We evaluate uncertainty calculations in the calstis pipeline for data in the low-count regime. Due to the low dark rate and read-noise free nature of MAMA detectors, observations of UV-dim sources can result in exposures with 0 or 1 counts in some pixels. In this regime, the "root-N" approximation widely used to calculate uncertainties breaks down, and one must compute Poisson confidence intervals for more accurate uncertainty calculations. The CalCOS pipeline was updated in 2020 to account for these low-count uncertainties. Here, we assess how STIS observations are currently affected by this phenomenon, describe a new Jupyter notebook exploring the issue, and introduce a new utility, stistools.poisson_err, to manually calculate Poisson confidence intervals for 1D STIS spectra. Additionally, we describe a related software bug in the stistools$.$inttag utility, which splits TIME-TAG data into sub-exposures. This newly fixed bug serves as a useful case-study for the proper use of Poisson confidence intervals.

Context. The internal structure of the intracluster medium (ICM) is tightly linked to the assembly history and physical processes in groups and clusters, but the role of recent accretion in shaping these profiles has not been fully explored. Aims. We investigate to what extent mass accretion accounts for the variability in ICM density and thermodynamic profiles, and what can present-day structures reveal about their formation histories. Methods. We analyze a hydrodynamical cosmological simulation including gas cooling but no feedback, to isolate the effects of heating from structure formation. Median profiles of ICM quantities are introduced as a robust description of the bulk ICM. We then examine correlations between mass accretion rates or assembly indicators with the profiles of temperature, entropy, pressure, gas and dark-matter density, as well as their scatter. Results. Accretion in the last dynamical time strongly lowers central gas densities, while leaving dark matter largely unaffected, producing a distinct signature in the baryon depletion function. Pressure and entropy show the clearest dependence on accretion, whereas temperature is less sensitive. The radii of steepest entropy, temperature, and pressure shift inward by $\sim (10-20)\%$ between high- and low-accretion subsamples. Assembly-state indicators are also related to the location of these features, and accretion correlates with the parameters of common fitting functions for density, pressure, and entropy. Conclusions. Recent accretion leaves measurable imprints on the ICM structure, highlighting the potential of thermodynamic profiles as diagnostics of cluster growth history.

The magnetar Swift J1555.2-5402 was discovered in outburst on 2021 June 3 by the Burst Alert Telescope on board the Swift satellite. Early X-ray follow-up revealed a spin period P~3.86 s, a period derivative Pdot~3e-11 s/s, dozens of short bursts, and an unusually flux decline. We report here on the X-ray monitoring of Swift J1555.2-5402 over the first ~29 months of its outburst with Swift, NICER, NuSTAR, INTEGRAL and Insight-HXMT, as well as radio observations with Parkes soon after the outburst onset. The observed 0.3-10 keV flux remained at levels >~1e-11 erg/cm^2/s for nearly 500 days before dropping by a factor of ~10 from its June 2021 peak towards the end of the monitoring campaign. During this time span, the spectrum was dominated by a single blackbody, with temperature attaining approximately a constant value (~1.2 keV) while the inferred radius shrank from ~1.7 km to ~0.3 km (assuming a source distance of 10 kpc). The long-term spin-down rate (Pdot~3.6e-11 s/s) is only ~15 % higher than that measured in the first 30 days. No periodic or burst-like radio emission was detected, in line with what has been previously reported using different radio facilities. The persistently high temperature, shrinking hotspot, and a prolonged bright flux plateau followed by a fast dimming observed during the outburst evolution pose a challenge for the outburst mechanisms proposed so far.

The Milky Way nuclear star cluster (MWNSC) is located together with its surrounding nuclear stellar disc (MWNSD) in the Galactic centre and they dominate the gravitational potential within the inner 300\,pc. However, the formation and evolution of both systems and their possible connections are still under debate. We reanalyse the low-resolution KMOS spectra in the MWNSC with the aim to improve the stellar parameters ($\rm T_{eff}$, $\rm \log\,g$, and $\rm [M/H])$ for the MWNSC. We use an improved line-list, especially dedicated for cool M giants allowing to improve the stellar parameters and to obtain in addition global $\rm α$-elements. A comparison with high-resolution IR spectra (IGRINS) gives very satisfactory results pinning down the uncertainties to $\rm T_{eff} \simeq 150\,K$, $\rm log\,g \simeq 0.4\,dex$, and $\rm [M/H] \simeq 0.2\,dex$. Our $\rm α$-elements agree within 0.1\,dex compared to the IGRINS spectra. We obtain a high-quality sample of 1140 M giant stars where we see an important contribution of a metal-poor population ($\rm \sim 20\,\%$) centered at $\rm [M/H] \simeq -0.7\,dex$ while the most dominant part comes from the metal-rich population with $\rm [M/H] \simeq 0.26\,dex$. We construct a metallicity map and find a metallicity gradient of $\rm \sim -0.1 \pm 0.02 \,dex/pc$ favouring the inside-out formation scenario for the MWNSC.

The heavy element content of giant exoplanets, inferred from structure models based on their radius and mass, often exceeds predictions based on classical core accretion. Pebble drift, coupled with volatile evaporation, has been proposed as a possible remedy to this with the level of heavy element enrichment a planet can accrete, as well as its atmospheric composition, being strongly dependent on where in the disc it is forming. We use a planet formation model which simulates the evolution of the protoplanetary disc, accounting for pebble growth, drift and evaporation, and the formation of planets from pebble and gas accretion. The growth and migration of planetary embryos is simulated in 10 different protoplanetary discs which have their chemical compositions matched to the host stars of the planets which we aim to reproduce, providing a more realistic model of their growth than previous studies. The heavy element content of giant exoplanets is used to infer their formation location and thus make a prediction of their atmospheric abundances. We focus here on giants more massive than Saturn, as we expect that their heavy element content is dominated by their envelope rather than their core. The heavy element content of 9 out of the 10 planets simulated is successfully matched to their observed values. Our simulations predict formation in the inner disc regions, where the majority of the volatiles have already evaporated and can thus be accreted onto the planet via the gas. As the majority of the planetary heavy element content originates from water vapour accretion, our simulations predict a high atmospheric O/H ratio in combination with a low atmospheric C/O ratio, in general agreement with observations. For certain planets, namely WASP-84b, these properties may be observable in the near future, offering a method of testing the constraints made on the planet's formation.

Understanding the alignment between AGN jets and their host galaxies is crucial for interpreting AGN unification models, jet feedback processes, and the co-evolution of galaxies and their central black holes (BH). In this study, we use the high-resolution cosmological zoom-in simulation NewHorizon, which self-consistently evolves BH mass and spin, to statistically examine the relationship between AGN jet orientation and host galaxy structure. Building upon our previous work, we extend the analysis of projected (2-d) alignment angles to facilitate more direct comparisons with recent observational studies. In our methodology, galaxy orientations are estimated using optical position angles derived from synthetic DESI-LS and Euclid images, while BH spin vectors serve as proxies for AGN jet directions. From a carefully selected sample of 100 BH-galaxy systems at low redshift, we generate a catalog of 5,000 mock optical images using a Monte Carlo approach that samples random viewing angles and redshifts. Our results reveal a statistically significant tendency for AGN jets to align with the orientation of their host galaxies, consistent with recent observations combining Very Long Baseline Interferometry (VLBI) and optical imaging of nearby AGNs. Furthermore, we find a slightly stronger alignment when using kinematic position angles derived from synthetic MaNGA-like stellar velocity fields. These findings underscore the importance of combining morphological, kinematic, and polarimetric information to disentangle the complex interplay between black hole spin evolution, accretion mode, and the galactic environment in shaping the direction of relativistic jets.

We present JWST/NIRCam imaging of dusty star-forming galaxies (DSFGs) detected by Atacama Large Millimeter/submillimeter Array (ALMA) in the Spiderweb protocluster at $z=2.16$. We identify 22 DSFGs detected by both ALMA and JWST, 10 of which are spectroscopically confirmed as protocluster members. This is the first systematic analysis of a statistical DSFG sample in $z\sim2$ protocluster environments using JWST/NIRCam data. Most of the DSFG members exhibit very red colors and reside in the dusty star-forming region of the rest-frame UVJ diagram, indicating strong dust obscuration. The Gini-M20 diagram suggests that most DSFGs in this protocluster are late-type disks, with a significant fraction displaying clumpy and disturbed rest-frame UV/optical morphologies, but few showing clear merger signatures. The DSFG members exhibit relatively large stellar disks and effective radii with a median stellar mass of log(M/Msun) = 10.8 +/- 0.3, placing them above coeval field DSFGs and typical protocluster galaxies in the size-mass relation at both rest-frame optical and near-infrared wavelengths. These sizes are comparable to those of more evolved field DSFGs at z~1-2, indicating accelerated structural growth in dense environments. Moreover, these DSFG members show a decreasing trend in stellar size from shorter to longer wavelengths, with a moderately steep slope comparable to coeval field DSFGs. These results may support an inside-out growth scenario for protocluster evolution, in which massive galaxies near the center are more evolved and more strongly affected by AGN feedback and environmental effects, e.g., ram-pressure stripping. We propose that the cold gas accretion at the protocluster outskirts drives intense star formation and stellar disk growth in ALMA-detected DSFGs, which are expected to evolve into massive elliptical galaxies at later stages.

Recent intensive monitoring campaigns of active galactic nuclei (AGN) have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations reveal a strong correlation between the UV and optical variability, but a weaker correlation between the X-ray and UV bands, challenging the standard X-ray reprocessing scenario. We revisit the X-ray/UV connection in NGC 5548 by fitting archival 2014 HST and Swift/XRT light curves assuming X-ray reverberation from a dynamically evolving X-ray corona. Our results show that, as long as the corona height, photon index and power vary over time, X-ray reverberation can explain the observed UV and optical variability within 2% and 5%, respectively (on average). The evolution of the best-fit parameters suggests that fast changes in coronal geometry and energetics on a time scale of days are required to explain the observed variability.

We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES$^+$ so as to provide the most constrained results possible at high resolution. We removed telluric and stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-correlation technique. Following standard procedures for undetected species, we performed injection recovery tests and Bayesian retrievals to place constraints on the detectability of the main near-infrared absorbers. In addition, we simulated ELT/ANDES observations by computing end-to-end in silico datasets with EXoPLORE. No molecular signals were detected in the atmosphere of GJ 436 b, which is consistent with previous studies. Combined CARMENES-CRIRES$^+$ injection-recovery and Bayesian retrieval analyses show that the atmosphere is likely covered by high-altitude clouds ($\sim$ $1$ mbar) at low and intermediate metallicities or, alternatively, is very metal-rich ($\gtrsim$ $900\times$ solar), which would suppress spectral features without invoking clouds. Simulations of ELT/ANDES observations suggest a boost by nearly an order of magnitude to the upper limit in the photon-limited regime, reaching $0.1$ mbar at $10$-$300\times$ solar metallicities. The joint analysis of all useful transit observations from CARMENES and CRIRES$^+$ provides the most stringent constraints to date on the atmospheric properties of GJ 436 b. Complementary CCF-based and retrieval approaches consistently indicate that the atmosphere is either cloudy or highly metal enriched. Any weak near-infrared absorption lines, if present, are likely to be below current detection limits. However, according to our simulations, these features may be revealed with ELT/ANDES even in single-transit observations.

AM Canum Venaticorum (AM CVn) stars are ultra-compact binary systems composed of a white dwarf (WD) primary accreting from a H-deficient donor. They are important as potential progenitors of Type Ia supernovae and laboratories for gravitational-wave studies, yet their evolutionary history remains unsolved. Three formation channels have been proposed: the WD channel, the He-star channel, and the cataclysmic variable (CV) channel. We aim to provide the first accurate measurements of the fundamental parameters of the accretor in ZTFJ225237.05-051917.4, including the abundances of key elements such as C, N, and Si, by analysing UV spectra obtained with the Hubble Space Telescope. These measurements provide new insight into the system's evolutionary history and establish it as a benchmark to develop our pipeline for application to a larger sample of AM CVns. We determine the binary parameters from photometric modelling and constrain the atmospheric parameters of the WD accretor, including Teff, logg, and chemical abundances, by fitting the UV spectrum with synthetic spectral models. We then infer the system's formation channel by comparing our results with theoretical evolutionary models. We measure a Teff=23300$\pm$600K and a surface gravity of logg=8.4$\pm$0.3, which implies an accretor mass of 0.86$\pm$0.16 solar masses. We find a high N/C abundance ratio by mass of >153. The accretor is significantly hotter than previous estimates based on simplified blackbody fits to the spectral energy distribution, underscoring the importance of detailed spectral modelling for determining accurate system parameters. Our results show that UV spectroscopy is well-suited to constraining the formation channels of AM CVn systems. We conclude that the He-star channel can be excluded based on the high N/C ratio, while the WD and CV channels remain consistent with the observations.

We analyzed archival Herschel observations of water vapor emission toward the Horsehead photon dominated region (PDR), along with supporting ground-based and airborne observations of CO isotopologues and fine structure lines of ionized and atomic carbon to determine the distribution and abundance of water vapor in this low-UV illumination PDR. Water emission in the Horsehead nebula is very weak and, surprisingly, extends outward beyond other PDR tracers such as $^{12}$CO or [CI] 609 $μ$m, reaching as far out as [CII] 158 $μ$m. We model the observations using a newly developed PDR wrapper that takes into account the geometry of this region. PDR modeling of the molecular and atomic lines studied here provides strong constraints on the thermal pressure, but not on the UV illumination. Maximum model line intensities %typically agree to within ~40\% with the observations. and spatial profiles are well reproduced, except for CO isotopologues, where the increase on the illuminated side of the PDR is steeper than observed. Water vapor abundance in the model reaches $3.6 \times 10^{-7}$ at $A_V \sim 3$ mag. However, the ground state $o$-H$_2$O 557 GHz line is systematically overestimated by the models by at least a factor of 7 for any values of the model parameters. This line has a very high optical depth and the emergent line intensity is sensitive to radiative transfer effects such as line scattering by water molecules in a low-density halo surrounding the dense PDR and the assumed microturbulent line width. A more accurate model of the water surface chemistry is required.

Interchange reconnection is believed to play a significant role in the production of solar jets and solar wind. However, the dynamics of interchange reconnection in the low corona might be more complex than recognized before in higher temporal and spatial resolutions. Using unprecedentedly high-resolution observations from the Extreme Ultraviolet Imager (EUI) onboard the Solar Orbiter, we analyze the dynamics of interchange reconnection in a small-scale fan-spine-like topology. Interchange reconnection that continuously occurs around the multi-null points of the fan-spine-like system exhibits a quasi-periodicity of ~200 s, nearly covering the entire evolution of this system. Continuous evolution and reversal of multiple current sheets are observed over time near the null point. These results reveal that the dynamics of interchange reconnection are likely modulated by the emerging magnetic structures, such as mini-filaments and emerging arcades. Moreover, a curtain-like feature with a width of 1.7 Mm is also observed near the interchange reconnection region and persistently generates outflows, which is similar to the separatrix curtain reported in the pseudo-streamer structure. This study not only demonstrates the complex and variable reconnection dynamics of interchange reconnection within small-scale fan-spine topology but also provides insights into the self-similarity of magnetic field configurations across multiple temporal and spatial scales.

Context: The VISTA Variables in the Via Lactea (VVV) and its extension (VVVX) are near-infrared surveys mapping the Galactic bulge and adjacent disk. These data have enabled the discovery of numerous star clusters obscured by high and spatially variable extinction. Most previous searches relied on visual inspection of individual tiles, which is inefficient and biased against faint or low-density systems. Aims: We aim to develop an automated, homogeneous algorithm for systematic cluster detection across different surveys. Here, we apply our method to VVVX data covering low-latitude regions of the Galactic bulge and disk, affected by extinction and crowding. Methods: We introduce the Consensus-based Algorithm for Nonparametric Detection of Star Clusters (CANDiSC), which integrates kernel density estimation, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN), and nearest-neighbour density estimation within a consensus framework. A stellar overdensity is classified as a candidate if identified by at least two of these methods. We apply CANDiSC to 680 tiles in the VVVX PSF photometric catalogue, covering approximately 1100 square degrees. Results: We detect 163 stellar overdensities, of which 118 are known clusters. Cross-matching with recent catalogues yields five additional matches, leaving 40 likely new candidates absent from existing compilations. The estimated false-positive rate is below 5 percent. Conclusions: CANDiSC offers a robust and scalable approach for detecting stellar clusters in deep near-infrared surveys, successfully recovering known systems and revealing new candidates in the obscured and crowded regions of the Galactic plane.

Shock types of low-velocity molecular outflows are not always well constrained. Astrochemical comparisons are often made between low-velocity and high-velocity outflows, but without considering the question of the shock type. We investigated molecular abundances of post-shock regions to determine whether strong differences between non-irradiated C-type and J-type shocks can be highlighted. One of the main application goals is to diagnose the shock type of the protostellar object L1157 B2 through the use of molecular tracers. We simulated grid sets of shock models with the Paris-Durham Shock code with velocities ranging from 5 to 19 km/s and low densities from $10^2$ to $10^5$ cm$^{-3}$. We computed the desorption percentage of methanol in these simulations and estimated it at higher velocities. We compared our results to observational measurements of L1157 B2 and with a benchmark of four already identified shocks. L1157 B2 has been diagnosed as a non-irradiated C-type shock, and the method showed a good applicability through the benchmark. Methanol formed in the icy mantle of grains can serve to trace the differences between shock types, at least in non-irradiated conditions. A requirement for the applicability of a species as a shock-type tracer is that it does not undergo significant enhancement or destruction, but is mainly impacted by desorption processes under shocked conditions. The desorption percentage of methanol is a good criterion in characterizing the shock type of L1157 B2 and should be investigated as a general method to diagnose the shock type in non-irradiated regions. We identify L1157 B2 as a non-irradiated C-type shock with velocities and densities fitting with previous studies.

Context: Globular clusters (GCs) around the Milky Way (MW) are expected to host white dwarf (WD) binaries emitting gravitational waves that could be detectable by LISA. Aims: Our aim is to investigate whether LISA can resolve WD binaries in GCs well enough in terms of sky location and distance that they can be distinguished from binaries in the MW disc. Methods: We used a sample of 20 of the most massive GCs around the MW and simulated LISA's sky location and distance measurement errors for WD binaries in these GCs using the software package GWToolbox. We did this in the context of a model of the LISA-detectable binaries in the MW from the population synthesis code SeBa. Results: We find that for five of the GCs in our sample, binaries in the GC could be easily distinguished from MW disc binaries using the sky location alone; for another five, binaries in the GCs could be distinguished using a combination of LISA's sky location and distance measurements; and for the final ten, binaries in the GCs could not be distinguished from overlapping MW disc binaries. The results depend strongly on the sky locations of the GCs, with GCs far away from the Galactic plane being easy to resolve, while GCs close to the Galactic centre overlap with many MW disc binaries. The most promising GC for finding a WD binary that could be resolved to that GC, based on sky location and GC mass, is 47 Tucanae.

The enrichment history of galaxy clusters and groups remains far from being fully understood. Recent measurements in massive clusters have revealed remarkably flat iron abundance profiles out to the outskirts, suggesting that similar enrichment processes have occurred for all systems. In contrast, abundance profiles in galaxy groups have sometimes been measured to decline with radius, challenging our understanding of the physical processes at these scales. In this paper, we present a pilot study aimed at accurately measuring the iron abundance profiles of MKW3s, A2589, and Hydra A, three poor clusters with total masses of $M_{500} \simeq 2.0-2.5 \times 10^{14}$ M$_\odot$, intermediate between the scales of galaxy groups and massive clusters. Using XMM-Newton to obtain nearly complete azimuthal coverage of the outer regions of these systems, we show that abundance measurements in the outskirts are more likely to be limited by systematics than by statistical errors. In particular, inaccurate modelling of the soft X-ray background can significantly bias metallicity estimates in regions where the cluster emission is faint. Once these systematics are properly accounted for, the abundance profiles of all three clusters appear to be flat at $Z \sim 0.3$ Z$_{\odot}$, in agreement with values observed in massive clusters. Using available stellar mass estimates, we also computed their iron yields, thereby beginning to probe a largely unexplored mass range. We find $Y_{Fe,500} = 2.68\pm0.34$, $2.54\pm0.64$, and $7.51\pm1.47$ Z$_{\odot}$ for MKW3s, A2589, and Hydra A, respectively, spanning the transition regime between galaxy groups and massive clusters. Future observations of systems with temperatures of $2-4$ keV will be essential to further populate this intermediate-mass regime and to draw firmer conclusions on the chemical enrichment history of galaxy systems across the full mass scale.

Compared to the well-studied infrared and radio domains, galaxy emission in the millimeter (mm) - centimeter (cm) range has been less observed. In this domain, galaxy emission consists of thermal dust, free-free and synchrotron emissions with a possible additional contribution from anomalous microwave emission (AME) peaking near 1 cm.The aim of this study is to accurately characterize the integrated spectral energy distribution (SED) of galaxies in the mm-cm range. We used COBE-DIRBE, IRAS, Planck, and WMAP all-sky surveys, brought to the same resolution of $1^\circ$, to cover 18 photometric bands from 97$μ$m to 1.3 cm. Given the low angular resolution and mixing with foreground and background emission that hampers the detection of the galaxy, our sample consists of 6 of the brightest, nearby galaxies: LMC, SMC, M31, M33, NGC 253 and NGC 4945. We subtract Milky Way dust emission, distant unresolved galaxies, and foreground point sources in the fields. We fit each integrated SED with a model of thermal dust, free-free, synchrotron, AME and Cosmic Microwave Background (CMB) temperature fluctuations. The integrated SEDs of our sample of galaxies are well fitted by the model within the uncertainties, although degeneracies between the different components contributing to the mm-cm emission complicate the estimation of their individual contributions. We do not clearly detect AME in any of our target galaxies, and AME emissivity upper limits are weak compared to Galactic standards, suggesting that the signal of AME might be diluted at the scale of a whole galaxy. We infer positive CMB fluctuations in the background of 5 out of our 6 galaxies. This effect might be related to the degeneracy between the dust emissivity index and CMB fluctuations in the background, or linked to the specific spatial distribution of CMB fluctuations coupled with the low resolution and small number statistics.

KK 153 is a star-forming dwarf galaxy that has been recently proposed as a new member of the sparsely populated class of gas-rich ultra faint dwarfs, lying in the outskirts of the Local Group. We used the Large Binocular Telescope under sub-arcsec seeing conditions to resolve for the first time the outer regions of KK 153 into individual stars, reaching the red giant branch. The magnitude of the red giant branch tip was used to measure a distance of D=3.06 (+0.17/-0.14) Mpc, much more accurate and precise than the estimate previously available in the literature, based on the baryonic Tully-Fisher relation (D=2.0 (+1.7/-0.8) Mpc). The new distance places KK 153 clearly beyond the boundaries of the Local Group, and, together with a new measure of the integrated magnitude, implies a stellar mass of M_*=2.4 \pm 0.2 X 10^6 M_{\sun}. The dwarf populates the extreme low-mass tail of the M_* distribution of gas-rich galaxies but it is significantly more massive than the faintest local gas-rich dwarfs, Leo T and Leo P. In analogy with similar systems, the star formation history of KK 153 may have been impacted by the re-ionisation of the Universe while keeping a sufficient gas reservoir to form new stars several Gyr later.

Variability is a striking features of quasars, observed at all timescales wavelengths. Studying its properties and the correlations with the physical parameters (e.g. black hole mass and accretion rate) provides significant insights into accretion physics. However, the detailed picture and the exact interplay between different emitting regions are not yet clear. We combine data from Sloan Digital Sky Survey (SDSS), the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1, PS1), the Zwicky Transient Facility (ZTF), and the Gaia space telescope to constrain the power spectrum of quasars in the Stripe-82 region over a broad frequency range, 10^{-1} to 10^{-3} day^{-1}(rest frame). Light curves are matched and cross-calibrated to reach \sim 20 years in the r-band for 4037 quasars. We split the sample into bins of the same black hole mass, accretion rate, and redshift, and measure the ensemble power spectral density (PSD) in each bin. The power spectra of SDSS, ZTF, and Gaia are measured independently. We do not measure it on PS1 data due to more erratic cadence, but we discuss the use of interpolation techniques, eventually allowing us to use the data together. We find significant evidence that the long-term UV/optical variability of quasars is stationary, as the ensemble PSD estimates from SDSS, Gaia and ZTF are consistent within the errors despite coming from different surveys and years. The PSD shape is consistent with a bending power law with spectral indices of -2.7 and -1 at high and low frequencies. A fit with the PSD associated with a damped random walk is significantly worse. The PSD amplitude below the break does not depend on black hole mass, but there is some evidence for anti-correlation with the accretion rate. The bending frequency, instead, scales with the black hole mass as $ν_b$ \propto M_{\mathrm{BH}}^{-0.6\pm0.1} and does not depend on the accretion rate.

Blind source separation (BSS) plays a pivotal role in modern astrophysics by enabling the extraction of scientifically meaningful signals from multi-frequency observations. Traditional BSS methods, such as those relying on fixed wavelet dictionaries, enforce sparsity during component separation, but may fall short when faced with the inherent complexity of real astrophysical signals. In this work, we introduce the Learnlet Component Separator (LCS), a novel BSS framework that bridges classical sparsity-based techniques with modern deep learning. LCS utilizes the Learnlet transform: a structured convolutional neural network designed to serve as a learned, wavelet-like multiscale representation. This hybrid design preserves the interpretability and sparsity, promoting properties of wavelets while gaining the adaptability and expressiveness of learned models. The LCS algorithm integrates this learned sparse representation into an iterative source separation process, enabling effective decomposition of multi-channel observations. While conceptually inspired by sparse BSS methods, LCS introduces a learned representation layer that significantly departs from classical fixed-basis assumptions. We evaluate LCS on both synthetic and real datasets, demonstrating superior separation performance compared to state-of-the-art methods (average gain of about 5 dB on toy model examples). Our results highlight the potential of hybrid approaches that combine signal processing priors with deep learning to address the challenges of next-generation cosmological experiments.

Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ~4 days, defining the so-called Neptune desert region. Therefore, the detection of each individual planet in this region holds a high value, providing detailed insights into how such a population came to form and evolve. Here we report the detection of TOI-333b, a Neptune desert planet with a mass, radius, and bulk density of 20.1 $\pm$ 2.4 M$_{\oplus}$, 4.26 $\pm$ 0.11 R$_{\oplus}$, and 1.42 $\pm$ 0.21 \gccc, respectively. The planet orbits a F7V star every 3.78 d, whose mass, radius and effective temperature are of 1.2 $\pm$ 0.1 \msun, 1.10 $\pm$ 0.03 \rsun, and 6241$^{+73}_{-62}$ K, respectively. TOI-333b is likely younger than 1 Gyr, which is supported by the presence of the doublet Li line around 6707.856 textup{~Å} and its comparison to Li abundances in open clusters with well constrained ages. The planet is expected to host only 8.5$^{+10.9}_{-8.3}\%$ gas-to-core mass ratio for a H/He envelope. On the other hand, irradiated ocean world models predict 20$^{+11}_{-10}\%$ H$_2$O mass fraction with a core fraction of 35$^{+20}_{-23}\%$. Therefore, we expect that TOI-333b internal composition may be dominated by a pure rocky composition with almost no H/He envelope, or a rocky world with almost equal mass fraction of water. Finally, TOI-333b is more massive and larger than 77$\%$ and 82$\%$ of its Neptune desert counterparts, respectively, while its host ranks among the hottest known for Neptune Desert planets, making this system a unique laboratory to study the evolution of such planets around hot stars.

Warm ionized gas is ubiquitous at the centers of X-ray bright elliptical galaxies. While it is believed to play a key role in the feeding and feedback processes of supermassive black holes, its origins remain under debate. Existing studies have primarily focused on the morphology and kinematics of warm ionized gas. This work aims to provide a new perspective on warm (10,000 K) ionized gas and its connection to X-ray-emitting hot gas (>10^6 K) by measuring and comparing their metallicities. We conducted a joint analysis of 13 massive elliptical galaxies using MUSE/VLT and Chandra observations. Emission-line ratios were measured for the warm ionized gas using MUSE observation, and used to infer the ionization mechanisms and derive metallicities of the warm ionized gas using HII, and LIN(E)R calibrations. We also computed the warm phase metallicity using X-ray/EUV, and pAGB stars models. For two sources at higher redshift, direct Te method was also used to measure warm gas metallicities. Our observations reveal that most sources exhibit composite ionization, with contributions from both star formation and LINER-like emission. A positive linear correlation was found between the gas-phase metallicities of the warm and hot phases, ranging from 0.3 to 1.5 Zsun, and suggest the intimate connection between the two gas phases, likely driven by gas cooling and/or mixing. In some sources the warm gas metallicity shows a central drop. A similar radial trend has been reported for the hot gas metallicity in some galaxy clusters. The ionization mechanisms of cooling flow elliptical galaxies are diverse, suggesting multiple channels for powering the warm ionized gas. The large variation in the warm gas metallicity further suggests that cold gas mass derived under the assumption of solar metallicity for the CO-to-H2 conversion factor needs to be revised by approximately an order of magnitude.

The T-Tauri type young stellar object RY Tau exhibits a dust depleted inner cavity characteristic of a transition disk. We constrain the spatial distribution and mineralogy of dust in the RY Tau protoplanetary disk in the inner few astronomical units using spectrally resolved interferometric observations in the L, M, and N bands obtained with VLTI/MATISSE. Employing a 2D temperature gradient model we estimate the orientation of the inner disk finding no evidence of significant misalignment between the inner and outer disk of RY Tau. Successively, we analyze the chemical composition of silicates depending on spatial region in the disk and identify several silicate species commonly found in protoplanetary disks. Additionally, a depletion of amorphous dust grains toward the central protostar is observed. Monte Carlo radiative transfer simulations show that hot dust close to the protostar and in the line of sight to the observer, either in the uppermost disk layers of a strongly flared disk or in a dusty envelope, is necessary to model the observations. The shadow cast by a dense innermost disk midplane on the dust further out explains the observed closure phases in the L band and to some extent in the M band. However, the closure phases in the N band are underestimated by our model, hinting at an additional asymmetry in the flux density distribution not visible at shorter wavelengths.

Hot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch. They populate the extreme horizontal branch (EHB) in the Hertzsprung-Russell diagram (HRD). Using the high-quality, homogeneous spectra of 336 hot subluminous star candidates from the Arizona-Montréal Spectroscopic Survey, we aim to improve our understanding of the atmospheric and stellar properties of hot subdwarf stars. We used large grids of model atmospheres to fit the observed spectra and derived their atmospheric parameters: effective temperature (Teff), surface gravity, and helium abundance. The model grids were further utilized to fit the spectral energy distribution of each star and the $Gaia$ parallax was used to compute the stellar parameters radius, luminosity, and mass. We detected helium stratification in six sdB stars with Teff around 30 kK, making them good candidates for also showing $^3$He enrichment in their atmospheres. The mass distributions of H-rich sdBs and sdOs are similar and centered around 0.47 $\text{M}_\odot$, consistent with the canonical formation scenario of helium ignition under degenerate conditions. Among the H-rich hot subdwarfs, we found no difference between the mass distributions of close binaries and apparently single stars. The He-sdOs have a significantly wider mass distribution than their H-rich counterparts, with an average mass of about 0.78 $\text{M}_\odot$. This strongly favors a merger origin for these He-rich objects. We identified a small number of candidate low-mass ($<$0.45$ \text{M}_\odot$) sdBs located below the EHB that might have originated from more massive progenitors. Finally, we identified more than 80 pulsating stars in our sample and found these to fall into well-defined $p$- and $g$-mode instability regions.

We investigate if systems of multiple Lyman-alpha emitters (LAEs) can serve as a proxy for dark matter halo mass, assess how their radiative properties relate to the underlying halo conditions, and explore the physics of star formation activity in LAEs and its relation to possible physically related companions. We use data from the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey, which targets LAEs in three narrow redshift slices. We identify physically associated LAE multiples in the COSMOS field at $z = 2.4$, $z = 3.1$, and $z=4.5$, and use a mock catalog from the IllustrisTNG100 simulation to assess the completeness and contamination affecting the resulting sample of LAE multiples. We then study their statistical and radiative properties as a function of multiplicity, where we adopt the term multiplicity to refer to the number of physically associated LAEs. We find a strong correlation between LAE multiplicity and host halo mass in the mocks, with higher multiplicity systems preferentially occupying more massive halos. In both ODIN and the mock sample, we find indications that the mean Ly$α$ luminosity and UV magnitude of LAEs in multiples increase with multiplicity. The halo-wide LAE surface brightness densities in Ly$α$ and UV increase with multiplicity, reflecting more compact and actively star-forming environments. The close agreement between the model and ODIN observations supports the validity of the Ly$α$ emission model in capturing key physical processes in LAE environments. Finally, a subhalo-based perturbation induced star formation model reproduces the minimum subhalo mass distribution in simulations at $z=2.4$, suggesting that local perturbations, rather than the presence of LAE companions, drive star formation in these systems. For the higher redshifts, neighbor perturbations do not seem to be the main driver that triggers star formation.

Context: The Solar System giant planets harbour a wide variety of moons. Moons around exoplanets are plausibly similarly abundant, even though most of them are likely too small to be easily detectable with modern instruments. Moons are known to affect the long-term dynamics of the spin of their host planets; however, their influence on warm exoplanets (i.e.\ with moderately short periods of about $10$ to $200$~days), which undergo significant star-planet tidal dissipation, is still unclear. Aims: Here, we study the coupled dynamical evolution of exomoons and the spin dynamics of their host planets, focusing on warm exoplanets. Methods: Analytical criteria give the relevant dynamical regimes at play as a function of the system's parameters. Possible evolution tracks mostly depend on the hierarchy of timescales between the star-planet and the moon-planet tidal dissipations. We illustrate the variety of possible trajectories using self-consistent numerical simulations. Results: We find two principal results: i) Due to star-planet tidal dissipation, a substantial fraction of warm exoplanets naturally evolve through a phase of instability for the moon's orbit (the `Laplace plane' instability). Many warm exoplanets may have lost their moon(s) through this process. ii) Surviving moons slowly migrate inwards due to the moon-planet tidal dissipation until they are disrupted below the Roche limit. During their last migration stage, moons -- even small ones -- eject planets from their tidal spin equilibrium. Conclusions: The loss of moons through the Laplace plane instability may contribute to disfavour the detection of moons around close-in exoplanets. Moreover, moons (even those that have been lost) play a critical role in the final obliquities of warm exoplanets. Hence, the existence of exomoons poses a serious challenge in predicting the present-day obliquities of observed exoplanets.

Tidal disruptions of stars by supermassive black holes produce multi-wavelength emission, of which the optical emission is of ambiguous origin. A unification scenario of tidal disruption events (TDEs) has been proposed to explain the different classes of X-ray and optically selected events by introducing a dependence on the viewing angle and geometry. This work aims to test the unification scenario among optically bright TDEs using polarimetry. By studying the optical linear polarisation of 19 TDEs (of which 9 newly analysed in this work), we place constraints on their photosphere geometry, inclination, and the emission process responsible for the optical radiation. We study how these properties correlate with the relative X-ray brightness. We find that 14/16 non-relativistic events can be accommodated by the unification model. Continuum polarisation levels of optical TDEs lie most often in the range P ~ 1-2% (13 events), and for all except one event, remain below 6%. For those optical TDEs that have multi-epoch polarimetry, the continuum polarisation decreases after peak light for 5/10 events, increases for 3/10 events, and stays nearly constant for 2/10 events. When observed after +70 days (7/16 events), they become consistent with P = 0% within uncertainties (5/7 events). This implies the photosphere geometries of TDEs are at least initially asymmetric and evolve rapidly which, if tracing the formation of the accretion disk, suggests efficient circularisation. The polarisation signatures of emission lines of 7 TDEs directly support a scenario in which optical light is reprocessed in an electron-scattering photosphere. [...] However, a subset of events deviates from the unification model to some extent, suggesting this model may not fully capture the diverse behaviour of TDEs. Multi-epoch polarimetry plays a key role in understanding the evolution and emission mechanisms of TDEs.

Gaia DR3 data have revealed new massive runaway stars, while spectroscopic surveys enable detailed characterization. The relative contributions of binary supernova (BSS) and dynamical ejection (DES) scenarios to explain their runaway origin remain poorly constrained, particularly in the Milky Way. We aim to characterize the largest sample of Galactic O-type runaway stars ever investigated through their kinematics, rotation, and binarity to shed light into their origins. We use the GOSC-Gaia DR3 catalog, and IACOB spectroscopic information to build a sample with 214 O-type stars with projected rotational velocities ($v \sin{i}$), and a subsample of 168 O-type stars with additional information about their likely single (LS) or single-lined (SB1) spectroscopic binary nature. We also consider an additional sample of 65 double-lined (SB2) spectroscopic binaries. We find that among our sample of Galactic O-type runaways, most (74%) have $v \sin{i}<200$ km/s, whereas for normal stars this fraction is slightly higher (82%). There are no fast-moving runaways being fast rotators, except for HD 124 979. Runaways show lower SB1 fractions than normal stars, with no runaway SB1 fast-rotating systems; on average, runaways rotate faster than normal stars; and their runaway fraction is higher among fast rotators (44%) vs. the slow rotators (34%). This is consistent with BSS dominance for fast rotators. We also found that SB2 systems hardly reach runaway velocities with a low runaway fraction (10%). Runaways with 2D velocities > 60 km/s are mostly single and interpreted as DES products, while runaways with 2D velocities > 85 km/s are also interpreted as two-step products. Three of 12 runaway SB1 systems are HMXBs. Our study reveals that most Galactic O-type runaways are slow rotators, suggests a dominance of BSS among fast-rotating runaways, and of DES and two-step among the high-velocity ones. (Abridged)

The evolution of galaxies is shaped by both internal processes and their external environments. Galaxy clusters and their surroundings provide ideal laboratories to study these effects, particularly mechanisms such as quenching and morphological transformation. The Chilean Cluster galaxy Evolution Survey (CHANCES) Low-z sub-survey is part of the CHileAN Cluster galaxy Evolution Survey, a 4MOST community survey designed to uncover the relationship between the formation and evolution of galaxies and hierarchical structure formation as it happens, through deep and wide multi-object spectroscopy. We present the target selection strategy followed to select galaxy cluster candidate members for the CHANCES low-z sub-survey, in and around 50 clusters and two superclusters at z<0.07, out to (5XR200) and down to mr= 20.4. Combining public photometric redshift estimates from the DESI Legacy Imaging Survey and T80S/S-PLUS iDR5, with custom photometric redshifts, we identify likely galaxy cluster candidate members whose photometric redshifts are consistent with being at the known redshift of the cluster and measure the average deviations of their photometric redshifts with respect to the spectroscopic redshift measurements σNMAD. We have successfully compiled our CHANCES-low-redshift catalogues, split into three different sub-surveys: low-z bright (mr<18.5), low-z faint (18.5<=mr<20.4) and low-z faint supplementary, by selecting>= 500,000 galaxy cluster candidate members and including confirmed spectroscopic galaxy cluster members, from which we expect to obtain 4MOST low-resolution (R~6500) spectra for ~320,000 galaxies. The CHANCES Low-z target catalogues form a statistically robust sample for spectroscopic follow-up, allowing studies of galaxy evolution and environmental effects in nearby cluster and supercluster environments.

Thermal dust is the major polarized foreground hindering the detection of primordial cosmic microwave background (CMB) B-modes. Its signal exhibits complex behavior in frequency space, arising from the combined variation in our Galaxy of the orientation of magnetic fields and the spectral properties of dust grains aligned with magnetic field lines. In this work, we present a new framework for analyzing the thermal dust signal using polarized microwave data. We introduce residual maps, represented as complex quantities, which capture deviations of the local polarized spectral energy distribution (SED) from the mean complex SED averaged over the sky mask. We present simple predictions that relate the values of the statistical correlation and covariances between the residual maps to the physical properties of the emitting aligned grains. Testing these predictions provides valuable information about the nature of the dust signal. We evaluated our predictions using Planck data over a 97% mask excluding the inner Galactic plane. Despite its simplicity, our model captures a significant part of the statistical properties of the data. For the SRoll2 version of the data, the spectral dependence of the covariances between residual maps is compatible with a dust model that includes only temperature variations rather than spectral index variations. In contrast, for the PR4 Planck official release, it is incompatible with both models. Our methodology can be used to analyze future high-precision polarization data and to build more accurate dust models for use by the CMB community.