Sazuna/UAT_keywords huggingface dataset:
Discovery of a Rich Population of Compact Hub-filament Systems in a Single Star-forming Complex. We report the discovery of 45 compact hub-filament systems (HFSs; median size ∼2.4 pc) in infrared-dark clouds (IRDCs) in the W33 complex, located at the junction of the Scutum and Norma spiral arms. Using Spitzer 8 and 24 µm, and unWISE 12 μm images, HFSs are identified as regions where three or more filaments converge onto a central hub, appearing as absorption features toward IRDCs. In each IRDC, HFSs mainly lie at the intersections of elongated substructures, associated with groups of protostars and lacking radio continuum emission. Minimum Spanning Tree (MST) analysis shows that protostars are closely associated with the HFSs, with protostellar core separations of ≤0.7 pc, indicating strong clustering within fragmented structures. The HFSs form two main groupings spanning 10─15 pc, with member separations of 1─3.3 pc. Around 65% are tightly clustered (&lt;2 pc), exhibiting rich small-scale structures and emphasizing the uniqueness of the complex. MST analysis of ALMAGAL 1.38 mm continuum cores—predominantly low-mass and embedded in 10 HFSs—reveals a median core separation of ∼0.03 pc. The protostellar spacing (∼0.7 pc) significantly exceeds the thermal Jeans length (∼0.08 pc for temperature ∼18 K and density ∼105 cm−3), whereas the core spacing is smaller than the Jeans length, suggesting that thermal fragmentation may influence core formation but alone cannot explain the larger-scale protostellar distribution. All these findings together support a picture in which fragments of clouds/filaments form clumps hosting compact HFSs that facilitate efficient and clustered star formation, often yielding massive stars.

Keywords: Star formation
Disintegration of Long-period Comet C/2019 Y4 (ATLAS). II. Postperihelion Remnant Recovery. We present an investigation into the fate of disrupting near-Sun comet C/2019 Y4 (ATLAS). Imaging observations with the Lowell Discovery Telescope, obtained 3─5 months after the reported disruption and the last sighting, constrained the primary component C/2019 Y4-B to an absolute magnitude of H &gt; 20.5 or a diameter of D &lt; 0.5 km (assuming a geometric albedo of 0.04) at an outbound heliocentric distance of 2.71 au. A search of shallower data obtained from the Zwicky Transient Facility survey, conducted when components A and B receded from 2.5 to 2.9 au from the Sun, yielded no detections, suggesting that the fragments had either ceased to exist or were not substantially active during this period. The uncertain fate of C/2019 Y4 highlights the challenge in understanding the state of presumably disrupted comets. Our review of six other presumably disrupted long-period comets reveals that negative confirmations were not reported for half of them, leaving their disruption presumptions inconclusive.

Keywords: Long period comets, Near-sun comets
The Compilation and Validation of the Spectroscopic Redshift Catalogs for the DESI-COSMOS and DESI-XMM-LSS Fields. Over several dedicated programs that include targets beyond the main cosmological samples, the Dark Energy Spectroscopic Instrument collected spectra for 304,970 unique objects in two fields centered on the COSMOS and XMM-LSS fields. In this work, we develop spectroscopic redshift robustness criteria for those spectra, validate these criteria using visual inspection, and provide two custom value-added catalogs with our redshift characterizations. With these criteria, we reliably classify 212,935 galaxies below z &lt; 1.6, 9713 quasars, and 35,222 stars. The resulting catalogs achieve a redshift purity exceeding 99.4% across all galaxy samples. As a critical element in characterizing the selection function, we provide the description of 70 different algorithms that were used to select these targets from imaging data. To facilitate joint imaging/spectroscopic analyses, we provide row-matched photometry from the Dark Energy Camera, Hyper-Suprime Cam, and public COSMOS2020 photometric catalogs. Finally, we demonstrate example applications of these large catalogs to photometric redshift estimation, cluster finding, and completeness studies.

Keywords: Cosmology, Catalogs, Galaxy photometry, Spectroscopy, Photometry, Galaxy spectroscopy, Redshift surveys, Galaxies
Dynamical and Photometric Analysis of NGC 146 and King 14: Evidence for a Comoving, Unbound Cluster Pair. To understand the nature of the NGC 146─King 14 cluster pair, we conducted a detailed photometric, astrometric, and dynamical study using multiwavelength data from Gaia DR3, Pan-STARRS1, WISE, and TESS. Using a probabilistic approach, we identified 770 and 690 high-probability members of NGC 146 and King 14, respectively. Both clusters exhibit well-defined radial density profiles consistent with King models. We estimate the cluster ages as 20 ± 5 Myr and 50 ± 10 Myr from isochrone fitting, and distances of 2.98 ± 0.33 kpc and 2.51 ± 0.23 kpc from parallaxes after applying the Bailer-Jones criteria. The clusters show consistent mean proper motions. The mass function slopes (1.51 ± 0.18 and 1.50 ± 0.15) are close to the Salpeter value, and the extinction follows a normal Galactic reddening law (RV ≍ 3.1). Three-dimensional mapping gives a projected separation of ∼9 pc. Orbit integration using the galpy MWPotential2014 model shows that NGC 146 and King 14 move in nearly circular, disk-like orbits with similar mean orbital radii (Rm ∼ 9 kpc) and orbital periods of roughly 255 Myr. A dynamical separation of ∼32 pc indicates that both clusters share a common spatial and kinematic association, consistent with a comoving pair. However, their relative velocity exceeds the escape velocity set by their combined mass, indicating they are not gravitationally bound. TESS light curves reveal seven variable stars, including γ Doradus, SPB stars, and eclipsing binaries, though only one is a likely member. Overall, the clusters likely formed within the same giant molecular cloud and now exist as an unbound comoving pair.

Keywords: Initial mass function, Stellar kinematics, Stellar dynamics, Time domain astronomy, Open star clusters
Millisecond-cadence Radio Frequency Interference Filters. Radio frequency interference (RFI) greatly reduces the sensitivity of radio observations to astrophysical signals and creates false-positive candidates in searches for radio transients. Real signals are missed while considerable computational and human resources are needed to remove RFI candidates. Effective RFI removal is vital to carry out successful searches for fast radio bursts and pulsars. Mitigation techniques that excise RFI on short timescales account for changing radio frequency and pulse environments. We evaluate the effectiveness of three filters, as well as a novel composite of the three, that excise RFI at the cadence at which the data is recorded. Each of these filters operates in a different domain and thus excises a different RFI morphology. The composite filter removes RFI not accessible to other filtering methods. We analyze the performance of these four filters in three different situations: (i) synthetic pulses in Gaussian noise; (ii) synthetic pulses injected into observed spectra; and (iii) test observations of four pulsars. From these tests, we gain insight into how the filters affect both the pulse and the noise level. This allows us to outline which filters should be used and how based on the RFI present and the characteristics of the source signal. These filters both increase sensitivity and reduce the number of false positives. By flagging less than 5% of the spectrum, we demonstrate a 53% increase in detected pulses and a 34% decrease in the number of RFI candidates relative to the HEIMDALL─FETCH─YOUR search pipeline.

Keywords: Radio transient sources, Light pollution, Astronomy software, Radio pulsars
Determining the Detectability of H<SUB>2</SUB>O with Photometric Observations Using Bayesian Analysis for Remote Biosignature Identification on exo-Earths (BARBIE). We examine the detectability of water (H2O) in the reflected-light spectrum of an Earth-like exoplanet assuming a photometric observational approach rather than spectroscopic. By quantifying the detectability as a function of normalized exposure time, resolving power (R), and amount of spectral points, we can constrain whether spectroscopy or photometry is the more efficient observing procedure to detect H2O at varying abundances by measuring the broad 0.94 μm absorption feature using the Habitable Worlds Observatory (HWO). We simulate low-resolution spectroscopy (R = 10, 20, and 30, presented as a photometric bandwidth fraction of 10%, 5%, and 3% herein) as a proxy for narrowband photometric observations, and constrain the wavelength range from 0.85 to 1.05 μm to narrow focus on the 0.9 μm feature. We then constrain the number of spectral points to two or three points at each bandwidth fraction to investigate the impact of spectral point placement on detectability. Additionally, we take the signal-to-noise ratios for strong H2O detection and calculate the resultant exoplanet yields assuming photometric observation and compare to the yields from higher-resolution spectroscopic observations under different noise instances, characterization wavelengths, noise floors, and aperture sizes. We find that H2O is strongly detectable at all bandwidth fractions depending on the spectral point placement, requiring a minimum of three spectral points, at a variety of normalized exposure times depending on the abundance of H2O. We also find that the detector noise is the main driver in determining whether photometry or spectroscopy results in higher yields. Photometry is the preferred observational method in high-noise cases, while spectroscopy is preferred in low-noise scenarios.

Keywords: Exoplanet astronomy, Exoplanet atmospheres
The Transition from Giant Planets to Brown Dwarfs Beyond 1 au from the Stellar Metallicity Distribution. Giant planets and brown dwarfs are thought to form via a combination of pathways, including bottom-up mechanisms in which gas is accreted onto a solid core and top-down mechanisms in which gas collapses directly into a gravitationally bound object. One can distinguish the prevalence of these mechanisms using host star metallicities. Bottom-up formation thrives in metal-rich environments, whereas top-down formation is weakly dependent on ambient metal content. Using a hierarchical Bayesian model and the results of the California Legacy Survey (CLS), a low-bias and homogeneously analyzed radial velocity survey, we find evidence for a transition in the stellar metallicity distribution at a companion mass of  γ=27−8+12MJup  for companions with orbital separations between 1 and 50 au. Companions below and above this threshold tend to orbit stars with higher ([Fe/H] = 0.17 ± 0.12 dex) and lower ([Fe/H] = −0.03 ± 0.10 dex) metallicities, respectively. Previous studies of relatively close-in companions reported evidence of a lower transition mass of ≤10 MJup. When applied to the CLS sample, our model predicts the probability of a transition in the stellar metallicity distribution at or below 10 MJup to be &lt;1%. We compare our results to estimates of γ gleaned from other observational metrics and discuss implications for planet-formation theory.

Keywords: Brown dwarfs, Binary stars, Star formation, Exoplanet formation, Extrasolar gaseous giant planets
A Catalog of Galactic Atomic Hydrogen Position─Position─Velocity Filaments. We present a catalog of 3D Galactic H I filaments over one-third of the sky using Galactic Arecibo L-band Feed Array H I data. The 3D filaments are defined to be linear H I features that are continuous in position─position─velocity (PPV) space and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 H I filaments between ±50 km s−1 at a range of Galactic positions. One thousand five hundred and forty-two of the PPV filaments are identified as local at the distance of the wall of the Local Bubble, and 209 are likely at the disk─halo interface of our Galaxy. The catalog and properties of the PPV filaments are obtained after an unsharp mask (USM) is applied to the data. The widths of the filaments are consistently ∼12 '  (0.34 pc at 100 pc), and constrained by the 4 '  resolution. The local filaments have median properties of NHI(med) (USM) = 6 × 1018 cm−2, MHI = 0.17 M⊙, FWHM = 3.2 km s−1, and a length of 6.4 pc. The disk─halo population has similar column densities, but the median FWHM = 7.7 km s−1, consistent with them being higher z height, warmer structures. The L ∝ M0.5 relationship found for the H I filaments and their bundling on the sky are consistent with a hierarchical structure, and are likely related to turbulence playing a role in their formation.

Keywords: Interstellar filaments, Interstellar atomic gas, Galaxy structure, Circumgalactic medium, Milky Way Galaxy
Dynamical Architectures of S-type Transiting Planets in Binaries. II. A Dichotomy in Orbital Alignment of Small Planets in Close Binary Systems. Stellar multiplicity plays a crucial role in shaping planet formation and dynamical evolution. We present a survey of 54 TESS objects of interest (TOIs) within 300 pc that exhibit significant Hipparcos−Gaia astrometric accelerations. We identified 35 TOIs with stellar companions at projected separations between 0 .″ 1 and 2″ (or 10─200 au). We also identified 12 TOIs that could host planetary-mass or brown dwarf companions, including six that are newly discovered. Furthermore, we perform 3D orbital characterization for 12 binaries hosting confirmed planets or planet candidates, allowing us to constrain the line-of-sight mutual inclination, ∆Ilos, between the planetary and binary orbits. Combining our sample with previous measurements, we apply Bayesian hierarchical analysis to a total of 26 binary systems with S-type transiting planets (rp &lt; 5R⊕). Specifically, we fit the ∆Ilos distribution with both single (Rayleigh) and mixture models (two-component Rayleigh and Rayleigh-isotropic mixture). We find the mixture models are strongly favored ( logZ≳13.9 , or ≍5σ), indicating the observed planet-binary ∆Ilos values likely originate from two underlying populations: one nearly aligned ( σ1=2.°4−0.9+0.7 ) and one with more scattered mutual inclinations ( σ2=23.°6−7.1+8.8 ). Alternatively, the misaligned systems can be equally well described by an isotropic distribution of inclinations. This observed dichotomy likely reflects different dynamical histories. Notably, the misaligned population only emerges in systems with stellar periastron distances &gt;40 au, while systems with close-in or eccentric stellar companions (periastron distances &lt;40 au) preserve planet−binary alignment.

Keywords: Exoplanet dynamics, Transits, Close binary stars, Space astrometry, Exoplanet formation
Dual-backend Multibeam Position-switching Targeted SETI Observations toward Nearby Active Planet-hosting Systems with FAST. The Five-hundred-meter Aperture Spherical Telescope (FAST), the world's largest single-dish radio telescope, lists the search for extraterrestrial intelligence (SETI) as one of its key scientific objectives. In this work, we present a targeted SETI observation for seven nearby active stars utilizing the FAST L-band multibeam receiver, employing an observational strategy that combines position switching with multibeam tracking to balance on-source integration time with the accuracy of the beam response. Using both pulsar and SETI backends, we perform a comprehensive search for narrowband drifting signals with Doppler drift rates within diversified ranges and channel-width periodic signals with periods between 0.12 and 100 s and duty cycles between 10% and 50%. No credible radio technosignatures were detected from any of the target systems. Based on this null result, we place constraints on the presence of transmitters at a 95% confidence level, ruling out narrowband transmitters with EIRP above 3.98 × 108 W and periodic transmitters with EIRP above 1.80 × 1010 W within the observation band.

Keywords: Search for extraterrestrial intelligence, Astrobiology, Radio astronomy, Exoplanets
Distributions of Wide Binary Stars in Theory and in Gaia Data. III. Orbital Momenta, Masses, and Manifestations of MOND. Using the censored catalog of 103,169 resolved Gaia DR3 binary stars with accurate astrometric data for each component, a new observable, object-specific parameter is computed for each pair: the projected orbital momentum. This parameter is the product of four functions of physical characteristics: total mass, semimajor axis, eccentricity, and inclination angle. Using the previously estimated marginal probability densities of eccentricity and semimajor axis, and assuming an isotropic orientation of binary systems, the sample distribution of mass was adjusted using a concordance metric of the observed and synthetic distributions of orbital momenta and an ad hoc functional model. The best-fitting mass density model is found to faithfully reproduce the observed dependence of orbital momenta on apparent separation, although the absolute luminosity distributions indicate a tendency of the widest systems to more frequently include solar-type primaries. The anticipated manifestation of modified Newtonian dynamics is computed in the investigated parameter space {separation, momentum}. This effect is absent in the given data. The median total mass of the widest Gaia binaries is found to be somewhat higher than that of the tighter pairs, which is interpreted as a dynamical age effect.

Keywords: Orbital motion, Monte Carlo methods, Orbital evolution, Modified Newtonian dynamics, Wide binary stars, Gaia
Keck Observations in the INfrared of Taurus and ρ Oph Exoplanets And Ultracool Dwarfs (KOINTREAU) I: A Planetary-mass Companion and a Disk-obscured Stellar Companion Discovered in Taurus. We present the first discoveries from Keck Observations in the Infrared of Taurus and ρ Oph Exoplanets and Ultracool dwarfs (KOINTREAU), an adaptive optics imaging survey of young stars in the Taurus and ρ Oph star-forming regions using the Keck infrared pyramid wavefront sensor. We have found two faint (∆K∼7 mag), wide-separation companions to two ≍3 Myr old Taurus members. Relative astrometry for these systems shows that both companions are bound to their host stars. We obtained near-infrared spectra of these companions using the Infrared Telescope Facility/SpeX (R ∼100) and the Gemini North InfraRed Spectrograph (Gemini/GNIRS; R ∼ 1000─2000), and combined these with photometry from our NIRC2 imaging, the Pan-STARRS survey, and Spitzer/IRAC archival imaging to constrain their properties. One companion, KOINTREAU-1b (at a projected separation of 690 au), has an average near-infrared spectral type of M9 ± 2, a gravity classification of VL-G, and a changing spectral type between the SpeX (M7) and GNIRS (L1) observations. We estimate this object's mass to be  10.6−2.3+2.5  MJup, making KOINTREAU-1b the fifth planetary-mass companion found in Taurus. The other companion, KOINTREAU-2b (projected separation 560 au), has a spectral type of M4.5 ± 1 but is ≍4 mag underluminous relative to other Taurus stars of the same spectral type. We detect exceptionally strong He I 1.083 μm emission from this object, indicative of outflows driven by ongoing accretion, but with a conspicuous lack of accompanying H emission. We conclude that KOINTREAU-2b is a young star obscured by an edge-on disk and observed in scattered light. Finally, we derive a distortion solution for NIRC2 imaging, which shows a 0 .° 118 difference in position angle from the previous distortion solution.

Keywords: M dwarf stars, Observational astronomy, Substellar companion stars, Infrared spectroscopy, Adaptive optics, Exoplanet astronomy, Pre-main sequence stars, Direct imaging, Circumstellar disks, Occulting disks
PEPSI Investigation, Retrieval, and Atlas of Numerous Giant Atmospheres (PIRANGA). II. Phase-resolved Cross-correlation Transmission Spectroscopy of KELT-20b. KELT-20b is a well-studied (Teq = 2262 K) ultrahot Jupiter, but its multidimensional atmospheric structure remains unconstrained. We performed high-resolution cross-correlation transmission spectroscopy (HRCCTS) on a single-transit time series of KELT-20b, observed with the Potsdam Echelle Polarimetric and Spectroscopic Instrument on the Large Binocular Telescope. Upon combining nineteen in-transit exposures, we detect Fe I (11.9σ) and Fe II (23.7σ) and tentatively detect Na I (3.4σ) and Cr I (3.3σ). The full-transit velocity offsets of the strongest absorbers are ∆VFe I = −1.0 ± 0.7 km s−1 and ∆VFe II = 0.0 ± 0.5 km s−1, which are mostly inconsistent with previously published values for KELT-20b, although the previous measurements are mostly inconsistent with each other. By correcting for discrepant systemic velocity solutions of up to 1.7 km s−1 between studies, our Fe II offset becomes consistent with previous measurements (≤1.7σ), while Fe I remains significantly less blueshifted than in earlier studies (≥2.2−4.5σ). We propose a set of detection criteria to improve future reproducibility in HRCCTS work. Phase-resolving the Fe I and Fe II absorption signatures into eight orbital phase bins reveals distinct dynamical regimes: Fe II exhibits a strong phase-dependent blueshift from ingress to egress along with significant limb asymmetry, while Fe I shows weaker signals and a more modest blueshift with phase. These patterns indicate day-to-night winds and suggest scale height differences are a significant driver of limb asymmetry in KELT-20b.

Keywords: High resolution spectroscopy, Hot Jupiters, Exoplanet atmospheric dynamics, Transmission spectroscopy, Doppler shift, Exoplanet atmospheric structure
A Photometric Study of the Late-type Contact Binary MT Cassiopeiae: A Robust Detection of Three Periodic Eclipse Timing Variations. We present 10 sets of light curves of the contact binary MT Cas, obtained over a span of 12 yr from new multiband photometric observations and archival data from Transiting Exoplanet Survey Satellite and American Association of Variable Star Observers. The light curves display flat-bottomed primary eclipses and a variable O'Connell effect, which we modeled with two starspots─one hot and one cool─on the more massive, cooler primary. Photometric solutions using the Wilson─Devinney code classify MT Cas as a W-subtype contact binary with a mass ratio of q = 2.40, inclination i = 83.7°, temperature difference ∆T = 263 K, fill-out factor f = 14%, and third light contribution of 1% ∼ 6%. A total of 719 times of minimum light over 86 yr, including 651 newly determined epochs, reveals a complex period variation comprising a linear trend, a small secular increase of +3.47 × 10−9 day yr−1, and three strictly periodic variations with periods of 2.9247, 8.500, and 18.33 yr. We suggest that the observed period increase results from mass transfer from the secondary to the primary, slightly exceeding angular momentum loss due to magnetic braking. The light-travel time effect periods are found to follow an approximate (1:3:6) commensurability. The dynamical stability and physical implications of the MT Cas system as a multiple system are investigated.

Keywords: Starspots, CCD photometry, Multiple stars, W Ursae Majoris variable stars, Variable star period change