Sazuna/UAT_keywords huggingface dataset:
Multiheight Observations of Atmospheric Gravity Waves at Solar Disk Center. Atmospheric gravity waves (AGWs) are low-frequency, buoyancy-driven waves that are generated by turbulent convection and propagate obliquely throughout the solar atmosphere. Their proposed energy contribution to the lower solar atmosphere and sensitivity to atmospheric parameters (e.g., magnetic fields and radiative damping) highlight their diagnostic potential. We investigate AGWs near a quiet-Sun disk center region using multiwavelength data from the Interferometric Bidimensional Spectrometer and the Solar Dynamics Observatory. These observations showcase the complex wave behavior present in the entire acoustic-gravity wave spectrum. Using Fourier spectral analysis and local helioseismology techniques on simultaneously observed line core Doppler velocity and intensity fluctuations, we study both the vertical and horizontal properties of AGWs. Propagating AGWs with perpendicular group and phase velocities are detected at the expected temporal and spatial scales throughout the lower solar atmosphere. We also find previously unobserved, varied phase difference distributions among our velocity and intensity diagnostic combinations. Time-distance analysis indicates that AGWs travel with an average group speed of 4.5 km s-1, which is only partially described by a simple simulation, suggesting that high-frequency AGWs dominate the signal. Analysis of the median magnetic field (4.2 G) suggests that propagating AGWs are not significantly affected by quiet-Sun photospheric magnetic fields. Our results illustrate the importance of multiheight observations and the necessity of future work to properly characterize this observed behavior.

Keywords: Solar atmosphere, Solar photosphere, Quiet sun, Solar physics, Solar oscillations
Cluster-counterpart Voids: Void Identification from Galaxy Density Field. We identify cosmic voids from galaxy density fields under the theory of void-cluster correspondence. We extend the previous novel void-identification method developed for the matter density field to the galaxy density field for practical applications. From cosmological N-body simulations, we construct galaxy number- and mass-weighted density fields to identify cosmic voids that are counterparts of galaxy clusters of a specific mass. The parameters for the cluster-counterpart void identification such as Gaussian smoothing scale, density threshold, and core volume fraction are found for galaxy density fields. We achieve about 60%-67% of completeness and reliability for identifying the voids of corresponding cluster mass above 3 × 1014 h -1 M ⊙ from a galaxy sample with the mean number density, $\bar{n}=4.4\times {10}^{-3}{({h}^{-1}\,\mathrm{Mpc})}^{-3}$ . When the mean density is increased to $\bar{n}={10}^{-2}{({h}^{-1}\,\mathrm{Mpc})}^{-3}$ , the detection rate is enhanced by ~2%-7% depending on the mass scale of voids. We find that the detectability is insensitive to the density weighting scheme applied to generate the density field. Our result demonstrates that we can apply this method to the galaxy redshift survey data to identify cosmic voids corresponding statistically to the galaxy clusters in a given mass range.

Keywords: Voids, Large-scale structure of the universe
Halted-pendulum Relaxation: Application to White Dwarf Binary Initial Data. Studying compact-star binaries and their mergers is integral to determining progenitors for observable transients. Today, compact-star mergers are typically studied via state-of-the-art computational fluid dynamics codes. One such numerical technique, smoothed particle hydrodynamics (SPH), is frequently chosen for its excellent mass, energy, and momentum conservation. The natural treatment of vacuum and the ability to represent highly irregular morphologies make SPH an excellent tool for the study of compact-star binaries and mergers. For many scenarios, including binary systems, the outcome of simulations is only as accurate as the initial conditions. For SPH, it is essential to ensure that the particles are distributed regularly, representing the initial density profile but without long-range correlations. Particle noise in the form of high-frequency local motion and low-frequency global dynamics must be damped out. Damping the latter can be as computationally intensive as the actual simulation. We discuss a new and straightforward relaxation method, halted-pendulum relaxation (HPR), to remove global oscillation modes of SPH particle configurations. In combination with effective external potentials representing gravitational and orbital forces, we show that HPR has an excellent performance in efficiently relaxing SPH particles to the desired density distribution and removing global oscillation modes. We compare the method to frequently used relaxation approaches and test it on a white dwarf binary model at its Roche-lobe overflow limit. We highlight the importance of our method in achieving accurate initial conditions and its effect on achieving circular orbits and realistic accretion rates when compared with other general relaxation methods.

Keywords: Hydrodynamical simulations, White dwarf stars, Compact binary stars, Astronomical simulations
Three-dimensional Particle-in-cell Simulations of the Solar Wind Interaction with Asteroid 2016 HO<SUB>3</SUB>. The recently discovered asteroid 2016 HO3 is the most stable quasi-satellite of our Earth. Several missions to 2016 HO3 have been proposed, including the Tianwen-2 mission of China. Here we study the solar wind interaction with 2016 HO3 with three-dimensional particle-in-cell simulations. It is found that the sunlit surface can be positively charged to more than +10 V, and the shadowed surface is negatively charged to lower than -30 V. The typical electric field on the sunlit surface is about 2 V m-1 but can increase up to 20 V m-1 near the terminator. There is a plasma wake behind 2016 HO3 with a reduced plasma density. Normally, the ion density can be reduced to about 0.3 of the solar wind density at 100 m downstream from 2016 HO3, and the plasma wake is confined by a Mach cone with a cone angle of about 6.°5. In addition, we find that both the solar wind parameters and the secondary electron emission can affect the surface charging, which, in return, changes the wake structure.

Keywords: Solar wind, Asteroids
Modeling of Thermal Emission from ULX Pulsar Swift J0243.6+6124 with General Relativistic Radiation MHD Simulations. We perform general relativistic radiation magnetohydrodynamics simulations of super-Eddington accretion flows around a neutron star with a dipole magnetic field for modeling the Galactic ultraluminous X-ray source exhibiting X-ray pulsations, Swift J0243.6+6124. Our simulations show the accretion columns near the magnetic poles, the accretion disk outside the magnetosphere, and the outflows from the disk. It is revealed that the effectively optically thick outflows, consistent with the observed thermal emission at ~107 K, are generated if the mass accretion rate is much higher than the Eddington rate ${\dot{M}}_{\mathrm{Edd}}$ and the magnetospheric radius is smaller than the spherization radius. In order to explain the blackbody radius (~100-500 km) without contradicting the reported spin period (9.8 s) and spin-up rate ( $\dot{P}=-2.22\times {10}^{-8}\,{\rm{s}}\,{{\rm{s}}}^{-1}$ ), a mass accretion rate of $(200\mbox{--}1200){\dot{M}}_{\mathrm{Edd}}$ is required. Since the thermal emission was detected in two observations with $\dot{P}$ of -2.22 × 10-8 s s-1 and -1.75 × 10-8 s s-1 but not in another with $\dot{P}=-6.8\times {10}^{-9}\,{\rm{s}}\,{{\rm{s}}}^{-1}$ , the surface magnetic field strength of the neutron star in Swift J0243.6+6124 is estimated to be between 3 × 1011 G and 4 × 1012 G. From this restricted range of magnetic field strength, the accretion rate would be $(200\mbox{--}500){\dot{M}}_{\mathrm{Edd}}$ when the thermal emission appears and $(60\mbox{--}100){\dot{M}}_{\mathrm{Edd}}$ when it is not detected. Our results support the hypothesis that the super-Eddington phase in the 2017-2018 giant outburst of Swift J0243.6+6124 is powered by highly super-Eddington accretion flows onto a magnetized neutron star.

Keywords: Neutron stars, Accretion, Radiative magnetohydrodynamics, High energy astrophysics, General relativity, X-ray sources
Magnetic Activity-Rotation-Age-Mass Relations in Late-pre-main-sequence Stars. We study the four-dimensional relationships between magnetic activity, rotation, mass, and age for solar-type stars in the age range 5-25 Myr. This is the late-pre-main-sequence (l-PMS) evolutionary phase when rapid changes in a star's interior may lead to changes in the magnetic dynamo mechanisms. We carefully derive rotational periods and spot sizes for 471 members of several l-PMS open clusters using photometric light curves from the Zwicky Transient Facility. Magnetic activity was measured in our previous Chandra-based study, and additional rotational data were obtained from other work. Several results emerge. Mass-dependent evolution of rotation through the l-PMS phase agrees with astrophysical models of stellar angular momentum changes, although the data suggest a subpopulation of stars with slower initial rotations than commonly assumed. There is a hint of the onset of unsaturated tachoclinal dependency of X-ray activity on rotation, as reported by Argiroffi et al., but this result is not confidently confirmed. Both X-ray luminosity and starspot area decrease approximately as t -1 for solar-mass stars, suggesting that spot magnetic fields are roughly constant and l-PMS stars follow the universal solar-scaling law between the X-ray luminosity and surface magnetic flux. Assuming convective dynamos are dominant, theoretical magnetic fluxes fail to reveal the universal law for l-PMS stars that enter late Henyey tracks. Altogether we emerge with a few lines of evidence suggesting that the transition from the turbulent to solar-type dynamo occurs at the later stages of l-PMS evolution as stars approach the zero-age main sequence.

Keywords: Stellar magnetic fields, Pre-main sequence stars, Protoplanetary disks, X-ray stars, Stellar rotation, Single x-ray stars
Massive Hypervelocity Runaway Stars in the Large Magellanic Cloud. Since the hypervelocity stars were discovered in the Milky Way, various mechanisms have been proposed to explain these runaway stars. Up to now, however, the dominant ejected mechanism of hypervelocity stars is still unclear. As the largest and closest face-on satellite galaxy of the Milky Way, the Large Magellanic Cloud (LMC) serves as a good target, allowing us to study this issue. Based on the high-precision astrometric parameters provided by Gaia Data Release 3, we researched the proper motions of 3119 massive O-B2-type stars in the LMC and identified 98 (~3%) as having the ability to escape from the LMC, with more than 50% confidence. Furthermore, by investigating the characteristics of the identified massive stars and adopting a regression analysis, we find that the dynamic ejection scenario might be the dominant mechanism of the massive hypervelocity runaway stars in the LMC.

Keywords: Stellar kinematics, Stellar dynamics, Large Magellanic Cloud, Proper motions
A Comprehensive Perturbative Formalism for Phase Mixing in Perturbed Disks. II. Phase Spirals in an Inhomogeneous Disk Galaxy with a Nonresponsive Dark Matter Halo. We develop a linear perturbative formalism to compute the response of an inhomogeneous stellar disk embedded in a nonresponsive dark matter (DM) halo to various perturbations like bars, spiral arms, and encounters with satellite galaxies. Without self-gravity to reinforce it, the response of a Fourier mode phase mixes away due to an intrinsic spread in the vertical (Ω z ), radial (Ω r ), and azimuthal (Ω ϕ ) frequencies, triggering local phase-space spirals. The detailed galactic potential dictates the shape of phase spirals: phase mixing occurs more slowly and thus phase spirals are more loosely wound in the outer disk and in the presence of an ambient DM halo. Collisional diffusion due to scattering of stars by structures like giant molecular clouds causes superexponential damping of the phase spiral amplitude. The z-v  z  phase spiral is one-armed (two-armed) for vertically antisymmetric (symmetric) bending (breathing) modes. Only transient perturbations with timescales (τ P) comparable to the vertical oscillation period (τ  z  ~ 1/Ω z ) can trigger vertical phase spirals. Each (n, l, m) mode of the response to impulsive (τ P &lt; τ = 1/(nΩ z  + lΩ r  + mΩ ϕ )) perturbations is power-law (~τ P/τ) suppressed, but that to adiabatic (τ P &gt; τ) perturbations is exponentially weak ( $\sim \exp \left[-{\left({\tau }_{{\rm{P}}}/\tau \right)}^{\alpha }\right]$ ) except for resonant (τ → ∞ ) modes. Slower (τ P &gt; τ  z ) perturbations, e.g., distant encounters with satellite galaxies, induce stronger bending modes. Sagittarius (Sgr) dominates the solar neighborhood response of the Milky Way (MW) disk to satellite encounters. Thus, if the Gaia phase spiral was triggered by a MW satellite, Sgr is the leading contender. However, the survival of the phase spiral against collisional damping necessitates an impact ~0.6-0.7 Gyr ago.

Keywords: Galaxy stellar disks, Milky Way dark matter halo, Galaxy interactions, Galaxy dynamics, Milky Way dynamics, Orbital resonances, Gravitational interaction, Galaxy disks, Milky Way disk, Galaxy kinematics, Perturbation methods
A Blueprint for the Milky Way's Stellar Populations. IV. A String of Pearls-the Galactic Starburst Sequence. We continue our series of papers on phase-space distributions of stars in the Milky Way based on photometrically derived metallicities and Gaia astrometry, with a focus on the halo-disk interface in the local volume. To exploit various photometric databases, we develop a method of empirically calibrating synthetic stellar spectra based on a comparison with observations of stellar sequences and individual stars in the Sloan Digital Sky Survey, the SkyMapper Sky Survey, and the Pan-STARRS1 surveys, overcoming band-specific corrections employed in our previous work. In addition, photometric zero-point corrections are derived to provide an internally consistent photometric system with a spatially uniform metallicity zero-point. Using our phase-space diagrams, we find a remarkably narrow sequence in the rotational velocity (v  ϕ ) versus metallicity ([Fe/H]) space for a sample of high proper-motion stars (&gt;25 mas yr-1), which runs along Gaia Sausage/Enceladus (GSE) and the Splash substructures and is linked to the disk, spanning nearly 2 dex in [Fe/H]. Notably, a rapid increase of v  ϕ  from a nearly zero net rotation to ~180 km s-1 in a narrow metallicity interval (-0.6 ≲ [Fe/H] ≲ -0.4) suggests that some of these stars emerged quickly on a short gas-depletion timescale. Through measurements of a scale height and length, we argue that these stars are distinct from those heated dynamically by mergers. This chain of high proper-motion stars provides additional support for recent discoveries suggesting that a starburst took place when the young Milky Way encountered the gas-rich GSE progenitor, which eventually led to the settling of metal-enriched gas onto the disk.

Keywords: Milky Way formation, Stellar populations, Stellar abundances, Milky Way dynamics, Milky Way stellar halo, Milky Way evolution, Milky Way Galaxy
A Comprehensive Study on the Relation between the Metal Enrichment of Ionized and Atomic Gas in Star-forming Galaxies. We study the relation between the metallicities of ionized and atomic gas in star-forming galaxies at z = 0-3 using the Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological, hydrodynamical simulations. This is done by constructing a dense grid of sight lines through the simulated galaxies and obtaining the star formation rate- and H I column density-weighted metallicities, Z SFR and Z H I, for each sightline as proxies for the metallicities of ionized and atomic gas, respectively. We find Z SFR ≳ Z H I for almost all sight lines, with their difference generally increasing with decreasing metallicity. The stellar masses of galaxies do not have a significant effect on this trend, but the positions of the sight lines with respect to the galaxy centers play an important role: the difference between the two metallicities decreases when moving toward the galaxy centers, and saturates to a minimum value in the central regions of galaxies, irrespective of redshift and stellar mass. This implies that the mixing of the two gas phases is most efficient in the central regions of galaxies where sight lines generally have high column densities of H I. However, a high H I column density alone does not guarantee a small difference between the two metallicities. In galaxy outskirts, the inefficiency of the mixing of star-forming gas with H I seems to dominate over the dilution of heavy elements in H I through mixing with the pristine gas. We find good agreement between the available observational data and the Z SFR-Z H I relation predicted by the EAGLE simulations. Though, observed regions with a nuclear starburst mode of star formation appear not to follow the same relation.

Keywords: Hydrodynamical simulations, Interstellar medium, Metallicity, Galaxy chemical evolution
A Search for Stellar Siblings of the  200 Myr TOI-251 b Planetary System. Young planets (&lt;1 Gyr) are helpful for studying the physical processes occurring at the early stage of planet evolution. TOI-251 b is a recently discovered sub-Neptune orbiting a young G dwarf, which has an imprecise age estimation of 40-320 Myr. We select TOI-251 sibling candidates based on kinematics and spatial proximity to TOI-251 and further use the color-magnitude diagram to refine the list and to compare to multiple open clusters. We report the stellar rotational period for 321 sibling candidates in a 50 pc radius around TOI-251 by analyzing their stellar light curves and find a color-rotational period sequence that lies in between the Group X (300 Myr) and Pleiades (120 Myr) members, suggesting an age ~ 200 Myr. A quantitative age analysis using gyrochronology relations gives 204 ± 45 Myr, consistent with the average Li age of selected siblings (238 ± 38 Myr) and the Gaia variability age (193 ${}_{-54}^{102}$ Myr). The detection fraction of comoving candidates that have a short rotational period is 68.1%, much higher than the typical value in the field (14%-16% from Kepler). The overdensity of young stars and consistency in age of stellar siblings suggest a potential young association candidate in the Phoenix-Grus constellation. Though TOI-251 b has a radius larger than most of its field-age counterparts, we are uncertain whether TOI-251 is inflated, due to a lack of knowledge on the planet's mass.

Keywords: Early stellar evolution, Stellar ages, Stellar dynamics, Exoplanet evolution, Stellar rotation, Stellar associations
Robust Field-level Likelihood-free Inference with Galaxies. We train graph neural networks to perform field-level likelihood-free inference using galaxy catalogs from state-of-the-art hydrodynamic simulations of the CAMELS project. Our models are rotational, translational, and permutation invariant and do not impose any cut on scale. From galaxy catalogs that only contain 3D positions and radial velocities of ~1000 galaxies in tiny ${(25\,{h}^{-1}\mathrm{Mpc})}^{3}$ volumes our models can infer the value of Ωm with approximately 12% precision. More importantly, by testing the models on galaxy catalogs from thousands of hydrodynamic simulations, each having a different efficiency of supernova and active galactic nucleus feedback, run with five different codes and subgrid models-IllustrisTNG, SIMBA, Astrid, Magneticum, SWIFT-EAGLE-we find that our models are robust to changes in astrophysics, subgrid physics, and subhalo/galaxy finder. Furthermore, we test our models on 1024 simulations that cover a vast region in parameter space-variations in five cosmological and 23 astrophysical parameters-finding that the model extrapolates really well. Our results indicate that the key to building a robust model is the use of both galaxy positions and velocities, suggesting that the network has likely learned an underlying physical relation that does not depend on galaxy formation and is valid on scales larger than ~10 h -1 kpc.

Keywords: Cosmology, Hydrodynamical simulations, Cosmological parameters, Astrostatistics, Magnetohydrodynamical simulations
Robust RFI Excision for Pulsar Signals by a Novel Nonlinear M-type Estimator with an Application to Pulsar Timing. Radio frequency interference (RFI) mitigation for pulsar signals is a long perplexing issue in astrophysical measurements. Linear mitigation methods are often criticized for limited RFI excision range and weakness of RFI modeling. Meanwhile, thresholding methods (e.g., the SumThreshold) suffer from empirical factors. In our opinion, the main defect of the current status is the lack of a concise definition to distinguish signals from RFI with the aid of certain techniques, e.g., sparse representation. This point is the root cause of these problems and also forms our motivation. This paper aims to expand the excision range (e.g., the on-pulse and quasiperiodic RFI) and cut down some empirical factors. The main contribution is that we give a definition and derive a widely practicable nonlinear framework for RFI excision. This framework can overcome the susceptibility of the least-square criterion to RFI, and excise almost all types of RFI once and for all. A robust LnCosh criterion based nonlinear maximum likelihood-type (M-type) penalized smoothing estimator is introduced. The novelty is that this estimator is first embedded into the iterative shrinkage-thresholding algorithm (ISTA) and the fast ISTA. Nonlinearity highlights this method. Curvelet sparsity gives satisfying approximation for pulsar signals containing dispersion feature. Finally, useful signal details will be retrieved from the excision residual by a morphological component analysis. This method is applied to the time-frequency signals collected by the Nanshan 26 m Radio Telescope. The numerical experiments can persuasively prove that it has desired application prospects.

Keywords: Astronomy data modeling, Astronomical techniques, Wavelet analysis, Maximum likelihood estimation, Algorithms, Radio pulsars