Sazuna/UAT_keywords huggingface dataset:
Once a Triple, Not Always a Triple: The Evolution of Hierarchical Triples That Yield Merged Inner Binaries. More than half of all main-sequence (MS) stars have one or more companions, and many of those with initial masses &lt;8 M ⊙ are born in hierarchical triples. These systems feature two stars in a close orbit (the inner binary) while a tertiary star orbits them on a wider orbit (the outer binary). In hierarchical triples, three-body dynamics combined with stellar evolution drives interactions and, in many cases, merges the inner binary entirely to create a renovated "post-merger binary" (PMB). By leveraging dynamical simulations and tracking binary interactions, we explore the outcomes of merged triples and investigate whether PMBs preserve signatures of their three-body history. Our findings indicate that in 26%–54% of wide double white dwarf (DWD) binaries (s ≳ 100 au), the more massive white dwarf (WD) is a merger product, implying that these DWD binaries were previously triples. Overall, we estimate that 44% ± 14% of observed wide DWDs originated in triple star systems and thereby have rich dynamical histories. We also examine MS+MS and MS+red giant mergers manifesting as blue straggler stars (BSSs). These PMBs have orbital configurations and ages similar to most observed BSS binaries. While the triple+merger formation channel can explain the observed chemical abundances, moderate eccentricities, and companion masses in BSS binaries, it likely only accounts for ∼20%–25% of BSSs. Meanwhile, we predict that the majority of observed single BSSs formed as collisions in triples and harbor long-period (&gt;10 yr) companions. Furthermore, both BSS binaries and DWDs exhibit signatures of WD birth kicks.

Keywords: Blue straggler stars, White dwarf stars, Three-body problem, Stellar mergers
A Novel Approach to Understanding the Link between Supermassive Black Holes and Host Galaxies. The strongest and most universal scaling relation between a supermassive black hole (BH) and its host galaxy is known as the M •–σ relation, where M • is the mass of the central BH, and σ is the stellar velocity dispersion of the host galaxy. This relation has been studied for decades and is crucial for estimating BH masses of distant galaxies. However, recent studies suggest the potential absence of central BHs in some galaxies, and a significant portion of current data only provides upper limits for the mass. Here, we introduce a novel approach using a Bayesian hurdle model to analyze the M •–σ relation across 244 galaxies. This model integrates upper mass limits and the likelihood of hosting a central BH, combining logistic regression for BH hosting probability with a linear regression of mass on σ. From the logistic regression, we find that galaxies with a velocity dispersion of 11, 34, and 126 km s‑1 have a 50%, 90%, and 99% probability of hosting a central BH, respectively. Furthermore, from the linear regression portion of the model, we find that M • ∝ σ 5.8, which is significantly steeper than the slope reported in earlier studies. Our model also predicts a population of undermassive BHs (M • = 10–105 M ⊙) in galaxies with σ ≲ 127 km s‑1 and overmassive BHs (M • ≥ 1.8 × 107) above this threshold. This reveals an unexpected abundance of galaxies with intermediate-mass and ultramassive BHs, accessible to next-generation telescopes like the Extremely Large Telescope.

Keywords: Supermassive black holes, Black hole physics, Bayesian statistics, Black holes, M-sigma relation, Active galaxies, Astrostatistics, Active galactic nuclei, Interdisciplinary astronomy, Hierarchical models, Galaxies
Glitches and Glitching Clusters in Rotation-powered Pulsars. The study of pulsar glitch phenomena serves as a valuable probe into the dynamic properties of matter under extreme high-density conditions, offering insights into the physics within neutron stars. Providing theoretical explanations for the diverse manifestations observed in different pulsars has proven to be a formidable challenge. By analyzing the distribution of glitch sizes and waiting times, along with the evolution of cumulative glitch sizes over time, we have uncovered a long-term clustering phenomenon for pulsar glitches. This perspective allows us to approach the distinct glitch representations in various pulsars from a unified standpoint, connecting the same periodicity of observational data to the randomness. Without relying on specific physical models, we utilized the coefficient of variation to numerically determine optimal clustering numbers and clustering periods for sample pulsars. Our analysis involving 27 pulsars has revealed a clear linear relationship between the glitch cluster period and characteristic age. Of interest, the cumulative distribution of functions of cluster sizes and interval times have the same patterns, which can be synchronously fitted by Gaussian processes. These results may indicate novel understandings of glitches and the resulting processes.

Keywords: Neutron stars, Astrostatistics, Pulsars
Radial Velocity and Astrometric Evidence for a Close Companion to Betelgeuse. We examine a century of radial velocity, visual magnitude, and astrometric observations of the nearest red supergiant, Betelgeuse, in order to reexamine the century-old assertion that Betelgeuse might be a spectroscopic binary. These data reveal Betelgeuse varying stochastically over years and decades due to its boiling, convective envelope, periodically with a 5.78 yr long secondary period (LSP), and quasiperiodically from pulsations with periods of several hundred days. We show that the LSP is consistent between astrometric and radial velocity data sets, and argue that it indicates a low-mass companion to Betelgeuse, less than a solar mass, orbiting in a 2110 day period at a separation of just over twice Betelgeuse's radius. The companion star would be nearly 20 times less massive and a million times fainter than Betelgeuse, with similar effective temperature, effectively hiding it in plain sight near one of the best-studied stars in the night sky. The astrometric data favor an edge-on binary with orbital plane aligned with Betelgeuse's measured spin axis. Tidal spin–orbit interaction drains angular momentum from the orbit and spins up Betelgeuse, explaining the spin–orbit alignment and Betelgeuse's anomalously rapid spin. In the future, the orbit will decay until the companion is swallowed by Betelgeuse in the next 10,000 yr.

Keywords: Binary stars, Red supergiant stars, Radial velocity, Astrometric binary stars, Tidal interaction
Analysis of Gamma-Ray Burst Closure Relationship in Multiple Wavelengths. Gamma-ray bursts (GRBs) are intense pulses of high-energy emission associated with the death of massive stars or compact objects' coalescence. Their multiwavelength observations help verify the reliability of the standard fireball model. We analyze 14 GRBs observed contemporaneously in gamma rays by the Fermi Large Area Telescope, in X-rays by the Swift Telescope, and in the optical bands by Swift and many ground-based telescopes. We study the correlation between the spectral and temporal indices using closure relations according to the synchrotron forward-shock model in a stratified medium (n ∝ r ‑k ) with k ranging from 0 to 2.5. We find that the model without energy injection is preferred over the one with energy injection in all the investigated wavelengths. In gamma rays, we only explored the ν &gt; max{ν  c , ν  m } (slow cooling, SC/fast cooling, FC) cooling condition (where ν  c  and ν  m  are the cooling and characteristic frequencies, namely the frequencies at the spectral break). In the X-ray and optical bands, we explored all the cooling conditions, including ν  m  &lt; ν &lt; ν  c  (SC), ν  c  &lt; ν &lt; ν  m  (FC), and SC/FC, and found a clear preference for SC for X-rays and SC/FC for optical. Within these cooling conditions, X-rays exhibit the highest rate of occurrence for the density profile with k = 0, while the optical band has the highest occurrence for k = 2.5 when considering no energy injection. Although we can pinpoint a definite environment for some GRBs, we find degeneracies in other GRBs.

Keywords: Gamma-ray bursts
Engine-fed Kilonovae (Mergernovae). II. Radiation. The radioactive power generated by materials within the ejecta of a binary-neutron-star (BNS) merger powers an optical transient known as a kilonova. When the central remnant of a BNS merger is a long-lived magnetar, it continuously produces a highly magnetized wind, altering both the dynamics and temperature of the ejecta, leading to the expected emergence of an engine-fed kilonova. In the first paper of this series, we conducted a detailed study of the dynamics of wind-ejecta interaction and the efficiency of energy injection through shocks. In this work, we combine this dynamical evolution with both shock-heating and additional X-ray irradiation to model photon diffusion within a constant-opacity ejecta. By calculating the radiation, we obtain the light curve and spectral energy distribution (SED). Our findings reveal that, with energy injection, a blue bump typically appears in the early stages (≲1 day). Furthermore, if the magnetar has not spun down by that time, a brightening in the later stages occurs. Despite this, in a large parameter space, the expected luminosity of the engine-fed kilonova is not significantly higher than the typical r-process kilonova due to limited heating efficiency. The SED of engine-fed kilonovae peaks in the relatively blue band in the early stages and evolves toward the red, but at a slower rate compared to the typical r-process kilonova.

Keywords: Magnetars, Gamma-ray bursts, Transient sources
The Rotation Properties of δ Sct and γ Dor Stars. Based on the LAMOST spectroscopy and TESS time-series photometry, we have obtained a main-sequence star sample of δ Scuti and γ Doradus stars. The sample includes 1534 δ Sct stars, 367 γ Dor stars, 1703 δ Sct ∣γ Dor stars, 270 γ Dor ∣δ Sct stars, along with 105 "dsct candidates" and 32 "gdor candidates". After correcting for projection effects, we derived the equatorial rotational velocity distribution for δ Sct and γ Dor stars and compared it with that of normal stars. The rotational velocity distributions of δ Sct and γ Dor stars are extremely similar, with the only difference potentially due to the rotational variable stars that have not been completely removed. In contrast, the rotational velocity distribution of normal stars is more dispersed compared to pulsating stars. Additionally, the peak rotational velocity of the pulsating stars is about 10 km s‑1 higher than that of normal stars. Unlike the normal stars, which show a monotonic increase in peak velocity with mass between 1.8 and 2.5 M ⊙, the rotational velocity distribution of δ Sct stars does not exhibit a strong mass dependence. We also found that normal stars accelerate during the late main-sequence evolutionary phase, while δ Sct stars decelerate. Furthermore, there may still be unclassified stars with diverse rotational properties in the normal star sample compared to the δ Sct stars, which is likely to be an important contributor to the broader dispersion observed in its rotational velocity distribution. The photometric amplitude in δ Sct stars is modulated with rotational velocity, with high-amplitude stars typically rotating slowly and low-amplitude stars showing a broad distribution of rotational velocities.

Keywords: Early-type stars, Stellar rotation, Gamma Doradus variable stars, Delta Scuti variable stars
Reverberation Mapping of Lamppost and Wind Structures in Accretion Thin Disks. To address the discrepancy where disk sizes exceed those predicted by standard models, we explore two extensions to disk size estimates within the UV/optical wavelength range: disk winds and color correction. We provide detailed, self-consistent derivations and analytical formulas, including those based on a power-law temperature approximation, offering efficient tools for analyzing observational data. Applying our model to four type I active galactic nuclei with intensive reverberation mapping observations, we find a shallower temperature slope (T ∝ R ‑0.66, compared to R ‑3/4 traditionally) and a color-correction factor (f col ≈ 1.6), consistent with previous studies. We observe a positive correlation between accretion rate and color correction with black hole mass. However, the small sample size limits our conclusions. The strong degeneracy between the temperature slope and accretion rate suggests that incorporating flux spectra or spectral energy distributions could improve fitting accuracy. Our simulation approach rapidly generates quasar light curves while accommodating various observational scenarios for reverberation mapping, making it well-suited for training machine learning algorithms.

Keywords: Accretion, Active galactic nuclei
Precise Measurements of the LMC Bar's Geometry with Gaia DR3 and a Novel Solution to Crowding-induced Incompleteness in Star Counting. We present new measurements of the 2D geometry of the LMC's stellar bar with precise astrometric observations of red clump stars in Gaia DR3. We develop a novel solution to tackle crowding-induced incompleteness in Gaia data sets with the Gaia BP-RP color excess. Utilizing the color excess information, we derive a 2D completeness map of the LMC's disk. We find that incompleteness biases the bar measurements and induces large uncertainties. With the completeness-corrected 2D red clump map, we precisely measure the LMC bar's properties using Fourier decomposition. The bar radius (semimajor axis) is   kpc, and its position angle is 121.°26 ± 0.°21. The bar's strength as quantified by the Fourier bi-symmetric amplitude is S bar = 0.27, indicating that the LMC has a significant bar perturbation. We find the bar has an axis ratio of 0.54 ± 0.03, and is offset with respect to the center of the outer disk isophote at R ≍ 5 kpc by 0.76 ± 0.01 kpc. These LMC bar properties agree with a hydrodynamic model where the SMC has undergone a recent direct collision with the LMC. We compare the LMC's bar properties with other barred galaxies in the local Universe, and discover that the LMC is similar to other barred galaxies in terms of bar-galaxy scaling relations. We discuss how our completeness correction framework can be applied to other systems in the Local Group.

Keywords: Hydrodynamical simulations, Galaxy bars, Dwarf galaxies, Large Magellanic Cloud, Astronomical methods
Long Plateau Doth So: How Internal Heating Sources Affect Hydrogen-rich Supernova Light Curves. Some hydrogen-rich core-collapse supernovae (SNeIIP) exhibit evidence of a sustained energy source powering their light curves, resulting in a brighter and/or longer-lasting hydrogen recombination plateau phase. We present a semi-analytic SNIIP light-curve model that accounts for the effects of an arbitrary internal heating source, considering as special cases 56Ni/56Co decay, a central engine (magnetar or accreting compact object), and shock interaction with a dense circumstellar disk. While a sustained internal power source can boost the plateau luminosity commensurate with the magnitude of the power, the duration of the recombination plateau can typically be increased by at most a factor of ∼2–3 compared to the zero-heating case. For a given ejecta mass and initial kinetic energy, the longest plateau duration is achieved for a constant heating rate at the highest magnitude that does not appreciably accelerate the ejecta. This finding has implications for the minimum ejecta mass required to explain particularly long-lasting SNe, such as iPTF14hls, and for confidently identifying rare explosions of the most massive hydrogen-rich (e.g., Population III) stars. We present a number of analytic estimates that elucidate the key features of the detailed model.

Keywords: Type II supernovae
Instabilities along the Axis of the Heliospheric Jets. The heliosphere is influenced by the interaction of neutral hydrogen atoms from the interstellar medium with protons in the heliosheath (HS). The confinement by the solar magnetic field of the HS plasma forms distinct north and south heliospheric jets. Previous global MHD simulations of the heliosphere reveal that instabilities can develop in the heliospheric jets and make them become unstable, giving rise to large-scale turbulence. In this study, we show that there is a low-speed region of solar wind in the HS that provides a precondition for instabilities to develop. The low-speed region is formed due to charge exchange and magnetic tension. This region allows sufficient time for the instabilities to develop and induces a shear flow inside the HS leading to the development of a Kelvin─Helmholtz (K-H) instability. The estimated growth timescale of the K-H instability based on the simulation results is around 5─7 yr. Understanding the development of the instabilities in the HS is crucial for comprehending the dynamic processes within the HS and the structure of the heliosphere.

Keywords: Magnetohydrodynamics, Heliosphere, Termination shock, Solar wind, Solar system, Charge exchange ionization, Heliosheath, Magnetohydrodynamical simulations
Threshold Mass of the General-relativistic Instability for Supermassive Star Cores. The dependence of the final fate of supermassive star (SMS) cores on their mass and angular momentum is studied with simple modeling. SMS cores in the hydrogen-burning phase encounter the general-relativistic instability during stellar evolution if the mass is larger than ∼3 × 104 M ⊙. Spherical SMS cores in the helium-burning phase encounter the general-relativistic instability prior to the onset of the electron–positron pair instability if the mass is larger than ∼1 × 104 M ⊙. For rapidly rotating SMS cores, these values for the threshold mass are enhanced by up to a factor of ∼5, and thus, for SMSs with mass smaller than ∼104 M ⊙, the collapse is triggered by the pair instability, irrespective of the rotation. After the onset of the general-relativistic instability, SMS cores in the hydrogen-burning phase with reasonable metallicity are likely to collapse to a black hole irrespective of the degree of rotation, whereas SMS cores in the helium-burning phase could explode via nuclear burning with no black hole formation, as previous works demonstrate.

Keywords: Supermassive black holes, Massive stars, Gravitational collapse
Toward Understanding the Evolutionary Role of Star-forming Lenticular Galaxies: New H I Detections and Comparison with Quiescent S0s and Red Spirals. As one type of blue early-type galaxy, the evolutionary history and fate of star-forming lenticular galaxies (S0s) remain elusive. We selected 134 star-forming S0s from the Sloan Digital Sky Survey IV MaNGA survey and found that they have steep and warped size–mass relations, similar to quiescent S0s and red spirals, indicating that they may have similar gas dissipation scenarios. These galaxies have a higher central stellar mass surface density than normal blue spirals. The radial profiles of D n4000 and [Mgb/Fe] show that red spirals and quiescent S0s have similar old central populations and high [Mgb/Fe] values, suggesting rapid bulge formation, though red spirals exhibit a steeper gradient possibly due to residual star formation (SF) in outer regions. In contrast, star-forming S0s exhibit profiles between quiescent S0s/red spirals and normal blue spirals, with relatively flat D n4000 and [Mgb/Fe] gradients. More long-term SF history causes normal blue spirals to have very flat D n4000 and [Mgb/Fe] profiles, and the majority of them (79% ± 5%) have a Sérsic index of &lt;2. We also found that the halo mass of star-forming S0s resembles that of quiescent S0s/red spirals, with 82% ± 5% exceeding the critical mass (M halo = 1012 M ⊙ h ‑1). To supplement previous H I detection of star-forming S0s covered by H IMaNGA, we obtained new observations for H I emission from 41 star-forming S0s in our sample using the Five-hundred-meter Aperture Spherical Radio Telescope. We found that the H I mass distribution of star-forming S0s matches that of normal blue spirals, although both star-forming S0s and red spirals are relatively gas-poor, resulting in varying atomic gas depletion times due to different SF levels. Based on these observational results, we discuss the possible evolutionary scenarios of star-forming S0s.

Keywords: Lenticular galaxies, Galaxy evolution, Spiral galaxies, H I line emission
Grain Size in the Class I Protostellar System TMC-1A Constrained with ALMA and Very Large Array Observations. The disk mass and substructure in young stellar objects suggest that planet formation may start at the protostellar stage, through the growth of dust grains. To accurately estimate the grain size at the protostellar stage, we have observed the Class I protostar TMC-1A using the Jansky Very Large Array (VLA) at the Q (7 mm) and Ka (9 mm) bands at a resolution of ∼0.″2 and analyzed archival data of the Atacama Large Millimeter/submillimeter Array (ALMA) at Bands 6 (1.3 mm) and 7 (0.9 mm) that cover the same spatial scale. The VLA images show a compact structure with a size of ∼25 au and a spectral index of ∼2.5. The ALMA images show compact and extended structures with a spectral index of ∼2 at the central ∼40 au region and another index of ∼3.3 in the outer region. Our spectral energy distribution analysis using the observed fluxes at the four bands suggests one branch with a small grain size of ∼0.12 mm and another with a grown grain size of ∼4 mm. We also model polarized dust continuum emission adopting the two grain sizes and compare them with an observational result of TMC-1A, suggesting that the small grain size is preferable to the grown grain size. The small grain size implies gravitational instability in the TMC-1A disk, which is consistent with a spiral-like component recently identified.

Keywords: Protostars, Low mass stars, Circumstellar grains, Circumstellar disks
Constraining the Galactic Structure Using Time Domain Gravitational Wave Signal from Double White Dwarfs Detected by Space Gravitational Wave Detectors. The gravitational wave (GW) signals from a large number of double white dwarfs (DWDs) in the Galaxy are expected to be detected by space GW detectors, e.g., the Laser Interferometer Space Antenna (LISA), Taiji, and Tianqin in the millihertz band. In this paper, we present an alternative method by directly using the time-domain GW signal detected by space GW detectors to constrain the anisotropic structure of the Galaxy. The information of anisotropic distribution of DWDs is naturally encoded in the time-domain GW signal because of the variation of the detectors' directions and consequently the pattern functions due to their annual motion around the Sun. The direct use of the time-domain GW signal enables simple calculations, such as utilizing an analytical method to assess the noise arising from the superposition of random phases of DWDs and using appropriate weights to improve the constraints. We investigate the possible constraints on the scale of the Galactic thin disk and bulge that may be obtained from LISA and Taiji by using this method with mock signals obtained from population synthesis models. We further show the different constraining capabilities of the low-frequency signal (foreground) and the high-frequency signal (resolvable sources) via the Markov Chain Monte Carlo method, and find that the scale height and length of the Galactic thin disk and the scale radius of the bulge can be constrained to a fractional accuracy of ∼30%, 30%, 40% (or 20%, 10%, 40%) by using the low-frequency (or high-frequency) signal detected by LISA or Taiji.

Keywords: Close binary stars, White dwarf stars, Galaxy structure, Gravitational wave sources, Milky Way Galaxy