Sazuna/UAT_keywords huggingface dataset:
Burstiness in Low Stellar Mass Hα Emitters at z ∼ 2 and z ∼ 4─6 from JWST Medium-band Photometry in GOODS-S. We analyze a sample of ∼4500 photometrically selected Hα emitter galaxies at redshifts z ∼ 2 and z ∼ 4─6 selected from James Webb Space Telescope Near-Infrared Camera medium-band images in the Great Observatories Origins Deep Survey South. The bulk (80%) of the galaxies in our sample have stellar masses lower than 108 M⊙, with a median stellar mass of ∼107.3 M⊙. We derive Hα rest-frame equivalent widths (EW 0Hα ), line fluxes, and star formation rates (SFRs) using a robust photometric excess technique tested against spectroscopic measurements, being sensitive to EW 0Hα&gt;75 Å. Both  EW0Hα  and sSFR(Hα) exhibit an anticorrelation with stellar mass. At fixed stellar mass, low-mass galaxies (M⋆ &lt; 108 M⊙) display a steep increase in sSFR(Hα) with redshift, following a relation sSFR(Hα) ∝ (1 + z)2.4 ± 0.3. In contrast, more massive galaxies (M⋆ &gt; 108 M⊙) show a significantly flatter evolution, with sSFR(Hα) ∝ (1 + z)1.0 ± 0.2. By comparing the Hα and rest-frame UV-derived SFRs, we probe the star formation histories of our galaxies in the past 100 Myr. The fraction of low-mass galaxies with signs of bursty star formation from their SFR(Hα)/SFR(UV) is ∼46%. It quickly drops to ∼25% for M⋆ &gt; 108 M⊙. This is consistent with the results from sSFR(Hα), showing 72% and 10%, respectively. SFR(Hα)/SFR(UV) is a stricter criterion than those based on the galaxy sSFR(Hα), as it only identifies starbursts that are at the initial phases of a bursty star formation episode.

Keywords: Infrared astronomy, Galaxy photometry, High-redshift galaxies, Galaxy evolution
Hints of Spin-magnitude Correlations and a Rapidly Spinning Subpopulation of Binary Black Holes. The complex astrophysical processes leading to the formation of binary black holes and their eventual merger are imprinted on the spins of the individual black holes. We revisit the astrophysical distribution of those spins based on gravitational waves from the third Gravitational-wave Transient Catalog, looking for structure in the two-dimensional space defined by the dimensionless spin magnitudes of the heavier (χ1) and lighter (χ2) component black holes. We find support for two distinct subpopulations with greater than 95% credibility. The dominant population is made up of black holes with small spins, preferring χ1 ≍ 0.2 for the primary and χ2 ≍ 0 for the secondary; we report signs of an anticorrelation between χ1 and χ2, as well as evidence against a subpopulation of binaries in which both components are nonspinning. The subdominant population consists of systems in which both black holes have relatively high spins and contains  20−18+18%  of the binaries. The binaries most likely to belong in this subpopulation are massive and slightly more likely to have spin orientations aligned with the orbital angular momentum—potentially consistent with isolated binary formation channels capable of producing large spins, like chemically homogeneous evolution. This hint of a rapidly spinning subpopulation hinges on GW190517, a binary with large, well-measured spins. Our results, enabled by novel hierarchical inference methods, represent a first step towards more descriptive population models for black hole spins and will be strengthened or refuted by the large number of gravitational-wave detections expected in the next several years.

Keywords: Observational astronomy, Black hole physics, Bayesian statistics, Kerr black holes, Compact binary stars, Stellar mass black holes, Gravitational waves, Compact objects, LIGO, Hierarchical models, Astrophysical black holes, Stellar evolution
Impulsively Excited Quasiperiodic Fast-propagating Waves in the Solar Corona. Quasiperiodic fast-propagating (QFP) waves excited by an impulsive, spatially localized velocity perturbation in a curved coronal loop are investigated with three-dimensional numerical simulations. The equilibrium consists of a density-enhanced loop embedded in a magnetic arcade. The initial perturbation is a velocity pulse with either sausage symmetry or kink symmetry (vertically or horizontally polarized), applied near one loop footpoint. Fast magnetoacoustic wave trains guided along the loop (i.e., trapped fast wave trains) arise in both cases due to waveguide dispersion. However, in the kink case, the trapped wave trains are less pronounced than in the sausage case because kink modes exhibit weaker dispersion and weaker compression. Leaky fast magnetoacoustic wave trains also form for all considered symmetries. In the sausage case, the leaky-wave density perturbation is symmetric about the loop plane; in the kink cases it is either symmetric or antisymmetric, depending on whether the excitation is vertically or horizontally polarized. Forward modelling of the observational manifestation of the waves in the optically thin regime shows that trapped wave trains are detectable for all examined viewing angles, whereas leaky-wave signals can be very faint for certain viewing directions. These results support the notion that coronal QFP waves can be excited by a velocity pulse and suggest that the infrequent detection of broad QFP waves may stem from line-of-sight integration effects.

Keywords: Solar coronal loops, Solar coronal waves, Solar corona
Spectral Analysis of the 2019 and 2022 Outbursts of SAX J1808.4-3658. The accreting millisecond pulsar SAX J1808.4-3658 went into outburst from July to November in 2019 and August to October in 2022, which were observed by the Neutron Star Interior Composition Explorer (NICER) and Nuclear Spectroscopic Telescope Array (NuSTAR). In this paper, we first present the light curve for both outbursts using NICER data. Several thermonuclear bursts occurred during these outbursts. We analyze the evolution of the spectra of two thermonuclear bursts that took place during the 2019 NuSTAR observation. We proceed by analyzing the combined broadband spectrum using NICER and NuSTAR for the first time for this source. We jointly modeled the combined quiescent spectra of both outbursts with a self-consistent reflection component. In our best-fit model, we find evidence of reflection, consistently constrain the inclination to 72° −4°+1°  considering this reflection, and identify a 1 keV feature during persistent emission.

Keywords: Low-mass x-ray binary stars, Astronomy data analysis, X-ray bursts, Millisecond pulsars
The Relation between Helium White Dwarf Mass and Orbital Period under Two Types of Opacity. Helium white dwarfs (He WDs) are end products of low-mass red giant donors in close binary systems via stable mass transfer or common envelope evolution. At the end of stable mass transfer, there is a well-known relation between the He WD mass and orbital period. Although this relation has been widely investigated, the influence of different types of opacity at low temperatures is ignored. In this work, we modeled the evolution of white dwarf (WD) binaries with the stellar evolution code MESA and two types of opacity at low temperatures from Ferguson et al. and Freedman et al. We investigated the relation between the WD mass and orbital period and compared these results with observations. We find that the relation derived from the opacity of Freedman et al. is below that from the opacity of Ferguson et al., and the relation derived from the opacity of Freedman et al. can better explain the observations. In addition, we provided fitting formulae for the relations derived from the opacity of Freedman et al. at different metallicities.

Keywords: Millisecond pulsars, Close binary stars, White dwarf stars, Compact binary stars, Roche lobe overflow
Stable Collisionless Tori around Kerr Black Holes. In low-luminosity active galactic nuclei like M87* and Sgr A*, the accretion flow in the vicinity of the black hole is in the collisionless regime, meaning that the collisional mean free path of charged particles is much larger than the dynamical length scales. To properly model the particle energization and emission from the collisionless accretion flow, a promising approach is to employ the global general-relativistic particle-in-cell simulations—a newly developed, fully kinetic, first-principles method. However, it has been challenging to set up an initial condition that involves collisionless gas with finite angular momentum. We present, for the first time, a class of analytic kinetic equilibria of collisionless tori around a Kerr black hole. We have successfully implemented the collisionless tori in our GPU-based GRPIC code framework Aperture, and found them to be stable for hundreds to thousands of dynamical times in 2D axisymmetric simulations when there is no initial seed magnetic field. These kinetic equilibria serve as ideal starting points for future studies of the physics of collisionless accretion and jet launching.

Keywords: Black hole physics, Plasma astrophysics, High energy astrophysics
Advancing the Classification of Gamma-Ray Bursts Using Machine Learning. I. Gamma-Ray Bursts with Extended Emission. Gamma-ray bursts (GRBs) with extended emission (EE) challenge traditional GRB classification schemes, yet their origins remain unknown. In this paper, we employ unsupervised machine learning methods to classify Swift EE GRBs using multidimensional observational parameters. We apply PCA-tSNE and PCA-UMAP for dimensionality reduction followed by AutoGMM clustering and hierarchical consolidation, yielding two distinct machine-classified populations (Merged Clusters I/II). These clusters are systematically evaluated against established classification frameworks, including the Amati-relation-based classification, the Dainotti fundamental plane correlation, the duration-based long/short GRB taxonomy, and the EE GRB categories associated with kilonovae/supernovae (KNe/SNe). Our results indicate that Merged Cluster I (EE-I) predominantly exhibits an association with long GRBs, corresponding to progenitors from massive stellar collapse, while Merged Cluster II (EE-II) is primarily composed of short GRBs, with characteristics consistent with compact binary merger events. The clusters' distinct properties are further validated by the Dainotti relation, with Cluster II showing a tighter fundamental plane correlation. Moreover, the concentration of plateau shift outliers within this cluster reveals properties consistent with a potential merger origin. While the traditional T90 remains broadly effective for subclass discrimination, we demonstrate critical discrepancies that expose inherent limitations of univariate classification. Additionally, our results show that SN/KN-associated EE GRBs typically appear in separate subclusters. Crucially, the discovery of hybrid GRBs unexpectedly coexisting within a shared subcluster reveals remarkable complexity and diversity in the physical origins of EE GRBs. We hope that this data-driven machine learning approach can provide meaningful insights into the physical origins and subclass differentiation of EE GRBs.

Keywords: Gamma-ray bursts
The Compton─Getting Origin of the Large-scale Anisotropy of Galactic Cosmic Rays. Recent studies suggest that the anisotropy in cosmic-ray (CR) arrival directions can provide insight into local acceleration sites and propagation conditions. We developed a unified framework to interpret both the observed energy spectra and the large-scale anisotropy. In this work, we explore the influence of the Sun's motion relative to the local plasma frame—the Compton─Getting (CG) effect—on the anisotropy. We find that incorporating the CG effect could slightly reduce the dipole amplitude and shift the phase away from the direction of the local regular magnetic field at tens of TeV. At lower energies, where the anisotropy from the CR density gradient is weak, the Sun's relative motion becomes more prominent. Below ∼200 GeV, the dipole amplitude increases again, approaching the value expected from the CG effect. Additionally, a phase flip is observed at a few hundred GeV, aligning with the CG direction. Future anisotropy measurements from 100 GeV to TeV energies could serve as a critical test of this effect.

Keywords: Galactic cosmic rays, Cosmic anisotropy, Galaxy magnetic fields, Supernova remnants
The Host Galaxies of Fast Radio Bursts Track a Combination of Stellar Mass and Star Formation, Similar to Type Ia Supernovae. We develop a new statistical framework for studying the host galaxies of astrophysical sources that accounts for both redshift evolution and the multivariate nature of the properties of host galaxies. These aspects are critical when dealing with sources that span a wide range of redshifts, and/or with unknown redshift-dependent selection effects. We apply our method to a sample of fast radio burst (FRB) host galaxies as a means of probing the uncertain progenitor(s) of these events. Using our method, we are able to rule out that FRBs track star formation rate (SFR), as would be expected if FRBs are associated exclusively with young neutron stars born via core-collapse supernovae (SNe). Furthermore, we rule out a recently proposed metallicity-dependent model whereby FRBs track SFR only above an oxygen abundance of  12+log(O/H)∼8 . Motivated by the fact that at least one FRB has been localized to a globular cluster (GC), we also investigate the hypothesis that FRB sources track GC mass and explicitly rule out this scenario. Alternatively, we find that a "mixed" model, whereby FRBs track a linear combination of SFR and stellar mass, best explains the data. The preferred parameters of such a mixed model are similar to those inferred for Type Ia SNe and imply a possible connection between the progenitors of these different transients.

Keywords: High energy astrophysics, Radio bursts, Star formation, Magnetars, Galaxies, Radio transient sources
UVOIR Spectrum, X-Ray Emission, and Proper Motion of the Isolated Neutron Star RX J2143.0+0654. We observed the isolated neutron star (NS) RX J2143.0+0654 with the Hubble Space Telescope (HST) in the UVOIR wavelength range (0.14─1.7 μm). The UV part is consistent with a Rayleigh─Jeans tail of a thermal spectrum, fν ∝ ν2, while a power-law spectrum, fν ∝ να with α ∼ −0.8, dominates in the near-IR─optical. A joint fit of the UVOIR and contemporaneous X-ray spectra with a two-component blackbody with possible absorption features + power-law optical spectrum yields the following temperature and apparent radius of the colder component (which gives the main contribution in the UV): kTcold ≍ 45 eV and Rcold ≍ 6d260 km, where d260 is the distance in units of 260 pc. The temperature and radius of the hotter component, kThot ≍ 106 eV and Rhot ≍ 1.5d260 km; the parameters of an absorption feature at 0.74 keV; and the properties of X-ray pulsations are the same as found in previous X-ray observations. In the near-IR images, the NS is possibly surrounded by extended emission with a characteristic size of ∼2″ and flux densities of about 1.7 and 0.9 μJy at 1.54 and 1.15 μm, respectively. Comparison with a previous HST observation in the optical 14 yr ago shows a proper motion μ ≍ 6 mas yr−1, which corresponds to a small transverse velocity of 7d260 km s−1. It is consistent with the hypothesis that the NS was born in the vicinity of the solar system about 0.5 Myr ago. *Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #17476.

Keywords: Neutron stars
Recovering Ion Distribution Functions. II. Gyrotropic Slepian Reconstruction of Solar Wind Electrostatic Analyzer Measurements. Velocity distribution functions (VDFs) are an essential observable for studying kinetic and wave─particle processes in solar wind plasmas. To experimentally distinguish modes of heating, acceleration, and turbulence in the solar wind, precise representations of particle phase-space VDFs are needed. In the first paper of this series, we developed the Slepian basis reconstruction (SBR) method to approximate fully agyrotropic continuous distributions from discrete measurements of electrostatic analyzers (ESAs). The method enables accurate determination of plasma moments, preserves kinetic features, and prescribes smooth gradients in phase space. In this paper, we extend the SBR method by imposing gyrotropic symmetry (g-SBR). Incorporating this symmetry enables high-fidelity reconstruction of VDFs that are partially measured, as from an ESA with a limited field of view (FOV). We introduce three frameworks for g-SBR, the gyrotropic SBR: (A) 1D angular Slepian functions on a polar cap, (B) 2D Slepian functions in a Cartesian plane, and (C) a hybrid method. We employ model distributions representing multiple anisotropic ion populations in the solar wind to benchmark these methods, and we show that the g-SBR method produces a reconstruction that preserves kinetic structures and plasma moments, even with a strongly limited FOV. For our choice of model distribution, g-SBR can recover ≥90% of the density when only 20% is measured. We provide the package gdf for open-source use and contribution by the heliophysics community. This work establishes direct pathways to bridge particle observations with kinetic theory and simulations, facilitating the investigation of gyrotropic plasma heating phenomena across the heliosphere.

Keywords: Space plasmas, Solar wind, Regression, Solar instruments
Testing the Correlation between Bending Angle and Polarization Properties of Bent Radio Galaxies. The bending of radio galaxies in galaxy clusters is expected to be caused by interactions with the local environment. The physical processes responsible for jet bending, and their influence on the polarization properties of radio galaxies, remain poorly understood, leading to the question of whether the jet properties in bent radio galaxies differ from those in linear radio galaxies. Using a sample of 24 polarized bent radio galaxies, observed with the Karl G. Jansky Very Large Array at 1─2 GHz, we test for correlation of the bending angle with polarization parameters, measuring Faraday rotation, intrinsic fractional polarization, and Faraday rotation dispersion, used here as a measure of turbulence along the line of sight. We find no statistically significant correlations. At the spatial resolution of our dataset (3─46 kpc, median = 18.4 kpc), our results indicate that we are primarily probing larger-scale intracluster medium effects not related to bending angle. The absence of a statistically significant correlation suggests that bent radio galaxies are reliable probes of intracluster magnetic fields, because their intrinsic properties do not appear to introduce systematic biases into measured polarization parameters. We do detect a preference for source magnetic field vectors to align with the direction of jet bending. Finally, we estimate that the POSSUM and Square Kilometre Array surveys will contain ≳300 and ≳1000 polarized radio galaxies, respectively, providing large future samples with a range of bending angles and similar redshift distribution and number of beams per source as in our sample, enabling our results to be tested with greater statistical power.

Keywords: Astrophysical magnetism, Radio galaxies, Polarimetry
A Catalog of M&M Eclipsing Binaries with TESS. We present a catalog of 1292 low-mass (M&M) short-period eclipsing binaries (EBs) observed by the TESS mission. EBs are useful for many aspects of stellar astrophysics, including calibrating stellar models, and catalogs of eclipsing binary properties provide context for population-level inferences. In this work, we present our selection criteria for our catalog, along with steps taken to characterize the orbital and physical properties of our EBs. We further detail crucial steps in vetting our catalog to ensure that the systems in our catalog have a high likelihood of being true M&Ms. Our sample consists primarily of binaries with short-period, circular orbits and often manifest as high-mass ratio "twin" M&Ms. We find that our sample of M&Ms does not exhibit the same excess of contact binaries that similar samples of solar-type binaries do. Using a novel statistical approach, we find a tidal circularization period of approximately 2 days for these binaries, which is significantly shorter than the value typically given in the literature of 7 days. Finally, we explore the prospects for additional companions to our M&Ms. Future avenues include spectroscopic follow-up of bright M&Ms to better characterize low-mass stellar properties and a deeper assessment of the presence of tertiary companions.

Keywords: M dwarf stars, Binary stars, Stellar properties, Star formation, Eclipsing binary stars
Validating the 1D─3D Coupling Stellar Models via Asteroseismology of 18 Kepler Main-sequence Stars. The standard 1D stellar evolution model has poor descriptions of the near-surface layers of stars, and this can be improved by using the atmosphere model computed from 3D hydrodynamical simulations. In this work, we validated the model inferences of the 1D─3D coupling models using 18 well-studied stars from the Kepler LEGACY Sample. We compared our estimates of the fundamental parameters determined with the other six pipelines and obtained good consistency. The results indicate that the 1D─3D coupling models can be applied to characterizing solar-like stars with confidence. Our analysis showed a similar pattern for the surface term in stars with an effective temperature range from ∼5000 to ∼6400 K, suggesting that the surface term of the 1D─3D coupling models is simpler and easier to deal with than that of models using classical atmosphere.

Keywords: Stellar oscillations, Asteroseismology
Subsecond Periodic Fast Radio Bursts from Tidally Induced Starquakes near Black Hole─Neutron Star/Binary Neutron Star Coalescence. More than 800 fast radio bursts (FRBs) have been observed, including some FRBs with unusual properties. Notably, in 2022, the CHIME/FRB Collaboration reported three FRBs exhibiting subsecond periodic/quasiperiodic structures, although FRB 20191221A has recently been reclassified to originate from a galactic pulsar rather than a genuine FRB. In this paper, we propose a novel scenario to account for this class of FRBs with very short subsecond quasiperiodicity. When a neutron star (NS) follows an elliptical orbit around a stellar-mass black hole or another NS near coalescence, its crust may fracture due to direct tidal force from its companion and magnetic stress from the nonuniform magnetic field within, triggering starquake-induced FRBs. The subsecond period in the FRB is explained by the orbital period. We apply our model to current observations and explain the periodic property in FRB 20210206A and FRB 20210213A from CHIME using the appropriate model parameters. The strong magnetic field required by the fitting results of these two FRBs suggests that their central engine is a magnetar.

Keywords: Neutron stars, High energy astrophysics, Radio transient sources