Papers for Friday, Aug 08 2025

We present CLARA, a modular framework for unsupervised transit detection in TESS light curves, leveraging Unsupervised Random Forests (URFs) trained on synthetic datasets and guided by morphological similarity analysis. This work addresses two core questions: (a) How does the design of synthetic training sets affect the performance and generalization of URFs across independent TESS sectors? (b) Do URF anomaly scores correlate with genuine astrophysical phenomena, enabling effective identification and clustering of transit-like signals? We investigate these questions through a two-part study focused on (1) detection performance optimization, and (2) the physical interpretability of anomalies. In Part I, we introduce three URF model variants tuned via alpha-controlled scoring objectives, and evaluate their generalization across five TESS sectors. This large-scale test involved scoring 384,000 individual light curves (128,000 light curves per alpha variant), revealing stable, interpretable differences between recall-optimized, precision-optimized, and balanced models. In Part II, our optimized clustering (DPMM Cluster 2) yields a 14.04% detection rate (16 confirmed transits among 114 candidates) from the first five TESS SPOC sectors. This reflects a substantial enrichment over baseline rates: 0.4569% for the full TESS-SPOC project candidate set (7658 candidates across 1.68 million light curves), and 0.2650% for the FFI-based SPOC sample (7658 candidates across 2.89 million light curves;). All computations were performed on a personal, CPU-only desktop with an Intel Core i3-8100 processor and 32 GB RAM, using parallelized scoring and classification routines across four physical cores. CLARA processed over 87,000 TESS SPOC light curves (Sectors 1-5) without GPU acceleration in Part-II.

Investigating chemically peculiar pulsating stars is crucial for understanding the pulsation driving mechanism in detail. To reveal the true peculiarity properties of stars detailed spectroscopic analysis is essential. Therefore, in this study, we focused on Delta Scuti stars previously identified as chemically peculiar but needed comprehensive updated spectroscopic analysis to uncover the chemical abundance structure of them. We selected ten targets which have public high-resolution spectroscopic and photometric data. Performing spectral analyses, we determined the spectral classification, atmospheric parameters, and detailed chemical abundance distributions of the selected stars. The pulsation properties were also analyzed using TESS data and pulsation modes for the highest amplitude pulsation frequencies were derived. We estimated the masses and ages of the targets using the evolutionary tracks and isochrones. As a result of the study, we show that only three targets exhibit chemical peculiarity: AU Scl and FG Eri as metallic A (Am) stars, and HZ Vel as a $\lambda$ Bootis. However, others were found to be chemically normal stars. This study show us the importance of chemical abundance analysis in the classification of chemical peculiar stars.

Prestellar cores represent early sites of low-mass ($M$ $\leq$ few M$_\odot$) star and planet formation and provide insight into initial chemical conditions of complex organic molecules (COMs). Deuterated COMs trace the degree of molecular inheritance and/or reprocessing, as high deuteration in protostellar systems suggests COMs forming during the prestellar stage when deuteration is enhanced. Within the L1689N molecular cloud, the prestellar core IRAS 16293E sits $90^{"}$ eastward of the chemically-rich IRAS 16293-2422 A and B protostellar system. A unique view of star formation inside a common natal cloud, IRAS 16293A, B, and E all show some of the highest levels of deuteration in the ISM, with a number of D/H ratios $10^{5}$ times higher than Solar. We investigate for the first time the deuteration levels of the simplest COM, methanol (CH$_3$OH), in IRAS 16293E. Using the Arizona Radio Observatory (ARO) 12 m telescope, we target favorable transitions of CH$_2$DOH, CHD$_2$OH, $^{13}$CH$_3$OH, and several higher complexity COMs (including acetaldehyde, CH$_3$CHO, methyl formate, HCOOCH$_3$, and dimethyl ether, CH$_3$OCH$_3$) in the 3 mm band. Follow-up observations with the Yebes 40 m telescope provided additional transitions in the 7 mm (Q-band). We report the first detections of these COMs and deuterated methanol in prestellar core IRAS 16293E and use our observations to calculate excitation temperatures, column densities, and relative abundance ratios. Striking similarities are found between relative molecular ratios and D/H values when comparing IRAS 16293E to the A and B protostars, as well as to a heterogeneous sample of other prestellar cores, protostars, and the comet 67P/Churyumov-Gerasimenko. Our results support the idea that there is a limited amount of chemical reprocessing of COMs when prestellar cores collapse and heat-up during the protostellar phase.

We present updated constraints on the abundance of primordial black holes (PBHs) dark matter from the high-redshift Lyman-$\alpha$ forest data from MIKE/HIRES experiments. Our analysis leverages an effective field theory (EFT) description of the 1D flux power spectrum, allowing us to analytically predict the Lyman-$\alpha$ fluctuations on quasi-linear scales from first principles. Our EFT-based likelihood enables robust inference across redshifts $z = 4.2-5.4$ and down to scales of 100 kpc, within previously unexplored regions of parameter space for this dataset. We derive new bounds on the PBH fraction with respect to the total dark matter $f_{\text{PBH}}$, excluding populations with $f_{\text{PBH}} \gtrsim 10^{-3}$ for masses $M_{\text{PBH}} \sim 10^{4}-10^{16} M_{\odot}$. This offers the leading constraint for PBHs heavier than $10^{9} M_{\odot}$ and highlights the Lyman-$\alpha$ forest as a uniquely sensitive probe of new physics models that modify the structure formation history of our universe.

Observations of distant galaxies suggest that the physics of galaxy formation at high redshifts differs significantly from later times. In contrast to large, steady disk galaxies like the Milky Way, high-redshift galaxies are often characterized by clumpy, disturbed morphologies and bursty star formation histories. These differences between low-mass, bursty galaxies and higher-mass, steady star-forming galaxies have recently been studied in galaxy formation simulations with resolved multiphase ISM. These simulation studies indicate that while steady disk galaxies can be well-modeled as "equilibrium disks" embedded in a distinct, hot CGM, bursty galaxies are much more dynamic and their star formation occurs in a dispersion-dominated medium that extends to halo scales, with no clear boundary between the ISM and the CGM. We develop an analytic framework to model star formation in bursty galaxies that are not adequately modeled as equilibrium disks. The framework approximates the gas in low-mass halos as a continuous, supersonically turbulent medium with large density fluctuations. Star formation occurs locally in the high-density tail of a roughly lognormal density distribution. This is analogous to turbulent models of star formation in molecular clouds, but here applied on inner CGM scales. By comparing with galaxy formation simulations from the FIRE project, we show that this framework can be used to understand star formation efficiencies and radial profiles in halos. The turbulent framework shows explicitly how the instantaneous galaxy-averaged star formation efficiency can be relatively low even if the local efficiency in dense gas approaches unity.

We investigate the extraction of energy from a Kerr black hole via Alfvén waves (i.e., Alfvénic superradiance) in a force-free magnetosphere, in which the plasma inertia effects are ignored. We analyze the Poynting flux generated by Alfvén waves that propagate toward the event horizon across the inner light surface, the causal boundary for the waves. We find the relationship between the energy flux associated with Alfvén waves and that of the Blandford-Znajek (BZ) process. That is, both mechanisms can be described within a unified formulation of the Poynting flux, where the BZ process can be regarded as the long wavelength limit of the Alfvénic superradiance, and depending on the wave's frequency, Alfvén waves enhance or suppress the Poynting flux in the BZ process. This unified framework for the BZ process and the Alfvénic superradiance would offer a valuable perspective for understanding the energy sources of high-energy astrophysical phenomena, such as relativistic jets.

Leveraging the large sample size of low-resolution spectroscopic surveys to constrain white dwarf stellar structure requires an accurate understanding of the shapes of hydrogen absorption lines, which are pressure broadened by the Stark effect. Using data from both the Sloan Digital Sky Survey and the Type Ia Supernova Progenitor Survey, we show that substantial biases (5-15 km/s) exist in radial velocity measurements made from observations at low spectral resolution relative to similar measurements from high-resolution spectra. Our results indicate that the physics of line formation in high-density plasmas, especially in the wings of the lines, are not fully accounted for in state-of-the-art white dwarf model atmospheres. We provide corrections to account for these resolution-induced redshifts in a way that is independent of an assumed mass-radius relation, and we demonstrate that statistical measurements of gravitational redshift with these corrections yield improved agreement with theoretical mass-radius relations. Our results provide a set of best practices for white dwarf radial velocity measurements from low-resolution spectroscopy, including those from the Sloan Digital Sky Survey, the Dark Energy Spectroscopic Instrument, the 4-meter Multi-Object Spectroscopic Telescope, and the Wide-Field Multiplexed Spectroscopic Facility.

Cold Classical Kuiper belt objects (CCKBOs) are considered first-generation planetesimals that formed 42-47 au from the Sun and remained untouched since. Formation is thought to proceed by clumping of dust particles in protoplanetary disk gas by the streaming instability, followed by gravitational collapse. Previous calculations along these lines are inconsistent with the CCKB's supposedly pristine nature, because they assume orders of magnitude more solid mass than is actually present in the CCKB (a few thousandths of an Earth mass) and do not explain how to expel the >99% extra mass. Here we show from 3D numerical simulations of dust and gas that the total mass in CCKBOs, their characteristic sizes of ~100 km, and the preponderance of prograde binaries can all be reproduced at the tail end of the solar nebula's life, when it contained just 2-5% of its original (minimum-mass) gas. As a solar metallicity's worth of mm-sized solids drains out from 42-47 au from nebular headwinds, about 1% of the dust collapses into planetesimals that remain behind in the CCKB region. Binarity is guaranteed from a simple analytic estimate, confirmed numerically, of the spin angular momentum in clumps seeded by the streaming instability. We show that other formation scenarios, including trapping of dust within a gas pressure bump, fail to reproduce the low-mass CCKB. Outstanding problems are identified.

Recent studies of galaxy clusters found peculiar cases at the boundary between non-cool core and cool core systems. While unusual, these objects can help us understand the evolution of the most massive clusters. We investigated the role of active galactic nucleus (AGN) feedback in the starburst brightest cluster galaxy (BCG) of the merging cool core cluster CHIPS 1911+4455 (z = 0.485). We conducted new multifrequency (0.3 - 5 GHz) Very Long Baseline Array (VLBA) and Jansky Very Large Array (JVLA) observations of CHIPS 1911+4455 across a wide range of scales (0.01 to 20 kpc). Our analysis reveals that the AGN in the BCG has recently awakened, showing a compact core with symmetric, ~30 pc long jets in VLBA data. The onset of the AGN may be linked to the enhanced cooling of the hot gas found in a previous study. At larger scales (10 kpc), faint radio whiskers extending to the south show a striking alignment with star-forming knots and are thus interpreted as synchrotron-emitting regions associated with the starburst BCG. The implied radio star formation rate of 100 - 155 M$_{\odot}$/yr agrees with the optical/infrared one (140 - 190 M$_{\odot}$/yr). Our JVLA and VLBA radio study, informed by previous X-ray/optical/millimeter works, indicates that CHIPS 1911+4455 represents a transitional phase in cluster evolution, where the AGN in the central galaxy has just begun to respond to copious hot gas cooling.

Modelling perturbations of the Milky Way (MW) halo induced by the infall of the Large Magellanic Cloud (LMC) offers new avenues to constrain the dark matter (DM) distribution in our Galaxy. A key observable is the reflex motion of the MW disc with respect to the halo induced by the LMC's infall, which imprints a velocity dipole on kinematics of halo stars. Here we investigate how the dipole varies with Galactocentric radius, and study the sensitivity of the reflex motion signal to different DM outer-halo profiles. Using a suite of basis function expansion (BFE) simulations with truncated NFW profiles ($\rho \propto r^{-\beta}$ beyond $r=50$ kpc), our $N$-body models show that (i) The reflex motion amplitude varies with Galactocentric radius but is largely insensitive to the outer DM slope, implying that the MW-LMC mass ratio alone does not set the dipole strength. (ii) In contrast, the direction of the disc motion is very sensitive to the density distribution of the outer DM halo. (iii) The contraction of the MW halo induced by the LMC's gravitational pull also depends strongly on the outer DM halo profile. (iv) We find a halo instability whose oscillation frequency increases with $\beta$ producing a potentially observable signature - a sinusoidal pattern of the mean radial velocity of halo stars. Finally, using BFE coefficients we find that steeper truncations produce smaller dipole distortions, while amplifying the quadrupole distortion. These results highlight the limited constraining power of the reflex motion amplitude alone for outer MW profile parameters.

The nature of Type Ia supernova (SN Ia) progenitor systems and the mechanisms that lead up to their explosions are still widely debated. In rare cases the SN ejecta interact with circumstellar material (CSM) that was ejected from the progenitor system prior to the SN. The unknown distance between the CSM and SN explosion site makes it impossible to predict when the interaction will start. If the time between the SN and start of CSM interaction is of the order of months to years the SN has generally faded and is not actively followed up anymore, making it even more difficult to detect the interaction while it happens. Here we report on a real-time monitoring program which ran between 13-11-2023 and 09-07-2024, monitoring 6914 SNe Ia for signs of late-time rebrightening using the Zwicky Transient Facility (ZTF). Flagged candidates were rapidly followed up with photometry and spectroscopy to confirm the late-time excess and its position. We report the discovery of a $\sim50$ day rebrightening event in SN 2020qxz around 1200 days after the peak of its light curve. SN 2020qxz had signs of early CSM interaction but faded from view over 2 years before its reappearance. Follow-up spectroscopy revealed 4 emission lines that faded shortly after the end of the ZTF detected rebrightening. Our best match for these emission lines are H$\beta$ (blue shifted by $\sim5900$ km s$^{-1}$) and CaII$_{\lambda8542}$, NI$_{\lambda8567}$, and KI$_{\lambda\lambda 8763, 8767}$, all blue shifted by 5100 km s$^{-1}$ (although we note that these identifications are uncertain). This shows that catching and following up on late-time interactions as they occur can give new clues about the nature of the progenitor systems that produce these SNe by putting constraints on the possible type of donor star, and the only way to do this systematically is to use large sky surveys such as ZTF to monitor a large sample of objects.

We present measurements of the rest-frame ultraviolet luminosity function (UVLF) in three redshift bins over $z\sim5.5$-14 from the JWST COSMOS-Web survey. Our samples, selected using the dropout technique in the HST/ACS F814W, JWST/NIRCam F115W, and F150W filters, contain a total of 3099 galaxies spanning a wide luminosity range from faint ($M_{\rm UV}\sim-19$ mag) to bright ($M_{\rm UV}\sim-22.5$ mag). The galaxies are undergoing rapid star formation, with blue stellar populations. Surprisingly, their median UV spectral slope $\beta$ does not evolve at $z>8$, suggesting minimal dust, or physical separation of dust and star formation at early epochs. The measured UVLF exhibits an excess at the bright-end ($M_{\rm UV}<-21$ mag) compared to pre-JWST empirical results and theoretical predictions of an evolving Schechter function, with the excess beginning at $z\sim9$ and becoming increasingly prominent toward $z\sim12$. Our analysis suggests that reproducing the observed abundance of UV-bright galaxies at high redshift requires a combination of physical processes, including elevated star formation efficiencies, moderate levels of stochasticity in galaxy luminosities, and minimal dust attenuation.

TRAPPIST-1 is an M8 dwarf hosting seven known exoplanets and is currently one of the most frequently observed targets of the James Webb Space Telescope (JWST). However, it is notoriously active, and its surface is believed to be covered by magnetic features that contaminate the planetary transmission spectra. The radiative spectra of these magnetic features are needed to clean transmission spectra, but they currently remain unknown. Here, we develop a new approach for measuring these spectra using time-resolved JWST/NIRISS observations. We detect a persistent post-flare enhancement in the spectral flux of TRAPPIST-1. Our analysis rules out lingering flare decay as the cause of the flux enhancement and, thus, points to structural changes on the stellar surface induced by flares. We suggest that the flaring event triggers the disappearance of (part of) a dark magnetic feature, producing a net brightening. This suggestion is motivated by solar data: flare-induced disappearance of magnetic features on the solar surface has been directly detected in high spatial resolution images, and our analysis shows that this process produces changes in solar brightness very similar to those we observe on TRAPPIST-1. The proposed explanation for the flux enhancement enables, to our knowledge, the first measurement of the spectrum of a magnetic feature on an M8 dwarf. Our analysis indicates that the disappearing magnetic feature is cooler than the TRAPPIST-1 photosphere, but by at most a few hundred kelvins.

We observed Io's optical aurora in eclipse on six nights between 2022 and 2024 using Keck I/HIRES. Spectra revealed 13 new auroral emissions not identified previously, tripling the total number of optical emissions lines detected at Io. These included the O I lines at 777.4 and 844.6 nm, the Na I lines at 818.3 and 819.5 nm, the [S I] lines at 458.9 and 772.5 nm, the S I triplet at 922.3 nm, the [O II] lines at 732.0 and 733.0 nm and the [S II] lines at 406.9, 407.6, 671.6 and 673.1 nm. We leveraged these new detections by comparing with imaging data from the 2001 Cassini flyby to better understand the distribution of atmospheric species and their contribution to the observed auroral brightnesses. Our auroral emission model showed that the observed 557.7, 777.4 and 844.6 nm oxygen emission line brightnesses could be explained by excitation by electron impact of canonical 5 eV torus electrons on an atmosphere composed of O, SO2 and an isoelectronic proxy for SO. The SO2 emission did not decrease immediately after eclipse ingress, suggesting the emitting column may be restricted to higher altitudes. The derived O/SO2 mixing ratio was typically about 10%, but it also exhibited order-of-magnitude variance during some observations. Io's 630.0 nm [O I] brightness did not strongly vary with plasma sheet distance, suggesting electron flux at Io varies substantially beyond model predictions.

Semi-analytic models are a valuable tool to study the first stars and galaxies. Their numerical efficiency makes it possible to survey broad regions of astrophysical parameter space across large volumes and redshift ranges. Following reionization in these models is necessary since star formation is suppressed in ionized regions due to photoheating of the gas. Here we evaluate the accuracy of three semi-analytic reionization prescriptions (two previously developed and one new model) by comparing their three-dimensional distribution of ionized bubbles to the Renaissance hydrodynamical cosmological radiative transfer simulations. We find that the previously existing models accurately determine the distribution of the larger bubbles within our ${\sim}6$ comoving Mpc simulation box, but that these models fail to take into account self-shielded neutral gas in dense filaments. Thus, these prescriptions overestimate the fraction of halos in HII regions impacted by reionization feedback by up to an order of magnitude (depending on halo mass and redshift). This leads to an unrealistically large effect of reionization feedback on Pop III stars and low-mass metal-enriched galaxies. Our newly developed model takes into account the density structure of the cosmic web, leading to good agreement with Renaissance in the fraction of halos found in ionized regions.

Extended X-ray emission observed in the direction of several molecular clouds in the Central Molecular Zone (CMZ) of our Galaxy exhibits spectral and temporal properties consistent with the `X-ray echo' scenario. It postulates that the observed signal is a light-travel-time delayed reflection of a short ($\delta t<$1.5 yr) and bright ($L_{\rm X}>10^{39}~{\rm erg~s^{-1}}$) flare, most probably produced a few hundred years ago by Sgr A*. This scenario also predicts a distinct polarization signature for the reflected X-ray continuum, with the polarization vector being perpendicular to the direction towards the primary source and polarization degree (PD) being determined by the scattering angle. We report the results of two deep observations of the currently brightest (in reflected emission) molecular complex Sgr A taken with the Imaging X-ray Polarimetry Explorer (IXPE) in 2022 and 2023. We confirm the previous polarization measurement for a large region encompassing Sgr A complex with higher significance, but also reveal an inconsistent polarization pattern for the brightest reflection region in its center. X-ray polarization from this region is almost perpendicular to the expected direction in the case of Sgr A* illumination and shows a smaller PD compared to the large region. This could indicate the simultaneous propagation of several illumination fronts throughout the CMZ, with the origin of one of them not being Sgr A*. The primary source could be associated with the Arches stellar cluster or a currently unknown source located in the closer vicinity of the illuminated cloud, potentially lowering the required luminosity of the primary source. Although significantly deeper observations with IXPE would be required to unequivocally distinguish between the scenarios, a combination of high-resolution imaging and micro-calorimetric spectroscopy offers an additional promising path forward.

Solar activity seems quite understandable when considered on the scales comparable with a solar cycle, i.e. about 11 years, and on a short time scale of about a year. A solar cycle looks basically (anti)symmetric with respect to the solar equator, while the sunspot distribution is more or less random. We investigated the difference in the spatial distribution of magnetic structures on both time scales in terms of sunspots and the surface large-scale magnetic field and arrived at the conclusion that the structures of each type are created by a specific mechanism. For long-term structures, it is the mean-field dynamo. For the short-term ones, it is the spot production considered as a separate physical mechanism. The relationship between the mean-field dynamo mechanism and the processes of sunspot formation is a complex problem of current interest. The 11-year cycle itself is created by the mean-field dynamo and is most likely determined by processes in the convection zone. However, the transformation of magnetic flux into spots and active regions occurs, apparently, on significantly shorter time scales and probably develops directly in the subsurface layers, i.e., Near-Surface Shear Layer (NSSL) or leptocline.

We present the first application of semi-coherent strategies in the search for optical pulsations from binary systems, which resulted in the tightest constraints on pulsations from Sco X-1. We analysed observations from the SiFAP2 fast photometer mounted at the TNG spread across four years, for a total of $\sim$56 ks divided in two datasets. The great efficiency of semi-coherent techniques when only limited knowledge on the orbital parameters is available allowed us to set an upper limit at $9.23 \cdot 10^{-5}$ in pulsed amplitude for this source, improving on previous results by a factor of 4. Reaching the same upper limit with fully coherent searches would have required a number of trials more than two orders of magnitude larger. We also applied the same algorithm to an optical observation of a system containing a known pulsar, PSR J1023+0038, ignoring the refined knowledge of the orbital parameters that was allowed by the identification of the pulsar itself in the radio band: through this analysis, we proved that detection of the pulsar would have followed even with data in the optical band alone.

We compare predictions of how Active Galactic Nuclei (AGN) populate host galaxies at low redshifts to observations, finding large discrepancies between cosmological simulation predictions and observed patterns. Modern cosmological simulations include AGN feedback models tuned to reproduce the observed galaxy stellar mass function. However, due to a lack of real understanding of the physics of AGN feedback, these models vary significantly across simulations. To distinguish between the models and potentially test the underlying physics, we carry out independent tests of these models. In an earlier study, we found that $F_{\rm AGN}$ -- the observed completeness-corrected fraction of galaxies hosting radio AGN with an Eddington ratio $\lambda > 10^{-3}$ -- to be a strong function of host galaxy stellar mass ($M_\star$) but nearly independent of host specific star formation rates (sSFR) at fixed $M_\star$. In this study, we test the radio mode AGN feedback models of the EAGLE, SIMBA, and TNG100 simulations by comparing their predictions of $F_{\rm AGN} \left(M_\star \right)$ to our observational constraint. We find that none of these simulations even qualitatively reproduce the observed dependencies of $F_{\rm AGN}$ on $M_\star$ and sSFR. Finally, we find that although the given TNG100 model could be modified in order to better reproduce the observed $F_{\rm AGN}$ trend, this modification would likely also change its prediction for the local stellar mass function and star formation rates -- key observations used for calibrating the simulation in the first place. Our findings highlight a pressing need to revisit the AGN feedback prescriptions in EAGLE, SIMBA, TNG100 and other similar models.

We perform three-dimensional smoothed particle hydrodynamics simulations to investigate the formation of spiral arms in misaligned circumbinary discs. In a nearly broken disc the misaligned inner and outer discs interact at two nodes, launching leading spiral arms that do not rotate with the disc. These spirals vanish when the disc is fully broken or aligned. Our results show that the formation of leading spirals is driven by the relative misalignment of the inner and outer disc, and does not depend on the disc physics. With live radiative transfer, the shadows cast by the misaligned inner disc are also able to launch trailing spiral arms that only appear at high misalignments when the discs are disconnected. When the disc is strongly misaligned, leading and trailing spiral arms can both appear and interact with each other. At lower misalignments, the impact of shadows is negligible and leading spiral arms are seen instead. The presence of both leading and trailing spiral arms implies that the rotation of the disc cannot be assumed based on the orientation of the spiral arms alone. Unlike spirals formed by gravitational instability, the spirals in this work can also form in low-mass, gravitationally stable discs.

We present $\sim$500 ks XRISM observations covering the central and two northern regions of the Abell 2029 galaxy cluster. Resolve enables us to distinguish multiple emission lines from hydrogen-like and helium-like iron (Fe) ions. This study focuses on the multi-temperature structure of Abell 2029 using line-ratio diagnostics. Using a single-temperature collisionally ionized equilibrium model, we measure average plasma temperatures of 6.73 keV, 7.61 keV, and 8.14 keV in the central, inner northern, and outer northern regions, respectively, spanning a radial range up to 700 kpc. To further investigate thermal structure, we derive excitation and ionization temperatures by comparing observed emission-line flux ratios with atomic database predictions. Significant deviations from the single-temperature CIE model in the central and inner northern regions indicate the presence of multi-phase gas. The excitation and ionization temperatures range from 2.85 keV to 8.5 keV in the central region, 4.3 keV to 9.8 keV in the inner northern region, and 8.3 keV to 10.4 keV in the outer northern region. These temperature distributions are largely consistent with the previously observed temperature gradient of A2029. However, Resolve detects two notably cooler components--3.42 keV in the central region and $\sim$4.3 keV in the inner northern region--likely associated with displaced cool gas due to gas sloshing. Additionally, we thermally resolve a 2.85 keV gas component at the core of A2029--potentially a significant development in our understanding of gas cooling. We propose that this cooler gas is a direct product of ongoing cooling processes in A2029, having already cooled to its present temperature. If this temperature structure is stable and no heating mechanism is present, this reservoir is likely to cool to even lower temperatures and form stars.

Standard Bayesian retrievals for exoplanet atmospheric parameters from transmission spectroscopy, while well understood and widely used, are generally computationally expensive. In the era of the JWST and other upcoming observatories, machine learning approaches have emerged as viable alternatives that are both efficient and robust. In this paper we present a systematic study of several existing machine learning regression techniques and compare their performance for retrieving exoplanet atmospheric parameters from transmission spectra. We benchmark the performance of the different algorithms on the accuracy, precision, and speed. The regression methods tested here include partial least squares (PLS), support vector machines (SVM), k nearest neighbors (KNN), decision trees (DT), random forests (RF), voting (VOTE), stacking (STACK), and extreme gradient boosting (XGB). We also investigate the impact of different preprocessing methods of the training data on the model performance. We quantify the model uncertainties across the entire dynamical range of planetary parameters. The best performing combination of ML model and preprocessing scheme is validated on a the case study of JWST observation of WASP-39b.

This study presents optical and near-infrared photometric observations, alongside mid-infrared spectroscopic data from the ISO SWS instrument, to examine potential correlations between Aromatic Infrared Band (AIB) features and the optical properties of carbon-rich evolved stars. Identifying such correlations can provide valuable constraints on the evolutionary pathways of low- to intermediate-mass stars beyond the asymptotic giant branch (AGB) phase. Photometric measurements in the U, B, V, R, I, J, H, K, and L bands were obtained for five well-known carbon-rich objects at various post-AGB or planetary nebula (PN) stages: CRL 2688, PN M 2-43, NGC 7027, BD${+}$30${^\circ}$3639, and AFGL 2132. Our analysis reveals that all five objects exhibit prominent AIB features; however, their spectral profiles show notable variation. These differences are attributed to variations in the chemical composition and physical conditions of the surrounding circumstellar material. In particular, the 3.28$\mu$m polycyclic aromatic hydrocarbon (PAH) feature is detected in all objects except AFGL 2132, indicating a potentially distinct PAH population or environmental condition in its vicinity. Although these sources share broadly similar evolutionary stages, the observed diversity in AIB characteristics underscores the complexity and heterogeneity of their circumstellar environments.

Understanding the deep atmospheric composition of Jupiter provides critical constraints on its formation and the chemical evolution of the solar nebula. In this study, we combine one-dimensional thermochemical kinetic-transport modeling with two-dimensional hydrodynamic simulations to constrain Jupiter's deep oxygen abundance using carbon monoxide (CO) as a proxy tracer. Leveraging a comprehensive chemical network generated by Reaction Mechanism Generator (RMG), we assess the impact of updated reaction rates, including the often-neglected but thermochemically significant Hidaka reaction (CH3OH + H -> CH3 + H2O). Our 1D-2D coupled approach supports a modest supersolar oxygen enrichment of 1.0-1.5x the solar value. We also present a method for deriving Jupiter's eddy diffusion coefficient Kzz = 3e6 to 5e7 cm2/s) from 2D hydrodynamic simulations using the quasi steady-state approach. This method is applicable to exoplanet atmospheres, where Kzz remains highly uncertain despite its strong influence on atmospheric chemistry. Finally, our results imply a significantly elevated planetary carbon-to-oxygen (C/O) ratio of ~2.9, highlighting the importance of clarifying the mechanisms behind the preferential accretion of carbon-rich material during Jupiter's formation. By integrating thermochemical and hydrodynamic processes, our study offers a more complete framework for constraining chemical and dynamical processes in (exo)planetary atmospheres.

Understanding the morphological structures of Lyman-alpha emitters (LAEs) is crucial for unveiling their formation pathways and the physical origins of Ly$\alpha$ emission. However, the evolution of their sizes and structural scaling relations remains debated. In this study, we analyze a large sample of 876 spectroscopically confirmed LAEs at $3 \lesssim z < 7$, selected from the MUSE, VANDELS, and CANDELSz7 surveys in the GOODS-S, UDS, and COSMOS fields. Utilizing deep, high-resolution near-infrared images from the James Webb Space Telescope (JWST), we measure their rest-frame UV and optical V-band effective radii ($R_{\rm e}$) through two-dimensional Sérsic profile fitting. Our results show that these LAEs are generally compact with weak size evolution, following $R_{\rm e,UV} \propto (1 + z)^{-0.91 \pm 0.10}$ and $R_{\rm e,V} \propto (1 + z)^{-0.93 \pm 0.18}$, respectively. Their UV and optical sizes are statistically comparable, indicating negligible UV-to-optical color gradients. For the first time, we establish the rest-frame optical size-mass relation for LAEs at $z>3$, finding slopes comparable to typical star-forming galaxies (SFGs), but with slightly smaller sizes at a given stellar mass. These results provide important clues for understanding the formation mechanisms and structural evolution of LAEs in the early universe.

We present results from XRISM/Resolve observations of the core of the galaxy cluster Abell 2319, focusing on its kinematic properties. The intracluster medium (ICM) exhibits temperatures of approximately 8 keV across the core, with a prominent cold front and a high-temperature region ($\sim$11 keV) in the northwest. The average gas velocity in the 3 arcmin $\times$ 4 arcmin region around the brightest cluster galaxy (BCG) covered by two Resolve pointings is consistent with that of the BCG to within 40 km s$^{-1}$ and we found modest average velocity dispersion of 230-250 km s$^{-1}$. On the other hand, spatially-resolved spectroscopy reveals interesting variations. A blueshift of up to $\sim$230 km s$^{-1}$ is observed around the east edge of the cold front, where the gas with the lowest specific entropy is found. The region further south inside the cold front shows only a small velocity difference from the BCG; however, its velocity dispersion is enhanced to 400 km s$^{-1}$, implying the development of turbulence. These characteristics indicate that we are observing sloshing motion with some inclination angle following BCG and that gas phases with different specific entropy participate in sloshing with their own velocities, as expected from simulations. No significant evidence for a high-redshift ICM component associated with the subcluster Abell 2319B was found in the region covered by the current Resolve pointings. These results highlight the importance of sloshing and turbulence in shaping the internal structure of Abell 2319. Further deep observations are necessary to better understand the mixing and turbulent processes within the cluster.

Understanding demographic properties of planet populations and multiple star systems constrains theories of planet and star formation. Surveys for very low-mass companions to M-A type stars detect brown dwarfs from multiple star formation and planets from circumstellar disks. We fit a composite model describing both very low-mass brown dwarf companions from "multiple-like processes" and gas giants from "planet-like processes" as functions of orbital separation and host star mass. We assemble a database of companion frequency estimates for masses from $< 1$ to $> 75$ Jupiter masses, separations from $< 0.3$ to $> 300$ AU, and host masses from $< 0.3$ to $> 2 M_{\odot}$. Using multinest, we fit these data to various models, performing model selection and deriving probability density functions. We assume companion mass ratio distributions are independent of orbital separation and fit a common log-normal orbital distribution to gas giant populations around M dwarfs, FGK, and A stars. A six-parameter model based on companion mass ratio distributions for planets and brown dwarfs is preferred. The planet CMRD slope is consistent with previous studies ($dN/dq \sim q^{-1.3} \pm 0.03$). Gas giant planets around stars from $< 0.3$ to $> 2.0 M_{\odot}$ follow a log-normal distribution peaking at ln(a) = 1.30 $\pm$ 0.03 (3.8 AU) with dispersion 0.22 $\pm$ 0.04. M dwarf distributions peak at smaller orbital radii than A stars, consistent with iceline considerations. Brown dwarf companion distributions extend stellar binary patterns, with the brown dwarf desert explained by flat-in-q mass functions and limited mass ratios below 0.1.

Theoretical models of star formation consistently underestimate the rates observed in astronomical surveys. Stars form within giant molecular clouds, which fragment into dense clumps under the combined influences of turbulence, magnetic fields, radiation and gravity. While some of these clumps collapse spontaneously, others require an external trigger, a mechanism estimated to account for 14-25% of star formation in regions such as the Elephant Trunk Nebula. Laboratory astrophysics has emerged as a powerful approach for investigating such triggering processes, particularly those involving supernova remnants (SNRs). Recent experiments, guided by well-established scaling laws, have successfully replicated the dynamics of SNRs and their interactions with dense clumps or other SNRs. In this work, we present a comprehensive numerical study of these experimental configurations using the 3D radiation-hydrodynamics code TROLL. The simulations provide enhanced insight into the underlying physical mechanisms, accurately reproduce key experimental phenomena and offer valuable comparisons with analytical models. This study underscores the strong synergy between laboratory experiments and numerical simulations, laying a robust foundation for future advancements in laboratory astrophysics. Furthermore, we propose a new experimental setup that offers improved scaling for the asymmetric collision observed in the DEM L316 system. Our findings also show that SNR collisions in dense environments can decrease the gravitational stability of dense clumps, thereby promoting their collapse and potentially triggering star formation.

Context. Recent JWST observations have shown that brown dwarfs (BD) are chemically rich, offering valuable insights into giant planet formation. Aims. As part of the MIRI mid-INfrared Disk Survey (MINDS) JWST guaranteed time program, we aim to characterize the gas and dust composition of the disk around the brown dwarf [NC98] Cha HA 1, hereafter Cha H$\alpha$ 1, in the mid-infrared. Methods. We obtain data from the MIRI Medium Resolution Spectrometer (MRS) from 4.9 to 28$\mu$m. We use the dust fitting tool DuCK to investigate the dust composition and grain sizes while we identify and fit molecular emission using slab models. Results. Compared with disks around very low mass stars, clear silicate emission features are seen in this BD disk. In addition, JWST reveals a plethora of hydrocarbons, including C$_2$H$_2$, $^{13}$CCH$_2$, CH$_3$, CH$_4$, C$_2$H$_4$, C$_4$H$_2$, C$_3$H$_4$, C$_2$H$_6$, and C$_6$H$_6$ which suggest a disk with a gas C/O > 1. Additionally, we detect CO$_2$, $^{13}$CO$_2$, HCN, H$_2$, and H$_2$O. CO and OH are absent from the spectrum. The dust is dominated by large $\sim$4 $\mu$m size amorphous silicates (MgSiO$_3$). We infer a small dust mass fraction ($>$10$\%$) of 5 $\mu$m size crystalline forsterite. We do not detect polycyclic aromatic hydrocarbons. Conclusions. Cha H$\alpha$ 1 shows the most diverse chemistry seen to date in a BD protoplanetary disk, consisting of a strong dust feature, 12 carbon-bearing molecules plus H$_2$, and water. The diverse molecular environment offers a unique opportunity to test our understanding of BD disks chemistry and how it affects the possible planets forming in them.

Fast radio bursts (FRBs) are among the most mysterious astronomical transients. Due to their short durations and cosmological distances, their dispersion measure (DM) - redshift ($z$) relation is useful for constraining cosmological parameters and detecting the baryons in the Universe. The increasing number of localized FRBs in recent years has provided more precise constraints on these parameters. In this project, we collect 117 of the latest, localized FRBs, discuss the effect of a more accurate $\sigma_{\rm diff}$ in the probability density function ($p_{\rm diff}$) for ${\rm DM}_{\rm diff}$, and rewrite their likelihood convolution to better constrain the parameters above. We find that the widely used approximation $\sigma_{\rm diff} \sim F/\sqrt{z}$ only works under contrived assumptions. In general, one should use an accurate method to derive this parameter from $p_{\rm diff}$. Our method yields a constraint of $H_0\Omega_b f_{\rm diff} = 2.812_{-0.258}^{+0.250}$ or $H_0 = 66.889_{-5.460}^{+6.754}$ when combining the FRB data with CMB measurements and taking $f_{\rm diff} = 0.84$. This fully analytical correction helps us to better constrain cosmological parameters with the increasing number of localized FRBs available today.

Anisotropic cosmological models have been gaining attention due to various observational hints of large-scale anisotropies. One of the most surprising evidences for the latter is the discovery of a dipole-like directional variation in cosmological parameters extracted from the Cosmic Microwave Background (CMB) data. In this work, we show that the directional variation of the CMB angular acoustic angle calculated with the fully asymmetric Bianchi Type I metric, a simple extension of the standard Friedmann-Lemaître-Robertson-Walker metric, cannot account for the observed dipole-like anisotropy.

The velocity anisotropy profiles, $\beta(r)$, of galaxy clusters are directly related to the shape of the orbits of their member galaxies. Knowledge of $\beta(r)$ is important to understand the assembly process of clusters and the evolutionary processes of their galaxies, and to improve the determination of cluster masses based on cluster kinematics. We determine the $\beta(r)$ of nine massive clusters at redshift $0.19 \leq z \leq 0.45$ from the CLASH-VLT data set, with 150 to 950 spectroscopic members each, to understand how much cluster-to-cluster variance exists in the $\beta(r)$ of different clusters and what is the main driver of this variance. We select spectroscopic cluster members with the CLUMPS algorithm calibrated on cosmological simulations. We apply the MAMPOSSt code to the distribution of cluster members in projected phase-space to constrain the cluster mass profile, $M(r)$, using priors derived from a previous gravitational lensing analysis. Given the MAMPOSSt best-fit solution for $M(r)$, we then solve the inversion of the Jeans equation to determine $\beta(r)$ without assumptions of its functional form. We also run the DS+ code to identify subclusters and characterize the dynamical status of our clusters. The average $\beta(r)$ is slightly radial, with the anisotropy increasing from $\beta \simeq 0.2$ at the cluster center, to $\beta \simeq 0.4$ at the virial radius. There is substantial variance in the $\beta(r)$ of the individual clusters, that cannot be entirely accounted for by the observational uncertainties. Clusters of lower mass and with a low concentration per given mass have more tangential $\beta(r)$'s. Clusters hosting a rich subcluster have $\beta(r)$ deviating more strongly from the average $\beta(r)$.

Modern spectroscopic surveys combined with Gaia distances are enabling reliable estimates of fundamental parameters for hundreds of Galactic O-type stars and the full range of spectral types and luminosity classes. Here we provide updated, statistically robust empirical calibrations of the fundamental parameters of Galactic O-type stars, as well as of their absolute visual magnitudes (Mv) and bolometric corrections (BC), based on high-quality observational data. We perform a homogeneous analysis of a sample of 358 Galactic O-type stars, combining high-resolution spectroscopy and Gaia distances. A subset of 234 stars meeting strict quality criteria involving parallax, extinction, and multi-band photometry was used to derive empirical calibrations of fundamental parameters. For those same stars, calibrated parameters were estimated from their measured Mv using the derived relations, allowing us to assess the internal consistency and predictive power of the calibrations. We present updated spectral-type-based calibrations of fundamental parameters for luminosity classes V, III, and I. Compared to previous works, we find systematic shifts, particularly in effective temperature for dwarfs and in Mv across all classes, which propagate into derived quantities. Applying the Mv calibrations to the full sample yields consistent estimates of radius and luminosity, while spectroscopic mass (Msp) shows significant scatter. We also evaluate the FW3414 parameter (from the Hbeta line) as a calibrator for Mv, useful in large surveys lacking reliable spectral classification. Excluding SB1 systems has a noticeable impact only on the Msp calibration for LC V. These updated empirical calibrations offer a robust reference for Galactic O-type stars and will support studies of massive star populations in both Galactic and extragalactic contexts, particularly in the era of large spectroscopic surveys.

The number of Ultraluminous X-ray Sources (ULXs) is observed to be correlated with the current star formation rate in late-type galaxies and with the stellar mass in early-type galaxies (ETGs). Since there is very little gas, dust or star formation in ETGs, it has been suggested that most of the ULXs associated with them could be high luminosity Low Mass X-ray Binaries (LMXBs) or foreground/background sources. It has been reported that NGC 5813, the central dominant (cD) galaxy in the NGC 5846 group of galaxies, which shows signs of a possible recent merger event, has an unusually high number of ULXs. We have undertaken a multi-epoch spectral study of the persistent ULXs in the galaxy using Chandra and XMM-Newton observations. Of the eight ULXs reported elsewhere, four have been re-identified, two are not consistently detected across all nine Chandra observations, and two are found to be foreground sources. One new persistent ULX has been identified. We present a spectral analysis of the five ULXs with luminosity consistently greater than $10^{39}$ erg/s in nine Chandra-ACIS observations, and assess their variability, adding data from XMM-Newton. The association of these ULXs with globular clusters was examined: we find one ULX lying within the field of an HST observation within 0.1$^\prime$ of the centre of a globular cluster. Optical and UV counterparts are found for another ULX. One of the ULXs is found to be variable over the time scale of days, but there is no unambiguous evidence of longer-term variability for the remaining ULXs.

The results of the analysis of the NEVOD-DECOR data on the study of inclined muon bundles (with zenith angles from 40 to 85 degrees) of cosmic rays for the period from 2012 to 2023 are presented. An original method for studying the muon component of extensive air showers, local muon density spectra, was used. The data are compared with the calculations based on the simulation of air showers using the CORSIKA program for different models of hadronic interactions. The estimates of the energy spectrum and the behavior of the mass composition of primary cosmic rays in a wide energy range from 2 PeV to 3 EeV were obtained. They are compared with the data of other experiments.

Context. Simulating stellar dynamics in a molecular cloud environment is numerically challenging due to the strong coupling between young stars and their surrounding gas, and the large range of length and time scales. Aims. This paper is the first of a suite aimed at investigating the complex early stellar dynamics in star-forming regions. We present a new simulation framework which is the key to generating a larger set of simulations, enabling statistical analysis. Methods. Methods originating from the stellar dynamics community, including regularisation and slowdown methods (SDAR), have been added to the hydrodynamical code Phantom to produce simulations of embedded cluster early dynamics. This is completed by a novel prescription of star formation to initialise stars with a low numerical cost, but in a way that is consistent with the gas distribution. Finally, a prescription for H ii region expansion has been added to model the gas removal. Results. We have run testcase simulations following the dynamical evolution of stellar clusters from the cloud collapse to a few Myr. Our new numerical methods fulfil their function by speeding up the calculation. The N-body dynamics with our novel implementation never appear as a bottleneck. Our first simulations show that massive stars largely impact the star formation process and shape the dynamics of the resulting cluster. Depending on the position of these massive stars and the strength of their feedback, they can prematurely dismantle part of the cloud or trigger a second event of cloud collapse, preferentially forming low-mass stars. This stochastic behaviour confirms the need for statistical studies. Conclusions. Our new Phantom N-Body framework enables efficient simulation of the formation and evolution of star clusters. It enables the statistical analysis needed to build models of the dynamical evolution of embedded star clusters.

The cross-correlation of galaxies at different redshifts with other tracers of the large-scale structure can be used to reconstruct the cosmic mean of key physical quantities, and their evolution over billions of years, at high precision. However, a correct interpretation of these measurements must ensure that they are independent of the clustering properties of the galaxy sample used. In this paper we explore different prescriptions to extract tomographic reconstruction measurements and use the FLAMINGO hydrodynamic simulations to show that a robust estimator, independent of the small-scale galaxy bias, can be constructed. We focus on the tomographic reconstruction of the halo bias-weighted electron pressure $\langle bP_e\rangle$ and star-formation density $\langle b\rho_{\rm SFR}\rangle$, which can be reconstructed from tomographic analysis of Sunyaev-Zel'dovich and cosmic infrared background maps, respectively. We show that these quantities can be reconstructed with an accuracy of 1-3\% over a wide range of redshifts, using different galaxy samples. We also show that these measurements can be accurately interpreted using the halo model, assuming a sufficiently reliable model can be constructed for the halo mass function, large-scale halo bias, and for the dependence of the physical quantities being reconstructed on halo mass.

Spatially resolved gas-phase metallicity maps are a crucial element in understanding the chemical evolution of galaxies. We present spatially resolved metallicity maps obtained from NIRISS/WFSS observations. This is the first such work presenting multiple individual galaxies. We investigate the source of ionisation, metallicity and its relation to star-formation in a spatially-resolved sense for a sample of eight galaxies -- four from JWST-PASSAGE and four from GLASS-JWST ERS. All but one galaxy are in the redshift range $1.9 \leq z \leq 2$, the outlier being at $z = 3.1$. Our sample covers a range of $8.0 <$ \logM $< 9.5$ in stellar mass, $0.2 <$ $\log{\rm{(SFR}}$/\Msunpyr) $< 1.1$ in star-formation rate (SFR) and $7.8 <$ \logOH $< 9.0$ in global metallicity. As a solution to the challenge of SF-AGN demarcation in absence of resolved \halpha, we present a new SF-demarcation line in the \textit{OHNO} parameter space based on MAPPINGS v5.1 publicly available \hii region model grids. We present the mass-metallicity gradient relation for our sample, which showed no clear trend with stellar mass, perhaps hinting at the fact that the high-$z$ galaxies have not yet started their accretion dominated phase. By interpreting the correlation between spatially resolved metallicity and SFR maps as a proxy for effective timescales of metal-transport in galaxies, we find a weak trend such that this timescale increases with stellar mass, implying a more effective feedback in lower mass galaxies.

The motivation of this paper is to obtain reliable constraints of transition redshift ($z_{ztr}$) and, in combination with the evolution of the Hubble constant ($H_{0}$) that could alleviate the Hubble tension, discuss the possible origin of the tension. Utilizing the latest H(z) measurements and different methods ($\Lambda$CDM model, Cosmography, and Gaussian process method), we investigated the impact of methodology and dataset on $z_{ztr}$ constraints, and find that the choice of method has a greater impact on $z_{tr}$ than the observations themselves. Through a statistical analysis of the $z_{ztr}$ constraints from 2004 to 2024, we find that total $z_{tr}$ constraints (2004$-$2024) can be well described by a Gaussian function with the mean value 0.65 and the standard deviation 0.16; that is, $\bar{z}_{tr}$(all) = 0.65 $\pm$ 0.16. And we confirmed that both dataset and methodology can indeed significantly affect the final constraints. The screened $z_{tr}$ constraints with free $H_{0}$ gives a new result $\bar{z}_{tr}$(free) = 0.64 $\pm$ 0.16. Coincidentally, the $z_{tr}$ results overlap with the initial moment of $H_{0}$ evolution ($H_{0}$ value starts to deviate from the Planck result). This may suggest that the Hubble tension might be closely related to this particular period in the evolution of the Universe.

We present a catalog of gravitational wave background (GWB) signal templates from cosmic-string networks, based on relevant models proposed in the literature. We classify templates as conventional, based on standard cosmology and Nambu-Goto results (VOS and BOS), and beyond conventional, based on modifications of a) the loop number density (LRS, super, metastable, current-carrying strings), b) the expansion history (non-standard cosmologies, extra degrees of freedom, either thermal or secluded), or c) the loop properties (birth length, power emission). Using the SBI package $\texttt{GWBackFinder}$, we quantify the reconstruction precision of each signal by LISA, scanning over their parameter space, and performing model comparisons. For conventional signals, LISA reconstructs the tension $G\mu$ with an error $\lesssim 10\%$ for $G\mu \gtrsim 5\cdot 10^{-15}$, which decreases down to $2-3\%$ for $G\mu \gtrsim 10^{-12}$. BOS and VOS modelings become distinguishable confidently for $G\mu \gtrsim 5\cdot 10^{-13}$. For beyond-conventional signals, we identify SNR and error-threshold intervals for each parameter, and determine (for few examples) the regions where they can be distinguished from conventional signals. Analogous quality reconstruction studies of cosmic-string GWBs, superimposed over leading astrophysical foregrounds in the LISA window, will be presented in a series of upcoming papers.

In this study, a new semi-empirical calibration is proposed between ultraviolet emission lines (\ion{C}{iii}]$\lambda1909$, \ion{C}{iv}$\lambda1549$, \ion{He}{ii}]$\lambda1640$) of type~2 AGNs and their metallicity ($Z$). This calibration is derived by comparing a large sample of 106 objects (data taken from the literature) located over a wide range of redshifts ($0 \: \lesssim \: z \: \lesssim \: 4.0$) with predictions from photoionization models that adopt a recent C/O-O/H relation derived via estimates using the $T_{\rm e}$ method, which is considered the most reliable method. We found that the new calibration produces $Z$ values in agreement (within an uncertainty of $\pm 0.1$ dex) with those from other calibrations and from estimates via the $T_{\rm e}$-method. We find also that AGN metallicities are already high at early epochs, with no evidence for monotonic evolution across the redshift range $0 \: \lesssim \: z \: \lesssim \: 12$. Notably, the highest metallicities in our sample, reaching up to $\rm 4\: Z_{\odot}$, are found in objects at $2 \lesssim z \lesssim 3$. This redshift range coincides with the peak of the cosmic star formation rate history, suggesting a strong connection between the major epoch of star formation, black hole growth, and rapid metal enrichment in the host galaxies of AGNs. Furthermore, our analysis reveals no significant correlation between AGN metallicity and radio properties (radio spectral index or radio luminosity) or host galaxy stellar mass. The lack of a clear mass-metallicity relation, consistent with findings for local AGNs, suggests that the chemical evolution of the nuclear gas is decoupled from the global properties of the host galaxy.

In this work, we investigate the Dirac Born Infeld chameleon scalar field model in light of the latest cosmological observations, analyzing the model both with the incorporation of the chameleon mechanism and without it. Results from current cosmological observations, such as Pantheon Plus, DES Y5, DESI DR2, and the compressed Planck likelihood, are used to constrain the model. We consider the AdS throat in the form of $f(\phi) = \lambda / \phi^4$ and a potential $V(\phi) = m_0^2 \phi^2 + m_1^2 \phi^4$ .One interesting finding from our analysis is that, without the chameleon mechanism, the mean value of $m_1 \simeq 0$ indicates the self-interaction of the DBI field could potentially be negligible. Constraints on the potential parameters do not appear when considering the chameleon mechanism, but the warp parameter and chameleon coupling parameter are forced to satisfy $\eta \geq 0$ and $\beta \leq 0$. Different choices of $\beta$ render the same background cosmological parameters. The equation of state $w_{\rm DE}$ resides more in the quintessence region in the past. There is no phantom crossing in this model under our assumption of the warp throat and potential. By computing the $\Delta \text{AIC}$ relative to the $\Lambda$CDM model, we study statistical model comparison. The model as a candidate of dynamical dark energy is observationally viable at the cosmological background level.

We report the first detection of circular polarization in 4.7 GHz excited OH masers in star-forming regions made using full Stokes measurements with the Green Bank 100m telescope. The Zeeman shift between the two circular components provides a measure of the magnetic field pervading these maser spots. Three different methods are used to determine the shift in velocity between the Right Circular Polarization and Left Circular Polarization components. We find fields with $B \sim 100$ mG using archival molecular parameters that have limited precision and uncertain values. Reservations of using 1.7 and 6.0 GHz OH masers to estimate magnetic fields in star-forming regions are discussed.

This paper demonstrates how the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) and future baryon acoustic oscillations (BAO) analyses can optimally combine overlapping tracers (galaxies of distinct types) in the same redshift range. We make a unified catalog of Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) in the redshift range 0.8 < z < 1.1 and investigate the impact on the BAO constraints. DESI DR1 contains ~30% of the final DESI LRG sample and less than 25% of the final ELG sample, and the combination of LRGs and ELGs increases the number density and reduces the shot noise. We developed a pipeline to merge the overlapping tracers using galaxy bias as an approximately optimal weight and tested the pipeline on a suite of Abacus simulations, calibrated on the final version of the DESI Early Data Release. When applying our pipeline to the DESI DR1 catalog, we find an improvement in the BAO constraints of 11% for $\alpha_\mathrm{iso}$ and ~7.0% for $\alpha_\mathrm{AP}$ consistent with our findings in mock catalogs. Our analysis was integrated into the DESI DR1 BAO analysis to produce the LRG+ELG result in the 0.8 < z < 1.1 redshift bin, which provided the most precise BAO measurement from DESI DR1 with a 0.86% constraint on the BAO distance scale and a $9.1\sigma$ detection of the isotropic BAO feature.

Recent asteroseismic determinations of {\Delta}M, the integrated mass loss on the red giant branch (RGB), for fields stars show a trend of {\Delta}M decreasing as metallicity increases. This trend among field stars is inconsistent with many existing models of RGB mass loss. The present paper is motivated by a 'plasmoid' model of RGB mass loss in which magnetic flux loops, generated by a shear dynamo operating below the convection zone, are buoyed up to the stellar surface starting at the evolutionary stage right after the RGB 'kink'. This model leads us to examine correlations between, on the one hand, the average post-kink RGB mass loss rate, determined from {\Delta}M and the post-kink RGB lifetime, and on the other hand, stellar properties which exist just after the end of the kink. For three distinct stellar samples, we find strong anti-correlations between the average post-kink RGB mass loss rate and the number of density scale heights in the convection zone. This leads us to propose that the number of density scale heights in the convection zone is a dominant factor in determining the rate of the mass loss process which sets in after the RGB kink.

Ultra-High-Energy (UHE, E $>100$ TeV) gamma rays are one of the few channels to search for and study Galactic PeVatrons. Among the most promising PeVatron candidates are the many UHE gamma-ray sources that have recently been identified on the Galactic Plane. Ground-based particle detectors see these sources as extended rather than point-like, and current generation Imaging Atmospheric Cherenkov Telescopes (IACTs) struggle to study them with effective areas and background rejection that are suboptimal at UHE. A cost-efficient way of constructing an array of IACTs explicitly designed for UHE sensitivity is to sparsely separate many small telescopes. We have simulated, prototyped, and twice deployed a pathfinder array that is instrumented with telescopes designed by the Panoramic Search for Extraterrestrial Intelligence (PANOSETI) team. These 0.5-meter Fresnel lens telescopes are purpose-built for imaging optical transients on nanosecond timescales and are equipped with a $10^\circ\times10^\circ$ silicon photomultiplier camera. Three PANOSETI telescopes were deployed twice in the same temporary configuration at Lick Observatory in March and October 2024. Here we give a brief description of the instrument and present a comparison of simulations with the data collected, including an analysis of the Crab Nebula. We also report on the ongoing deployment of PANOSETI telescopes for the Dark100 array that is planned to operate for five years at Palomar Observatory.

Fast Radio Burst (FRB) 20250316A, detected by CHIME on 2025 March 16 with a fluence of $1.7\pm0.1~\mathrm{Jy\,ms}$ and a dispersion measure of $161.3\pm0.4~\mathrm{pc\,cm^{-3}}$, ranks among the brightest extragalactic FRBs at $\sim 40$ Mpc. We obtained deep Karl G. Jansky Very Large Array follow-up at 15~GHz on 2025 April 5 and 9 and find no persistent radio source (PRS). Our best image reaches an rms of $2.8~\mu\mathrm{Jy\,beam^{-1}}$, yielding a $3\sigma$ upper limit of $<8.4~\mu\mathrm{Jy}$ at the FRB position, corresponding to $\nu L_\nu < 2.4\times10^{35}~\mathrm{erg\,s^{-1}}$. These results represent among the most stringent constraints for a non-repeating FRB, lying $\gtrsim 3$ orders of magnitude below the $\nu L_\nu$ of compact persistent radio sources around well-studied repeaters, thereby disfavoring bright magnetar-nebula scenarios and pointing to low-density, weakly magnetized environments. Interpreting our limit through pulsar-/magnetar-wind synchrotron frameworks places joint constraints on ambient density and engine power. If the empirical PRS--rotation-measure trend reported for repeaters extends to one-off sources, our limit implies $\vert \mathrm{RM} \vert \lesssim 30~\mathrm{rad\,m^{-2}}$, consistent with a clean magneto-ionic sight line and progenitor channels such as neutron-star mergers or giant flares from older magnetars.

We revisit a family of temperature-dependent van der Waals-type equations of state (EOS) to improve the estimation of the adiabatic lapse rate in planetary atmospheres. These EOS generalize the classical van der Waals and Berthelot models by introducing a single parameter that modulates the temperature dependence of intermolecular interactions. We analyze their thermodynamic properties, including critical behavior, spinodal and coexistence curves, and entropy. The adiabatic curves are computed by incorporating explicitly the contribution of molecular vibrational and rotational degrees of freedom. Using a generalized expression for the adiabatic lapse rate, we estimate the adiabatic lapse rate in the troposphere of Titan and Venus. Our results show that the van der Waals-type EOS reproduce observed lapse rates more accurately than the van der Waals EOS.

Context. Magnetic reconnection events are frequently observed in the solar wind. Understanding the patterns and structures within the solar wind is crucial to put observed magnetic reconnection events into context, since their occurrence rate and properties are likely influenced by solar wind conditions. Aims. We employed unsupervised learning techniques such as self-organizing maps (SOM) and K-Means to cluster and interpret solar wind data at 1 AU for an improved understanding of the conditions that lead to magnetic reconnection in the solar wind. Methods. We collected magnetic field data and proton density, proton temperature, and solar wind speed measurements taken by the Wind spacecraft. After preprocessing the data, we trained a SOM to visualize the high-dimensional data in a lower-dimensional space and applied K-Means clustering to identify distinct clusters within the solar wind data. Results. Our analysis revealed that the reconnection events are distributed across five different clusters: a) slow solar wind, b) compressed slow wind, c) highly Alfvénic wind, d) compressed fast wind, and e) ejecta. Compressed slow and fast wind and ejecta are clusters associated with solar wind transients such as stream interaction regions and interplanetary coronal mass ejections. The majority of the reconnection events are associated with the slow solar wind, followed by the highly Alfvénic wind, compressed slow wind, and compressed fast wind, and a small fraction of the reconnection events are associated with ejecta. Conclusions. Unsupervised learning approaches with SOM and K-Means lead to physically interpretable solar wind clusters based on their transients and allow for the contextualization of magnetic reconnection exhausts' occurrence in the solar wind.

This study presents a comparative analysis of mass-loss and dust-production rates in the dwarf galaxies NGC 147 and NGC 185, focusing on long-period variables (LPVs) and pulsating asymptotic giant branch (AGB) stars as primary indicators of dust feedback into the interstellar medium. For NGC 147, the total mass-loss rate is calculated as $(9.44 \pm 3.78) \times 10^{-4} M_{sun} yr^{-1}$, with LPV luminosities ranging from $(6.20 \pm 0.25) \times 10^{2} L_\odot$ to $( 7.87 \pm 0.32) \times 10^{3} L_\odot $. In NGC 185, the total mass-loss rate is higher, at $(1.58 \pm 0.63) \times 10^{-3} M_{sun} yr^{-1}$, with LPV luminosities spanning $ (5.68 \pm 0.23) \times 10^{2} L_\odot $ to $(1.54 \pm 0.66) \times 10^{4} L_\odot$. A positive correlation is observed between stellar luminosity, intrinsic reddening due to circumstellar dust self-extinction, and elevated mass-loss rates. Additionally, comparisons of calculated dust injection rates, two-dimensional dust distribution maps, and observed dust masses provide evidence for a gravitational interaction between NGC 147 and the Andromeda galaxy, which influences the dust distribution within the system.

The Large inclination Distant Objects LiDO survey has discovered the first securely classified object in the 10:1 mean motion resonance of Neptune. This object, 2020 VN40, is short-term stable in the 10:1 resonance, but not stable on Gyr timescales. 2020 VN40 is likely part of the scattering sticking population, and temporarily resides in the 10:1 resonance at ~139.5 au. This discovery confirms that this distant resonance is populated, as a single detection is likely to be indicative of a large population that is difficult to detect due to observational biases. This object has an inclination of 33.4 degrees, and n-body integrations of orbital clones of 2020 VN40 have revealed some unexpected evolutions. While clones of 2020 VN40 show resonant libration around the expected resonance centers of approximately 90, 180, and 270 degrees, for a restricted range of inclination and eccentricity values some clones librate around a resonant argument of 0 degrees. As this occurs for the slightly lower-eccentricity portions of the evolution, this behavior can also be quite stable. Our initial exploration suggests that this libration around a center of 0 degrees is a generic effect for highly inclined objects in n:1 resonances because the nature of their resonant interaction with Neptune becomes a strong function of their argument of pericenter, omega. At large inclination, the resonant islands shift as omega precesses, switching the center of symmetric libration to 0 degrees for omega=90 degrees and omega=270 degrees. 2020 VN40 provides interesting insight into the evolution of the large-inclination resonators, which become more common at increasing semi-major axis.

Cornelis Easton (1864-1929) became a journalist and newspaper editor. During most of his career he was active as an amateur astronomer and contributed important papers in international astronomical journals This concerned three areas. The first was mapping the Milky Way. The book, La Voie Lactee dans l'hemisphere boreal, which he published in 1893, made some impression. Since it had in addition to drawings of the surface brightness of the Milky Way, also extensive descriptions and discussions of features in the structure and a comprehensive, essentially complete, listing and discussion on everything that had ever been published on the Milky Way. Later he produce an isophotal chart and used photographs to improve the map. Easton had been struck by the idea that what he saw was actually a spiral nebula, but then seen edge-on. Considering bright and dark areas he proposed a form for the spiral in the Milky Way System with the center in the direction of the constellation Cygnus. His publications on this Theory of the Milky Way in the Astrophysical Journal in 1900 and 1913 drew much attention, although many astronomers, including Jacobus Kapteyn, kept quite some reservations. The third area concerned correlations between surface densities of stars and surface brightness of the Milky Way. Easton maintained that there was such a correlation for relatively bright stars. T There is a publication Easton failed to include in his list of his publications, namely an 1894 short article in Nature. The elliptical companion NGC205 of the Andromeda Nebula between had on in 1874 and 1889 rotated by 15 degrees. Isophote twists are responsible for the apparent rotation. In 1903 Kapteyn and the University of Groningen bestowed an honorary doctorate upon Easton.

We investigate the accretion of a collisionless, relativistic kinetic gas by a rotating Kerr black hole, assuming that at infinity the state of the gas is described by a distribution function depending only on the energy of the particles. Neglecting the self-gravity of the gas, we show that relevant physical observables, including the particle current density and the accretion rates associated with the mass, the energy, and the angular momentum, can be expressed in the form of closed integrals that can be evaluated numerically or approximated analytically in the slow-rotation limit. The accretion rates are computed in this manner for both monoenergetic particles and the Maxwell-Jüttner distribution and compared with the corresponding results in the non-rotating case. Whereas it is shown that the angular momentum accretion rate vanishes exactly, it is found that the rotation of the black hole has a small but non-vanishing effect on the mass and the energy accretion rates, which is remarkably well described by an analytic calculation in the slow-rotation approximation to quadratic order in the rotation parameter. The effects of rotation on the morphology of the accretion flow are also analyzed.

Dark matter (DM) models with a conserved particle$-$antiparticle number, $n_\chi-n_{\tilde \chi}$, and the asymmetry in the cosmological abundance $n_\chi\neq n_{\tilde \chi}$, are known to be challenged by the existence of old neutron stars (NSs), as the sufficient accumulation of DM will lead to the collapse of NSs into black holes. We demonstrate that the applicability of these constraints is much wider and covers models with symmetric populations of DM, $n_\chi = n_{\tilde \chi}$, as the process of DM capture regulated by a nucleon-DM scattering can be inherently asymmetric, $\sigma_{\chi n}\neq \sigma_{\tilde\chi n}$. The asymmetry is induced by the interference of different types of $\chi$-$n$ interactions, provided that their combination is odd under charge conjugation in the DM sector, $C_\chi$, and even under combined parity $P_{\chi + n}$. We provide a complete analysis of DM-nucleon bilinear $\chi$-$n$ interactions and find that this asymmetry is very generic. Using canonical NS parameters and local DM halo inputs, we exclude spin-averaged scattering cross sections down to $\sigma_{n\chi}\!\gtrsim\!10^{-46}\,{\rm cm}^{2}$ at DM mass $m_\chi\!\lesssim\!10^{10}\,{\rm GeV}$ for the maximally asymmetric capture rate, and show that the constraints persist down to very small values of the cross-section asymmetry, ${\cal A}=(\sigma_{\chi n}- \sigma_{\tilde\chi n})/(\sigma_{\chi n}+ \sigma_{\tilde\chi n})\gtrsim 10^{-5}$.

As gravitational wave astronomy has entered an era of routine detections, it becomes increasingly important to precisely measure the physical parameters of individual events and infer population properties. Eccentricity is a key observable, suggesting that binaries form in a dense stellar environment through dynamical encounters. This work performs the first matched-filtering search for gravitational waves from eccentric binary black holes (BBHs) covering the mass range $[5, 200]~M_\odot$ and eccentricity at 20 Hz up to 0.5 with a newly developed effective-one-body waveform model. Throughout the third observation run of LIGO, Virgo, and KAGRA, we identify 28 BBH events with a false alarm rate below once per 100 yr; all of which were previously reported in the GWTC-3 and 4-OGC catalogs. Additional candidates with false alarm rates between once per 1 and 100 yr are also reported. We perform an injection campaign to characterize the sensitive volume time of our search pipeline. Assuming that none of the eccentric BBH events were missed by previous searches, our results provide constraints on the event rate of eccentric BBHs in the mass range [5, 30] $M_\odot$. For a 30-30 $M_\odot$ BBH with eccentricity 0.5, the event rate is limited to less than 0.06 Gpc$^{-3}$ yr$^{-1}$; this marks an order of magnitude improvement for sensitive volume compared with the previous search with a minimally modeled algorithm without using templates.

We derive the phase acquired by a neutral scalar particle propagating along Reissner-Nordstrom geodesics. Considering two flavours propagating on different trajectories which intersect, we plot the interference pattern induced by gravitational lensing from the charged compact object. Although the effect of the charge is subdominant in the metric, it proves to be significant in the phase, and shifts the interference pattern, compared to the Schwarzschild case. This pattern is characterised by two oscillation lengths which, if known, would allow the determination of both eigen masses independently.