Sazuna/UAT_keywords huggingface dataset:
3D Localization of FRB 20190425A for Its Potential Host Galaxy and Implications. Fast radio bursts (FRBs) are high-energy, short-duration phenomena in radio astronomy. Identifying their host galaxies can provide insights into their mysterious origins. In this paper, we introduce a novel approach to identifying potential host galaxies in three-dimensional space. We use FRB 20190425A and GW190425 as examples to illustrate our method. Recently, due to spatial and temporal proximity, the potential association of GW190425 with FRB 20190425A has drawn attention, leading to the identification of a likely host galaxy, UGC 10667, albeit without confirmed kilonova emissions. We search for the host galaxy of FRB 20190425A with a full CHIME localization map. Regardless of the validity of the association between GW190425 and FRB 20190425A, we identify an additional potential host galaxy (SDSS J171046.84+212732.9) from the updated GLADE galaxy catalog, supplementing the importance of exploring the new volume. We employed various methodologies to determine the most probable host galaxy of GW190424 and FRB 20190425A, including a comparison of galaxy properties and constraints on their reported observation limits using various kilonova models. Our analysis suggests that current observations do not definitively identify the true host galaxy. Additionally, the kilonova models characterized by a gradual approach to their peak are contradicted by the observational upper limits of both galaxies. Although the absence of optical emission detection raises doubts, it does not definitively disprove the connection between the gravitational wave (GW) and FRB.

Keywords: Bayesian statistics, Astronomical object identification, Compact binary stars, Astronomy data analysis, Hubble constant, Astronomical research
Autogenous Electron Acceleration by Ion Flow Vortex in Space Plasmas. Plasma flow vortexes are ubiquitous in space and astrophysical settings and play a vital role in energy and mass transport, contributing to formation of stars and planets, launching and dissipation of astrophysical jets, and coupling between planetary magnetospheres and ionospheres. Here we present in situ observations showing that energetic electrons with energies up to 250 keV can be directly generated inside an ion flow vortex with finite spatial scale. The electron acceleration is achieved by establishment of Fermi acceleration trap and parallel electrostatic potential within the flow vortex, leading to dramatic enhancement of energetic electron flux by at least 1 order of magnitude. The accelerated electrons can drive mass and energy transport along local magnetic field lines and serve as a free energy source for broadband electrostatic emissions. Our observations, suggesting that the ion flow vortex can serve as novel electron accelerators, can be fundamentally important for understanding energetic phenomena in the cosmos, such as nonthermal emissions near astrophysical jets and killer electrons in geospace.

Keywords: Space plasmas, Plasma astrophysics
DA 362: A Gamma-Ray-emitting Compact Symmetric Object. The γ-ray detection from an astrophysical object indicates the presence of an extreme environment where high-energy radiation is produced. With the continuous monitoring of the γ-ray sky by the Fermi Large Area Telescope (LAT) leading to deeper sensitivity, high-energy γ-ray emission has now been detected from a diverse class of jetted active galactic nuclei (AGNs). Here, we present the results of a multiwavelength study of the radio source DA 362, which was reported to be a blazar candidate of uncertain type. However, it was recently identified as a bona fide compact symmetric object (CSO) based on its subkiloparsec, bipolar radio morphology, and lack of radio variability. This makes DA 362 only the fourth γ-ray-emitting object of this enigmatic class of radio-loud AGNs. Using five very-long-baseline interferometry observations covering 1996–2018, we found the jet separation velocity to be subluminal (vapp ~ 0.2c), thus supporting its CSO nature. Its Fermi-LAT observations revealed a γ-ray flaring activity, a phenomenon never detected from the other three γ-ray-detected CSOs. This object is bright in the near-infrared band but extremely faint in the optical-UV filters, hinting at possible obscuration. Swift X-Ray Telescope observation of DA 362 reveals an extremely hard X-ray spectrum, though a strong claim cannot be made due to large uncertainties. We conclude that deeper observations are needed to probe the broadband properties of this enigmatic object and to understand the origin of high-energy γ-ray emission.

Keywords: Gamma-ray astronomy, Relativistic jets, BL Lacertae objects, Radio jets
Are Stars Really Ingesting Their Planets? Examining an Alternative Explanation. Numerous stars exhibit surprisingly large variations in their refractory element abundances, often interpreted as signatures of planetary ingestion events. In this study, we propose that differences in the dust-to-gas ratio near stars during their formation can produce similar observational signals. We investigate this hypothesis using a suite of radiation-dust-magnetohydrodynamic STAR FORmation in Gaseous Environments (or STARFORGE) simulations of star formation. Our results show that the distribution of refractory abundance variations (Δ[X/H]) has extended tails, with about 10%–30% of all stars displaying variations around ∼0.1 dex. These variations are comparable to the accretion of 2–5 M⊕ of planetary material into the convective zones of Sun-like stars. The width of the distributions increases with the incorporation of more detailed dust physics, such as radiation pressure and back-reaction forces, as well as with larger dust grain sizes and finer resolutions. Furthermore, our simulations reveal no correlation between Δ[X/H] and stellar separations, suggesting that dust-to-gas fluctuations likely occur on scales smaller than those of wide binaries. These findings highlight the importance of considering dust dynamics as a potential source of the observed chemical enrichment in stars.

Keywords: Interstellar dust, Stellar abundances, Chemical abundances, Star formation, Interstellar dust processes, Chemically peculiar stars
The Fate of Oceans on First-generation Planets Orbiting White Dwarfs. Several groups have recently suggested that small planets orbiting very closely around white dwarf stars could be promising locations for life to arise, even after stellar death. There are still many uncertainties, however, regarding the existence and habitability of these worlds. Here we consider the retention of water during post-main-sequence evolution of a Sun-like star and during the subsequent migration of planets to the white dwarf's habitable zone. This inward migration is driven by dynamical mechanisms such as planet–planet interactions in packed systems, which can excite planets to high eccentricities, setting the initial conditions for tidal migration into short-period orbits. In order for water to persist on the surfaces of planets orbiting white dwarfs, the water must first survive the asymptotic giant branch phase of stellar evolution, then avoid being lost as a result of photoevaporation due to X-ray and extreme-ultraviolet radiation from the newly formed white dwarf, and finally survive the tidal migration of the planet inward to the habitable zone. We find that while this journey will likely desiccate large swaths of post-main-sequence planetary systems, planets with substantial reservoirs of water may retain some surface water, especially if their migration occurs at later white dwarf cooling ages. Therefore, although stellar evolution may pose a challenge for the retention of water on exoplanet surfaces, it is possible for planets to retain surface oceans even as their host stars die and their orbits evolve.

Keywords: Exoplanet astronomy, White dwarf stars, Habitable zone
Shock and SEP Modeling Study for the 2022 September 5 SEP Event. On 2022 September 5, during Parker Solar Probe's (PSP) 13th encounter, a fast shock wave and a related solar energetic particle (SEP) event were observed as the spacecraft approached the perihelion of its orbit. Observations from the Integrated Science Investigation of the Sun (IS⊙IS) instrument suite show that SEPs arrived at the spacecraft with a significant delay from the onset of the parent solar eruption and that the first arriving SEPs exhibited an inverse velocity dispersion (IVD) for energetic protons above ~1 MeV. Utilizing data from multiple spacecraft, we investigate the eruption dynamics and shock wave propagation. Our analysis includes 3D shock modeling and SEP transport simulations to examine the origins of this SEP event and explore the causes of the delayed SEP onset and the observed IVD. The data-driven SEP simulation reproduces the SEP event onset observed at PSP, its evolving energy spectrum, and the IVD. This IVD is attributed to a relatively slow, ongoing particle acceleration process occurring at the flank of the expanding shock wave intercepted by PSP. This has significant implications for the role of shocks in the release of SEPs at widespread events and for methods used to infer the SEP release times. Furthermore, the match between the simulation and observations worsens when cross-field diffusion is considered, indicating that SEP diffusion had a minor effect on this event. These findings underscore the complexity of SEP events and emphasize the need for advanced modeling approaches to better understand the role of shock waves and other physical processes in SEP acceleration and release.

Keywords: Solar energetic particles, Solar coronal mass ejection shocks, Solar physics
An Exceptionally Powerful, Radiatively Driven Ultrafast Outflow in the Rapidly Accreting AGN RE J1034+396. We report the analysis of ∼1 Ms of XMM-Newton observations of the rapidly accreting active galactic nucleus RE J1034+396. The 0.3–9 keV EPIC-pn spectra are well described by a model consisting of steep continuum emission from the corona accompanied by relativistically blurred reflection from a highly ionized accretion disk. The source is known to exhibit strong excess soft X-ray emission, which we show is well represented by thermal disk photons Comptonized by a warm plasma spanning the inner accretion flow. Additionally, the EPIC-pn data provide compelling evidence (ΔC ∼ 60 for four additional parameters) for the presence of an ultrafast outflow (UFO) with a line-of-sight velocity  , and an emission signature consistent with reflection of the corona from modestly ionized, outflowing gas. The simultaneous 0.5–2.5 keV RGS spectra show clear absorption lines. Modelling of these data confirms the presence of the UFO and constrains its equivalent hydrogen column density, log NH/(atom cm‑2) =  . The RGS data also reveal at least two warm absorber components with a modest outflow velocity (  km s‑1). The measured properties and time evolution of the UFO in RE J1034+396 suggest that it is formed from collisionally ionized plasma, launched from the disk surface and accelerated by radiation pressure. The high terminal velocity and substantial absorbing column density imply that the outflow carries sufficient momentum and energy to transform its environment, being capable of driving out essentially all dust and gas it interacts with along the line of sight, even if the AGN were initially surrounded by a Compton-thick absorber.

Keywords: Active galaxies
On the Use of Galaxy Catalogs in Gravitational-wave Parameter Estimation. A major challenge in gravitational-wave (GW) multimessenger astrophysics is the imprecise localization of GW compact binary mergers. We investigate the use of a method to include galaxy catalog information in performing parameter estimation of these events. We test its effectiveness with the GW events GW170817, GW190425, and GW190814, as well as with simulated binary neutron star mergers. For GW170817, we recover the true host galaxy as the most probable galaxy after a straightforward mass reweighting, with significantly decreased localization area and volume. On the simulated sample, however, we do not find improvement compared to performing a simple galaxy catalog crossmatch with a regular GW localization. Future investigations into sampling methods may yield improvements that increase the viability of this method.

Keywords: Neutron stars, Compact binary stars, Gravitational wave astronomy, Gravitational waves, Catalogs
The Age–Velocity Dispersion Relations of the Galactic Disk as Revealed by the LAMOST-Gaia Red Clump Stars. Using nearly 230,000 red clump stars selected from LAMOST and Gaia, we conduct a comprehensive analysis of the stellar age–velocity dispersion relations (AVRs) for various disk populations, within 5.0 ≤ R ≤ 15.0 kpc and ∣Z∣ ≤ 3.0 kpc. The AVRs of the whole red clump sample stars are accurately described as σv = σv,0 (τ + 0.1) , with βR, βϕ, and βZ displaying a global exponential decreasing trend with R, which may point to the difference in spatial distributions of various disk heating mechanisms. The measurements of β–R for various disks suggest that the thin disk exhibits a radial dependence, with a global exponential decreasing trend in βR–R and βZ–R, while βϕ remains a nearly constant value (around 0.20 ∼ 0.25) within 8.5 ≤ R ≤ 11.5 kpc. The thick disk displays a global increasing trend in βR–R, βϕ–R, and βZ–R. These results indicate that the thin disk stars are likely heated by long-term heating from giant molecular clouds and spiral arms, while thick disk stars are likely heated by some violent heating process from merger and accretion, and/or formed by the inside-out and upside-down star formation scenarios, and/or born in the chaotic mergers of gas-rich systems and/or turbulent interstellar medium. Our results also suggest that the disk perturbation by a recent minor merger from Sagittarius may have occurred within 3.0 Gyr.

Keywords: Stellar kinematics, Stellar abundances, Galaxy structure, Milky Way dynamics, Milky Way disk, Galaxy kinematics
Collisionless Tearing Instability in Relativistic Nonthermal Pair Plasma and Its Application to MHD Turbulence. Collisionless tearing instability with a power-law distribution function in a relativistic pair plasma with a guide field is studied. When the current sheet is supported by plasma pressure, the tearing mode is suppressed as the particle spectrum hardens. In the force-free limit, the instability growth rate becomes independent of the particle spectrum. We apply these results to relativistic MHD turbulence, where magnetic energy greatly exceeds plasma rest energy, and derive an expression for the transverse size of turbulent eddies unstable to tearing mode. We also establish the critical plasma magnetization parameter above which charge starvation prevents the tearing instability. These results might be useful for developing more accurate models of particle acceleration in relativistic astrophysical sources.

Keywords: Magnetohydrodynamics, Plasma astrophysics, High energy astrophysics
The First Exploration of the Correlations Between WISE 12 μm and CO Emission in Early-type Galaxies. We present the analysis of a comprehensive sample of 352 early-type galaxies using public data, to investigate the correlations between CO luminosities and mid-infrared luminosities observed by Wide-field Infrared Survey Explorer. We find strong correlations between both CO (1–0) and CO (2–1) luminosities and 12 μm luminosity, boasting a correlation coefficient greater than 0.9 and an intrinsic scatter smaller than 0.1 dex. The consistent slopes observed for the relationships of CO (1–0) and CO (2–1) suggest that the line ratio R21 lacks correlation with mid-infrared emission in early-type galaxies, which is significantly different from star-forming galaxies. Moreover, the slopes of LCO(1‑0)–L12 μm and LCO(2‑1)–L12 μm relations in early-type galaxies are steeper than those observed in star-forming galaxies. Given the absence of correlation with color, morphology, or specific star formation rate (sSFR), the correlation between deviations and the molecular gas mass surface density could be eliminated by correcting the possible 12 μm emission from old stars or adopting a systematically different αCO. The latter, on average, is equivalent to adding a constant CO brightness density, specifically   and   for CO (1–0) and (2–1), respectively. These explorations will serve as useful tools for estimating the molecular gas content in gas-poor galaxies and understanding associated quenching processes.

Keywords: Molecular gas, Galaxy evolution, Interstellar medium, Elliptical galaxies, Infrared photometry
Interplay of Large-scale Drift and Turbulence in the Heliospheric Propagation of Solar Energetic Particles. The gradient and curvature of the Parker spiral interplanetary magnetic field give rise to curvature and gradient guiding-center drifts on cosmic rays (CRs). The plasma turbulence present in interplanetary space is thought to suppress the drifts; however, the extent to which they are reduced is not clear. We investigate the reduction of the drifts using a new analytic model of heliospheric turbulence where the dominant 2D component has both a wavevector and magnetic field vector normal to the Parker spiral, thus fulfilling the main criterion of 2D turbulence. We use full-orbit test-particle simulations of energetic protons in the modeled interplanetary turbulence, and analyze the mean drift velocity of the particles in heliolatitude. We release energetic proton populations of 10, 100, and 1000 MeV close to the Sun and introduce a new method to assess their drift. We compare the drift in the turbulent heliosphere to drift in a configuration without turbulence, and to theoretical estimates of drift reduction. We find that drifts are reduced by a factor 0.2–0.9 of that expected for the heliospheric configuration without turbulence. This corresponds to a much less efficient suppression than what is predicted by theoretical estimates, particularly at low proton energies. We conclude that guiding-center drifts are a significant factor for the evolution of CR intensities in the heliosphere, including the propagation of solar energetic particles in the inner heliosphere.

Keywords: Solar energetic particles, Interplanetary turbulence, Interplanetary magnetic fields, Heliosphere
Photometric Selection of Type 1 Quasars in the XMM-LSS Field with Machine Learning and the Disk─Corona Connection. We present photometric selection of type 1 quasars in the ≍5.3 deg2 XMM-Large Scale Structure survey field with machine learning. We constructed our training and blind-test samples using spectroscopically identified Sloan Digital Sky Survey quasars, galaxies, and stars. We utilized the XGBoost machine learning method to select a total of 1591 quasars. We assessed the classification performance based on the blind-test sample, and the outcome was favorable, demonstrating high reliability (≍99.9%) and good completeness (≍87.5%). We used XGBoost to estimate photometric redshifts of our selected quasars. The estimated photometric redshifts span a range from 0.41 to 3.75. The outlier fraction of these photometric redshift estimates is ≍17%, and the normalized median absolute deviation (σNMAD) is ≍0.07. To study the quasar disk─corona connection, we constructed a subsample of 1016 quasars with Hyper Suprime-Cam i &lt; 22.5 after excluding radio-loud and potentially X-ray-absorbed quasars. The relation between the optical-to-X-ray power-law slope parameter (αOX) and the 2500 Å monochromatic luminosity (L2500Å) for this subsample is   with a dispersion of 0.159. We found this correlation in good agreement with the correlations in previous studies. We explored several factors, which may bias the αOX─L2500Å relation, and found that their effects are not significant. We discussed possible evolution of the αOX─L2500Å relation with respect to L2500Å or redshift.

Keywords: X-ray surveys, Quasars
Discoveries and Properties of EL CVn–type Binaries in the TESS Survey. EL CVn–type systems represent a rare evolutionary stage in binary star evolution, providing ideal laboratories for investigating stable mass-transfer processes and the formation of extremely low-mass white dwarfs (ELM WDs). The Transiting Exoplanet Survey Satellite (TESS) has delivered an extensive collection of high-precision time-domain photometric data, which is invaluable for studying EL CVn binaries. In this study, we identified 29 EL CVn systems from the TESS eclipsing binary catalogs (sectors 1–65), 11 of which are newly discovered. These systems consist of smaller, hotter prehelium WDs and A/F main-sequence stars. The orbital periods of these binaries range from 0.64 to 2.5 days. Utilizing TESS light curves, Gaia distances, and multiband photometric data (e.g., Galaxy Evolution Explorer, Two Micron All Sky Survey, Wide-field Infrared Survey Explorer, SkyMapper), we modeled the light curves and spectral energy distributions to derive system parameters, including effective temperatures, masses, and radii. These systems were then compared with the WD mass–period relation and the evolutionary tracks of ELM WDs. The comparison reveals that these binaries are consistent with the expected mass–period relation for WDs and align well with the evolutionary tracks on the Teff ‑   diagram for ELM WDs. This result suggests that these EL CVn systems likely formed through stable mass-transfer processes. We provide a catalog of complete parameters for 29 EL CVn systems identified from the TESS survey. This catalog will serve as an essential resource for studying binary mass transfer, WD formation, and pulsation phenomena in EL CVn–type systems.

Keywords: Fundamental parameters of stars, White dwarf stars, Astronomy data analysis, Eclipsing binary stars, Catalogs
Interaction of an Outflow with Surrounding Gaseous Clouds as the Origin of Late-time Radio Flares in Tidal Disruption Events. Close encounter between a star and a supermassive black hole (SMBH) results in the tidal disruption of the star, known as a tidal disruption event (TDE). Recently, a few TDEs, e.g., ASASSN-15oi and AT2018hyz, have shown late-time (hundreds of days after their UV/optical peaks) radio flares with radio luminosities of 1038∼39 erg s‑1. The super-Eddington fallback or accretion in a TDE may generate a mass outflow. Here, we investigate a scenario that the late-time radio flares come from the interaction of the outflow with the circumnuclear gaseous clouds, in addition to the slow-evolving emission component due to the outflow–diffuse medium interaction. We calculate the associated radio temporal and spectral signatures and find that they reproduce well the observations. The outflows have the inferred velocity of 0.2c ∼ 0.6c, the total mass of 10‑3 ∼ 10‑1M⊙ and the ejection duration of a month to a year. The distances of the clouds to the SMBH are 0.1 ∼ 1 pc. This scenario has advantages in explaining the long delay, sharpness of the rise, and the multiplicity of the late radio flares. Future observations may build up a much larger sample of late-time radio flares and enable their use as a probe of the TDE physics and the host circumnuclear environment.

Keywords: Tidal disruption, Radio sources