Papers for Thursday, Sep 11 2025

Observations of extreme starbursts, often located in the cores of protoclusters, challenge the classical bottom-up galaxy formation paradigm. Giant elliptical galaxies at $z=0$ must have assembled rapidly, possibly within few 100 Myr through an extreme growth phase at high-redshift, characterized by elevated star-formation rates of several thousand solar masses per year distributed over concurrent, gas-rich mergers. We present a novel view of the $z=4.3$ protocluster core SPT2349$-$56 from sensitive multi-cycle ALMA dust continuum and [CII]158$\mu$m line observations. Distributed across 60 kpc, a highly structured gas reservoir with a line luminosity of $L_\mathrm{[CII]}=3.0\pm0.2\times10^9$ $L_\odot$ and an inferred cold gas mass of $M_{gas}= 8.9\pm0.7\times10^{9}$ $M_\odot$ is found surrounding the central massive galaxy triplet. Like ``beads on a string'', the newly-discovered [CII] streamers fragment into a few kpc-spaced and turbulent clumps that have a similar column density as local Universe spiral galaxy arms at $\Sigma_{gas}=20$--$60$ $M_\odot$ pc$^{-2}$. For a dust temperature of 30 K, the [CII] emission from the ejected clumps carry $\gtrsim$3% of the FIR luminosity, translating into an exceptionally low mass-to-light ratio of $\alpha_\mathrm{[CII]}=2.95\pm0.3$ $M_\odot$ $L_\odot^{-1}$, indicative of shock-heated molecular gas. In phase space, about half of the galaxies in the protocluster core populate the same caustic as the [CII] streamers ($r/r_{vir}\times|\Delta v|/\sigma_{vir}\approx0.1$), suggesting angular momentum dissipation via tidal ejection while the brightest cluster galaxy (BCG) is assembling. Our findings provide new evidence for the importance of tidal ejections of [CII]-bright, shocked material following multiple major mergers that might represent a landmark phase in the $z\gtrsim4$ co-evolution of BCGs with their hot, metal enriched atmospheres.

We investigate the redshift and group richness dependence of the quiescent fraction and red-sequence (RS) parameters in COSMOS galaxy groups from z=0 to z=3.7. We analyzed the deep and well-characterized sample of groups detected with AMICO in the COSMOS(-Web) field. Our study of the quiescent galaxy population is based on a machine-learning classification tool based on rest-frame magnitudes. The algorithm learns from several traditional methods to estimate the probability of a galaxy being quiescent, achieving high precision and recall. Starting from this classification, we computed quiescent galaxy fractions within groups via two methods: one based on the membership probabilities provided by AMICO, which rely on an analytical model, and another using a model-independent technique. We then detected the RS by estimating the ridgeline position using photometric data, followed by sigma clipping to remove outliers. This analysis was performed using both rest-frame and observed-frame magnitudes with rest-frame matching. We compared the results from both approaches and investigated the $z$ and richness dependence of the RS parameters. We found that the quiescent galaxy population in groups builds up steadily from z=1.5-2 across all richnesses, with faster and earlier growth in the richest groups. The first galaxies settle onto the RS ridgeline by $z \sim 2$, consistent with current evolutionary scenarios. Notably, we reported a rare overdensity of quiescent galaxies at z=3.4, potentially one of the most distant early RSs observed. Extending our study to X-rays, we found that X-ray faint groups have, on average, lower quiescent fractions than X-ray bright ones, likely reflecting their typical location in filaments. Leveraging the broad wavelength coverage of COSMOS2025, we traced RS evolution over $\sim 12$ Gyr, finding no significant trends in either slope or scatter of the ridgeline.

I present spherical (this https URL), a software package and database designed for the ESO VLT/SPHERE high-contrast imager. SPHERE has produced the world's largest archive of direct imaging observations of exoplanets and circumstellar disks, but its heterogeneous metadata and fragmented reduction tools make end-to-end analysis labor-intensive. spherical addresses this by combining (1) a curated, regularly updated, and searchable database of all SPHERE observations, cross-matched with stellar properties and observing conditions, and (2) a Python-based, script-driven pipeline for the Integral Field Spectrograph (IFS). The database, archived on Zenodo (this https URL) and reproducible from the ESO archive, currently includes about 6000 IRDIS dual-band imaging, about 1000 IRDIS polarimetric, and about 4500 IFS sequences, with additional modes (ZIMPOL, IRDIS-LSS, SAM) planned. The pipeline automates raw data retrieval, calibration, and IFS reduction with the adapted open-source CHARIS instrument pipeline, followed by astrometric and photometric calibration and post-processing with TRAP for companion detection and spectral extraction. spherical lowers the barrier from raw files to science-ready products, enabling homogeneous population studies, atmospheric characterization of companions, and efficient survey follow-up, while remaining interoperable with community tools such as VIP, pyKLIP, and IRDAP.

We used observations from the \emph{JWST} Emission Line Survey (JELS) to measure the half-light radii ($r_{e}$) of 23 H$\alpha$-emitting star-forming (SF) galaxies at $z=6.1$ in the PRIMER/COSMOS field. Galaxy sizes were measured in \emph{JWST} Near-infrared Camera observations in rest-frame H$\alpha$ (tracing recent star formation) with the F466N and F470N narrowband filters from JELS, and compared against rest-$R$-band, $V$-band (tracing established stellar populations) and near-ultraviolet sizes. We find a size-stellar mass ($r_{e}-M_{*}$) relationship with a slope that is consistent with literature values at lower redshifts, though offset to lower sizes. We observe a large scatter in $r_{e}$ at low stellar mass ($M_{*}<10^{8.4}$ M$_{\odot}$) which we believe is the result of bursty star formation histories (SFHs) of SF galaxies at the Epoch of Reionization (EoR). We find that the stellar and ionised gas components are similar in size at $z=6.1$. The evidence of already-established stellar components in these H$\alpha$ emitters (HAEs) indicates previous episodes of star formation have occurred. As such, following other JELS studies finding our HAEs are undergoing a current burst of star formation, we believe our results indicate that SF galaxies at the end of the EoR have already experienced a bursty SFH. From our $r_{e}-M_{*}$ relationship, we find $r_{e, \text{F444W}}=0.76\pm0.46$ kpc for fixed stellar mass $M_{*}=10^{9.25}$ M$_{\odot}$, which is in agreement with other observations and simulations of star forming galaxies in the literature. We find a close-pair (major) merger fraction of ($f_{\text{maj. merger}}=0.44\pm0.22$) $f_{\text{merger}}=0.43\pm0.11$ for galaxy separations $d\lesssim25$ kpc, which is in agreement with other $z\approx6$ studies.

Type I superluminous supernovae (SLSNe-I) are at least an order of magnitude brighter than standard supernovae, with the internal power source for their luminosity still unknown. The central engines of SLSNe-I are hypothesized to be magnetars, but the majority of SLSNe-I light curves have multiple bumps or peaks that are unexplained by the standard magnetar model. Existing explanations for the bumps either modulate the central engine luminosity or invoke interactions with material in the circumstellar environment. Systematic surveys of the limited sample of SLSNe-I light curves find no compelling evidence favoring either scenario, leaving both the nature of the light-curve fluctuations and the applicability of the magnetar model unresolved. Here, we report high-cadence multiband observations of an SLSN-I with clear "chirped" (i.e., decreasing period) light-curve bumps that can be directly linked to the properties of the magnetar central engine. Our observations are consistent with a tilted, infalling accretion disk undergoing Lense-Thirring precession around a magnetar centrally located within the expanding supernova ejecta. Our model demonstrates that the overall light curve and bump frequency independently and self-consistently constrain the spin period and the magnetic field strength of the magnetar. Assuming standard accretion disk parameters, we constrain the accretion rate onto the magnetar. Our results provide the first observational evidence of the Lense-Thirring effect in the environment of a magnetar, and confirm the magnetar spin-down model as an explanation for the extreme luminosity observed in SLSNe-I. We anticipate this discovery will create avenues for testing general relativity in a new regime -- the violent centers of young supernovae.

Stage IV cosmological surveys will map the universe with unprecedented precision, reducing statistical uncertainties to levels where unmodelled systematics can significantly bias inference. In particular, photometric redshift (photo-z) errors and intrinsic alignments (IA) must be robustly accounted for to ensure accurate inference of cosmological parameters. The increasing depth of Stage IV surveys exacerbates these challenges by producing low signal-to-noise galaxy populations prone to inaccurate photo-z measurements. Catastrophically misidentified redshifts are especially problematic for 3$\times$2pt inferences that combine weak lensing and galaxy clustering information. We demonstrate that even modest outlier fractions (e.g. 5%) can lead to substantial biases in cosmological parameter estimates: up to 1.8${\sigma}$ in ${\Omega}_M$ and ${\sigma}_8$, and over 8${\sigma}$ in the IA redshift evolution parameter ${\eta}$. To address this, we introduce a flexible weighting scheme at the likelihood level that down-weights the most contamination-sensitive elements of the data vector during inference. This method mitigates biases without inflating the parameter space, reducing cosmological parameter biases to below 1${\sigma}$ without substantially degrading constraining power. Our approach offers a practical solution for future analyses, enabling robust cosmological inference in the presence of catastrophic redshift errors.

To improve our knowledge of nuclear emission in luminous QSOs at Cosmic Noon, we studied the X-ray emission of the WISE/SDSS-selected hyper-luminous (WISSH) QSO sample: 85 broad-line AGN with $L_{bol}>few\times 10^{47}\,erg\,s^{-1}$ at $z\sim 2-4$. Our aim is to characterise their X-ray spectra and explore relations between X-ray luminosity and other bands, comparing powerful QSOs with the general AGN population. We performed spectral analysis for about half of the sample; 16 sources were analysed via their hardness ratio; for the others we estimated their intrinsic luminosity $L_{2-10\,keV}$. Only 8 sources are undetected. We report a large dispersion in $L_{2-10\,keV}$ despite the narrow distribution of $L_{bol}$, $L_{2500\,Å}$ and $\lambda L_{6\,\mu m}$ (about one-third of the sources classified as X-ray weak). This suggests differences in X-ray corona and accretion flow physics between hyper-luminous and less powerful AGN. X-ray photon index distribution is consistent with that of lower-$z$, lower-$L_{bol}$ AGN, and does not depend on the Eddington ratio ($\lambda_{Edd}$) or X-ray weakness. Most WISSH QSOs with intrinsic absorption estimates show little to no obscuration ($N_H \le 5\times 10^{22}\,cm^{-2}$). Among the obscured sources we find blue QSOs without broad absorption lines within the "forbidden region" of the $Log(N_H)-Log(\lambda_{Edd})$ plane, typically occupied by dust-reddened QSOs and associated with intense feedback. We confirm a correlation between $L_{2-10\,keV}$ and CIV line blueshift, a tracer of nuclear ionized outflows. Multi-wavelength data and complete X-ray coverage enabled the investigation of the disk-corona interplay at the highest luminosity regimes. The broad distribution of bolometric correction and X-ray - to - optical index suggest caution when using $L_{bol}$, $L_{2500\,Å}$ or $L_{6\,\mu m}$ as direct X-ray proxy for individual luminous QSOs.

Measuring relativistic effects on cosmological scales would provide further confirmation of the validity of general relativity in the still poorly tested condition of weak gravity. Despite their relevance, relativistic imprints in the distribution of galaxies on large scales have so far eluded detection, mainly because they are stronger on the largest cosmic scales, which are plagued by cosmic variance. Expanding on previous works, we study galaxy clustering by subdividing a galaxy population into two sub-samples -- bright and faint -- and we here focus on their two-point correlation function in harmonic space, i.e. via the angular power spectrum. Thanks to such a split in magnitude and by exploiting the multi-tracer technique, we are able to boost the impact of the relativistic contributions. We first focus on the leading relativistic contribution given by the Doppler effect and show that, with a carefully tailored luminosity cut, it can be detected. Then, we look at the sub-dominant effects predicted by general relativity and quantify how their statistical significance, as yet undetectable, varies with redshift binning and survey specifications. As case studies, we consider in our forecasts a bright galaxy sample at low redshift, an H$\alpha$ emission-line galaxy survey at intermediate redshifts, and high-redshift Lyman-break galaxies at high redshift.

We assess the impact of the fiducial cosmology choice on cosmological inference from full-shape (FS) fits of the galaxy power spectrum in the DESI 2024 Data Release 1 (DR1). Using a suite of AbacusSummit DR1 mock catalogues based on the Planck 2018 best-fit cosmology, we quantify potential systematic shifts introduced by analysing the data under five secondary cosmologies - featuring variations in matter density, thawing dark energy, higher effective number of neutrino species, reduced clustering amplitude, and the DESI DR1 BAO best-fit $w_0w_a$CDM cosmology - relative to DESI's baseline Planck 2018 cosmology. We investigate two complementary FS analysis approaches: full-modelling (FM) and ShapeFit (SF), each with distinct sensitivities to the assumed fiducial model. Across all tracers, we find for FM that systematic shifts induced by fiducial cosmology mismatches remain well below the DESI DR1 statistical uncertainties, with maximum deviations of 0.22$\sigma_\mathrm{DR1}$ in $\Lambda$CDM scenarios and 0.12$\sigma_\mathrm{DR1+SN}$ when including SN Ia mock data in extended $w_0w_a$CDM fits. For SF, the shifts in the compressed parameters remain below $0.45\sigma_\mathrm{DR1}$ for all tracers and cosmologies.

Radio halos are diffuse synchrotron sources that trace the turbulent intracluster medium (ICM) of galaxy clusters. However, their origin remains unknown. Two main formation models have been proposed: the hadronic model, in which relativistic electrons are continuously injected by cosmic-ray protons; and the leptonic turbulent re-acceleration model, where cluster mergers re-energise electrons in situ. A key discriminant between the two models would be the existence of ultra-steep spectrum radio halos (USSRHs), which can only be produced through turbulent re-acceleration. Here we report the discovery of an USSRH in the galaxy cluster SPT-CLJ2337$-$5942 at redshift $z = 0.78$ in the MeerKAT-South Pole Telescope 100 deg$^2$ survey. This discovery is noteworthy for two primary reasons: it is the highest redshift USSRH system to date; and the close correspondence of the radio emission with the thermal ICM as traced by $\mathit{Chandra}$ X-ray observations, further supporting the leptonic re-acceleration model. The halo is under-luminous for its mass, consistent with a minor merger origin, which produces steep-spectrum, lower luminosity halos. This result demonstrates the power of wide-field, high-fidelity, $\lesssim1$ GHz surveys like the MeerKAT-SPT 100 deg$^2$ programme to probe the origin and evolution of radio halos over cosmic time, ahead of the Square Kilometre Array.

We apply the model-agnostic anomaly detection method Cathode - originally developed for particle physics - to search for stellar streams in Gaia data. We combine Cathode with Via Machinae 3.0: a re-optimized version of the stellar stream detection method that was previously applied to Gaia data together with the related anomaly detection technique Anode. We demonstrate that the combination of Via Machinae 3.0 with Cathode, called VM3-C, not only re-discovers previously known streams, but also confirms many candidate streams identified in combination with Anode (denoted VM3-A). Compared to VM3-A, the number of stream candidates detected by VM3-C increases by around 10%. Moreover, both of the methods discover the same two large clusters of stream candidates in the Northern Galactic hemisphere. We dub these highly significant anomalous structures the Raritan stream and the Passaic stream. These two structures may indicate the presence of larger objects, such as dwarf galaxy streams, or non-trivial orbital dynamics resulting in bifurcation or fanning, and are promising and high-priority targets for further analysis.

The Moon is our future. It may seem like a chimera with a projected cost in excess of 100 billion\$, and counting, dispensed on ARTEMIS with little to show to date. However it is the ideal site for the largest telescopes that we can dream about, at wavelengths spanning decimetric radio through optical to terahertz FIR. And it is these future telescopes that will penetrate the fundamental mysteries of the first hydrogen clouds, the first stars, the first galaxies, the first supermassive black holes, and the nearest habitable exoplanets. Nor does it stop there. Our lunar telescopes will take us back to the first months of the Universe, and even back to the first 10$^{-36}$ second after the Big Bang when inflation most likely occurred. Our lunar telescopes will provide high resolution images of exoplanets that are nearby Earth-like 'twins' and provide an unrivalled attempt to answer the ultimate cosmic question of whether we are alone in the universe. Here I will set out my vision of the case for lunar astronomy over the next several decades.

Doppler planet searches are complicated by stellar activity, through which cyclical changes in the host star's photosphere and chromosphere can mask or mimic planetary signals. A popular technique for modeling stellar activity is to apply a quasiperiodic Gaussian process (GP) kernel, which provides a flexible model with rigorous error propagation. However, observers must guard against overfitting, as a GP may be flexible enough to subsume other signals besides the one it is intended to model. To counteract overfitting, we introduce a curvature-penalizing objective function for fitting GP models to long-term magnetic activity cycles. We also demonstrate that a Gaussian filter can be an effective method of detrending radial velocities (RVs) so that shorter-period signals can be extracted even in the absence of a mathematical model of the long-term trend. We apply our methods to the heavily studied 55 Cancri system, fitting Keplerian orbits plus the GP activity-cycle model. We show that a 4-Keplerian model that includes planets b, c, e, and f combined with a GP for the activity cycle performs at least as well as the widely agreed-upon 5-planet system with its own GP activity model. Our results suggest that the existence of planet d cannot be established from the RVs alone; additional data are required for confirmation.

Mass transfer between stars in binary systems profoundly impacts their evolution, yet many aspects of this process (especially the stability, mass loss, and eventual fate of such systems) remain poorly understood. One promising avenue to constrain these processes is through the identification and characterisation of systems undergoing active mass transfer. Inspired by the slow brightening preceding stellar merger transients, we worked on a method to identify Galactic mass-transferring binaries in which the donor is a Hertzsprung gap (HG) star. We constructed an initial sample of HG stars using the Gaia EDR3 contribution Starhorse catalogue, and we identified candidate mass-transferring systems by selecting sources that exhibit Balmer emission features (using the low-resolution Gaia XP spectra), mid-infrared excess (from WISE photometry), and photometric variability (inferred from the error in the Gaia G-band magnitude). This multi-criteria selection yielded a sample of 67 candidates, which we further analysed using complementary photometric and spectroscopic data. Among our candidates, we identified at least nine eclipsing binaries and some sources that are potential binaries as well. Three sources in our sample are strong candidates for mass-transferring binaries with a yellow component, and three more are binaries with a Be star. Notably, four sources in our sample are strong candidates for hosting a compact companion, based on their UV or X-ray signatures. The main sources of contamination in our search are hot but highly reddened stars (primarily Oe and Be stars). As an additional outcome of this work, we present a refined catalogue of 308 bona fide HG stars, selected using improved extinction corrections and stricter emission-line criteria. This enhanced sample is expected to contain a significantly higher fraction of scientifically valuable mass-transferring binaries.

Obtaining a complete census of gas in the local interstellar medium (<100 pc) is challenging given the limited available tracers of the warm, partially-ionized medium. Medium-to-high resolution UV absorption spectroscopy toward individual nearby stars is the primary method used, and incomplete spatial sampling of this complex medium makes a global map of the material difficult. Using H I column density measurements derived from H I Lyman alpha spectroscopy toward 164 stars inside 100 pc, we have generated 2D spatially-interpolated N(HI) maps for different distance shells. Based on the area-weighted sky averages, we find that sightlines inside 10 pc typically have log N(HI) ~ 17.9. For greater distance shells, log N(HI) increases to 18.3 (10-20 pc), then to 18.4 (20-70 pc), and finally increasing to 18.6 (70-100 pc). This last increase is likely associated with the detection of the Local Bubble boundary, thus making the plateau of column density from 20-70 pc notable and suggestive of the rarity of warm LISM material beyond ~10-20 pc. We estimate that the uncertainties associated with N(HI) values inferred from the interpolated sky maps are approximately inversely correlated with the number of samples in each distance shell and are in the range of 0.20-0.48 dex, compared to 0.01-0.30 dex typically determined from direct Lyman alpha observations. We discuss the impact of these uncertainties on ISM corrections of EUV and Lyman alpha observations for nearby stars. Denser spatial sampling of the sky via UV absorption spectroscopy of nearby stars is required to improve the accuracy of these N(HI) estimates.

We model the short gamma-ray bursts (GRB) 090510 as the product of a magnetized neutron star (NS) binary merger. Accounting for the NS critical mass constraint given by the mass of PSR J0952--0607, we infer that GRB 090510 was a highly-magnetized NS-NS merger that left as remnant a Kerr black hole (BH) of $2.4 M_\odot$ with a low-mass accretion disk. The gamma-ray precursor is powered by the magnetic energy released during the merger of the NSs. The prompt emission originates at the transparency of an ultra-relativistic $e^+e^-$ pair-plasma produced by the overcritical electric field induced by the rotating strong magnetic field around the merged object before it reaches the critical mass, the GeV emission by the extractable energy of the newborn BH, and the X-ray afterglow by accretion onto it. We derive the masses of the merging NSs, their magnetic fields, the BH mass, spin, and irreducible mass, the strength of the magnetic field, the disk mass, and obtain an estimate of the gravitational-wave emission during the merger phase preceding the prompt short GRB emission. The inferred parameters agree with up-to-date numerical relativity simulations, confirming that strong magnetic fields above $10^{14}$ G develop in NS-NS mergers and that mergers leading to a central BH remnant have low-mass disks of $\sim 10^{-2} M_\odot$. We also advance the possibility that quasi-period oscillations of tens of Hz of frequency due to Lense-Thirring precession of the matter surrounding the merged object before BH formation can explain the successive spikes following the prompt emission peak.

We present a new and independent methodology for identifying gravitational lens candidates using data from the H-ATLAS and AllWISE surveys. Unlike previous approaches, which are typically biased toward bright, strongly lensed submillimeter galaxies (SMGs), our method uncovers fainter systems with lower magnifications. This enables the identification and individual study of lensing events that would otherwise only be accessible through statistical weak lensing analyses. Our approach focuses on high-redshift SMGs from H-ATLAS in the range $1.2 < z < 4.0$, and searches for associated AllWISE sources within an angular distance of 18 arcsec. Candidate lenses are selected based on their WISE colors ($0.5 < \mathrm{W2} - \mathrm{W3} < 1.5$ mag), consistent with those of elliptical galaxies, and further filtered using $J-\mathrm{W1}$ color and photometric redshift cuts to reduce stellar contamination. This conservative selection yields 68 new lens candidates. We then performed SED fitting with CIGALE across UV to submillimeter wavelengths to estimate the physical properties of both the lenses and the background SMGs, and to assess the lensing nature of these candidates. Despite the uncertainties, we were able to constrain key parameters such as stellar and dust masses, infrared luminosities, and star formation rates. In addition, the estimated magnifications for most candidates are modest, consistent with the weak lensing regime ($\mu \simeq 1{-}1.5$), although a few sources may require more precise modeling. Future efforts could refine this methodology to recover potential candidates outside our selection, and high-resolution follow-up observations will be essential to confirm the lensing nature of these sources and to further investigate their physical properties.

The advent of large-scale photometric surveys has led to the discovery of over a million contact binary systems. Conventional light curve analysis methods are no longer adequate for handling such massive datasets. To address this challenge, we developed a neural network-based model capable of rapid analysis of multiple-band light curves of contact binaries. Our model can determine the fundamental physical parameters, including temperature and mass ratios, orbital inclination, potential, fillout factor, primary and secondary luminosities and radii, third light contribution, and spot parameters. Notably, unlike previous works, our model can simultaneously process multiple-band light curves and the four parameters of a starspot. The model's reliability was verified through analysis of the synthetic light curves generated by PHOEBE and the light curves of eight targets from \cite{2024ApJ...976..223W}'s work. The discrepancy distribution between the physical parameters determined by our model and true values for the synthetic light curves shows very good agreement. In addition, the physical parameters determined by our model and the corresponding light curve fits show remarkable consistency with \cite{2024ApJ...976..223W}'s results. By applying our model to OGLE contact binaries, physical parameters of 3,541 systems were obtained. We have packaged our model into an executable (this http URL) file and archived it in the China-VO repository (this https URL). The software supports light curve analysis of 19 standard filters and allows for processing the data, whether from large-scale sky surveys or individual telescope observations.

In the multiverse hypothesis, a range of universes exist with differing values of our physical constants. Here, we investigate how the probabilities of observing our values of these constants depend on the assumptions made about the theories governing particle physics and cosmology, along with habitability. The particle physics effects we consider include constraints on the Higgs vacuum expectation value from big bang nucleosynthesis and supernovae, grand unified theories (GUTs), and standard model stability. Cosmology effects we consider are different theories of dark matter and baryogenesis, and for galactic habitability effects we include star formation efficiency, stellar encounters, supernova explosions, and active galactic nuclei. We find the following to be disfavored in the multiverse scenario: flexible GUTs, pessimistic galactic disruption rates, some origin of life theories, and freeze-out dark matter with high energy baryogenesis. These predictions can be tested in future experiments to either confirm or rule out the multiverse.

Gamma-ray bursts (GRBs) are generally believed to originate from two distinct progenitors, compact binary mergers and massive collapsars. Traditional and some recent machine learning-based classification schemes predominantly rely on observer-frame physical parameters, which are significantly affected by the redshift effects and may not accurately represent the intrinsic properties of GRBs. In particular, the progenitors usually could only be decided by successful detection of the multi-band long-term afterglow, which could easily cost days of devoted effort from multiple global observational utilities. In this work, we apply the unsupervised machine learning (ML) algorithms called t-SNE and UMAP to perform GRB classification based on rest-frame prompt emission parameters. The map results of both t-SNE and UMAP reveal a clear division of these GRBs into two clusters, denoted as GRBs-I and GRBs-II. We find that all supernova-associated GRBs, including the atypical short-duration burst GRB 200826A (now recognized as collapsar-origin), consistently fall within the GRBs-II category. Conversely, all kilonova-associated GRBs (except for two controversial events) are classified as GRBs-I, including the peculiar long-duration burst GRB 060614 originating from a merger event. In another words, this clear ML separation of two types of GRBs based only on prompt properties could correctly predict the results of progenitors without follow-up afterglow properties. Comparative analysis with conventional classification methods using $T_{90}$ and $E_{\rm p,z}$--$E_{\rm iso}$ correlation demonstrates that our machine learning approach provides superior discriminative power, particularly in resolving ambiguous cases of hybrid GRBs.

We aim to improve cluster lens modeling and source reconstruction by utilizing the full information in giant, caustic-crossing arcs lensed by galaxy clusters. Lens models are generally constrained using image positions and assuming point sources, but spatially extended giant arcs provide more constraints; however, they require a more complex model that accounts for the structure of the extended source. We seek to determine whether improvements to the lens model and reconstructed source merit the difficulty of handling the extra constraints. We choose the spatially extended $z=0.725$ giant arc in the $z=0.375$ Abell 370 galaxy cluster field for our study. We present 1) a series of pixel-based source reconstructions for cluster mass models exploring the range of uncertainties in our fiducial model, 2) a similar analysis done using a prototype \textit{python} de-lensing code for cluster mass models from each of the Hubble Frontier Fields modeling teams, 3) an optimized model with pixel-based source reconstructions, and 4) and an investigation of how our optimized model affects the cluster mass model locally and globally in the highest-magnification regions. We find that our optimized model 1) is able to correct resolution-limited assumptions in cluster model inputs local to the arc, 2) has significantly smaller arc model residuals than results from the standard Hubble Frontier Fields models, and 3) affects the critical curves and therefore the information derived from highest-magnification zones most significantly in regions local to the arc.

GW231123 exhibits exceedingly massive components and high spins, which challenges the formation of first-generation (1G) black holes from stellar collapse and implies that this event might originate from hierarchical mergers. Here we show that the \texttt{2G+2G} merger scenario for GW231123 is favored over a \texttt{2G+1G} (or \texttt{3G+2G}) merger, with odds ratios of $>$$\mathcal{O}(10^3)$. The primary (secondary) black hole is consistent with merging binary black holes with masses of $75^{+7}_{-7}\,M_\odot$ and $66^{+4}_{-10}\,M_\odot$ ($64^{+8}_{-10}\,M_\odot$ and $59^{+7}_{-9}\,M_\odot$; 90\% credible intervals), respectively. Our results reveal that the treatment of spin priors from the population level and waveform model choice are decisive in interpreting potential hierarchical gravitational-wave signals.

Mid-IR wavelengths are of particular interest to exoplanet science due to the fact they can extend the searchable parameter space to planets that are older and/or colder. However, a significant source of uncertainty at mid-IR wavelengths on ground-based telescopes is the thermal background. This background comes from blackbody radiation in the atmosphere and telescope and is therefore dependent on instrument design and atmospheric conditions. When performing imaging observations, this background manifests as a slowly varying, inhomogeneous signal throughout the image, underlying our data. Photometry at mid-IR can greatly constrain atmospheric models but existing data are usually scarce or have significant error bars due to the difficulty of subtracting the background. Using M-band direct imaging observing sequences on NIRC2, we evaluate the thermal background of the Keck II telescope and attempt to subtract the background in a more comprehensive way. For our primary science target, the forming protoplanet AB Aur b, we present a contrast upper limit of $2 \times 10^{-4}$ in M-band and address the limiting factors in our observation due to the thermal background. We determine that the origin of the systematic components of the thermal background comes from the K-mirror and find that the thermal background is also strongly influenced by emission from the secondary spiders on Keck II.

Recent infrared spectroscopy from the James Webb Space Telescope (JWST) has spurred analyses of common volcanic gases such as carbon dioxide (CO2), sulfur dioxide (SO2), alongside alkali metals sodium (Na I) and potassium (K I) surrounding the hot Saturn WASP-39 b. We report more than an order-of-magnitude of variability in the density of neutral Na, K, and SO2 between ground-based measurements and JWST, at distinct epochs, hinting at exogenic physical processes similar to those sourcing Io's extended atmosphere and torus. Tidally-heated volcanic satellite simulations sputtering gas into a cloud or toroid orbiting the planet, are able to reproduce the probed line-of-sight column density variations. The estimated SO2 flux is consistent with tidal gravitation predictions, with a Na/SO2 ratio far smaller than Io's. Although stable satellite orbits at this system are known to be < 15.3 hours, several high-resolution alkali Doppler shift observations are required to constrain a putative orbit. Due to the Roche limit interior to the planetary photosphere at ~ 8 hours, atmosphere-exosphere interactions are expected to be especially important at this system.

The Murchison Widefield Array (MWA) is a low frequency radio interferometer designed and developed by an international consortium, operated on behalf of the consortium by Curtin University. The MWA is a Precursor for the low frequency Square Kilometre Array (SKA) and is located at the SKA site in Western Australia, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. Commencing science operations in 2013 after an extended development period, the MWA has performed observations over a wide set of science objectives, has been upgraded multiple times, and has played a fundamental role in the development of the low frequency SKA. As MWA Program Manager from 2008 to 2011, as Director from 2011 until 2015, and then again from 2021 to the present, I describe some personal reflections on the MWA's activities and successes in these different dimensions, as well as my view of some of the approaches that have enabled these successes. I offer some of the lessons I've perceived over the last 17+ years in the project.

Direct measurements of the matter power spectrum, $P_\mathrm{m}(k,z)$, provide a powerful tool to investigate observed tensions between models of structure growth while also testing the internal consistency of cosmological probes. We analyse cosmic shear data from the final data release of the Kilo-Degree Survey (KiDS), presenting a deprojected $P_\mathrm{m}(k,z)$, measured in up to three redshift bins. Compared to analyses using previous KiDS releases, we find improved internal consistency in the $z\lesssim0.7$ regime. At large scales, $k\lesssim0.1\,h\,\rm Mpc^{-1}$, our power spectrum reconstruction aligns with $\Lambda$CDM predictions with a density fluctuation amplitude $\sigma_8=0.81$. Furthermore, at small scales, $k=3$-$20\,h\,\rm Mpc^{-1}$, the average matter power spectrum is suppressed by $30\%\pm10\%\,{\rm (stat.)}\pm4\%\,{\rm (sys.)}$ with $2.8\sigma$ significance relative to a dark-matter-only model, consistent with expectations of strong baryonic feedback.

The central regions of disc galaxies host a rich variety of stellar structures: nuclear discs, bars, bulges, and boxy-peanut (BP) bulges. These components are often difficult to disentangle, both photometrically and kinematically, particularly in star-forming galaxies where dust obscuration and complex stellar motions complicate interpretation. In this work, we use data from the GECKOS-MUSE survey to investigate the impact of dust on axisymmetric Jeans Anisotropic Multi-Gaussian Expansion (JAM) models, and assess their ability to recover kinematic structure in edge-on disc galaxies. We construct JAM models for a sample of seven edge-on ($i \gtrapprox 85^\circ$) galaxies that span a range of star formation rates, dust content, and kinematic complexity. We find that when dust is appropriately masked, the disc regions of each galaxy are fit to $\chi^2_{\text{reduced}}\leq 5$. We analyse two-dimensional residual velocity fields to identify signatures of non-axisymmetric structure. We find that derived dynamical masses are constant within 10% for each galaxy across all dust masking levels. In NGC 3957, a barred boxy galaxy in our sample, we identify velocity residuals that persist even under aggressive dust masking, aligned with bar orbits and supported by photometric bar signatures. We extend this analysis to reveal a bar in IC 1711 and a possible side-on bar in NGC 0522. Our results highlight both the capabilities and limitations of JAM in dusty, edge-on systems and attempt to link residual velocities to known non-axisymmetric kinematic structure.

Describing the large-scale field topology of protoplanetary disks faces significant difficulties and uncertainties. The transport of the large-scale field inside the disk plays an important role in understanding its evolution. We aim to improve our understanding of the dependencies that stellar magnetic fields pose on the large-scale field. We focus on the innermost disk region ($\lesssim$ 0.1 AU), which is crucial for understanding the long-term disk evolution. We present a novel approach combining the evolution of a 1+1D hydrodynamic disk with a large-scale magnetic field, consisting of a stellar dipole truncating the disk and a fossil field. The magnetic flux transport includes advection and diffusion due to laminar, non-ideal MHD effects, such as Ohmic and ambipolar diffusion. Due to the implicit nature of the numerical method, long-term simulations (in the order of several viscous timescales) are feasible. The large-scale magnetic field topology in stationary models shows a distinct dependence on specific parameters. The innermost disk region is strongly affected by the stellar rotation period and magnetic field strength. The outer disk regions are affected by the X-ray luminosity and the fossil field. Varying the mass flow through the disk affects the large-scale disk field throughout its radial extent. The topology of the large-scale disk field is affected by several stellar and disk parameters. This will affect the efficiency of MHD outflows, which depend on the magnetic field topology. Such outflows might originate from the very inner disk region, the dead zone, or the outer disk. In subsequent studies, we will use these models as a starting point for conducting long-term evolution simulations of the disk and large-scale field on scales of $\sim$ 106 years to investigate the combined evolution of the disk, the magnetic field topology, and the resulting MHD outflows.

The detection of interstellar C$_{60}^{+}$ has been debated for 30 years. The contested attribution of a weaker DIB at 9365 Å was re-evaluated here on the basis of a Pearson correlation relative to 9577 Å, which was previously tied to C$_{60}^{+}$ by diverse collaborations. An assessment of 11 sightlines revealed a high correlation amongst 9365$-$9577 Å equivalent widths ($r=0.93 \pm 0.05$), after contamination from an adjacent line was mitigated using both numerical integration and Gaussian fits. In tandem with a recent separate study's high-$r$ evaluation linking 9577$-$9632 Å across a sizable baseline: three interrelated DIBs matching C$_{60}^{+}$ laboratory findings were independently reaffirmed (9365, 9577, 9632 Å). Yet further investigations are required to strengthen the case via two other weak DIBs disputedly linked to C$_{60}^{+}$, particularly owing to potential overlapping lines arising from an expansive chemical space (PAHs).

High-precision and long-duration light curves from space telescopes have revolutionized the fields of asteroseismology and binary star systems. In particular, the number of pulsating systems in eclipsing binaries has drastically increased thanks to space-based observations covering almost the entire sky. When combined with multi-epoch spectroscopy, this allows us not only to measure model-independent dynamical masses and radii for thousands of eclipsing binary systems, but also facilitates the powerful synergy of binarity and asteroseismology. Moreover, asteroseismology of pre- and post-interaction binary stars allows the physics of binary evolution to be constrained, including tides, mass transfer, and even mergers. We conclude that: (1) eclipsing binaries are among the best laboratories for testing stellar structure and evolution theory because we are able to measure their masses and radii independently of models; (2) combining binary and asteroseismic modeling yields precise constraints on the physical processes at work within stellar interiors, such as rotation and mixing; (3) pulsating binaries are challenging to study given the plethora of different techniques and physical processes that need to be considered depending on their orbital and physical properties; and (4) the impact of tides on the pulsational, stellar structure, and orbital properties of a binary system can be tested through tidal asteroseismology.

The escape of accelerated particles from supernova remnants remains one of the central and yet least understood aspects of the origin of cosmic rays. Here we use the results of the recent LHAASO observation of gamma rays from a region of $\sim 2$ degrees around the Cassiopeia A (Cas A) supernova remnant to constrain the process of particle escape from this remnant. We dedicate special attention to discuss the impact of shock evolution and particle propagation in the near source region on the gamma ray emission. This is very important to assess the possibility that very high-energy protons may have been accelerated in past activity of Cas A. Given the core collapse nature of Cas A and its young age ($\sim 340$ years), the non detection of $\gtrsim 100$ TeV gamma rays from this remnant allows us to draw some conclusions on the role of supernova explosions for the origin of cosmic rays at the knee. In particular we calculate the spectrum of cosmic rays that may have escaped this remnant to make a clear distinction between the instantaneous maximum energy and the one that appears as a flux suppression in the time integrated spectrum from an individual supernova. LHAASO observation of the region around Cas A as well as gamma ray observations of the remnant itself confirm that this remnant is not operating as a PeVatron and that, although in the early stages the maximum energy may have reached $\sim$Peta-electronVolt, the number of such particles in the surroundings of Cas A is exceedingly small.

The James Webb Space Telescope (JWST) has observed compact, massive proto-stellar clusters of low metallicity in the Cosmic Gems arc galaxy at high redshift, which represent likely precursors to globular clusters. We model the mass growth of stellar black holes (BHs) during the first few Myr of the life of a massive, compact, gaseous stellar cluster before stellar feedback expels the primordial gas. At high redshift, in a lower metallicity environment stellar winds get weaker allowing for larger gas-depletion time-scales in the cluster despite of energetic pair-instability supernova (PISN) feedback for sufficiently compact clusters. Mass segregation drives the massive stellar progenitors of BHs in the center of the cluster where gas is most dense. We estimate the conditions for which the initial black hole mass function (BHMF), with a PISN-induced cut-off $<55{\rm M}_\odot$, gets shifted to values within the upper BH mass gap, $\sim 60-130{\rm M}_\odot$, or higher, as observed by Gravitational Wave (GW) experiments LIGO-Virgo-KAGRA. We find that the BHs are shifted by the end of gas depletion to values within and above the mass gap, well within the range of BH components of the recent GW-signal GW231123, depending on total mass, star formation efficiency, metallicity and compactness. The individual BH mass increase follows approximately a surprisingly steep power law with respect to initial BH mass with an exponent in the range $\approx 4-6$. This occurs in gaseous proto-stellar clusters that are sufficiently massive and compact, with typical values of total mass $\sim 10^6{\rm M}_\odot$ and size $\sim 1{\rm pc}$. Our analysis suggests that proto-stellar clusters at high redshift such as Cosmic Gems arc clusters have generated through early gas accretion, BHs as heavy as $\sim 10^2-10^3{\rm M}_\odot$.

We report new constraints on the velocity-independent annihilation cross section $\langle \sigma v \rangle$ of keV-scale dark matter particles based on 11 years of observations with the NuSTAR X-ray telescope. Using the unfocused stray light mode of the instrument, which provides a wide field-of-view and a stable instrumental background, we perform a sensitive search for photon signatures from dark matter annihilation in the Galactic halo. We model the resulting diffuse X-ray spectrum over the 3-20 keV energy range and search for line-like spectral features that may arise from the annihilation of dark matter particles into photons. No statistically significant excess over the expected astrophysical background is found. We therefore place upper limits on $\langle \sigma v \rangle$ as a function of dark matter mass, assuming a velocity-independent s-wave annihilation and several Galactic dark matter profiles. Across most of the explored mass range our results provide the strongest X-ray constraints to date, reaching the level of $\langle\sigma v\rangle \lesssim 10^{-33}$ -- $10^{-34}$ cm$^3$ s$^{-1}$, and they are complementary to the most recent bounds derived from SRG/ART-XC observations.

Prominences (PRs) are among the most common solar phenomena, yet their full physical picture, particularly their chromospheric mm emission, remains incomplete. The new Atacama Large Millimeter/submillimeter Array (ALMA) presents an opportunity to study PRs at mm and sub-mm wavelengths through a combination of measurements and theoretical modeling. We utilize ALMA single-dish measurements alongside data from other radio instruments to model the PR brightness temperature through adaptation and modification the 1D semi-empirical Avrett-Tian-Landi-Curdt-Wülser (ATLCW) quiet-Sun (QS) model. The calculated and measured PR brightness temperatures were found to be lower than the measured QS value and predictions from the unperturbed ATLCW QS model across the ALMA wavelength range, consistent with PRs appearing in absorption. The PR density was found to be 60 - 163 times higher and temperature 155 - 163 times lower than the QS level, aligning with previous measurements. A key finding emerged with the non-hydrostatic equilibrium assumption, yielding a more physically consistent PR brightness temperature. This suggests that PR stability is most likely maintained by its magnetic field obeying magnetostatic conditions rather than by pure hydrostatic equilibrium, supporting recent studies. Additionally, our results confirm that thermal bremsstrahlung is the dominant radiation mechanism for PRs at mm and sub-mm wavelengths.

The geodesy of irregularly shaped small bodies presents fundamental challenges for gravitational field modeling, particularly as deep space exploration missions increasingly target asteroids and comets. Traditional approaches suffer from critical limitations: spherical harmonics diverge within the Brillouin sphere where spacecraft typically operate, polyhedral models assume unrealistic homogeneous density distributions, and existing machine learning methods like GeodesyNets and Physics-Informed Neural Networks (PINN-GM) require extensive computational resources and training time. This work introduces MasconCubes, a novel self-supervised learning approach that formulates gravity inversion as a direct optimization problem over a regular 3D grid of point masses (mascons). Unlike implicit neural representations, MasconCubes explicitly model mass distributions while leveraging known asteroid shape information to constrain the solution space. Comprehensive evaluation on diverse asteroid models including Bennu, Eros, Itokawa, and synthetic planetesimals demonstrates that MasconCubes achieve superior performance across multiple metrics. Most notably, MasconCubes demonstrate computational efficiency advantages with training times approximately 40 times faster than GeodesyNets while maintaining physical interpretability through explicit mass distributions. These results establish MasconCubes as a promising approach for mission-critical gravitational modeling applications requiring high accuracy, computational efficiency, and physical insight into internal mass distributions of irregular celestial bodies.

We present an analysis of Si-III absorption and its effect on the 1D Ly$\alpha$ forest power spectrum using the Sherwood-Relics hydrodynamical simulation suite. In addition to the well-understood oscillations arising from the Ly$\alpha$--Si-III cross correlation, we find an enhancement in small-scale power that has been ignored in previous studies. We therefore develop a new analytical fitting function that captures two critical effects that have previously been neglected: distinct Ly$\alpha$ and Si-III line profiles, and a variable ratio for coeval Ly$\alpha$ and Si-III optical depths. In contrast to earlier work, we also predict amplitudes for the Si-III power spectrum and Ly$\alpha$--Si-III cross power spectrum that decrease toward lower redshift due to the hardening metagalactic UV background spectrum at $z\lesssim 3.5$. The fitting function is validated by comparison against multiple simulated datasets at redshifts $2.2\leq z \leq 5.0$ and wavenumbers $k < 0.2\rm\,s\,km^{-1}$. Our model remains in good agreement with earlier work at large scales ($k \lesssim 0.06\rm\,s\,km^{-1}$) and it has little effect on existing warm dark matter constraints from the Ly$\alpha$ forest when adopting a physically motivated prior on the silicon abundance. It will, however, be an essential consideration for future, high-precision Ly$\alpha$ forest power spectrum measurements.

As part of the upgrade of the Pierre Auger Observatory, known as AugerPrime, the Underground Muon Detector is being installed in the low-energy extension of the Surface Detector, allowing for a direct measurement of the muonic component of air showers produced by ultra-high-energy cosmic rays with energies between 10^{16.8} and 10^{19} eV. The detector consists of an array of 30 m2 plastic scintillator detectors buried 2.3 m underground near a water-Cherenkov detector. Two modes of operation are implemented to achieve an extended dynamic range: the binary mode, conceived for low muon densities, and the calorimetric mode, designed for high muon densities. In this contribution, we present the current status and improvements in the reconstruction and performance of this component of AugerPrime.

Recent high resolution mapping of the circum-nuclear regions of Active Galactic Nuclei (AGN) has revealed the existence of geometrically thin nuclear disks, in general randomly oriented with respect to their galaxy hosts. These molecular tori have typical radii of 10~pc, and contain a few 10$^7$ M$_\odot$ of H$_2$, with H$_2$ column densities between 10$^{23}$ and 10$^{25}$ cm$^{-2}$. We mapped two of the most massive of these molecular tori with higher resolution, in order to unveil their morphology and kinematics, their possible warp and clumpiness, and derive their stability and life-time. We used the highest resolution possible with ALMA (16~km baseline) in Band 7, taking into account for mapping CO(3-2) and HCO$^+$(4-3) the compromise between sensitivity and resolution. New features are discovered at the high resolution, obtained with a beam of 0.015\arcsec, equivalent to $\sim$ 1~pc scale, at their $\sim$ 15~Mpc distance. The molecular torus in NGC~613 appears like a ring, depleted in molecular gas near the center. The depletion region is displaced by 3~pc towards the NW from the AGN position, meaning some $m=1$ asymmetry in the torus. The molecular torus in NGC~1672 has now a different position angle from previous observations, and is edge-on, revealing a geometrically very thin torus, with a clear warp. This confirms that the classical model of a simple geometrically thick dusty torus is challenged by high resolution observations. The nuclear disks appear clumpy, and slightly lopsided. The molecular outflow in NGC~613 is now resolved out. Well inside the sphere of influence of the black holes (BH), we are now able to determine more accurately their mass, for those Seyfert spiral galaxies, in a region of the M-sigma relation where the scatter is maximum.

In the near ultraviolet (NUV) part of the solar spectrum, there are several Fe I lines with very broad profiles, typical of chromospheric lines. These lines are largely unexplored due to the lack of high-resolution data in this region. This changed with the successful Sunrise III flight in 2024, when spectro-polarimetric data were recorded with high spatial, spectral, and temporal resolution covering a large variety of solar targets. The aim of this work is to investigate the formation of the lines and lay the groundwork for further studies. We compute the spectrum of the lines at 358.12 nm, 371.99 nm, 406.36 nm, and 407.17 nm emerging from the standard 1D FAL-atmospheres using the non-local thermodynamic equilibrium (NLTE) radiative transfer code RH. We find that the lines are affected by overionization in the wings, but have line cores strongly affected by scattering. The line cores form well into the chromosphere in the tested atmosphere models except the colder FALX model where the line core forms in the temperature minimum (which lies at traditional chromospheric heights). In the presence of a vertical magnetic field, the Stokes $V$ signal is multi-lobed. The profile can be decomposed into two broad photospheric lobes and two sharper lobes forming in the flanks of the chromospheric line core. We have investigated the properties of four lines of Fe I that form in the lower chromosphere. The results provide a basic understanding of the formation of the lines, which will be useful for later analysis of formation in 3D magnetohydrodynamic simulations and an eventual investigation into their diagnostic potential.

Accurate X-ray spectroscopic measurements are fundamental for deriving basic physical parameters of the most abundant baryon components in the Universe. The plethora of X-ray observatories currently operational enables a panchromatic view of the high-energy emission of celestial sources. However, uncertainties in the energy-dependent calibration of the instrument transfer functions (e.g. the effective area, energy redistribution, or gain) can limit - and historically, did limit - the accuracy of X-ray spectroscopic measurements. We revised the status of the cross-calibration among the scientific payload on board four operation missions: Chandra, NuSTAR, XMM-Newton, and the recently launched XRISM. XRISM carries the micro-calorimeter Resolve, which yields the best energy resolution at energies above 2 keV. For this purpose, we used the data from a 10-day-long observational campaign targeting the nearby active galactic nucleus NGC 3783, carried out in July 2024. We present a novel model-independent method for assessing the cross-calibration status that is based on a multi-node spline of the spectra with the highest-resolving power (XRISM/Resolve in our campaign). We also estimated the impact of the intrinsic variability of NGC 3783 on the cross-calibration status due to the different time coverages of participating observatories and performed an empirical reassessment of the Resolve throughput at low energies. Based on this analysis, we derived a set of energy-dependent correction factors of the observed responses, enabling a statistically robust analysis of the whole spectral dataset. They will be employed in subsequent papers describing the astrophysical results of the campaign.

Comparison between cosmological studies is usually performed in a statistical manner at the level of the posteriors of cosmological parameters. In this Letter, we show how this approach poorly reflects the differences between cosmological analyses, when applied to cosmological studies using galaxy cluster abundances. We illustrate this by deriving the implications of the best-fit cosmologies from the recent SPT and eROSITA cluster number counts analyses on the Planck thermal Sunyaev-Zeldovich (t-SZ) probes. We first fix the mass calibration, and find that the Planck cluster sample would theoretically contain 498 clusters with the SPT cosmology, and 1098 clusters with the eROSITA cosmology, instead of the 439 clusters observed. We then fit the Planck number counts to both cosmologies, only varying the hydrostatic mass bias, and find required biases of $0.790 \pm 0.070$ and $0.630 \pm 0.034$ for SPT and eROSITA respectively, instead of the $0.844^{+0.055}_{-0.062}$ derived in Aymerich et al. (2025). Lastly, we compute the expected t-SZ power spectrum obtained from the SPT and eROSITA cosmologies, and compare these to the Planck measurement. While the predicted SPT angular power spectrum is in good agreement with the Planck measurements, the normalisation of the predicted eROSITA angular power spectrum is two times higher at all scales. These two tests highlight the power of comparing predicted cluster abundances and t-SZ power spectra to measured data in a physically interpretable way.

This investigation examines QPOs in two quantum-corrected BH spacetimes that preserve general covariance while incorporating quantum gravitational effects through a dimensionless parameter \zeta. We combine analytical derivations of epicyclic frequencies with comprehensive numerical simulations of BHL accretion to explore how quantum corrections manifest in observable astrophysical phenomena. Using a fiducial BH mass of M=10M_\odot representative of stellar-mass X-ray binaries, we demonstrate that the two models exhibit fundamentally different behaviors: Model-I modifies both temporal and radial metric components, leading to innermost stable circular orbit migration proportional to \zeta^4 and dramatic stagnation point evolution from 27M to 5M as quantum corrections strengthen. Model-II preserves the classical temporal component while altering only spatial geometry, maintaining constant stagnation points and stable cavity structures throughout the parameter range. Our numerical simulations reveal distinct QPO generation mechanisms, with Model-I showing systematic frequency evolution and cavity shrinkage that suppresses oscillations for \zeta \geq 3M, while Model-II maintains stable low-frequency modes up to \zeta \geq 5M. Power spectral density analyzes demonstrate characteristic frequency ratios (3:2, 2:1, 5:3) consistent with observations from X-ray binaries, providing specific targets for discriminating between quantum correction scenarios. The hydrodynamically derived constraints (\zeta \lesssim 4M) show remarkable agreement with independent EHT limits for M87* and Sgr A*, validating our theoretical framework through multiple observational channels. These results establish QPO frequency analysis as a probe for detecting quantum gravitational effects in astrophysical BHs and demonstrate the complementary nature of timing and imaging observations in constraining fundamental physics.

In April 2013, the TeV blazar Markarian~421 underwent one of its most powerful emission outbursts to date. An extensive multi-instrument campaign featuring MAGIC, VERITAS, and \textit{NuSTAR} provided comprehensive very-high-energy (VHE; $E > 100$\,GeV) and X-ray coverage over nine consecutive days. In this work, we perform a detailed spectral analysis of the X-ray and VHE emissions on sub-hour timescales throughout the flare. We identify several clockwise spectral hysteresis loops in the X-rays, revealing a spectral evolution more complex than a simple harder-when-brighter trend. The VHE spectrum extends beyond 10\,TeV, and its temporal evolution closely mirrors the behavior in the X-rays. We report the first evidence of VHE spectral hysteresis occurring simultaneously with the X-ray loops. To interpret these findings, we apply a time-dependent leptonic model to 240 broadband spectral energy distributions (SEDs) binned on a 15-minute scale, allowing us to self-consistently track the particle distribution's history. Our modeling shows that the majority of the sub-hour flux and spectral variations are driven by changes in the luminosity and slope of the injected electron distribution. The required variations in the electron slope are difficult to reconcile with magnetic reconnection but are consistent with a shock-acceleration scenario where the shock compression ratio evolves by a factor of $\sim2$. The model also points to a relatively stable magnetic field and emitting region size, favoring a scenario where the emission originates from a stationary feature in the jet, such as a recollimation shock. However, this scenario requires a jet Lorentz factor that significantly exceeds values from VLBI measurements to account for the high minimum electron energy implied by the lack of variability in the optical band.

The stellar initial mass function (IMF) and the fraction of binary systems are fundamental ingredients that govern the formation and evolution of galaxies. Whether the IMF is universal or varies with environment remains one of the central open questions in astrophysics. Dwarf galaxies such as the Small Magellanic Cloud (SMC), with their low metallicity and diffuse star-forming regions, offer critical laboratories to address this issue. In this work, we exploit ultra-deep photometry from the James Webb Space Telescope to investigate the stellar populations in the field of the SMC. Using the $m_{\rm F322W2}$ versus $m_{\rm F115W}-m_{\rm F322W2}$ color-magnitude diagram (CMD), we derive the luminosity function and measure the fraction of unresolved binary systems. We find a binary fraction of $f_{\rm bin}^{q>0.6}=0.14\pm0.01$, consistent with results from synthetic CMDs incorporating the metallicity distribution of the SMC. Additionally, the measured binary fraction in the SMC field is consistent with those observed in Galactic open clusters and Milky Way field stars of similar ages and masses, suggesting similar binary formation and evolutionary processes across these low-density environments. By combining the luminosity function with the best-fit isochrone, we derive the the mass function (MF) down to $0.22\,M_{\odot}$, the lowest mass limit reached for the SMC to date. The resulting MF follows a power-law with a slope of $\alpha=-1.99\pm0.08$. This value is shallower than the canonical Salpeter slope of $\alpha=-2.35$, providing new evidence for IMF variations in low-metallicity and low-density environments.

We present a comprehensive statistical analysis of brown dwarf companions to investigate the physical mechanisms responsible for the observed "brown dwarf desert", the notable paucity of brown dwarf companions, at orbital separations between 0.1 and 5 AU. Using a sample of 108 confirmed brown dwarf companions from the NASA Exoplanet Archive with masses between 13-80 Jupiter masses and orbital semi-major axes between 0.1-5.0 AU, we employ Kolmogorov-Smirnov statistical (KS) tests to compare observed orbital distributions with three proposed formation scenarios: (A) disk migration with stellar infall, (B) core accretion with mass-dependent survival probability, and (C) formation bias through dynamical migration. Our systematic grid-search analysis spans 27 parameter combinations for disk migration, 9 for core accretion, and 3 for formation bias models. The disk migration model provides the best statistical fit to observations (KS statistic = 0.100, p-value = 0.216), with optimal parameters {\mu}_rate = 0.5, {\sigma}_rate = 0.5, and t-myr = 0.5. The formation bias model achieves intermediate performance (KS = 0.173, p-value = 0.005) with optimal migration fraction p_move = 0.05, while the core accretion scenario shows the poorest fit (KS = 0.417, p-value = 3.5{\times}10^-17) despite its theoretical appeal. Our results suggest that brown dwarfs primarily form at wide separations and undergo limited inward migration, challenging scenarios that invoke in-situ formation through core accretion processes at close orbital separations.

In this work, we search for empirical relationships for irregular dwarf galaxies using a collection of observational data published in the NASA and HyperLeda databases. Us- ing a complex statistical analysis, we calculated correlation coefficients between various physical parameters of irregular dwarf galaxies. We found strong correlations between mass and distance, apparent stellar magnitude and distance, mass and absolute mag- nitude, redshift, and mass for all types of irregular dwarf galaxies as well as for their individual types.

In the last decade, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the European Virgo observatory have opened a new observational window on the universe. These cavity-enhanced laser interferometers sense spacetime strain, generated by distant astrophysical events such as black hole mergers, to an RMS fluctuation of a few parts in $10^{21}$ over a multi-kilometer baseline. Optical advancements in laser wavefront control are key to advancing the sensitivity of current detectors and enabling a planned next-generation 40-km gravitational wave observatory in the United States, known as Cosmic Explorer. We report the first experimental demonstration of a new wavefront control technique for gravitational-wave detection, obtained from testing a full-scale prototype on a 40-kg LIGO mirror. Our results indicate that this design can meet the unique and challenging requirements of providing higher-order precision wavefront corrections at megawatt laser power levels, while introducing extremely low effective displacement noise into the interferometer. This new technology will have a direct and enabling impact on the observational science, expanding the gravitational-wave detection horizon to very early times in the universe, before the first stars formed, and enabling new tests of gravity, cosmology, and dense nuclear matter.

We present results from a systematic search for transiting short-period Giant Exoplanets around M-dwarf Stars (GEMS; $P < 10$ days, $R_p \gtrsim 8~R_\oplus$) within a distance-limited 100\,pc sample of 149,316 M-dwarfs using TESS-Gaia Light Curve (TGLC) data. This search led to the discovery of one new candidate GEM, following spectroscopic vetting of 12 additional candidates to eliminate astrophysical false positives and refine our occurrence rate estimates. We describe the development and application of the \texttt{TESS-miner} package and associated vetting procedures used in this analysis. To assess detection completeness, we conducted $\sim$ 72 million injection-recovery tests across $\sim$ 26,000 stars with an average of $\sim$3 sectors of data per star, subdivided into early-type (M0--M2.5), mid-type (M2.5--M4), and late-type (M4 or later) M-dwarfs. Our pipeline demonstrates high sensitivity across all M-dwarf subtypes within the injection bounds. We estimate the occurrence rates of short-period GEMS as a function of stellar mass, and combine our measured occurrence rates with those derived for FGK stars and fit an exponential trend with stellar mass, consistent with core-accretion theory predictions. We find GEMS occurrence rates of $0.067\% \pm 0.047\%$ for early-type M-dwarfs, $0.139\% \pm 0.069\%$ for mid-type, and $0.032\% \pm 0.032\%$ for late-type M-dwarfs, with a mean rate of $0.065^{+0.025}_{-0.027}\%$ across the full M-dwarf sample. We note that while our search spanned $1.0~\mathrm{days} < P < 10.0$ days, these occurrence rates were calculated using planets orbiting with $1.0~\mathrm{days} < P < 5.0$ days. This work lays the foundation for future occurrence rate investigations for GEMS.

Multiple photometric studies have reported the presence of seemingly older accreting pre-main sequence stars (PMS) in optical colour-magnitude diagrams (CMDs). We investigate this phenomenon in the Orion Nebula, which harbors a subset of stars that show infrared excess detected by Spitzer and Halpha excess emission, yet display significantly older isochronal ages (>10 Myr) compared to the bulk population (~1-3 Myr) in the r, (r-i) CMD. We perform a detailed spectroscopic analysis of 40 Orion Nebula stars using VLT/X-Shooter, covering CMD-based isochronal ages from 1 to over 30 Myr. We derive extinction values, stellar properties, and accretion parameters by modeling the ultraviolet excess emission through a multicomponent fitting procedure. The sample spans spectral types from M4.5 up to K6, and masses in the range ~0.1-0.8 Msun. We demonstrate that, when extinction and, most importantly, accretion effects are accurately constrained, the stellar luminosity and effective temperature of the majority of the seemingly old stars become consistent with a younger population (~1-5 Myr). This is supported by strong lithium absorption, which corroborates their youth, and by the accretion-to-stellar luminosity ratios typical for young, accreting stars. Three of these sources, however, remain old even after our analysis, despite showing signatures consistent with ongoing accretion from a protoplanetary disc. More generally, our analysis indicates that excess continuum emission from accretion shocks affects the placement of PMS stars in the CMD, displacing sources towards bluer optical colours. This study highlights the critical role of accretion in shaping the stellar properties estimates (including age) derived from optical CMDs and emphasizes the need to carefully account for accretion effects when interpreting age distributions in star-forming regions.

We present a comprehensive study of galaxy intrinsic alignment (IA) as a probe of parity-violating primordial non-Gaussianity (PNG). Within the effective field theory (EFT) framework, we show that the parity-odd IA power spectrum is sensitive to the collapsed limit of the parity-odd primordial trispectrum. For a $U(1)$-gauge inflationary model, the IA power spectrum is proportional to the power spectrum of the curvature perturbation, $P_\zeta(k) \propto k^{-3}$. However, the proportionality constants contain not only the PNG amplitude but also undetermined EFT bias parameters. We use $N$-body simulations to determine the bias parameters for dark matter halos. Using these bias parameters, we forecast IA's constraining power, assuming data from the Dark Energy Spectroscopic Instrument (DESI) and the Rubin Observatory Legacy Survey of Space and Time (LSST). We find that the IA power spectrum can improve the current limits on the amplitude of parity-violating PNG derived from galaxy four-point correlation and CMB trispectrum analyses. Moreover, galaxy shapes are complementary to these probes as they are sensitive to different scales and trispectrum configurations. Beyond galaxy shapes, we develop a new method to generate initial conditions for simulations and forward models from the parity-odd trispectrum with an enhanced collapsed limit.

We report on the prediscovery observations and constraints of the new interstellar comet 3I/2025 N1 (ATLAS), made by the Zwicky Transient Facility (ZTF), for the inbound leg of the comet out to a heliocentric distance of $r_\mathrm{h}=17$ au, or approximately a year before its discovery. We find that 3I/ATLAS has been active inward of a heliocentric distance of at least $r_\mathrm{h}=6.5$ au. The comet followed a brightening rate of $\propto r_\mathrm{h}^{-3.8}$, which is significantly steeper than the only other known interstellar comet 2I/Borisov, and is more consistent with dynamically old long-period comets and short-period comets in the Solar System. By measuring the brightening of the dust coma, we estimate that 3I had a dust production rate of $\dot{M_\mathrm{d}}\sim5 \mathrm{kg s^{-1}}$ in early May of 2025 ($r_\mathrm{h}\sim6$ au), increasing to $\dot{M_\mathrm{d}}\sim30 \mathrm{kg s^{-1}}$ towards mid-July 2025 ($r_\mathrm{h}\sim4$ au) assuming 100 micron dust grains, in line with the more recent Hubble Space Telescope measurement made at $r_\mathrm{h}=3.8$ au. Comparison with the prediscovery photometry by the Transiting Exoplanet Survey Satellite (TESS) suggested that 3I started producing constant dust outflow probably around $r_\mathrm{h}\sim9$ au, coinciding with the turn-on distance of CO$_2$ ice. We also conduct a deep search of 3I/ATLAS with multiple nights of data taken in 2024 when the comet was at $r_\mathrm{h}=13$-$17$ au and conclude that the comet was no brighter than 2-5 magnitudes above the coma or bare-nucleus lightcurves. This suggests that the comet did not exhibit strong outbursts during these periods, consistent with 2I/Borisov as well as most long-period Solar System comets.

The existence of abundant post-starburst/quiescent galaxies just $\sim$1-2 Gyrs after the Big Bang challenges our current paradigm of galaxy evolution. Cosmological simulations suggest that quasar feedback is likely the most promising mechanism responsible for such rapid quenching. Here we report a high detection rate (6/27) of exceptionally fast and powerful galaxy-scale outflows traced by [O III] emission in z $\sim$ 5-6 luminous quasars as revealed by the James Webb Space Telescope (JWST), with velocity up to $\sim$8400 km s$^{-1}$ and order-of-magnitude kinetic energy outflow rates up to $\sim$260% the observed quasar bolometric luminosities. This fraction is $\gtrsim$6.6 times larger than that in luminosity-matched comparison samples at z $\sim$ 1.5-3.5 (0/58) and z $<$ 1 (5/148). These extreme outflows are comparable to or even faster than the most rapid [O III] outflows reported at z $\lesssim$ 3, and could reach the circumgalactic medium (CGM) or even the intergalactic medium (IGM). The average kinetic energy outflow rate of our entire sample is $\sim$230$\times$ higher than that at cosmic noon. The substantially higher frequency of outflows with energetics well above the threshold for negative feedback in our sample strongly suggests that quasar feedback plays a significant role in efficiently quenching/regulating early massive galaxies.

We consider quantum decoherence and entropy increase in early universe cosmology. We first study decoherence in a discrete bipartite quantum system for which a single qubit gets entangled with an environment and the entropy increase is correlated with the decay of the off-diagonal terms of the reduced density matrix. We compare this system with continuous systems relevant for cosmology for which there is a natural external intervention, corresponding to the time-dependent separation between the sub- and super-horizon inflationary fluctuations. We find, in this case, that the off-diagonal terms of the density matrix, in a field basis, do not decay as sometimes assumed in cosmological set-ups. Nevertheless, following a recent treatment in terms of open Effective Field Theories (EFTs), we compute the entanglement entropy for a Gaussian state and show that it actually increases monotonically ($\dot S>0$) during the accelerated phases ($\ddot a>0$ with $a(t)$ the scale factor). We generalise this result to include non-Gaussian states and briefly discuss the relevance of computing the von Neumann entropy as compared to the thermodynamic entropy.

Geoengineering may offer a way to pause global warming, providing the time for more permanent solutions to become effective. Erection of a high-altitude hose offers an affordable and near-term approach to deliver sulfur-bearing fluids to the stratosphere in order to perform geoengineering via solar radiation management. We discuss the design of a hose extending to an altitude of 20 km and sized to deliver 100 ktons of sulfur per year. The sulfur, in the form of H$_2$S, is pushed up the hose by a pump on the ground and then sprayed out at the top, forming H$_2$SO$_4$ aerosols which scatter enough sunlight to perform geoengineering. Because the hose operates continuously, it only has to deliver about 50 gallons/minute (little more than a garden hose). The flux from a single hose is not sufficient to stop global warming by itself, but is enough to test the effect of the aerosols, and, once replicated to about 20 sites across the planet, can offset all the warming caused by atmospheric CO$_2$. Two varieties of hose are presented here, one delivering H$_2$S as a liquid and the other as a gas. Pumping liquid H$_2$S through a narrow 20 km hose requires high pressure, which can be handled by strong and lightweight hose walls or by placing intermediate pumps along the hose. The hose is held up by a suite of balloons, either all at its top, or with some placed along its length as well. The greatest challenge in suspending such a hose is wind, which if not dealt with properly (by streamlining both the balloons and the hose) will collapse the hose. The wide hoses needed to deliver gaseous H$_2$S are particularly susceptible to wind, so must be enclosed within lightweight aero-shrouds to reduce wind forces. After treating the design of these two hoses, we lay out the steps needed to develop and fabricate them, and conclude with some thoughts on how the hoses might be fielded.

We examine the status of benchmark simplified dark matter models that have been proposed to explain the GeV gamma-ray Galactic Center excess. We constrain the available parameter space using updated observations from indirect detection, cosmology, direct detection, and accelerators. We show that there is still unconstrained parameter space in both classes of models we consider (a secluded dark sector with a vector portal coupling, and a two-Higgs doublet with a pseudoscalar mediator), and discuss the prospects for potential improvement of these constraints in future experiments.

The gravitational-wave signal GW250114 was observed by the two LIGO detectors with a network matched-filter signal-to-noise ratio of 80. The signal was emitted by the coalescence of two black holes with near-equal masses $m_1 = 33.6^{+1.2}_{-0.8}\,M_\odot$ and $m_2 = 32.2^{+0.8}_{-1.3}\,M_\odot$, and small spins $\chi_{1,2} \leq 0.26$ (90% credibility) and negligible eccentricity $e \leq 0.03$. Post-merger data excluding the peak region are consistent with the dominant quadrupolar $(\ell = |m| = 2)$ mode of a Kerr black hole and its first overtone. We constrain the modes' frequencies to $\pm 30\%$ of the Kerr spectrum, providing a test of the remnant's Kerr nature. We also examine Hawking's area law, also known as the second law of black hole mechanics, which states that the total area of the black hole event horizons cannot decrease with time. A range of analyses that exclude up to 5 of the strongest merger cycles confirm that the remnant area is larger than the sum of the initial areas to high credibility.

In the study presented here, we model the gas phase chemistry induced by plasma discharge at low temperature (150 K) in the NASA Ames COSmIC Simulation Chamber (COSmIC) using a 1-dimensional multi-fluid plasma model named CO-PRISM (COSmIC Plasma Reactivity and Ionization Simulation Model). Our model incorporates an extensive chemical reaction network to simulate the neutral-neutral and ion-neutral reactions occurring in the COSmIC experiments when using N2-CH4-based gas mixtures relevant to Titan's atmosphere. Our reaction network now includes crucial reactions involving the first electronically-excited state of atomic nitrogen, recent electron collision cross-sections, and radical chemistry. In particular, we have investigated the influence of C2H2 on the gas phase polymeric growth and the elemental composition of the chemical products, and we have compared our findings to recently published solid phase analyses. The modeling results are consistent with experimental measurements of N2-CH4-C2H2 plasmas on COSmIC, showing the production of C6Hx intermediates and precursors of larger organics, as well as methanimine in small concentration. Our numerical results point to cationic pathways enabling efficient intermediate-sized and nitrogen-rich \ce{C2H2}-driven chemistry driving tholin production. Comparison of the modeled gas phase elemental composition with elemental composition of the solid phase samples produced in COSmIC reveal similar trends, with C/N increasing when C2H2 is present in the gas mixture. Finally, our results demonstrate the importance of such synergistic studies using low-temperature plasma chemistry experiments combined with modeling efforts to improve our understanding of cold planetary environments.

The binary black hole signal GW250114, the loudest gravitational wave detected to date, offers a unique opportunity to test Einstein's general relativity (GR) in the high-velocity, strong-gravity regime and probe whether the remnant conforms to the Kerr metric. Upon perturbation, black holes emit a spectrum of damped sinusoids with specific, complex frequencies. Our analysis of the post-merger signal shows that at least two quasi-normal modes are required to explain the data, with the most damped remaining statistically significant for about one cycle. We probe the remnant's Kerr nature by constraining the spectroscopic pattern of the dominant quadrupolar ($\ell = m = 2$) mode and its first overtone to match the Kerr prediction to tens of percent at multiple post-peak times. The measured mode amplitudes and phases agree with a numerical-relativity simulation having parameters close to GW250114. By fitting a parameterized waveform that incorporates the full inspiral-merger-ringdown sequence, we constrain the fundamental $(\ell=m=4)$ mode to tens of percent and bound the quadrupolar frequency to within a few percent of the GR prediction. We perform a suite of tests -- spanning inspiral, merger, and ringdown -- finding constraints that are comparable to, and in some cases 2-3 times more stringent than those obtained by combining dozens of events in the fourth Gravitational-Wave Transient Catalog. These results constitute the most stringent single-event verification of GR and the Kerr nature of black holes to date, and outline the power of black-hole spectroscopy for future gravitational-wave observations.

We propose a scenario to produce large primordial lepton flavor asymmetries with vanishing total lepton asymmetry, based on the Affleck-Dine mechanism with Q-ball formation. This scenario can produce large lepton flavor asymmetries while automatically maintaining the vanishing total lepton number without fine-tuning, evading the current BBN and the CMB constraints by neutrino oscillations at MeV temperature. The asymmetries can be produced at cosmic temperatures of $T\gtrsim 1\ {\rm GeV}$, early enough to have broad impacts from the early Universe to the present cosmology. This scenario could affect various aspects of early Universe cosmology simultaneously or separately: (i) explaining the observed baryon asymmetry by the same origin as the lepton flavor asymmetries, (ii) affecting the nature of the QCD transition, (iii) opening up a new parameter space of sterile neutrino dark matter by enhancing their production, and (iv) altering the abundance of the light elements, in particular, resolving the recently reported helium-4 anomaly.

We propose a new strategy to probe non-tensorial polarizations in the stochastic gravitational-wave (GW) background. Averaging over polarization angles, we find that three-point correlations of the GW signal vanish for tensor and vector modes, while scalar modes generically leave a nonzero imprint. This property makes the GW bispectrum a distinctive and robust diagnostic of scalar polarizations predicted in theories beyond General Relativity. We derive the corresponding response functions for ground-based interferometers, pulsar timing arrays, and astrometric observables, and we construct an optimal estimator together with simple Fisher forecasts for pulsar-timing sensitivity. As a proof of principle, we show that second-order GWs sourced by primordial magnetogenesis can be characterized by large three-point functions. Our results demonstrate that GW three-point correlations provide a novel observational window on physics beyond General Relativity.

We examine the red-shift emission from special orbits (horizons replicas) where photons have the same angular velocity, in magnitude, as those of the Kerr black hole (BH) Killing horizons. We focus on two particular contexts of special significance for their observational implications. A set of these orbits is located in the BH photons shell. Therefore the analysis also connects the red-shifting or blue-shifting from replicas (defined through the BH light surfaces) to the BH shadow boundaries. We then concentrate on the equatorial, general relativistic, axially symmetric accretion disks, orbiting around the central attractor. In the analysis we adopted in particular the Polish doughnut models of geometrically thick toroids, to investigate the signals frequency-shifting from the horizons replica as related to the disks surface, inner edge and accretion flows. The findings map the red-shifting and blue-shifting regions of the signals in dependence to the photons impact parameter, view-angle, angular velocity of the emitter and BH spin. Co-rotating and counter-rotating replica could be identified through the red-shifting or blue-shifting of the emitted signals from the mapped regions.

This work evaluates the ability of a water Cherenkov detector to measure thermal neutrons and explores its application to soil-moisture monitoring. We study a NaCl-doped detector and model its response to (i) monochromatic thermal neutrons and (ii) the natural thermal-neutron flux expected from dry soil at the elevation of Bucaramanga, Colombia. The ambient flux is estimated with the ARTI framework, and the detector response is simulated with MEIGA in Geant4. Doping with NaCl introduces additional capture channels on $^{35,37}\mathrm{Cl}$ and $^{23}\mathrm{Na}$; in particular, $^{35}\mathrm{Cl}$ has a thermal-neutron absorption cross section up to two orders of magnitude larger than hydrogen, boosting the capture signal. Our results indicate that water Cherenkov detectors can detect thermal neutrons with practical sensitivity under field conditions, enabling their integration into precision agriculture networks for soil moisture sensing. More broadly, this approach extends the cosmic-ray detection range of Cherenkov detectors using non-toxic, low-cost materials.

We consider the motion of a particle in the geometry of a Schwarzschild-like black hole embedded in a dark matter (DM) halo with Dehnen type density profile and calculate the orbital periods along with the evolution of the semi-latus rectum and eccentricity for extreme mass ratio inspirals (EMRIs). Such a system emits gravitational waves (GWs), and the particle's orbit evolves under radiation reaction. We also consider the effects of dynamical friction and accretion of DM on the orbital parameters. We find that the eccentricity and semi-latus rectum decrease faster with respect to the case in which EMRI is in empty spacetime.

The properties of a remnant black hole can be probed by analyzing the gravitational waves emitted during its ringdown phase. This signal provides a direct test of general relativity in the strong-field regime. In this study, we apply a time-domain F-statistic framework to the ringdown of GW231028_153006 and find decisive evidence for the presence of the first overtone mode in the signal. The detection of the $\ell|m|n=221$ mode is statistically significant, achieving a Bayes factor of $193$ for an analysis beginning at $10\,M$ after the signal's peak amplitude--a time consistent with the linear perturbation regime. The inclusion of both the fundamental and overtone modes in our model allows for precise constraints on the remnant's properties. We infer a redshifted final mass of $243.0^{+22.7}_{-22.7}\,M_{\odot}$ and a final spin of $0.80_{-0.11}^{+0.07}$ (at $90\%$ credibility), derived from a ringdown signal with a network signal-to-noise ratio of approximately $10.5$. A test of the no-hair theorem, enabled by this two-mode detection, shows consistency with the predictions of general relativity.

We introduce a fast method to measure the conversion gain in Complementary Metal-Oxide-Semiconductors (CMOS) Active Pixel Sensors (APS), which accounts for nonlinearity and interpixel capacitance (IPC). The standard 'mean-variance' method is biased because it assumes pixel values depend linearly on signal, and existing methods to correct for nonlinearity are still introducing significant biases. While current IPC correction methods are prohibitively slow for a per-pixel application, our new method uses separate measurements of the IPC kernel to make an almost instantaneous calculation of gain. Validated using test data from a flight detector from the ESA Euclid mission, the IPC correction recovers the results of slower methods within 0.1% accuracy. Meanwhile the nonlinearity correction ensures an estimation of the gain that is independent of signal, correcting a bias of more than 2.5% on gain estimation.