Sazuna/UAT_keywords huggingface dataset:
Transition Probabilities and Collision Strengths for Fine-structure Levels Excitation of Ti II. Several spectral features from the stellar and nebular objects arise due to the iron-peak Ti II fine-structure excitations. Transition probabilities and electron excitation collision strengths of iron-peak elements are important for a meaningful interpretation and analysis of the observed astrophysical spectra. Accurate description of atomic structure with open 3d-shell elements is the key to the reliable and accurate computation of radiative and collision rates. The term-dependent one-electron orbitals in the multiconfiguration Hartree-Fock approach with adjustable configuration expansions and semi-empirical fine-tuning for energy corrections have been used in achieving highly accurate target description. A total of 314 Ti II fine-structure levels of the ground 3d24s and excited 3d3, 3d4s2, 3d24p, 3d25s, 3d4s4p, 3d24d, 3d25p, and 3d24f configurations have been included in the calculations of these atomic parameters. The present calculation of collision strengths has been performed in a close-coupling approximation based on the B-spline Breit-Pauli R-matrix method with inclusion of spin-orbit interaction term in the Hamiltonian matrices. Effective collision strengths over a Maxwellian distribution of electron velocities at temperatures in the range from 103 to 105 K have been reported for transitions between the 314 fine-structure levels. These wide array of transitions give rise to many main Ti II infrared, optical, and ultraviolet lines from a variety of astrophysical objects. Our calculated parameters are compared with the available other theoretical and experimental results, and through this comparison likely uncertainties in our results have been estimated, especially for transitions among the low-lying fine-structure levels of astrophysical importance.

Keywords: Excitation rates, Laboratory astrophysics
Predictions of the L<SUB>[C II]</SUB>-SFR and [CII] Luminosity Function at the Epoch of Reionization. We present the first predictions for the L[C II]-SFR relation and [CII] luminosity function (LF) in the epoch of reionization (EOR) based on cosmological hydrodynamics simulations using the SIMBA suite plus radiative transfer calculations via SÍGAME. The sample consists of 11,137 galaxies covering halo mass log Mhalo ∈ [9, 12.4] M⊙, star formation rate SFR ∈ [0.01, 330] M⊙ yr-1, and metallicity ⟨Zgas⟩SFR ∈ [0.1, 1.9] Z⊙. The simulated L[C II]-SFR relation is consistent with the range observed, but with a spread of ≃0.3 dex at the high end of SFR (&gt;100 M⊙ yr-1) and ≃0.6 dex at the lower end, and there is tension between our predictions and the values of L[C II] above 108.5 L⊙ observed in some galaxies reported in the literature. The scatter in the L[C II]-SFR relation is mostly driven by galaxy properties, such that at a given SFR galaxies with higher molecular mass and metallicity have higher L[C II]. The [CII] LF predicted by SIMBA is consistent with the upper limits placed by the only existing untargeted flux-limited [CII] survey at the EOR and those predicted by semianalytic models. We compare our results with existing models and discuss the differences responsible for the discrepant slopes in the L[C II]-SFR relation.

Keywords: Hydrodynamical simulations, Galaxy properties, Galactic and extragalactic astronomy, Interstellar emissions, Galaxy evolution, Interstellar medium, Radiative transfer simulations
A Large Massive Quiescent Galaxy Sample at z ∼ 1.2. In this paper we present a simple color-magnitude selection and obtain a large sample of 33,893 massive quiescent galaxies at intermediate redshifts (1 &lt; z &lt; 1.5). We choose the longest wavelength available in the Hyper-Supreme-Cam (HSC) deep survey, the Y band and i - Y color, to select the 4000 Å Balmer jump in passive galaxies to the highest redshift possible within the survey. With the rich multiwavelength data in the HSC deep fields, we then confirm that the selected galaxies are in the targeted redshift range of 1 &lt; z &lt; 1.5, lie in the passive region of the UVJ diagram, and have high stellar masses at log(M*/M⊙) &gt; 10.5, with a median of log(M*/M⊙) = 11.0. A small fraction of our galaxies is also covered by the HST CANDELS. Morphological analysis in the observed H band shows that the majority of this subsample are early-type galaxies. As massive early-type galaxies trace the high-density regions in the large-scale structure in the universe, our study provides a quick and simple way to obtain a statistically significant sample of massive galaxies in a relatively narrow redshift range. Our sample is 7-20× larger at the massive end (log(M*/M⊙) &gt; 10.5) than any existing samples obtained in previous surveys. This is a pioneer study, and the technique introduced here can be applied to a future wide-field survey to study large-scale structure and to identify high-density regions and clusters.

Keywords: Catalogs, High-redshift galaxies, Galaxies
Determination of the Local Hubble Constant from Virgo Infall Using TRGB Distances. An independent determination of H0 is crucial given the growing tension between the Hubble constant, H0, derived locally and that determined from the modeling of the cosmic microwave background (CMB) originating in the early universe. In this work, we present a new determination of H0 using velocities and tip of the red giant branch (TRGB) distances to 33 galaxies located between the Local Group and the Virgo cluster. We use a model of the infall pattern of the local Hubble flow modified by the Virgo mass, which is given as a function of the cosmological constants (H0, ΩΛ), the radius of the zero-velocity surface R0, and the intrinsic velocity dispersion, σv. Fitting velocities and TRGB distances of 33 galaxies to the model, we obtain H0 = 65.8 ± 3.5 (stat) ± 2.4 (sys) km s-1 Mpc-1 and R0 = 6.76 ± 0.35 Mpc. Our local H0 is consistent with the global H0 determined from CMB radiation, showing no tension. In addition, we present new TRGB distances to NGC 4437 and NGC 4592, which are located near the zero-velocity surface: D = 9.28 ± 0.39 Mpc and D = 9.07 ± 0.27 Mpc, respectively. Their spatial separation is 0.29 ${}_{-0.03}^{+0.30}$ Mpc, suggesting that they form a physical pair.

Keywords: Cosmology, Cosmological parameters, Virgo Cluster, Galaxy stellar content, Distance indicators, Galaxy stellar halos, Hubble constant, Stellar distance
Probing Particle Acceleration through Broadband Early Afterglow Emission of MAGIC Gamma-Ray Burst GRB 190114C. Major Atmospheric Gamma Imaging Cerenkov Telescopes (MAGIC) detected the gamma-ray afterglow of GRB 190114C, which can constrain microscopic parameters of the shock-heated plasma emitting non-thermal emission. Focusing on the early afterglow of this event, we numerically simulate the spectrum and multi-wavelength light curves with constant and wind-like circumstellar medium using a time-dependent code. Our results show that the electron acceleration timescale at the highest energies is likely shorter than 20 times the gyroperiod to reproduce the GeV gamma-ray flux and its spectral index reported by Fermi. This gives an interesting constraint on the acceleration efficiency for Weibel-mediated shocks. We also constrain the number fraction of non-thermal electrons fe, and the temperature of the thermal electrons. The early optical emission can be explained by the thermal synchrotron emission with fe ≲ 0.01. On the other hand, the X-ray light curves restrict efficient energy transfer from protons to the thermal electrons, and fe ∼ 1 is required if the energy fraction of the thermal electrons is larger than ∼10%. The parameter constraints obtained in this work give important clues to probing plasma physics with relativistic shocks.

Keywords: Shocks, Gamma-ray bursts, Non-thermal radiation sources
Long-lived Eccentric Modes in Circumbinary Disks. Hydrodynamical simulations show that circumbinary disks become eccentric, even when the binary is circular. Here we demonstrate that, in steady state, the disk's eccentricity behaves as a long-lived free mode trapped by turning points that naturally arise from a continuously truncated density profile. Consequently, both the disk's precession rate and eccentricity profile may be calculated via the simple linear theory for perturbed pressure-supported disks. By formulating and solving the linear theory, we find that (i) surprisingly, the precession rate is roughly determined by the binary's quadrupole, even when the quadrupole is very weak relative to pressure; (ii) the eccentricity profile is largest near the inner edge of the disk and falls exponentially outward; and (iii) the results from linear theory indeed agree with what is found in simulations. Understanding the development of eccentric modes in circumbinary disks is a crucial first step for understanding the long-term (secular) exchange of eccentricity, angular momentum, and mass between the binary and the gas. Potential applications include the search for a characteristic kinematic signature in disks around candidate binaries and precession-induced modulation of accretion over long timescales.

Keywords: Supermassive black holes, Theoretical techniques, Binary stars, Protoplanetary disks, Stellar accretion disks
Flare Rates, Rotation Periods, and Spectroscopic Activity Indicators of a Volume-complete Sample of Mid- to Late-M Dwarfs within 15 pc. We present a study of flare rates, rotation periods, and spectroscopic activity indicators of 125 single stars within 15 parsecs and with masses between 0.1 and 0.3 M⊙ observed during the first year of the TESS mission, with the goal of elucidating the relationship between these various magnetically connected phenomena. We gathered multiepoch high-resolution spectra of each target, and we measured equivalent widths of the activity indicators helium I D3, Hα, and the calcium infrared triplet line at 8542.09 Å. We present 18 new rotation periods from MEarth photometry and 19 new rotation periods from TESS photometry. We present a catalog of 1392 flares. After correcting for sensitivity, we find the slope of the flare frequency distribution for all stars to have a standard value of α = 1.98 ± 0.02. We determine R31.5, the rate of flares per day with energies above E = 3.16 × 1031 ergs in the TESS bandpass. We find that below a critical value of Hα EW = -0.71 Å, log R31.5 increases linearly with increasing Hα emission; above this value, log R31.5 declines rapidly. The stars divide into two groups: 26% have Hα in emission, high flare rates with typical values of log R31.5 = -1.30 ± 0.08, and have Rossby numbers &lt;0.50. The remaining 74% show little to no Hα in emission and exhibit log R31.5 &lt; -3.86, with the majority of these stars not showing a single flare during the TESS observations.

Keywords: Stellar rotation, Stellar flares, Stellar activity
A Framework for Relative Biosignature Yields from Future Direct Imaging Missions. Future exoplanet direct imaging missions, such as HabEx and LUVOIR, will select target stars to maximize the number of Earth-like exoplanets that can have their atmospheric compositions characterized. Because one of these missions' aims is to detect biosignatures, they should also consider the expected biosignature yield of planets around these stars. In this work, we develop a method of computing relative biosignature yields among potential target stars, given a model of habitability and biosignature genesis, and using a star's habitability history. As an illustration and first application of this method, we use MESA stellar models to calculate the time evolution of the habitable zone and examine three simple models for biosignature genesis to calculate the relative biosignature yield for different stars. We find that the relative merits of K stars versus F stars depend sensitively on model choice. In particular, use of the present-day habitable zone as a proxy for biosignature detectability favors young, luminous stars lacking the potential for long-term habitability. Biosignature yields are also sensitive to whether life can arise on Cold Start exoplanets that enter the habitable zone after formation, an open question deserving of more attention. Using the case study of biosignature yields calculated for θ Cygni and 55 Cancri, we find that robust mission design and target selection for HabEx and LUVOIR depend on choosing a specific model of biosignature appearance with time, the terrestrial planet occurrence rate as a function of orbital separation, precise knowledge of stellar properties, and accurate stellar evolutionary histories.

Keywords: Stellar properties, Exoplanets, Exoplanet evolution, Astrobiology, Direct imaging, Planet hosting stars, Biosignatures, Habitable zone
Long-term Orbital Evolution of Galactic Satellites and the Effects on Their Star Formation Histories. We investigate the orbital motions of dwarf spheroidal galaxies (dSphs) in the halo of the Milky Way (MW) to understand their possible effects on the diversity of the star formation histories seen in these MW satellites. In this work, we explicitly consider a time-varying gravitational potential due to the growth of the MW's dark halo mass to calculate the long-term orbital evolutions of the dSphs, guided with Gaia DR2 proper motions, over the past 13.5 billion years. We find that the infall time of a satellite, defined as when the galaxy first crosses within the growing virial radius of the MW's halo, coincides well with the time when the star formation rate (SFR) is peaked for the sample of classical dSphs. On the other hand, ultra-faint dSphs already finished their SF activity prior to their infall times as already suggested in previous works, but there is a signature that their earlier SF histories are affected by interaction with the growing MW's halo to some extent. We also find, for classical dSphs, that the relative fraction of stars formed after the peak of the SFR to the current stellar mass is smaller for the smaller pericentric radius of the galaxy at its first infall. These results suggest that the infalling properties of the dSphs into the MW and the resultant environmental effects, such as ram pressure stripping and/or tidal disturbance in the MW's dark halo containing hot gas, play important roles in their star formation histories.

Keywords: Milky Way evolution, Milky Way dynamics, Milky Way formation
Flare Properties of A-type Stars in Kepler Data. We analyzed the long-cadence (LC) light curves of 5435 stars with effective temperatures of 7000-10,500 K in Data Release 25 of Kepler to extend the samples of A-type flare stars and study their flare properties. A total of 103 flare stars are detected, of which 72 have the Large Sky Area Multi-Object fiber Spectroscopic Telescope spectral types, resulting in 51 A-type stars, including 17 new and 34 known. A total of 352 flares are detected from the 51 stars. The flare durations, amplitudes, and energies in the Kepler band are calculated, with medians of 2.5 hr, 2.1 mmag, and 1035.8 erg, respectively. We give the flare frequency distribution (FFD) of the A-type stars. Within the same energy range, the flare rates of our FFD are lower than those in previous research, which was also based on Kepler LC data, and the FFD slope is consistent with that in the research. The activity-rotation relation of the A-type flare stars is shown for the first time, in which the flare activity decreases as the rotation period increases. The relation is similar to that of the late-type stars in previous studies. For the two relatively bright A-type flare stars, KIC 5360548 and KIC 9468475, three high-resolution spectra are observed on different nights for each of them, and radial velocities are calculated and compared with that of the previous research. The comparisons suggest that there is no evidence of the KIC 5360548 companion, and KIC 9468475 could have a low-mass companion.

Keywords: Early-type stars, A stars, Stellar flares, Optical flares, Catalogs
Flare Expansion to a Magnetic Rope Accompanied by Rare Radio Bursts. We present multispectral analysis (radio, Hα, ultraviolet (UV)/extreme ultraviolet (EUV), and hard X-ray) of a confined flare from 2015 March 12. This flare started within the active region NOAA 12 297 and then it expanded into a large preexisting magnetic rope embedded with a cold filament. The expansion started with several brightenings located along the rope. This process was accompanied by a group of slowly positively drifting bursts in the 0.8-2 GHz range. The frequency drift of these bursts was 45-100 MHz s-1. One of the bursts had an S-like form. During the brightening of the rope we observed a unique bright EUV structure transverse to the rope axis. The structure was observed in a broad range of temperatures and it moved along the rope with the velocity of about 240 km s-1. When the structure dissipated, we saw a plasma further following twisted threads in the rope. The observed slowly positively drifting bursts were interpreted considering particle beams and we show that one with the S-like form could be explained by the beam propagating through the helical structure of the magnetic rope. The bright structure transverse to the rope axis was interpreted considering line-of-sight effects and the dissipation-spreading process, which we found to be more likely.

Keywords: Solar flares
GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons. The Fermi-LAT collaboration presented the second gamma-ray burst (GRB) catalog covering its first 10 years of operations. A significant fraction of afterglow-phase light curves in this catalog cannot be explained by the closure relations of the standard synchrotron forward-shock model, suggesting that there could be an important contribution from another process. In view of the above, we derive the synchrotron self-Compton (SSC) light curves from the reverse shock in the thick- and thin-shell regime for a uniform-density medium. We show that this emission could explain the GeV flares exhibited in some LAT light curves. Additionally, we demonstrate that the passage of the forward shock synchrotron cooling break through the LAT band from jets expanding in a uniform-density environment may be responsible for the late time (≈102 s) steepening of LAT GRB afterglow light curves. As a particular case, we model the LAT light curve of GRB 160509A that exhibited a GeV flare together with a break in the long-lasting emission, and also two very high energy photons with energies of 51.9 and 41.5 GeV observed 76.5 and 242 s after the onset of the burst, respectively. Constraining the microphysical parameters and the circumburst density from the afterglow observations, we show that the GeV flare is consistent with an SSC reverse-shock model, the break in the long-lasting emission with the passage of the synchrotron cooling break through the Fermi-LAT band, and the very energetic photons with SSC emission from the forward shock, when the outflow carries a significant magnetic field (RB ≃ 30) and it decelerates in a uniform-density medium with a very low density ( $n={4.554}_{-1.121}^{+1.128}\times {10}^{-4}\,{\mathrm{cm}}^{-3}$ ).

Keywords: Gamma-ray bursts, Non-thermal radiation sources, Interstellar medium, Radiative processes, Magnetic fields
Modeling the Galactic Foreground and Beam Chromaticity for Global 21 cm Cosmology. In order to characterize and model the beam-weighted foreground for global 21 cm signal experiments, we present a methodology for generating basis eigenvectors that combines analytical and observational models of both the galactic spectral index and sky brightness temperature with simulations of beams having various angular and spectral dependencies and pointings. Each combination creates a unique beam-weighted foreground. By generating optimal eigenvectors to fit each foreground model using singular value decomposition (SVD), we examine the effects of varying the components of the beam-weighted foreground. We find that the eigenvectors for modeling an achromatic, isotropic beam—the ideal case—are nearly identical regardless of the unweighted foreground model used, and are practicably indistinguishable from polynomial-based models. When anisotropic, chromatic beams weight the foreground; however, a coupling is introduced between the spatial and spectral structure of the foreground that distorts the eigenvectors away from the polynomial models and induces a dependence of the basis upon the exact features of the beam (chromaticity, pattern, pointing) and foreground (spectral index, sky brightness temperature map). We find that the beam has a greater impact upon the eigenvectors than the foreground models. Any model that does not account for its distortion may produce rms uncertainties on the order of $\sim 10\mbox{--}{10}^{3}$ K for six-parameter, single-spectrum fits. If the beam is incorporated directly using SVD and training sets, however, the resultant eigenvectors yield milli-Kelvin level uncertainties. Given a sufficiently detailed description of the sky, our methodology can be applied to any particular experiment with a suitably characterized beam for the purpose of generating accurate beam-weighted foreground models.

Keywords: Galaxy structure, Observational cosmology, Principal component analysis, Spectral index, Radio astronomy, Reionization
Fermi-LAT Observations of V549 Vel 2017: A Subluminous Gamma-Ray Nova?. We report on the Fermi Large Area Telescope detection (with ≈5.7σ significance) as well as the multiwavelength analysis of the 2017 nova eruption V549 Vel. Unlike the recent shock-powered novae ASASSN-16ma and V906 Car, the optical and γ-ray light curves of V549 Vel show no correlation, likely implying relatively weak shocks in the eruption. Gaia detected a candidate progenitor of V549 Vel and found a parallax measurement of ϖ = 1.91 ± 0.39 mas, equivalent to a mode distance of d ≈ 560 pc (90% credible interval of 380-1050 pc). The progenitor was also observed by the 2MASS and WISE surveys. When adopting the Gaia distance, the spectral energy distribution of the progenitor is close to that of a G-type star. The Swift X-Ray Telescope detected the supersoft X-ray emission of the nova (kT = 30-40 keV) since day 236, and the inferred blackbody size is comparable to that of other novae assuming d ≈ 560 pc (i.e., Rbb ∼ 5 × 108 cm). However, there is also an unknown astrometric excess noise of ɛi = 3.2 mas found in the Gaia data, and the inferred distance becomes controversial. If the Gaia distance is accurate, the γ-ray luminosity of V549 Vel will be as low as Lγ ∼ 4 × 1033 erg s-1, making it the least luminous γ-ray nova known so far. This may imply that the shock properties responsible for the γ-ray emission in V549 Vel are different from those of the more luminous events. If the nova is located farther away, it is likely a symbiotic system with a giant companion as the observed progenitor.

Keywords: Gamma-ray transient sources, High energy astrophysics, Classical novae