves spectrum - in a fast and self-contained implementation.

In the framework of entropic cosmology, entropic forces arising at the cosmological horizon have been proposed as an alternative mechanism to explain the Universe's current accelerated phase. However, recent studies have shown that, under the Clausius relation and assuming a linear mass-to-horizon (MHR) relation, all entropic force models reduce to the original Bekenstein-Hawking formulation, regardless of the specific form of the horizon entropy. As a result, they inherit the same observational limitations in accounting for cosmic dynamics. To address this issue, a generalized MHR has been introduced, providing the foundation for a modified cosmological scenario rooted in the gravity-thermodynamics conjecture. In this work, we explore the implications of this generalized framework for early-Universe dynamics. Specifically, we analyze the growth of matter perturbations within the spherical Top-Hat formalism in the linear regime, showing that the density contrast profile is significantly influenced by the modified background dynamics predicted by the model. Moreover, considering the sensitivity of upcoming gravitational wave detectors in the sub-$10^3\,\mathrm{Hz}$ range, we examine the impact on the relic abundance of Primordial Gravitational Waves (PGWs), identifying parameter regions where deviations from standard cosmology may arise through an enhanced PGW spectrum.

We investigate asymptotic Schwarzschild exterior solutions in the context of modified gravity theories, specifically within the framework of $f(R)$ gravity, where the asymptotic behavior recovers the standard Schwarzschild solution of General Relativity. Unlike previous studies that rely mainly on analytical approximations, our approach combines asymptotic analysis with numerical integration of the underlying differential equations. Using these solutions, we analyze strong lensing effects to obtain the photon sphere radius and the corresponding capture parameter. Considering rings produced by total reflection, we define the photon sphere width as the difference between the first total reflection and the capture parameter; and study how it is modified in the $f(R)$ scenario. Our results show that the photon sphere width increases in the presence of $f(R)$-type modifications, indicating deviations from GR that could be observable in the strong-field regime.

Quantum effects in general induce scale dependence in the coupling constants. We explore this possibility in gravity, with a scale-dependent Newton coupling. When applied to Kerr black holes with such a running coupling, the consistency of black hole thermodynamics requires that the Newton coupling have a specific dependence on the black hole parameters. In this work, we consider such a class of Newton couplings and look for the possible observational implications on the highly lensed images of the black holes. In addition to placing constraints on the parameter space of the model through the latest Sgr A* images, we find that the variations in the shape of shadows in a large portion of the parameter space can be qualitatively captured by a quantity solely defined by the event horizon. Most importantly, the consistency of thermodynamics suggests a lower bound on the shadow size, beyond which either horizon disappears, or the shadow cannot keep the standard D-shaped structure. The possibility that the black holes in this model could spin faster than the Kerr bound, and the physical implications of the resulting cuspy shadows, are also discussed.

Decoding the internal structure of the proton is a fundamental challenge in physics. Historically, any new discovery about the proton has fuelled advances in several scientific fields. We have reported that gluons inside the proton accumulate near the critical momentum due to chaotic phenomena, forming gluon condensation. Surprisingly, the pion distribution predicted by this gluon distribution for the production of high-energy proton collisions could answer two puzzles in astronomy and high-energy physics. We find that during ultrahigh-energy cosmic ray collisions, gluon condensation may abruptly produce a large number of low-momentum pions, whose electromagnetic decays have the typical breakout properties appearing in various cosmic gamma-ray spectra. On the other hand, the Large Hadron Collider (LHC), which is well below the cosmic ray energy scale, also shows weak but recognisable signs of gluon condensation, which had been mistaken for BEC pions. The connection between these two phenomena, which occur at different scales in the Universe, supports the existence of a new structure within the proton-gluon condensation.

This brief study focuses on the application of autoencoders to improve the quality of low-amplitude signals, such as gravitational events. A pre-existing autoencoder was trained using cosmic event data, optimizing its architecture and parameters. The results show a significant increase in the signal-to-noise ratio of the processed signals, demonstrating the potential of autoencoders in the analysis of small signals with multiple sources of interference.

We report on a novel set of very-high-frequency quasi-periodic oscillations (VHFQPO's) in the context of compact, non-singular horizonless objects. Focussing on the static, spherically symmetric case we utilize metrics of non-singular black holes that are accompanied by a regulator length scale $L > 0$. The choice $L \gtrsim GM$ generically removes the horizon from these metrics leading to compact, horizonless but non-singular objects. This generically guarantees the existence of a stable orbit at small radii $r \ll r_\text{ISCO}$, independent of the angular momentum of the massive particle. Crucially, the absence of a horizon allows the resulting VHFQPO's to escape to infinity, spanning the range from 1kHz ($M = 10M_\odot$) to 25 kHz ($M = 2M_\odot$). Within the paradigm of non-singular spacetime geometries, the absence of such VHFQPO's from X-ray binary spectra implies the presence of a horizon around the central, compact object.

In this work, we study the effects of $\Lambda$-hyperons on neutron star properties employing a metamodel framework for the equation of state (EoS). Different choices for defining the hyperonic couplings with different levels of parametric freedom are discussed. In all models, the predicted NS maximum masses are reduced compared with the purely nucleonic composition as expected. In the case of relating hyperonic couplings via $SU(6)$-symmetry arguments to the nucleonic ones, we find that NS radii for intermediate mass stars are shifted to higher values compared with purely nucleonic stars, in agreement with the existing literature. However, allowing for more freedom for the hyperonic couplings, the effect is strongly reduced, and the distributions in the NS mass-radius plane of models with and without hyperons become very close. We have also investigated how different nucleonic density functionals influence the hyperon matter composition and neutron star properties.

The horizon of a black hole, the "surface of no return," is characterized by its rotation frequency $\Omega_H$ and surface gravity $\kappa$. A striking signature is that any infalling object appears to orbit at $\Omega_H$ due to frame dragging, while its emitted signals decay exponentially at a rate set by $\kappa$ as a consequence of gravitational redshift. Recent theoretical work predicts that the merger phase of gravitational waves from binary black hole coalescences carries direct imprints of the remnant horizon's properties, via a "direct wave" component that (i) oscillates near $2\Omega_H$, reflecting the horizon's frame dragging and the quadrupole nature of the gravitational radiation, and (ii) decays at an increasing rate characterized by $\kappa$, with additional screening from the black hole's potential barrier. In this paper, we report observational evidence for the direct wave in GW250114 with a matched-filter signal-to-noise ratio of $14.0^{+0.2}_{-0.1}$ ($13.5^{+0.1}_{-0.2}$) in the LIGO Hanford (Livingston) detector. The measured properties are in full agreement with theoretical predictions. These findings establish a new observational channel to directly measure frame-dragging effects in black hole ergospheres and explore (near-)horizon physics in dynamical, strong-gravity regimes.

We investigate the development of tearing-mode instability using the highest resolution two-dimensional magnetohydrodynamic simulations of reconnecting current sheets on a uniform grid, for Lundquist numbers $10^3 \le S \le 2 \times 10^5$. Although the tearing-mode instability is commonly thought to trigger a plasmoid cascade that enables fast reconnection - i.e., independent of $S$ - our results, in broad agreement with the recent findings of Morillo \& Alexakis (2025), challenge this belief. We demonstrate a Sweet-Parker scaling of the reconnection rate $V_{\text{rec}} \sim S^{-1/2}$ up to Lundquist numbers $S \sim 10^4$. For larger values, plasmoid formation sets in leading to a slight enhancement of the reconnection rate, $V_{\text{rec}} \sim S^{-1/3}$, consistent with the prediction from linear tearing mode induced reconnection, indicating that reconnection remains resistivity dependent, and therefore slow. In our simulations, the plasmoids do not form a cascade of mergers, as they are rapidly advected out of the reconnection layer. Our findings call for the revision of the role of plasmoid formation in 2D high Lundquist number magnetic reconnection. Even if future studies demonstrate that 2D plasmoid-reconnection becomes resistivity-independent at sufficiently large $S$, directly extending those results to 3D astrophysical environments is not justified, as in realistic circumstances, the increase of $S$ also raises the Reynolds number of the outflows, making it essential to account for the dominant role of turbulence.