Sazuna/UAT_keywords huggingface dataset:
Asteroid Mass Estimation by Mutual Perturbations During Close Encounters After Gaia Focused Product Release. Mutual perturbations between asteroids during close encounters allow the estimation of their masses using precise astrometric observations. We use all astrometry reported to the Minor Planet Center, high-precision astrometry from ESA's Gaia Focused Product Release, and radar delay-Doppler data when available. A search for close encounters between all known asteroids and a preliminary list of the largest asteroids leads to approximately 975,000 asteroids that may have been perturbed in a measurable way. We find about 86,000 asteroids with signal in their astrometry for one or more asteroid masses. The multidimensional, weighted combination of all estimates yields 77 asteroid masses with signal-to-noise ratio (SNR) &gt; 10, and 232 asteroid masses with SNR &gt; 3, all in the main belt or outer main belt. We did not find any signal for individual masses of Trojans, Centaurs, or Trans-Neptunian Objects. From the estimated asteroid masses, we derive updated density estimates for asteroids with well-determined diameters. The updated total main belt mass estimate (sum of all a &lt; 4.6 au, H &lt; 18) is (13.11 ± 0.06) × 10−10 M⊙.

Keywords: Astrometry, Gaia, Asteroids, Orbit determination
A Refined Photometric Constraint for Exoplanet Direct Imaging Yield Estimation and Observation Scheduling. Science yield studies will drive the development of future direct imaging telescopes, such as the Habitable Worlds Observatory. These studies rely on a metric called completeness, which represents the fraction of planets from an assumed planet population that can be detected for a given observing scenario. Completeness is often calculated by comparing the brightness of planets in the population to the "photometric constraint," or the dimmest planet detectable in a given observing scenario. The photometric constraint has also been used to calculate the probability of directly imaging a planet detected by the radial velocity method. This work shows how to numerically and analytically invert the analytic exposure time calculator used by the Nancy Grace Roman Space Telescope's coronagraph instrument to calculate a precise photometric constraint that accounts for planet─star separation, integration time, zodiacal light brightness during observation, and assumed exozodiacal light. This refined photometric constraint is then used to calculate completeness and probability of detection in an efficient manner. Finally, we show that the probability of detection values calculated using the refined photometric constraint closely tracks the planet's true detectability. We validate our approach by generating realistic planetary systems, simulating an extreme-precision radial velocity survey, performing orbit fits, and computing the probability of directly imaging the fitted planets with a telescope design similar to the future Habitable Worlds Observatory. Our validation tests show that the probability of detection values predicts the number of direct imaging detections to within 4% when scheduling observations at high probability of detection values.

Keywords: Exoplanet detection methods, Exoplanet astronomy, Coronagraphic imaging, Direct imaging, Radial velocity
The Flocculent Structure of the Inner Milky Way Disk. Observations of H I published in 1957 by Westerhout and Schmidt were presented as showing a global face-on view of the spiral structure in the Milky Way. Since then, many studies have attempted to improve on the early map, perhaps presupposing our Galaxy to be characterized by a grand-design pattern of prominent spiral arms. We consider here two approaches to explore the nature of the spiral structure of the inner Milky Way disk using the HI4PI survey. The first is to search for shallow shoulders in the high-velocity wings of H I data along the Galactic equatorial disk of the inner Milky Way that would be expected if the lines of sight swept across interarm regions of low H I density. The second is to look for broad dips in the integrated H I brightness temperature over the high-velocity wings, pertaining to gas near the subcentral region, that would be expected for the interarm region of a grand design. We find neither shallow shoulders nor broad dips in either the northern quadrant I or the southern quadrant IV, indicating that the Milky Way seen interior to the solar orbit is not characterized by a majestic spiral-structure grand design; this conclusion is a robust one, in that it does not depend on measures of distance. Taken together with decades of work on the bits and pieces of the quite disorganized shambles of the inner Galaxy, we suggest that the Milky Way belongs to the category of flocculent spirals.

Keywords: Spiral arms, Milky Way disk, Galaxy structure
A Sample of Eccentric Eclipsing Binaries in TESS. Eccentric eclipsing binaries (EEBs) are the ideal objects to constrain the tidal theory. During the 2 yr mission, TESS 2 minutes cadence mode obtained high-precision photometry of more than 200,000 objects distributed over almost the entire sky. Among these objects, we identify 368 EEBs, including 23 newly discovered systems, through a detailed analysis of periods, light-curve shapes, and eclipses. We have also adopted the two recent TESS-based eclipsing binary catalogs, bringing our sample size to 514. The eccentricity, argument of periastron, absolute magnitude, and intrinsic color are determined for these EEBs. We find the absolute magnitude MG of EEBs has a span of at least 20 mag. Stars as low as 0.15 M⊙and as high as 30 M⊙ can have an eccentric orbit. Based on the parameters of Gaia Radial Velocity Spectrometer spectra, we find four EEBs contain evolved components, namely, TIC146039664, TIC141809359, TIC428249301, and TIC294261093. Overall, more luminous EEBs have a shorter circularization period. There are peculiarities in the eccentricity distribution of the brightest and faintest EEBs (MG &lt; 1 and MG &gt; 5). The former may not have a strict cutoff circularization period, while the latter may still have an eccentric orbit at periods shorter than 1 day.

Keywords: Binary stars
A Deep Search for Exomoons around WISE 0855 with JWST. The James Webb Space Telescope (JWST) is collecting time-series observations of many free-floating planets (FFPs) to study their weather, but these light curves provide ideal datasets for locating exomoons that transit FFPs during observations. In this paper, we present observations of the planetary-mass Y dwarf (T = 250─285 K, M = 6.5 ± 3.5MJup, d = 2.3 pc) WISE J085510.83─071442.5 (WISE 0855), whose proximity and brightness make it ideal for a transiting exomoon search. We examine 11 hr of time-series spectra from the JWST Near-infrared Spectrograph (NIRSpec), whose sensitivity, in combination with Gaussian process modeling, allows for the disentanglement of exomoon transits from WISE 0855's variability. We do not find statistically significant evidence of an exomoon transit in this dataset. Using injection and recovery tests of artificial transits for depths ranging between 0.1% and 1% (0.35─1.12 R⊕), we explore the exomoon parameter space where we could successfully detect transits. For transit depths ≥0.5% (1.96 RTitan), our detection rate is 96%, which for WISE 0855 corresponds to a moon with a companion-to-host mass ratio similar to that of Titan and Saturn. Given our sensitivity, transit probabilities, and observational duration, we determine a ∼91% probability of detecting a Titan mass analog exomoon after 18 such observations if every observed system hosts a Titan mass analog exomoon in a Galilean-like system. This suggests that JWST observations of dozens of FFPs could yield meaningful constraints on the occurrence rate of exomoons. This paper is the first demonstration that JWST is sensitive to Galilean moon mass analogs around FFPs.

Keywords: Natural satellites (Extrasolar), Transits, Brown dwarfs, Y dwarfs, Free floating planets
Modeling the Optical Colors of Galactic Cirrus Clouds in the Stripe 82 Region. Observations have shown that the optical colors of Galactic cirrus clouds differ significantly from those of extragalactic sources; thus, they can be used to distinguish Galactic cirrus from extragalactic low surface brightness (LSB) features. To understand these properties, we calculate radiative transfer models in dust clouds, where photons are incident from the ambient interstellar medium (ISM). Dust clouds are modeled to mimic a turbulent medium using a fractional Brownian motion algorithm, resulting in a lognormal density distribution and a power-law power spectral density that are appropriate for the ISM. The results are compared with optical observations of cirrus clouds in the Stripe 82 region. The observed color─color (g − r, r − i, and i − z) diagrams of the cirrus clouds can be reproduced by scattered light if the interstellar radiation field (ISRF) of Mathis et al. (as updated by Draine) is modified, either by reducing the intensities in the i and z bands or by enhancing those in the g and r bands. Similar results can also be obtained by adjusting the scattering albedos at the corresponding wavelengths. This demonstrates that the color─color diagrams are effective not only for identifying extragalactic LSB features but also for studying the ISRF and the properties of interstellar dust.

Keywords: Optical astronomy, Interstellar dust extinction, Interstellar medium, Radiative transfer simulations, Milky Way Galaxy
HST-COS Transit Spectroscopy of KELT-20b: First Detection of Excess Far-ultraviolet Absorption from an Ultrahot Jupiter. KELT-20 b is an ultrahot Jupiter with an equilibrium temperature of 2260 K orbiting a bright (V = 7.6), fast-rotating ( vsini  = 117 km s−1) A2 V star. The atmosphere of KELT-20 b has been studied extensively via transmission spectroscopy at optical wavelengths, showing strong hydrogen absorption and metals such as Na I, Ca II, Fe I, Fe II, Mg I, Si I, and Cr II. The atmospheric and ionization conditions of this planet may differ from Jupiter-mass exoplanets owing to the relatively weak extreme-ultraviolet radiation from its host star, as the stellar dynamo that generates chromospheric and coronal activity is thought to shut down at spectral types earlier than A4. We present the first spectroscopic observations of KELT-20 b in the far-ultraviolet (FUV) using the Hubble Space Telescope Cosmic Origins Spectrograph, searching for previously undetected low-ionization and neutral atoms in the upper atmosphere. We find that the FUV transit depth increases with decreasing wavelengths, from 1.88% ± 0.04% at 1600─1760 Å to 2.28% ± 0.04% at 1410─1570 Å, yielding planetary radii of 0.1139R* ± 0.06R* and 0.1222R* ± 0.07R*, respectively. We report tentative detections of Fe II and N I at 2.4σ each and nondetections of C I, S I, Al II, and Si II. We find no evidence for molecular absorption from CO or H2 and no sign of hydrodynamic escape.

Keywords: Hot Jupiters, Ultraviolet spectroscopy, Exoplanet atmospheres, Transmission spectroscopy
Ultracool dwarf Science with MachIne LEarning (USMILE). I. Scalable Tree-based Models for Photometric Spectral Classification and New Discoveries from LSST Data Preview 1 and Euclid Quick Data Release 1. We present Ultracool dwarf Science with MachIne LEarning (USMILE), a program applying machine learning tools for the discovery and characterization of ultracool dwarfs. We introduce USMILE Avocado, a spectral classification framework that uses broadband photometry from wide-field surveys—Rubin Observatory LSST Data Preview 1 (DP1), VISTA Hemisphere Survey (VHS), and CatWISE—as input features. The framework comprises two gradient-boosted decision-tree models scalable to the massive data volumes of modern surveys: the classifier, which distinguishes ultracool dwarfs from stellar/extragalactic contaminants, and the regressor, which predicts spectral types. A key strength is its ability to natively handle missing photometric features, common in wide-field searches, whereas earlier machine learning approaches required complete multiband detections or relied on imputation, thereby excluding genuine ultracool dwarfs or introducing bias. Trained on an augmented labeled data set of &gt;2 million sources built from known ultracool dwarfs, reddened early-type stars, and quasars, the models achieve strong performance: the classifier attains an Area Under the Curve of the Receiver Operating Characteristic of 0.976 and an F1 score of 0.92, while the regressor yields a mean squared error of 0.88 subtypes. Applying these models, we carried out the first ultracool dwarf search with LSST DP1, cross-matched against VHS and CatWISE. Crucially, Euclid Quick Data Release 1 provided near-infrared spectra for hundreds of candidates, enabling a rare, large-scale external spectroscopic validation. This confirmed 15 M6─L2 discoveries, verified USMILE performance, and clarified regimes where USMILE predictions are most reliable. Building on these insights, we identified 25 additional high-quality M6─L9 photometric candidates. These early discoveries demonstrate the effectiveness of scalable machine learning methods in the data-rich era of wide-field surveys, highlighting the synergy between LSST and Euclid in expanding the ultracool dwarf census.

Keywords: M dwarf stars, Brown dwarfs, Sky surveys, Photometry, Spectroscopy
Removing Atmospheric Turbulence from Ground-based Astrometry with Fast Correlation Function Measurements. We present a code that removes ∼90% of the variance in astrometric measurements caused by atmospheric turbulence, by using Gaussian process regression (GPR) to interpolate the turbulence field from the positions of stars measured by Gaia to the positions of arbitrary targets. This enables robust and routine accuracy of 1─3 milliarcsec on bright sources in single exposures of the Dark Energy Survey (DES) and the upcoming Legacy Survey of Space and Time (LSST). For the kernel of the GPR, we use the anisotropic correlation function of the turbulent displacement field, as measured directly from the Gaia reference stars, which should yield optimal accuracy if the displacement field is Gaussian. We test the code on 26 simulated LSST exposures and 604 real DES exposures in varying conditions. The average correlation function of the astrometric errors for separations  &lt;1'  is used to estimate the variance of turbulence distortions. On average, for DES, the post-GPR variance is ∼12× smaller than the pre-GPR variance. Application of the GPR to LSST is hence equivalent, for brighter stars and asteroids, to having 12 Rubin observatories running simultaneously. The expected improvement in the root mean square (rms) of turbulence displacement errors is the square root of this value, ∼3.5. The post-GPR rms displacement decreases with the density of reference stars as  ∼n⋆−0.5  for noiseless LSST simulations, and  ∼n⋆−0.3  for DES data.

Keywords: Atmospheric effects, Sky noise, Astrometry, Gaussian Processes regression
Search for Past Stellar Encounters and the Origin of 3I/ATLAS. 3I/ATLAS, the third discovered interstellar object, has a heliocentric speed of 58 km s−1 and exhibits cometary activity. To constrain the origin of 3I/ATLAS and its past dynamical evolution, we propagate the orbits of 3I/ATLAS and nearby stars to search for stellar encounters. Integrating orbits in the Galactic potential and propagating the astrometric and radial-velocity uncertainties of 30 million Gaia stars, we identify 25 encounters with median encounter distances less than 1 pc. However, because the encounter speeds between 3I/ATLAS and each encounter exceed 20 km s−1, none is a plausible host under common ejection mechanisms. We infer stellar masses for most stars and quantify the gravitational perturbations exerted by each individual star or each binary system on 3I/ATLAS. The strongest gravitational scattering perturber is a wide M dwarf binary. Among all past encounters, the binary's barycenter and 3I/ATLAS reach the small encounter distance of  0.242−0.084+0.089  pc and the encounter speed of  28.39−0.67+0.67  km s−1 1.64 Myr ago. We further demonstrate that the cumulative influence of the stellar encounters on both the speed and direction of 3I/ATLAS is weak. Based on the present kinematics of 3I/ATLAS to assess its origin, we find that a thin-disk origin is strongly favored because the thin disk both exhibits a velocity distribution closely matching that of 3I/ATLAS and provides the dominant local number density of stars.

Keywords: Milky Way disk, Close encounters, Gaia, Interstellar objects
The Next Generation Virgo Cluster Survey (NGVS). XL. The Morphological Classification of Virgo Cluster Galaxies. We present a study of morphologies, based on deep  u*g'i'z' imaging of the Virgo Cluster from the Next Generation Virgo Cluster Survey, for 3689 Virgo cluster members spanning a mass range of ∼1011─105M⊙. Our analysis introduces a new, two-component visual classification scheme developed to capture the morphological diversity of galaxies over more than 6 orders of magnitude in stellar mass. Our morphological classifications use two parameters to describe the global structure and star formation activity of each galaxy. Structural subcodes denote features such as spiral arms, bars, disks, shells, and streams, while star formation subcodes indicate the form and location of the current star formation activity (e.g., in cores, clumps, filaments). These visual classifications rely on deep  g' -band images, supplemented by  u*g'i'  color images, as well as unsharp-masked images for a subset of objects. We compare our classifications to previous results for bright member galaxies that used more established schemes, finding good agreement. We also measure quantitative classification statistics (e.g., CASGM20) for a subset of the brighter galaxies, and present catalogs for some galaxy types of special interest, including structurally compact galaxies, ultradiffuse galaxies, candidate ultracompact dwarf transition objects, as well as candidate postmerger systems. These morphological classifications may be useful as a training set in the application of machine learning tools to the next generation of wide-field imaging surveys.

Keywords: Galaxy clusters, Galaxy evolution, Galaxy classification systems
Can the Central Compact Object in HESS J1731–347 Be Indeed the Lightest Neutron Star Observed?. The exceptionally low mass of   for the central compact object (CCO) XMMU J173203.3–344518 (XMMU J1732) in the supernova remnant (SNR) HESS J1731–347 challenges standard neutron star (NS) formation models. The nearby post–asymptotic giant branch star IRAS 17287–3443 (≈0.6M⊙), also within the SNR, enriches the scenario. To address this puzzle, we advance the possibility that the gravitational collapse of a rotating presupernova (SN) iron core (≈1.2M⊙) could result in a low-mass NS. We show that angular momentum conservation during the collapse of an iron core rotating at ≈45% of the Keplerian limit results in a mass loss of ≈0.3M⊙, producing a stable newborn NS of ≈0.9M⊙. Considering the possible spin-down, this indicates that the NS is now slowly rotating, thus fulfilling the observed mass–radius relation. Additionally, the NS's surface temperature (≈2 × 106 K) aligns with canonical thermal evolution for its ≈4.5 kyr age. We propose the pre-SN star, likely an ultrastripped core of ≈4.2M⊙, formed a tidally locked binary with IRAS 17287–3443, with a 1.43 day orbital period. The SN led to a ≈3M⊙ mass loss, imparting a kick velocity ≲670 km s‑1, which disrupted the binary. This scenario explains the observed 0.3 pc offset between XMMU J1732 and IRAS 17287–3443 and supports the possibility of CCOs forming in binaries, with rotation playing a key role in core collapse, and the CCO XMMU J1732 being the lightest NS ever observed.

Keywords: Neutron stars, Close binary stars
Multiwavelength Study of Five Distant Transient Gamma-Ray AGNs with z &gt; 1. The multiwavelength emissions, especially gamma-rays, of active galactic nuclei (AGNs) are essential for studying the physical properties of jets emanating from supermassive black holes at galaxy centers. However, for high-redshift AGNs, it is challenging to identify their gamma-ray emissions due to limited angular resolution of gamma-ray instruments. In this work, using the infrared light curves of the Wide-field Infrared Survey Explorer (WISE) and spectral measurements through Sloan Digital Sky Survey DR16 quasar observations, we assemble 64 mid-infrared flares with redshift z &gt; 1 as the sample. Based on the Fermi-Large Area Telescope survey data, we search for gamma-ray emission from the 64 WISE sources. New quasi-simultaneous gamma-ray emissions are detected for five sample sources when their infrared emissions are at a flare state, and the infrared positions fall into the error bars of their best-fit gamma-ray positions, as well. We collect the optical data and historical data to perform a spectral energy distribution (SED) analysis. To investigate the multiband characteristics of these five gamma-ray AGNs at flare and quiescent states, a one-zone leptonic model is applied to reproduce their averaged SEDs.

Keywords: Blazars, Relativistic jets, Spectral energy distribution, Gamma-rays
The Impact of Void-finding Algorithms on Galaxy Classification. We explore how the definition of a void influences the conclusions drawn about the impact of the void environment on galactic properties using two void-finding algorithms in the Void Analysis Software Toolkit: Voronoi Voids (V  2 ), a Python implementation of ZOnes Bordering On Voidness (ZOBOV); and VoidFinder, an algorithm that grows and merges spherical void regions. Using the Sloan Digital Sky Survey Data Release 7, we find that galaxies found in VoidFinder voids tend to be bluer and fainter and to have higher (specific) star formation rates than galaxies in denser regions. Conversely, galaxies found in V  2  voids show less significant differences when compared to galaxies in denser regions, less consistent with the large-scale environmental effects on galaxy properties expected from both simulations and previous observations. These results align with previous simulation results that show V  2 -identified voids "leak" into the dense walls between voids because their boundaries extend up to the density maxima in the walls. As a result, when using ZOBOV-based void-finders, galaxies likely to be part of wall regions are instead classified as void galaxies, a misclassification that can be critical to our understanding of galaxy evolution.

Keywords: Galaxy properties, Galaxy environments, Galaxy physics, Voids, Cosmic web, Galaxies