Sazuna/UAT_keywords huggingface dataset:
Stromlo Stellar Tracks: Non-solar-scaled Abundances for Massive Stars. We present the Stromlo Stellar Tracks, a set of stellar evolutionary tracks, computed by modifying the Modules for Experiments in Stellar Astrophysics (MESA) 1D stellar evolution package, to fit the Galactic Concordance abundances for hot (T &gt; 8000 K) massive (≥10 M☉) main-sequence (MS) stars. Until now, all stellar evolution tracks have been computed at solar, scaled-solar, or α-element-enhanced abundances, and none of these models correctly represent the Galactic Concordance abundances at different metallicities. This paper is the first implementation of Galactic Concordance abundances to the stellar evolution models. The Stromlo tracks cover massive stars (10 ≤ M/M☉ ≤ 300) with varying rotations (v/vcrit = 0.0, 0.2, 0.4) and a finely sampled grid of metallicities (-2.0 ≤ [Z/H] ≤ +0.5; ∆[Z/H] = 0.1) evolved from the pre-main sequence to the end of 12C burning. We find that the implementation of Galactic Concordance abundances is critical for the evolution of MS, massive hot stars in order to estimate accurate stellar outputs (L, Teff, g), which, in turn, have a significant impact on determining the ionizing photon luminosity budgets. We additionally support prior findings of the importance that rotation plays on the evolution of massive stars and their ionizing budget. The evolutionary tracks for our Galactic Concordance abundance scaling provide a more empirically motivated approach than simple uniform abundance scaling with metallicity for the analysis of H II regions and have considerable implications for determining nebular emission lines and metallicity. Therefore, it is important to refine existing stellar evolutionary models for comprehensive high-redshift extragalactic studies. The Stromlo tracks are available to the astronomical community.

Keywords: Stellar abundances, Massive stars, Interstellar abundances, Chemical abundances, Stellar rotation, Stellar evolutionary tracks, Stellar evolution
Testing Blandford-Znajek Mechanism in Black Hole Hyperaccretion Flows for Long-duration Gamma-Ray Bursts. Long-duration gamma-ray bursts (GRBs) are generally related to the core-collapse of massive stars. In the collapsar scenario, a rotating stellar-mass black hole (BH) surrounded by a hyperaccretion disk has been considered as one of the plausible candidates of GRB central engines. In this paper, we work on a sample including 146 long GRBs with significant jet break features in the multiband afterglows. The jet opening angles can then be obtained by the jet break time. By assuming GRB jets powered by the Blandford-Znajek (BZ) mechanism in the BH hyperaccretion system, we analyze the distributions of the long GRB luminosities and durations in the samples, and constrain the accretion rates for the different BH spins. As a result, we find that the BZ mechanism is so powerful that it is possible to interpret the long GRB prompt emissions within reasonable accretion rates.

Keywords: Accretion, Black hole physics, Gamma-ray bursts, Massive stars, Magnetic fields
Temperature in Solar Sources of <SUP>3</SUP>He-rich Solar Energetic Particles and Relation to Ion Abundances. 3He-rich solar energetic particles (SEPs) are believed to be accelerated in solar flares or jets by a mechanism that depends on the ion charge-to-mass (Q/M) ratio. It implies that the flare plasma characteristics (e.g., temperature) may be effective in determining the elemental abundances of 3He-rich SEPs. This study examines the relation between the suprathermal (≲0.2 MeV nucleon-1) abundances of the He-Fe ions measured on the Advanced Composition Explorer and temperature in the solar sources for 24 3He-rich SEP events in the period 2010-2015. The differential emission measure technique is applied to derive the temperature of the source regions from the extreme ultraviolet imaging observations on the Solar Dynamics Observatory. The obtained temperature distribution peaks at 2.0-2.5 MK that is surprisingly consistent with earlier findings based on in situ elemental abundance or charge state measurements. We have found a significant anticorrelation between 3He/4He ratio and solar source temperature with a coefficient -0.6. It is most likely caused by non-charge-stripping processes, as both isotopes would be fully ionized in the inferred temperature range. This study shows that the elemental ratios 4He/O, N/O, Ne/O, Si/O, S/O, Ca/O, Fe/O generally behave with temperature as expected from abundance enhancement calculations at ionization equilibrium. The C and Mg, the two species with small changes in the Q/M ratio in the obtained temperature range, show no such behavior with temperature and could be influenced by similar processes as for the 3He/4He ratio.

Keywords: Solar abundances, Solar flares, Solar energetic particles, Solar extreme ultraviolet emission
Revealing the Structure and Internal Rotation of the Sagittarius Dwarf Spheroidal Galaxy with Gaia and Machine Learning. We present a detailed study of the internal structure and kinematics of the core of the Sagittarius dwarf spheroidal galaxy (Sgr). Using machine-learning techniques, we have combined the information provided by 3300 RR Lyrae stars, more than 2000 spectroscopically observed stars, and the Gaia second data release to derive the full phase space, i.e., 3D positions and kinematics, of more than 1.2 × 105 member stars in the core of the galaxy. Our results show that Sgr has a bar structure ∼2.5 kpc long, and that tidal tails emerge from its tips to form what it is known as the Sgr stream. The main body of the galaxy, strongly sheared by tidal forces, is a triaxial (almost prolate) ellipsoid with its longest principal axis of inertia inclined 43° ± 6° with respect to the plane of the sky and axis ratios of 1:0.67:0.60. Its external regions are expanding mainly along its longest principal axis, yet the galaxy conserves an inner core of about 500×330×300 pc that shows no net expansion and is rotating at vrot = 4.13 ± 0.16 km s-1. The internal angular momentum of the galaxy forms an angle θ = 18° ± 6° with respect to its orbital angular momentum, meaning that Sgr is in an inclined prograde orbit around the Milky Way. We compared our results with predictions from N-body models with spherical, pressure-supported progenitors and a model whose progenitor is a flattened rotating disk. Only the rotating model, based on preexisting simulations aimed at reproducing the line-of-sight velocity gradients observed in Sgr, was able to reproduce the observed properties in the core of the galaxy.

Keywords: Galaxy dynamics, Galaxy interactions, Sagittarius dwarf spheroidal galaxy, Galaxy evolution
Mutual Neutralization in Li<SUP>+</SUP>+H<SUP>-</SUP>/D<SUP>-</SUP> and Na<SUP>+</SUP>+H<SUP>-</SUP>/D<SUP>-</SUP> Collisions: Implications of Experimental Results for Non-LTE Modeling of Stellar Spectra. Advances in merged-beams instruments have allowed experimental studies of the mutual neutralization (MN) processes in collisions of both Li+ and Na+ ions with D- at energies below 1 eV. These experimental results place constraints on theoretical predictions of MN processes of Li+ and Na+ with H-, important for non-LTE modeling of Li and Na spectra in late-type stars. We compare experimental results with calculations for methods typically used to calculate MN processes, namely the full quantum (FQ) approach, and asymptotic model approaches based on the linear combination of atomic orbitals (LCAO) and semiempirical (SE) methods for deriving couplings. It is found that FQ calculations compare best overall with the experiments, followed by the LCAO, and the SE approaches. The experimental results together with the theoretical calculations, allow us to investigate the effects on modeled spectra and derived abundances and their uncertainties arising from uncertainties in the MN rates. Numerical experiments in a large grid of 1D model atmospheres, and a smaller set of 3D models, indicate that neglect of MN can lead to abundance errors of up to 0.1 dex (26%) for Li at low metallicity, and 0.2 dex (58%) for Na at high metallicity, while the uncertainties in the relevant MN rates as constrained by experiments correspond to uncertainties in abundances of much less than 0.01 dex (2%). This agreement for simple atoms gives confidence in the FQ, LCAO, and SE model approaches to be able to predict MN with the accuracy required for non-LTE modeling in stellar atmospheres.

Keywords: Stellar abundances, Laboratory astrophysics, Reaction rates, Collision physics, Stellar atmospheres
Broad-velocity-width Molecular Features in the Galactic Plane. We performed a systematic search for broad-velocity-width molecular features (BVFs) in the disk part of our Galaxy by using the CO J = 1-0 survey data obtained with the Nobeyama Radio Observatory 45 m telescope. From this search, 58 BVFs were identified. In comparisons with the infrared and radio continuum images, 36 BVFs appeared to have both infrared and radio continuum counterparts, and 15 of them are described as molecular outflows from young stellar objects in the literature. In addition, 21 BVFs have infrared counterparts only, and eight of them are described as molecular outflows in the literature. One BVF (CO 16.134-0.553) does not have any luminous counterpart in the other wavelengths, which suggests that it may be an analog of high-velocity compact clouds in the Galactic center.

Keywords: Interstellar molecules, Milky Way disk, Interstellar clouds
An Unsupervised Method for Identifying X-enriched Stars Directly from Spectra: Li in LAMOST. Stars with peculiar element abundances are important markers of chemical enrichment mechanisms. We present a simple method, tangent space projection (TSP), for the detection of X-enriched stars, for arbitrary elements X, even from blended lines. Our method does not require stellar labels, but instead directly estimates the counterfactual unenriched spectrum from other unlabeled spectra. As a case study, we apply this method to the 6708 Å Li doublet in LAMOST DR5, identifying 8428 Li-enriched stars seamlessly across evolutionary state. We comment on the explanation for Li-enrichment for different subpopulations, including planet accretion, nonstandard mixing, and youth.

Keywords: Lithium stars, Astronomy data modeling, Chemical abundances
Damage to Relativistic Interstellar Spacecraft by ISM Impact Gas Accumulation. As part of the NASA Starlight collaboration, we look at the implications of impacts with the interstellar medium (ISM) on a directed energy-driven relativistic spacecraft. The spacecraft experiences a stream of MeV/nucleon impacts along the forward edge primarily from hydrogen and helium nuclei. The accumulation of implanted slowly diffusing gas atoms in solids drives damage through the meso-scale processes of bubble formation, blistering, and exfoliation. This results in macroscopic changes to material properties and, in the cases of blistering and exfoliation, material erosion via blister rupture and delamination. Relativistic hydrogen and helium at constant velocity will stop in the material at a similar depth, as predicted by Bethe-Bloch stopping and subsequent simulations of the implantation distribution, leading to a mixed hydrogen and helium system similar to that observed within fusion plasma-facing components. However, the difference in depth of near-surface gas atoms with respect to the direction of exposure means that previously developed empirical models of blistering cannot be used to predict bubble formation or blistering onset. In this work, we present a model of the local gas concentration threshold for material blistering from exposure to the ISM at relativistic speeds. Expected effects on the spacecraft and mitigation strategies are also discussed. The same considerations apply to the Breakthrough Starshot mission.

Keywords: Deep space probes, Space probes, Interstellar medium
Constraints on the Rate of Supernovae Lasting for More Than a Year from Subaru/Hyper Suprime-Cam. Some supernovae, such as pair-instability supernovae, are predicted to have a duration of more than a year in the observer frame. To constrain the rates of supernovae lasting for more than a year, we conducted a long-term deep transient survey using Hyper Suprime-Cam (HSC) on the 8.2 m Subaru telescope. HSC is a wide-field (a 1.75 deg2 field-of-view) camera and it can efficiently conduct transient surveys. We observed the same 1.75 deg2 field repeatedly using the g-, r-, i-, and z-band filters with the typical depth of 26 mag for four seasons (from late 2016 to early 2020). Using these data, we searched for transients lasting for more than a year. Two supernovae were detected in two continuous seasons, one supernova was detected in three continuous seasons, but no transients lasted for all four seasons searched. The discovery rate of supernovae lasting for more than a year with the typical limiting magnitudes of 26 mag is constrained to be ${1.4}_{-0.7}^{+1.3}$ $(\mathrm{stat}.){}_{-0.3}^{+0.2}(\mathrm{sys}.)\,\mathrm{events}\,{\deg }^{-2}\,{\mathrm{yr}}^{-1}$ . All the long-lasting supernovae we found are likely Type IIn supernovae and our results indicate that about 40% of Type IIn supernovae have long-lasting light curves. No plausible pair-instability supernova candidates lasting for more than a year are discovered. By comparing the survey results and survey simulations, we constrain the luminous pair-instability supernova rate up to z ≃ 3 is of the order of 100 Gpc-3 yr-1 at most, which is 0.01-0.1% of the core-collapse supernova rate.

Keywords: Massive stars, Supernovae
ALMA Observations of the Inner Cavity in the Protoplanetary Disk around Sz 84. We present Atacama Large Millimeter/submillimeter Array observations of a protoplanetary disk around the T Tauri star Sz 84 and analyses of the structures of the inner cavity in the central region of the dust disk. Sz 84's spectral energy distribution (SED) has been known to exhibit negligible infrared excess at λ ≲ 10 μm due to the disk's cavity structure. Analyses of the observed visibilities of dust continuum at 1.3 mm and the SED indicate that the size of the cavity in the disk of large (millimeter size) dust grains is 8 au in radius and that in the disk of small (submicron size) dust grains is 60 au in radius. Furthermore, from the SED analyses, we estimate that the upper limit mass of small dust grains at r &lt; 60 au is less than ∼10-3 M⊕, which is ≲0.01% of the total (small + large) dust mass at r &lt; 60 au. These results suggest that large dust grains are dominant at r &lt; 60 au, implying that dust grains efficiently grow with less efficient fragmentation in this region, potentially due to weak turbulence and/or stickier dust grains. The balance of grain growth and dust fragmentation is an important factor for determining the size of large dust grains in protoplanetary disks, and thus Sz 84 could serve as a good testbed for investigations of grain growth in such disks.

Keywords: Protoplanetary disks, Planet formation
On the Nature of GW190814 and Its Impact on the Understanding of Supranuclear Matter. The observation of a compact object with a mass of 2.50-2.67M⊙ on 2019 August 14, by the LIGO Scientific and Virgo collaborations (LVC) has the potential to improve our understanding of the supranuclear equation of state. While the gravitational-wave analysis of the LVC suggests that GW190814 likely was a binary black hole system, the secondary component could also have been the heaviest neutron star observed to date. We use our previously derived nuclear-physics-multimessenger astrophysics framework to address the nature of this object. Based on our findings, we determine GW190814 to be a binary black hole merger with a probability of &gt;99.9%. Even if we weaken previously employed constraints on the maximum mass of neutron stars, the probability of a binary black hole origin is still ∼81%. Furthermore, we study the impact that this observation has on our understanding of the nuclear equation of state by analyzing the allowed region in the mass-radius diagram of neutron stars for both a binary black hole or neutron star-black hole scenario. We find that the unlikely scenario in which the secondary object was a neutron star requires rather stiff equations of state with a maximum speed of sound ${c}_{s}\geqslant \sqrt{0.6}$ times the speed of light, while the binary black hole scenario does not offer any new insight.

Keywords: Neutron stars, Neutron star cores, Stellar mergers, Nuclear astrophysics, Gravitational waves, Compact objects, Nuclear physics
Identifying Black Hole Central Engines in Gamma-Ray Bursts. The nature of the gamma-ray burst (GRB) central engine still remains an enigma. Entities widely believed to be capable of powering the extreme jets are magnetars and black holes. The maximum rotational energy that is available in a millisecond magnetar to form a jet is ∼1052 erg. We identify eight long GRBs whose jet-opening angle-corrected energetics of the prompt emission episode are &gt;1052 erg with high confidence level and, therefore, their central engines are expected to be black holes. The majority of these GRBs present significant emission in the sub-GeV energy range. The X-ray afterglow light curves of these bursts do not show any shallow decay behavior such as a plateau; however, a few cases exhibit flares and multiple breaks instead of a single power-law decay. For a minimum mass of the black hole (∼2 M⊙), we find the efficiency of producing a jet from its rotational energy to range between 2% and 270%. Highly energetic jets requiring high efficiencies implies that either the mass of these black holes are much larger or there are, in addition, other sources of energy that power the jet. By considering the Blandford-Znajek mechanism of jet formation, we estimate the masses of these black holes to range between ∼2 and 60 M⊙. Some of the lighter black holes formed in these catastrophic events are likely candidates to lie in the mass-gap region (2-5 M⊙).

Keywords: Magnetars, Gamma-ray bursts, Black holes, High energy astrophysics
The First Dynamical Mass Determination of a Nitrogen-rich Wolf-Rayet Star Using a Combined Visual and Spectroscopic Orbit. We present the first visual orbit for the nitrogen-rich Wolf-Rayet binary, WR 133 (WN5o + O9I), based on observations made with the CHARA Array and the MIRC-X combiner. This orbit represents the first visual orbit for a WN star and only the third Wolf-Rayet star with a visual orbit. The orbit has a period of 112.8 days, a moderate eccentricity of 0.36, and a separation of a = 0.79 mas on the sky. We combine the visual orbit with an SB2 orbit and Gaia parallax to find that the derived masses of the component stars are ${M}_{{\rm{WR}}}=9.3\pm 1.6{M}_{\odot }$ and ${M}_{{\rm{O}}}=22.6\pm 3.2{M}_{\odot }$ , with the large errors owing to the nearly face-on geometry of the system combined with errors in the spectroscopic parameters. We also derive an orbital parallax that is identical to the Gaia-determined distance. We present a preliminary spectral analysis and atmosphere models of the component stars, and find the mass-loss rate in agreement with polarization variability and our orbit. However, the derived masses are low compared to the spectral types and spectral model. Given the close binary nature, we suspect that WR 133 should have formed through binary interactions, and represents an ideal target for testing evolutionary models given its membership in the cluster NGC 6871.

Keywords: WN stars, Massive stars, Spectroscopic binary stars, Stellar masses, Wolf-Rayet stars, Interferometric binary stars, O supergiant stars
A Program for Multimessenger Standard Siren Cosmology in the Era of LIGO A+, Rubin Observatory, and Beyond. The most promising variation of the standard siren technique combines gravitational-wave (GW) data for binary neutron star (BNS) mergers with redshift measurements enabled by their electromagnetic (EM) counterparts, to constrain cosmological parameters such as H0, Ωm, and w0. Here we evaluate the near- and long-term prospects of multimessenger cosmology in the era of future GW observatories: Advanced LIGO Plus (A+, 2025), Voyager-like detectors (2030s), and Cosmic Explorer-like detectors (2035 and beyond). We show that the BNS horizon distance of ≈ 700 Mpc for A+ is well matched to the sensitivity of the Vera C. Rubin Observatory (VRO) for kilonova detections. We find that one year of joint A+ and VRO observations will constrain the value of H0 to percent-level precision, given a small investment of VRO time dedicated to target-of-opportunity GW follow-up. In the Voyager era, the BNS-kilonova observations begin to constrain Ωm with an investment of a few percent of VRO time. With the larger BNS horizon distance in the Cosmic Explorer era, on-axis short gamma-ray bursts (SGRBs) and their afterglows (though accompanying only some of the GW-detected mergers) supplant kilonovae as the most promising counterparts for redshift identification. We show that five years of joint observations with Cosmic Explorer-like facilities and a next-generation gamma-ray satellite with localization capabilities similar to that presently possible with Swift could constrain both Ωm and w0 to 15%-20%. We therefore advocate for a robust target-of-opportunity (ToO) program with VRO, and a wide-field gamma-ray satellite with improved sensitivity in the 2030s, to enable standard siren cosmology with next-generation gravitational-wave facilities.

Keywords: Neutron stars, Gravitational waves, Cosmological parameters
The Parallax of ω Centauri Measured from Gaia EDR3 and a Direct, Geometric Calibration of the Tip of the Red Giant Branch and the Hubble Constant. We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure the trigonometric parallax of ω Cen, the first high-precision parallax measurement for the most massive globular cluster in the Milky Way. We use a combination of positional and high-quality proper motion data from EDR3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where EDR3 parallaxes are best calibrated. We find the estimated parallax to be robust, demonstrating good control of systematics within the color-magnitude diagram of the cluster. We find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. The parallax of ω Cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (TRGB) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. Combined with the preexisting and most widely used measurements of the tip and foreground Milky Way extinction, we find MI,TRGB =-3.97 ± 0.06 mag for the I-band luminosity of the blue edge. Using the TRGB luminosity calibrated from the Gaia EDR3 parallax of ω Cen to calibrate the luminosity of Type Ia supernovae results in a value for the Hubble constant of H0 = 72.1 ± 2.0 km s-1 Mpc-1. We make the data for the stars in ω Cen available electronically and encourage independent analyses of the results presented here.

Keywords: Globular star clusters, Red giant tip, Distance measure, Distance indicators, Hubble constant