Sazuna/UAT_keywords huggingface dataset:
Measuring Frequency and Period Separations in Red-giant Stars Using Machine Learning. Asteroseismology is used to infer the interior physics of stars. The Kepler and TESS space missions have provided a vast data set of red-giant lightcurves, which may be used for asteroseismic analysis. These data sets are expected to significantly grow with future missions such as PLATO, and efficient methods are therefore required to analyze these data rapidly. Here, we describe a machine-learning algorithm that identifies red giants from the raw oscillation spectra and captures p- and mixed-mode parameters from the red-giant power spectra. We report algorithmic inferences for large frequency separation (Δν), frequency at maximum amplitude ( ${\nu }_{\max }$ ), and period separation (ΔΠ) for an ensemble of stars. In addition, we have discovered ~25 new probable red giants among 151,000 Kepler long-cadence stellar-oscillation spectra analyzed by this method, among which four are binary candidates that appear to possess red-giant counterparts. To validate the results of this method, we selected ~3000 Kepler stars, at various evolutionary stages ranging from subgiants to red clumps, and compare inferences of Δν, ΔΠ, and ${\nu }_{\max }$ with estimates obtained using other techniques. The power of the machine-learning algorithm lies in its speed: It is able to accurately extract seismic parameters from 1000 spectra in ~5 s on a modern computer (a single core of the Intel® Xeon® Platinum 8280 CPU).

Keywords: Red giant branch, Neural networks, Pulsation modes, Stellar oscillations, Asteroseismology
RW Aur A: SpeX Spectral Evidence for Differentiated Planetesimal Formation, Migration, and Destruction in an  3 Myr Old Excited CTTS System. We present 2007-2020 SpeX VISNIR spectral monitoring of the highly variable RW Aur A CTTS. We find direct evidence for a highly excited, IR-bright, asymmetric, and time-variable system. Comparison of the spectral and temporal trends found determines five different components: (1) a stable continuum from 0.7 to 1.3 μm, with color temperature ~4000 K, produced by the CTTS photospheric surface; (2) variable hydrogen emission lines emitted from hot excited hydrogen in the CTTS's protostellar atmosphere/accretion envelope; (3) hot CO gas in the CTTS's protostellar atmosphere/accretion envelope; (4) highly variable 1.8-5.0 μm thermal continuum emission with color temperature ranging from 1130 to 1650 K, due to a surrounding accretion disk that is spatially variable and has an inner wall at r ~ 0.04 au and T ~ 1650 K and outer edges at ~1200 K; and (5) transient, bifurcated signatures of abundant Fe II + associated S I, Si I, and Sr I in the system's jet structures. The bifurcated signatures first appeared in 2015, but these collapsed and disappeared into a small single-peaked protostellar atmosphere feature by late 2020. The temporal evolution of RW Aur A's spectral signatures is consistent with a dynamically excited CTTS system forming differentiated Vesta-sized planetesimals in an asymmetric accretion disk and migrating them inward to be destructively accreted. By contrast, nearby coeval binary companion RW Aur B evinces only a stable WTTS photospheric continuum from 0.7 to 1.3 μm + cold CO gas in absorption + stable 1.8-5.0 μm thermal disk continuum emission with color temperature ~1650 K.

Keywords: Planetary system formation, T Tauri stars, Astronomical techniques, Protoplanetary disks, Spectroscopy, Irregular variable stars, Near infrared astronomy
The Atmospheric Response to High Nonthermal Electron-beam Fluxes in Solar Flares. II. Hydrogen-broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope. Redshifted components of chromospheric emission lines in the hard X-ray impulsive phase of solar flares have recently been studied through their 30 s evolution with the high resolution of the Interface Region Imaging Spectrograph. Radiative-hydrodynamic flare models show that these redshifts are generally reproduced by electron-beam-generated chromospheric condensations. The models produce large ambient electron densities, and the pressure broadening of the hydrogen Balmer series should be readily detected in observations. To accurately interpret the upcoming spectral data of flares with the DKIST, we incorporate nonideal, nonadiabatic line-broadening profiles of hydrogen into the RADYN code. These improvements allow time-dependent predictions for the extreme Balmer line wing enhancements in solar flares. We study two chromospheric condensation models, which cover a range of electron-beam fluxes (1 - 5 × 1011 erg s-1 cm-2) and ambient electron densities (1 - 60 × 1013 cm-3) in the flare chromosphere. Both models produce broadening and redshift variations within 10 s of the onset of beam heating. In the chromospheric condensations, there is enhanced spectral broadening due to large optical depths at Hα, Hβ, and Hγ, while the much lower optical depth of the Balmer series H12-H16 provides a translucent window into the smaller electron densities in the beam-heated layers below the condensation. The wavelength ranges of typical DKIST/ViSP spectra of solar flares will be sufficient to test the predictions of extreme hydrogen wing broadening and accurately constrain large densities in chromospheric condensations.

Keywords: Solar flares, Solar flare spectra
Feedback-dominated Accretion Flows. We present new two-fluid models of accretion disks in active galactic nuclei (AGNs) that aim to address the long-standing problem of Toomre instability in AGN outskirts. In the spirit of earlier works by Sirko &amp; Goodman and others, we argue that Toomre instability is eventually self-regulated via feedback produced by fragmentation and its aftermath. Unlike past semianalytic models, which (i) adopt local prescriptions to connect star formation rates to heat feedback, and (ii) assume that AGN disks self-regulate to a star-forming steady state (with Toomre parameter Q T = 1), we find that feedback processes are both temporally and spatially nonlocal. The accumulation of many stellar-mass black holes embedded in AGN gas eventually displaces radiation, winds, and supernovae from massive stars as the dominant feedback source. The nonlocality of feedback heating, in combination with the need for heat to efficiently mix throughout the gas, gives rise to steady-state AGN solutions that can have Q T ≫ 1 and no ongoing star formation. We find self-consistent steady-state solutions in much of the parameter space of AGN mass and accretion rate. These solutions harbor large populations of embedded compact objects that may grow in mass by factors of a few over the AGN lifetime, including into the lower and upper mass gaps. These feedback-dominated AGN disks differ significantly in structure from commonly used 1D disk models, which has broad implications for gravitational-wave-source formation inside AGNs.

Keywords: Accretion, Black hole physics, Supermassive black holes, Galaxy accretion disks, Radio active galactic nuclei
Galaxy and Mass Assembly (GAMA): The Weak Environmental Dependence of Quasar Activity at 0.1 &lt; z &lt; 0.35. Understanding the connection between nuclear activity and galaxy environment remains critical in constraining models of galaxy evolution. By exploiting the extensive cataloged data from the Galaxy and Mass Assembly survey, we identify a representative sample of 205 quasars at 0.1 &lt; z &lt; 0.35 and establish a comparison sample of galaxies, closely matched to the quasar sample in terms of both stellar mass and redshift. On scales &lt;1 Mpc, the galaxy number counts and group membership of quasars appear entirely consistent with those of the matched galaxy sample. Despite this, we find that quasars are ~1.5 times more likely to be classified as the group center, indicating a potential link between quasar activity and cold gas flows or galaxy interactions associated with rich group environments. On scales of ~a few Mpc, the clustering strengths of both samples are statistically consistent, and beyond 10 Mpc, we find no evidence that quasars trace large-scale structures any more than the galaxy control sample. Both populations are found to prefer intermediate-density sheets and filaments to either very high-density environments or very low-density environments. This weak dependence of quasar activity on galaxy environment supports a paradigm in which quasars represent a phase in the lifetime of all massive galaxies and in which secular processes and a group-centric location are the dominant triggers of quasars at low redshift.

Keywords: Active galaxies, Galaxy evolution, Quasars
Spin Evolution of Stellar-mass Black Holes Embedded in AGN Disks: Orbital Eccentricity Produces Retrograde Circumstellar Flows. The spin evolution of stellar-mass black holes (sBHs) embedded in AGN accretion disks is an important process relevant to the production of gravitational waves from binary BH (BBH) merger events through the AGN channel. Because embedded sBHs are surrounded by circumstellar disks (CSDs), the rotation of CSD gas flows determines the direction of the angular momentum it accretes. In this Letter, we use global 2D hydrodynamic simulations to show that while a disk-embedded sBH on a circular orbit transforms the initial retrograde Keplerian shear of the background accretion disk into a prograde CSD flow, as in the classical picture of companion-disk interaction theory, moderate orbital eccentricity could disrupt the steady-state tidal perturbation and preserve a retrograde CSD flow around the sBH. This switch in CSD orientation occurs at a transition eccentricity that scales nearly proportional to the local sound speed. This bifurcation in the CSD flow and thereafter spin-up direction of SBHs leads to the formation of a population of nearly antialigned sBHs and should be incorporated in future population models of sBH and BBH evolutions.

Keywords: Accretion, Planetary-disk interactions, Black holes, Galaxy accretion disks, Gravitational wave sources
The Magnetic Field versus Density Relation in Star-forming Molecular Clouds. We study the magnetic field to density (B-ρ) relation in turbulent molecular clouds with dynamically important magnetic fields using nonideal three-dimensional magnetohydrodynamic simulations. Our simulations show that there is a distinguishable break density ρ T between the relatively flat low-density regime and a power-law regime at higher densities. We present an analytic theory for ρ T based on the interplay of the magnetic field, turbulence, and gravity. The break density ρ T scales with the strength of the initial Alfvén Mach number ${{ \mathcal M }}_{{\rm{A}}0}$ for sub-Alfvénic ( ${{ \mathcal M }}_{{\rm{A}}0}\lt 1$ ) and trans-Alfvénic ( ${{ \mathcal M }}_{{\rm{A}}0}\sim 1$ ) clouds. We fit the variation of ρ T for model clouds as a function of ${{ \mathcal M }}_{{\rm{A}}0}$ , set by different values of initial sonic Mach number ${{ \mathcal M }}_{0}$ and the initial ratio of gas pressure to magnetic pressure β 0. This implies that ρ T, which denotes the transition in mass-to-flux ratio from the subcritical to the supercritical regime, is set by the initial turbulent compression of the molecular cloud.

Keywords: Star formation, Magnetohydrodynamics, Magnetic fields, Molecular clouds
The Two Hot Corinos of the SVS13-A Protostellar Binary System: Counterposed Siblings. We present ALMA high-angular-resolution (~50 au) observations of the Class I binary system SVS13-A. We report images of SVS13-A in numerous interstellar complex organic molecules: CH3OH, 13CH3OH, CH3CHO, CH3OCH3, and NH2CHO. Two hot corinos at different velocities are imaged in VLA4A (V sys = +7.7 km s-1) and VLA4B (V sys = +8.5 km s-1). From a non-LTE analysis of methanol lines, we derive a gas density of 3 × 108 cm-3 and gas temperatures of 140 and 170 K for VLA4A and VLA4B, respectively. For the other species, the column densities are derived from an LTE analysis. Formamide, which is the only N-bearing species detected in our observations, is more prominent around VLA4A, while dimethyl ether, methanol, and acetaldehyde are associated with both VLA4A and VLA4B. We derive in the two hot corinos abundance ratios of ~1 for CH3OH, 13CH3OH, and CH3OCH3; ~2 for CH3CHO; and ~4 for NH2CHO. The present data set supports chemical segregation between the different species inside the binary system. The emerging picture is that of an onion-like structure of the two SVS13-A hot corinos, caused by the different binding energies of the species, also supported by ad hoc quantum chemistry calculations. In addition, the comparison between molecular and dust maps suggests that the interstellar complex organic molecules emission originates from slow shocks produced by accretion streamers impacting the VLA4A and VLA4B disks and enriching the gas-phase component.

Keywords: Astrochemistry
Toward a Better Understanding of Cosmic Chronometers: A New Measurement of H(z) at z   0.7. We analyze the stellar ages obtained from a combination of Lick indices in Borghi et al. for 140 massive and passive galaxies selected in the LEGA-C survey at 0.6 &lt; z &lt; 0.9. From their median age-redshift relation, we derive a new direct measurement of H(z) without any cosmological model assumption using the cosmic chronometer approach. We thoroughly study the main systematics involved in this analysis: the choice of the Lick indices combination, the binning method, the assumed stellar population model, and the adopted star formation history; these effects are included in the total error budget. We obtain H(z = 0.75) = 98.8 ± 33.6 km s-1 Mpc-1. In parallel, we also propose a simple framework based on a cosmological model to describe the age-redshift relations in the context of galaxy downsizing. This allows us to derive constraints on the Hubble constant H 0 and the typical galaxy formation time. This new H(z) measurement, whose accuracy is currently limited by the scarcity of the sample analyzed, paves the road for the joint study of the stellar populations of individual passive galaxies and the expansion history of the universe in light of future spectroscopic surveys.

Keywords: Galaxy ages, Cosmological evolution, Observational cosmology, Hubble constant
The Local Group Mass in the Light of Gaia. High-accuracy proper motions (PMs) of M31 and other Local Group (LG) satellites have now been provided by the Gaia satellite. We revisit the timing argument to compute the total mass M of the LG from the orbit of the Milky Way and M31, allowing for the cosmological constant. We rectify a systematic effect caused by the presence of the Large Magellanic Cloud (LMC). The interaction of the LMC with the Milky Way induces a motion toward the LMC. This contribution to the measured velocity of approach of the Milky Way and M31 must be removed. We allow for cosmic bias and scatter by extracting correction factors tailored to the accretion history of the LG. The distribution of correction factors is centered around 0.63 with a scatter of ±0.2, indicating that the timing argument significantly overestimates the true mass. Adjusting for all these effects, the estimated mass of the LG is $M={3.4}_{-1.1}^{+1.4}\times {10}^{12}{M}_{\odot }$ (68% CL) when using the M31 tangential velocity, ${v}_{\tan }={82}_{-35}^{+38}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . Lower tangential velocity models with ${v}_{\tan }={59}_{-38}^{+42}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ (derived from the same PM data with a flat prior on the tangential velocity) lead to an estimated mass of $M={3.1}_{-1.0}^{+1.3}\times {10}^{12}{M}_{\odot }$ (68% CL). By making an inventory of the total mass associated with the four most substantial LG members (the Milky Way, M31, M33, and the LMC), we estimate the known mass to be in the range ${3.7}_{-0.5}^{+0.5}\times {10}^{12}\,{M}_{\odot }$ .

Keywords: Local Group
Solar Energetic Particles Produced during Two Fast Coronal Mass Ejections. Two recent extremely fast coronal mass ejections (CMEs) are of particular interest. The first one originated from the southern hemisphere on 2021 October 28 and caused strong solar energetic particle (SEP) events over a wide longitude range from Earth, STEREO-A, to Mars. However, the other one, originating from the center of the Earth-viewed solar disk 5 days later, left weak SEP signatures in the heliosphere. Based on the white-light images of the CMEs from the Solar and Heliospheric Observatory (SOHO) and the Ahead Solar Terrestrial Relations Observatory (STEREO-A), in combination with the observations of the corresponding solar flares, radio bursts, and in situ magnetic fields and particles, we try to analyze the series of solar eruptions during October 28-November 2 as well as their correspondences with the in situ features. It is found that the difference in SEP features between the two CMEs is mainly due to (1) the seed particles probably supplied by associated flares and (2) the magnetic connection influenced by the preceding solar wind speed.

Keywords: Solar energetic particles, Solar flares, Solar coronal mass ejections
Analysis of a JWST NIRSpec Lab Time Series: Characterizing Systematics, Recovering Exoplanet Transit Spectroscopy, and Constraining a Noise Floor. The James Webb Space Telescope's (JWST) NIRSpec instrument will unveil the nature of exoplanet atmospheres across the wealth of planet types, from temperate terrestrial worlds to ultrahot Jupiters. In particular, the 0.6-5.3 μm PRISM mode is especially well suited for efficient spectroscopic exoplanet observations spanning a number of important spectral features. We analyze a lab-measured NIRSpec PRISM mode Bright Object Time Series observation from the perspective of a JWST user to understand the instrument performance and detector properties. We create two realistic transiting exoplanet time-series observations by performing injection-recovery tests on the lab-measured data to quantify the effects of real instrument jitter, drift, intrapixel sensitivity variations, and 1/f noise on measured transmission spectra. By fitting the time-series systematics simultaneously with the injected transit, we can obtain more realistic transit-depth uncertainties that take into account noise sources that are currently not modeled by traditional exposure time calculators. We find that sources of systematic noise related to intrapixel sensitivity variations and point-spread function motions are apparent in the data at the level of a few hundred ppm but can be effectively detrended using a low-order polynomial with detector position. We recover the injected spectral features of GJ 436 b and TRAPPIST-1 d and place a 3σ upper limit on the detector noise floor of 14 ppm. We find that the noise floor is consistent with &lt;10 ppm at the 1.7σ level, which bodes well for future observations of challenging targets with faint atmospheric signatures.

Keywords: Space telescopes, Exoplanet atmospheres, Transmission spectroscopy
A Massive AGB Donor in Scutum X-1: Identification of the First Mira Variable in an X-Ray Binary. The symbiotic X-ray binary Sct X-1 was suggested to be the first known neutron star accreting from a red supergiant companion. Although known for nearly 50 yr, detailed characterization of the donor remains lacking, particularly due to the extremely high reddening toward the source (A  V  ≳ 25 mag). Here, we present (i) improved localization of the counterpart using Gaia and Chandra observations, (ii) the first broadband infrared spectrum (≈1-5 μm; R ≈ 2000) obtained with SpeX on the NASA Infrared Telescope Facility, and (iii) the J-band light curve from the Palomar Gattini-IR survey. The infrared spectrum is characterized by (i) deep water absorption features (H2O index ≈ 40%), (ii) strong TiO, VO, and CO features, and (iii) weak/absent CN lines. We show that these features are inconsistent with known red supergiants but suggest an M8-9 III-type O-rich Mira donor star. We report the discovery of large-amplitude (ΔJ ≈ 3.5 mag) periodic photometric variability, suggesting a pulsation period of 621 ± 36 (systematic) ± 8 (statistical) days, which we use to constrain the donor to be a relatively luminous Mira (M  K  = -8.6 ± 0.3 mag) at a distance of ${3.6}_{-0.7}^{+0.8}$ kpc. Comparing these characteristics to recent models, we find the donor to be consistent with a ≈3-5 M ⊙ star at an age of ≈0.1-0.3 Gyr. Together, we show that Sct X-1 was previously misclassified as an evolved high-mass X-ray binary; instead, it is an intermediate-mass system with the first confirmed Mira donor in an X-ray binary. We discuss the implications of Mira donors in symbiotic X-ray binaries and highlight the potential of wide-field infrared time-domain surveys and broadband infrared spectroscopy to unveil their demographics.

Keywords: Mira variable stars, X-ray binary stars, Sky surveys, Asymptotic giant branch
The Composition and Power of the Jet of the Broad-line Radio Galaxy 3C 120. We calculated the electron-positron pair-production rate at the base of the jet of 3C 120 due to collisions of photons from the hot accretion flow using the measurement of its average soft gamma-ray spectrum by the Compton Gamma Ray Observatory. We found that this rate approximately equals the flow rate of leptons emitting the observed synchrotron radio-to-IR spectrum of the jet core, calculated using the extended jet model following Blandford &amp; Königl. This coincidence shows the jet composition is likely to be pair dominated. We then calculated the jet power in the bulk motion of ions and found it greatly exceeds that achievable by the magnetically arrested disk scenario for the maximum black hole spin unless the jet contains mostly pairs. Next, we found that the magnetic flux through the synchrotron-emitting jet equals the maximum poloidal flux that can thread the black hole. Finally, we compared two estimates of the magnetization parameter at the onset of the synchrotron emission and found they are in agreement only if pairs dominate the jet content.

Keywords: Accretion, Relativistic jets, Active galaxies, Radio galaxies, Non-thermal radiation sources
Schwarzschild and Ledoux are Equivalent on Evolutionary Timescales. Stellar evolution models calculate convective boundaries using either the Schwarzschild or Ledoux criterion, but confusion remains regarding which criterion to use. Here we present a 3D hydrodynamical simulation of a convection zone and adjacent radiative zone, including both thermal and compositional buoyancy forces. As expected, regions that are unstable according to the Ledoux criterion are convective. Initially, the radiative zone adjacent to the convection zone is Schwarzschild unstable but Ledoux stable due to a composition gradient. Over many convective overturn timescales, the convection zone grows via entrainment. The convection zone saturates at the size originally predicted by the Schwarzschild criterion, although in this final state the Schwarzschild and Ledoux criteria agree. Therefore, the Schwarzschild criterion should be used to determine the size of stellar convection zones, except possibly during short-lived evolutionary stages in which entrainment persists.

Keywords: Stellar evolutionary models, Stellar convective zones, Stellar physics