Sazuna/UAT_keywords huggingface dataset:
TIC 5724661: A Long-period Binary with a Pulsating sdB Star and δ Scuti Variable. Using TESS 20 s cadence data, we have discovered an unusual combination of pulsating stars in what we infer to be a binary system. The binary consists of a standard δ Scuti star with pulsations over the range 32-41 day-1; this is in a likely wide orbit with a hot subdwarf-B (sdB) star, which itself has a large-amplitude p-mode pulsation at 524 day-1. We establish constraints on the period of the putative binary by using radial velocity measurements of the δ Scuti star and show that any sdB companion star must orbit with a period greater than approximately thirty days. Our identification of this sdB binary serves as an important addition to the relatively small number of sdB binaries known to have orbital periods longer than a few days. We model such a binary using MESA and find that this system could be formed through stable, nonconservative mass transfer from either a low-mass or an intermediate-mass progenitor, without undergoing a common-envelope phase.

Keywords: Delta Scuti variable stars, Binary stars, Stellar pulsations, Pulsating variable stars, B subdwarf stars, Asteroseismology
Quenching in the Right Place at the Right Time: Tracing the Shared History of Starbursts, Active Galactic Nuclei, and Poststarburst Galaxies Using Their Structures and Multiscale Environments. This work uses multiscale environments and the structures of galaxies in the Sloan Digital Sky Survey as consistency checks on the evolution from starburst to quiescence at redshift z &lt; 0.2. The environmental indicators include fixed-aperture mass overdensities (δ  xMpc, x ∈ {0.5, 1, 2, 4, 8} h -1 Mpc), k-nearest neighbor distances, the tidal parameter, halo mass (M  h ), and satellite/central classification. The residuals of the specific star formation rates (Δ SSFRs) are used to select starbursts (ΔSSFR &gt; 0.6 dex, N ≈ 8600). Quenched poststarbursts (QPSBs) are selected using Hα &lt; 3 Å emission and Hδ  A  &gt; 4 Å absorption (N ≈ 750). The environments of starbursts and QPSBs are compared with those of active galactic nuclei (AGNs) and inactive galaxies of varying ΔSSFR. The environments of starbursts, AGNs, and QPSBs are unlike the environments of most quiescent galaxies (QGs). About 70%-90% of starbursts, AGNs with Hδ  A  &gt; 4 Å, and QPSBs are centrals; ~80%-90% have M  h  &lt; 1013 M ⊙, and only ~2%-4% have M  h  &gt; 1014 M ⊙ or live in clusters. Their M  h  and satellite fractions are also different from those of QGs. All QPSBs are matched to some SFGs, starbursts, AGNs, and QGs of similar M ⋆, environments, concentration indices, and velocity dispersions. A significant fraction (~20%-30%) of starbursts cannot be matched to QPSBs or QGs. The implications are that: (1) some starbursts do not quench rapidly; (2) the satellite-quenching mechanisms operating in high-density environments cannot account for most QPSBs; (3) the evolution from starbursts to QPSBs to QGs is not the dominant path at z &lt; 0.2; and (4) starbursts are not mainly triggered by tidal interactions.

Keywords: Starburst galaxies, Stellar feedback, Galaxy environments, Galaxy structure, Active galactic nuclei, Galaxy evolution, Star formation, Galaxy quenching, Post-starburst galaxies
Effects of Magnetic Shear and Thermodynamic Asymmetry on Spontaneous Magnetohydrodynamic Reconnection. The spontaneous evolution of magnetic reconnection in generalized situations (with thermodynamic asymmetry regarding the current sheet and magnetic shear) is investigated using a two-dimensional magnetohydrodynamic simulation. We focus on the asymptotic state of temporal evolution, i.e., the self-similarly expanding phase. (1) A long fast-mode shock is generated in front of the shorter plasmoid as in the shear-less thermodynamically asymmetric case; however, the sheared magnetic component weakens the shock. This fast shock may work as a particle acceleration site. (2) The shorter plasmoid-side plasma infiltrates the longer plasmoid across the current sheet. Then, the plasmas from both sides of the current sheet coexist on the same magnetic field lines in the longer plasmoid. This may result in efficient plasma mixing. (3) The thermodynamic asymmetry and magnetic shear drastically decrease the reconnection rate in many orders of magnitude.

Keywords: Solar magnetic reconnection, Plasma physics
Constraints on the Very High Energy Gamma-Ray Emission from Short GRBs with HAWC. Many gamma-ray bursts (GRBs) have been observed from radio wavelengths, and a few at very high energies (VHEs, &gt;100 GeV). The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is well suited to study transient phenomena at VHEs owing to its large field of view and duty cycle. These features allow for searches of VHE emission and can probe different model assumptions of duration and spectra. In this paper, we use data collected by HAWC between 2014 December and 2020 May to search for emission in the energy range from 80 to 800 GeV coming from a sample of 47 short GRBs that triggered the Fermi, Swift, and Konus satellites during this period. This analysis is optimized to search for delayed and extended VHE emission within the first 20 s of each burst. We find no evidence of VHE emission, either simultaneous or delayed, with respect to the prompt emission. Upper limits (90% confidence level) derived on the GRB fluence are used to constrain the synchrotron self-Compton forward-shock model. Constraints for the interstellar density as low as 10-2 cm-3 are obtained when assuming z = 0.3 for bursts with the highest keV fluences such as GRB 170206A and GRB 181222841. Such a low density makes observing VHE emission mainly from the fast-cooling regime challenging.

Keywords: Gamma-ray bursts, Theoretical models, High energy astrophysics, Gamma-ray detectors, Extragalactic astronomy, Gamma-ray transient sources
Nature and Scalings of Density Fluctuations of Compressible Magnetohydrodynamic Turbulence with Applications to the Solar Wind. The solar wind is a magnetized and turbulent plasma. Its turbulence is often dominated by Alfvénic fluctuations and often deemed as nearly incompressible far away from the Sun, as shown by in situ measurements near 1 au. However, for solar wind closer to the Sun, the plasma β decreases (often lower than unity) while the turbulent Mach number M  t  increases (can approach unity, e.g., transonic fluctuations). These conditions could produce significantly more compressible effects, characterized by enhanced density fluctuations, as seen by several space missions. In this paper, a series of 3D MHD simulations of turbulence are carried out to understand the properties of compressible turbulence, particularly the generation of density fluctuations. We find that, over a broad range of parameter space in plasma β, cross helicity, and polytropic index, the turbulent density fluctuations scale linearly as a function of M  t , with the scaling coefficients showing weak dependence on parameters. Furthermore, through detailed spatiotemporal analysis, we show that the density fluctuations are dominated by low-frequency nonlinear structures, rather than compressible MHD eigenwaves. These results could be important for understanding how compressible turbulence contributes to solar wind heating near the Sun.

Keywords: Solar wind, Magnetohydrodynamical simulations
Inhomogeneous Kinetic Alfvén Waves in the Near-Sun Solar Wind. Intervals of intense electromagnetic, broadband plasma waves are reported in the near-Sun solar wind. These waves are identified as kinetic Alfvén waves (KAWs), based on comparison between data and theory for their observed electric- to magnetic-field ratio, and magnetic compressibility, as a function of frequency. In contrast to KAW observations at 1 au, KAWs in the near-Sun solar wind are found to be spatially inhomogeneous, preferentially occurring where the ambient magnetic field experiences strong deviations from the Parker spiral direction, including during magnetic switchbacks and clusters of switchbacks. To the extent that turbulent fluctuations in the solar wind at small scales are characterized as KAWs, the observations reported here create an expectation that KAW-driven particle heating should also be inhomogeneous in the near-Sun solar wind, being strongest in regions of intense KAWs. Finally, a discrepancy between KAW observation and theory is identified at frequencies two decades above the frequency where kinetic effects begin to manifest, and possible origins of this discrepancy are considered.

Keywords: Space plasmas, Interplanetary turbulence, Solar wind, Alfven waves, Solar magnetic fields
Toward Understanding the B[e] Phenomenon. IX. Nature and Binarity of MWC645. We present the results of optical and near-IR spectroscopy and multicolor photometry of the emission-line star MWC 645, which exhibits the B[e] phenomenon. The presence of positionally variable absorption lines of a cool star detected for the first time indicates that the object is a binary system. Using a combination of the photometric and spectroscopic data as well as the Gaia EDR3 distance (D = 6.5 ± 0.9 kpc), we disentangled the components' contributions and estimated their surface temperatures and luminosities (18, 000 ± 2000 K and 4250 ± 250 K, log L/L ⊙ = 4.0 ± 0.5 and 3.1 ± 0.3 for the hot and cool components, respectively). Quasi-cyclic short-period (months) and long-period (~4 yr) photometric variations were detected in both optical and near-IR regions, and are most likely due to variable circumstellar extinction. Our analysis suggests that MWC 645 is a member of the FS CMa group. The object's properties can be described by an evolutionary model of a close binary system that currently undergoes a nonconservative mass transfer between intermediate-mass stars (e.g., 7 M ⊙ + 2.8 M ⊙).

Keywords: Binary stars, Emission line stars, A stars, Spectroscopic binary stars, Be stars
Observations and Simulations of Radio Emission and Magnetic Fields in Minkowski's Object. We combine new data from the Karl G. Jansky Very Large Array with previous radio observations to create a more complete picture of the ongoing interactions between the radio jet from galaxy NGC 541 and the star-forming system known as Minkowski's Object (MO). We then compare those observations with synthetic radio data generated from a new set of magnetohydrodynamic simulations of jet-cloud interactions specifically tailored to the parameters of MO. The combination of radio intensity, polarization, and spectral index measurements all convincingly support the interaction scenario and provide additional constraints on the local dynamical state of the intracluster medium and the time since the jet-cloud interaction first began. In particular, we show that only a simulation with a bent radio jet can reproduce the observations.

Keywords: Jets, Galaxy jets, Radio galaxies, Tailed radio galaxies, Magnetohydrodynamical simulations
Stellar Populations of Lyα-emitting Galaxies in the HETDEX Survey. I. An Analysis of LAEs in the GOODS-N Field. We present the results of a stellar population analysis of 72 Lyα-emitting galaxies (LAEs) in GOODS-N at 1.9 &lt; z &lt; 3.5 spectroscopically identified by the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We provide a method for connecting emission-line detections from the blind spectroscopic survey to imaging counterparts, a crucial tool needed as HETDEX builds a massive database of ~1 million Lyα detections. Using photometric data spanning as many as 11 filters covering 0.4 &lt; λ (μm) &lt; 4.5 from the Hubble Space Telescope and Spitzer Space Telescope, we study the objects' global properties and explore which properties impact the strength of Lyα emission. We measure a median stellar mass of ${0.8}_{-0.5}^{+2.9}\times {10}^{9}\ {M}_{\odot }$ and conclude that the physical properties of HETDEX spectroscopically selected LAEs are comparable to LAEs selected by previous deep narrowband studies. We find that stellar mass and star formation rate correlate strongly with the Lyα equivalent width. We then use a known sample of z &gt; 7 LAEs to perform a protostudy of predicting Lyα emission from galaxies in the epoch of reionization, finding agreement at the 1σ level between prediction and observation for the majority of strong emitters.

Keywords: Lyman-alpha galaxies, Galaxy formation, High-redshift galaxies, Galaxy evolution
Examining AGN UV/Optical Variability beyond the Simple Damped Random Walk. We present damped harmonic oscillator (DHO) light-curve modeling for a sample of 12,714 spectroscopically confirmed quasars in the Sloan Digital Sky Survey Stripe 82 region. DHO is a second-order continuous-time autoregressive moving-average process, which can be fully described using four independent parameters: a natural oscillation frequency (ω 0), a damping ratio (ξ), a characteristic perturbation timescale (τ perturb), and an amplitude for the perturbing white noise (σ  ϵ ). The asymptotic variability amplitude of a DHO process is quantified by σ DHO-a function of ω 0, ξ, τ perturb, and σ  ϵ . We find that both τ perturb and σ  ϵ  follow different dependencies with rest-frame wavelength (λ RF) on either side of 2500 Å, whereas σ DHO follows a single power-law relation with λ RF. After correcting for wavelength dependence, σ DHO exhibits anticorrelations with both the Eddington ratio and the black hole mass, while τ perturb-with a typical value of days in the rest frame-shows an anticorrelation with the bolometric luminosity. Modeling active galactic nuclei (AGN) variability as a DHO offers more insight into the workings of accretion disks close to the supermassive black holes at the center of AGN. The newly discovered short-term variability (characterized by τ perturb and σ  ϵ ) and its correlation with bolometric luminosity pave the way for new algorithms that will derive fundamental properties (e.g., Eddington ratio) of AGN using photometric data alone.

Keywords: Supermassive black holes, Quasars, Surveys, Active galactic nuclei, Time series analysis
Ram Pressure Stripping of the Multiphase ISM: A Detailed View from TIGRESS Simulations. Ram pressure stripping (RPS) is a process that removes the interstellar medium (ISM) quickly, playing a vital role in galaxy evolution. Previous RPS studies have treated the ISM as single-phase or lack the resolution and physical processes to properly capture the full multiphase ISM. To improve this simplification, we introduce an inflowing, hot intracluster medium (ICM) into a self-consistently modeled ISM in a local patch of star-forming galactic disks using the TIGRESS framework. Our simulations reveal that the workings of RPS are not only direct acceleration of the ISM by ICM ram pressure but also mixing-driven momentum transfer involving significant phase transition and radiative cooling. The hot ICM passes through the low-density channels of the porous, multiphase ISM; shreds the cool ISM; and creates mixing layers. The ICM momentum is transferred through the mixing layers while populating the intermediate-temperature gas and radiating thermal energy away. The mixed gas extends beyond galactic disks and forms stripped tails that cool back unless the ICM fluxes are large enough to prevent cooling until they escape the simulation domain. The mixing-driven momentum transfer predicts that the more ICM mixes in, the faster the ISM moves, resulting in the anticorrelation of outflow velocity and gas metallicity of the stripped ISM. The compression of the ISM disks due to the ICM ram pressure enhances star formation rates up to 50% compared to the model without ICM. With the ICM ram pressure higher than the disk anchoring pressure, star formation is quenched within ~100 Myr.

Keywords: Galaxy interactions, Intracluster medium, Interstellar medium, Magnetohydrodynamical simulations
Searching for Cataclysmic Variable Stars in Unidentified X-Ray Sources. We carry out a photometric search for new cataclysmic variable stars (CVs), with the goal of identification for candidates of AR Scorpii-type binary systems. We select GAIA sources that are likely associated with unidentified X-ray sources, and analyze the light curves taken by the Zwicky Transient Facility, Transiting Exoplanet Survey Satellite, and Lulin One-meter Telescope in Taiwan. We investigate eight sources as candidates for CVs, among which six sources are new identifications. Another two sources have been recognized as CVs in previous studies, but no detailed investigations have been done. We identify two eclipsing systems that are associated with an unidentified XMM-Newton or Swift source, and one promising candidate for polar associated with an unidentified ASKA source. Two polar candidates may locate in the so-called period gap of a CV, and the other six candidates have an orbital period shorter than that of the period gap. Although we do not identify a promising candidate for AR Scorpii-type binary systems, our study suggests that CV systems that have X-ray emission and do not show frequent outbursts may have been missed in previous surveys.

Keywords: Observatories, White dwarf stars, Binary stars, Cataclysmic variable stars
The Internal Proper Motion Kinematics of NGC 346: Past Formation and Future Evolution. We investigate the internal kinematics of the young star-forming region NGC 346 in the Small Magellanic Cloud (SMC). We used two epochs of deep F555W and F814W Hubble Space Telescope Advanced Camera for Surveys observations with an 11 yr baseline to determine proper motions and study the kinematics of different populations, as identified by their color-magnitude diagram and spatial distribution characteristics. The proper motion field of the young stars shows a complex structure with spatially coherent patterns. NGC 346's upper main sequence and pre-main sequence stars follow very similar motion patterns, with the outer parts of the cluster being characterized both by outflows and inflows. The proper motion field in the inner ~10 pc shows a combination of rotation and inflow, indicative of inspiraling motion. The rotation velocity in this regions peaks at ~3 km s-1, whereas the inflow velocity peaks at ~1 km s-1. Subclusters and massive young stellar objects in NGC 346 are found at the interface of significant changes in the coherence of the proper motion field. This suggests that turbulence is the main star formation driver in this region. Similar kinematics observed in the metal-poor NGC 346 and in the Milky Way's star-forming regions suggest that the differences in the cooling conditions due to different amounts of metallicity and dust density between the SMC and our galaxy are too small to alter significantly the process of star cluster assembly and growth. The main characteristics of our findings are consistent with various proposed star cluster formation models.

Keywords: Stellar motion, Stellar kinematics, Young massive clusters, Small Magellanic Cloud, Astrometry, Proper motions, Space astrometry
The Internal Line-of-Sight Kinematics of NGC 346: The Rotation of the Core Region. We present the stellar radial velocity analysis of the central $1^{\prime} \times 1^{\prime} $ of the young massive Small Magellanic Cloud star cluster NGC 346. Using VLT/MUSE integral field spectroscopy in combination with Hubble Space Telescope photometry, we extract 103 spectra of cluster member stars suited to measure accurate line-of-sight kinematics. The cluster member stars show two distinct velocity groups at ${v}_{1}=-{3.3}_{-0.2}^{+0.3}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ and ${v}_{2}={2.6}_{-0.1}^{+0.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ , relative to the systemic velocity of (165.5 ± 0.2) km s-1, and hint at a third group at ${v}_{3}={9.4}_{-0.1}^{+0.1}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . We show that there is neither a correlation between the velocity groups and the spatial location of the stars, nor their locus on optical color-magnitude diagrams, which makes the stellar velocity a key parameter to separate individual stellar components in such a young star cluster. Velocity group 2 shows clear rotation with Ω2 =(-0.4 ± 0.1) Myr-1, corresponding to (-4.9 ± 0.7) km s-1 at radial distance of 10 pc from the center, a possible remnant of the formation process of NGC 346 through the hierarchical collapse of the giant molecular cloud. The ionizing gas has lost any natal kinematic imprint and shows clear expansion, driven by far-ultraviolet fluxes and stellar winds of the numerous OB stars in the cluster center. The size of this expanding bubble and its expansion velocity of 7.9 km s-1 are in excellent agreement with the estimate that the latest star formation episode occurred about two million years ago.

Keywords: Stellar kinematics, Small Magellanic Cloud, Young star clusters, Spectroscopy, Radial velocity
Pressure-regulated, Feedback-modulated Star Formation in Disk Galaxies. The star formation rate (SFR) in galactic disks depends on both the quantity of the available interstellar medium (ISM) gas and its physical state. Conversely, the ISM's physical state depends on the SFR, because the "feedback" energy and momentum injected by recently formed massive stars is crucial to offsetting losses from turbulent dissipation and radiative cooling. The ISM's physical state also responds to the gravitational field that confines it, with increased weight driving higher pressure. In a quasi-steady state, it is expected that the mean total pressure of different thermal phases will match each other, that the component pressures and total pressure will satisfy thermal and dynamical equilibrium requirements, and that the SFR will adjust as needed to provide the requisite stellar radiation and supernova feedback. The pressure-regulated, feedback-modulated (PRFM) theory of the star-forming ISM formalizes these ideas, leading to a prediction that the SFR per unit area, ΣSFR, will scale nearly linearly with ISM weight ${ \mathcal W }$ . In terms of the large-scale gas surface density Σgas, stellar plus dark matter density ρ sd, and effective ISM velocity dispersion σ eff, an observable weight estimator is ${ \mathcal W }\approx {P}_{\mathrm{DE}}=\pi G{{\rm{\Sigma }}}_{\mathrm{gas}}^{2}/2+{{\rm{\Sigma }}}_{\mathrm{gas}}{(2G{\rho }_{\mathrm{sd}})}^{1/2}{\sigma }_{\mathrm{eff}}$ , and this is predicted to match the total midplane pressure P tot. Using a suite of multiphase magnetohydrodynamic simulations run with the TIGRESS computational framework, we test the principles of the PRFM model and calibrate the total feedback yield ϒtot = P tot/ΣSFR ~ 1000 km s-1, as well as its components. We compare the results from TIGRESS to theory, previous numerical simulations, and observations, finding excellent agreement.

Keywords: Star formation, Stellar feedback, Interstellar medium, Magnetohydrodynamical simulations