Sazuna/UAT_keywords huggingface dataset:
EXORCISM: A Spectroscopic Survey of Young Eruptive Variables (EXor and Candidates). We present an optical/near-IR survey of 11 variable young stars (EXors and EXor candidates) aimed at deriving and monitoring their accretion properties. About 30 optical and near-infrared spectra ( ${\mathfrak{R}}\sim 1500\mbox{--}2000$ ) were collected between 2014 and 2019 with the Large Binocular Telescope (LBT). From the spectral analysis we have derived the accretion luminosity (L acc ) and mass accretion rate ( ${\dot{M}}_{\mathrm{acc}}$ ), the visual extinction (A V), the temperature and density of the permitted line formation region (T, n H), and the signature of the outflowing matter. Two sources (ASASSN-13db and iPTF15afq) have been observed in outburst and quiescence, three during a high level of brightness (XZ Tau, PV Cep, and NY Ori), and the others in quiescence. These latter have L acc and ${\dot{M}}_{\mathrm{acc}}$ in line with the values measured in classical T Tauri stars of similar mass. All sources observed more than once present L acc and ${\dot{M}}_{\mathrm{acc}}$ variability. The most extreme case is ASASSN-13db, for which ${\dot{M}}_{\mathrm{acc}}$ decreases by two orders of magnitude from the outburst peak in 2015 to quiescence in 2017. Also, in NY Ori L acc decreases by a factor 25 in one year. In 80% of the sample we detect the [O I] 6300 Å line, a tracer of mass loss. From the variability of the Hα/[O I] 6300 Å ratio, we conclude that mass accretion variations are larger than mass loss variations. From the analysis of the H I recombination lines, a correlation is suggested between the density of the line formation region, and the level of accretion activity of the source.

Keywords: Eruptive phenomena, Pre-main sequence stars, Star formation, Stellar mass loss
A Possible 3 yr Quasi-periodic Oscillation in γ-Ray Emission from the FSRQ S5 1044+71. Variability is a typical observation feature of Fermi blazars, which sometimes shows quasi-periodic oscillation (QPO). In this work, we obtain 5 day binned light curves (with a time coverage of ~12.9 yr) for S5 1044+71, based on Fermi-LAT data; apply five different methods-Date-compensated Discrete Fourier Transform, Jurkevich, Lomb-Scargle Periodogram, a Fortran 90 program, and the Weighted Wavelet Z-transform-to the γ-ray light curve; and find a possible QPO of 3.06 ± 0.43 yr at the significance level of ~3.6σ. A binary black hole model, including an accretion model and a dual-jet model, is used to explain this quasi-periodic variability. We also estimate the Doppler factors and the apparent velocity for the two jet components. We speculate that this γ-ray quasi-periodic modulation suggests the presence of a binary supermassive black hole in S5 1044+71.

Keywords: Gamma-ray sources, Active galactic nuclei, Quasars
The Stellar Metallicities of Massive Quiescent Galaxies at 1.0 &lt; z &lt; 1.3 from KMOS + VANDELS. We present a rest-frame UV-optical (λ = 2500-6400 Å) stacked spectrum representative of massive quiescent galaxies at 1.0 &lt; z &lt; 1.3 with log(M */M ☉) &gt; 10.8. The stack is constructed using VANDELS survey data, combined with new KMOS observations. We apply two independent full-spectral-fitting approaches, measuring a total metallicity [Z/H] = -0.13 ± 0.08 with BAGPIPES and [Z/H] = 0.04 ± 0.14 with ALF, a fall of ~0.2-0.3 dex compared with the local universe. We also measure an iron abundance [Fe/H] = -0.18 ± 0.08, a fall of ~0.15 dex compared with the local universe. We measure the alpha enhancement via the magnesium abundance, obtaining [Mg/Fe] = 0.23 ± 0.12, consistent with galaxies of similar mass in the local universe, indicating no evolution in the average alpha enhancement of log(M */M ☉) ~ 11 quiescent galaxies over the last ~8 Gyr. This suggests the very high alpha enhancements recently reported for several bright z ~ 1-2 quiescent galaxies are due to their extreme masses, log(M */M ☉) ≳ 11.5, in accordance with the well-known downsizing trend, rather than being typical of the z ≳ 1 population. The metallicity evolution we observe with redshift (falling [Z/H], [Fe/H], constant [Mg/Fe]) is consistent with recent studies. We recover a mean stellar age of ${2.5}_{-0.4}^{+0.6}$ Gyr, corresponding to a formation redshift ${z}_{\mathrm{form}}={2.4}_{-0.3}^{+0.6}$ . Recent studies have obtained varying average formation redshifts for z ≳ 1 massive quiescent galaxies, and, as these studies report consistent metallicities, we identify models with different star formation histories as the most likely cause. Larger spectroscopic samples from upcoming ground-based instruments will provide precise constraints on ages and metallicities at z ≳ 1. Combining these with precise stellar mass functions for z &gt; 2 quiescent galaxies from the James Webb Space Telescope will provide an independent test of formation redshifts derived from spectral fitting.

Keywords: Metallicity, Quenched galaxies, Chemical abundances, Galaxy spectroscopy, High-redshift galaxies
Cosmology with One Galaxy?. Galaxies can be characterized by many internal properties such as stellar mass, gas metallicity, and star formation rate. We quantify the amount of cosmological and astrophysical information that the internal properties of individual galaxies and their host dark matter halos contain. We train neural networks using hundreds of thousands of galaxies from 2000 state-of-the-art hydrodynamic simulations with different cosmologies and astrophysical models of the CAMELS project to perform likelihood-free inference on the value of the cosmological and astrophysical parameters. We find that knowing the internal properties of a single galaxy allows our models to infer the value of Ωm, at fixed Ωb, with a ~10% precision, while no constraint can be placed on σ 8. Our results hold for any type of galaxy, central or satellite, massive or dwarf, at all considered redshifts, z ≤ 3, and they incorporate uncertainties in astrophysics as modeled in CAMELS. However, our models are not robust to changes in subgrid physics due to the large intrinsic differences the two considered models imprint on galaxy properties. We find that the stellar mass, stellar metallicity, and maximum circular velocity are among the most important galaxy properties to determine the value of Ωm. We believe that our results can be explained by considering that changes in the value of Ωm, or potentially Ωb/Ωm, affect the dark matter content of galaxies, which leaves a signature in galaxy properties distinct from the one induced by galactic processes. Our results suggest that the low-dimensional manifold hosting galaxy properties provides a tight direct link between cosmology and astrophysics.

Keywords: Hydrodynamical simulations, Galaxy formation, Astrostatistics, Cosmological models
Effects of an Immortal Stellar Population in AGN Disks. Stars are likely embedded in the gas disks of active galactic nuclei (AGN). Theoretical models predict that in the inner regions of the disk, these stars accrete rapidly, with fresh gas replenishing hydrogen in their cores faster than it is burned into helium, effectively stalling their evolution at hydrogen burning. We produce order-of-magnitude estimates of the number of such stars in a fiducial AGN disk. We find numbers of order 102-4, confined to the inner r cap ~ 3000r  s  ~ 0.03 pc. These stars can profoundly alter the chemistry of AGN disks, enriching them in helium and depleting them in hydrogen, both by order-unity amounts. We further consider mergers between these stars and other disk objects, suggesting that star-star mergers result in rapid mass loss from the remnant to restore an equilibrium mass, while star-compact object mergers may result in exotic outcomes and even host binary black hole mergers within themselves. Finally, we examine how these stars react as the disk dissipates toward the end of its life, and find that they may return mass to the disk fast enough to extend its lifetime by a factor of several and/or may drive powerful outflows from the disk. Post-AGN, these stars rapidly lose mass and form a population of stellar mass black holes around 10M ⊙. Due to the complex and uncertain interactions between embedded stars and the disk, their plausible ubiquity, and their order-unity impact on disk structure and evolution, they must be included in realistic disk models.

Keywords: Massive stars, Stellar physics, Stellar evolutionary models, Quasars
EMPRESS. VI. Outflows Investigated in Low-mass Galaxies with M <SUB>∗</SUB> = 10<SUP>4</SUP>-10<SUP>7</SUP> M <SUB>⊙</SUB>: Weak Feedback in Low-mass Galaxies?. We study emission line profiles of 21 nearby low-mass (M * = 104-107 M ⊙) galaxies in deep medium-high resolution spectra taken with Magellan/MagE. These low-mass galaxies are actively star-forming systems with high specific star formation rates of ~100-1000 Gyr-1 that are well above the star formation main sequence and its extrapolation. We identify broad-line components of Hα and [O III]λ5007 emission in 14 out of the 21 galaxies that cannot be explained by the MagE instrumental profile or the natural broadening of line emission. We conduct double-Gaussian profile fitting to the emission of the 14 galaxies, and find that the broad-line components have line widths significantly larger than those of the narrow-line components, indicative of galactic outflows. The broad-line components have moderately large line widths of ~100 km s-1. We estimate the maximum outflow velocities v max and obtain values of ≃60-200 km s-1, which are found to be comparable to or slightly larger than the escape velocities. Positive correlations of v max with star formation rates, stellar masses, and circular velocities extend down into this low-mass regime. Broad- to narrow-line flux ratios (BNRs) are generally found to be smaller than those of massive galaxies. The small v max and BNRs suggest that the mass-loading factors η can be as small as 0.1-1 or below, in contrast to the large η of energy-driven outflows predicted by numerical simulations.

Keywords: Galaxy evolution, Dwarf galaxies, Galaxy winds, Stellar feedback
Approximating Density Probability Distribution Functions Across Cosmologies. Using a suite of self-similar cosmological simulations, we measure the probability distribution functions (PDFs) of real-space density, redshift-space density, and their geometric mean. We find that the real-space density PDF is well-described by a function of two parameters: n  s , the spectral slope, and σ  L , the linear rms density fluctuation. For redshift-space density and the geometric mean of real- and redshift-space densities, we introduce a third parameter, ${s}_{L}=\sqrt{\langle {\left({{dv}}_{\mathrm{pec}}^{L}/{dr}\right)}^{2}\rangle }/H$ . We find that density PDFs for the LCDM cosmology is also well-parameterized by these three parameters. As a result, we are able to use a suite of self-similar cosmological simulations to approximate density PDFs for a range of cosmologies. We make the density PDFs publicly available and provide an analytical fitting formula for them.

Keywords: Cosmology, Cosmological evolution, Cosmological models, Redshifted, Large-scale structure of the universe, Cosmological parameters, Bianchi cosmology, N-body simulations, Hierarchical cosmology, Dark matter
Assessing the Impact of Hydrogen Absorption on the Characteristics of the Galactic Center Excess. We present a new reconstruction of the distribution of atomic hydrogen in the inner Galaxy that is based on explicit radiation transport modeling of line and continuum emission and a gas-flow model in the barred Galaxy that provides distance resolution for lines of sight toward the Galactic center. The main benefits of the new gas model are (a) the ability to reproduce the negative line signals seen with the HI4PI survey and (b) the accounting for gas that primarily manifests itself through absorption. We apply the new model of Galactic atomic hydrogen to an analysis of the diffuse gamma-ray emission from the inner Galaxy, for which an excess at a few GeV was reported that may be related to dark matter. We find with high significance an improved fit to the diffuse gamma-ray emission observed with the Fermi-LAT, if our new H I model is used to estimate the cosmic-ray induced diffuse gamma-ray emission. The fit still requires a nuclear bulge at high significance. Once this is included there is no evidence of a dark-matter signal, be it cuspy or cored. But an additional so-called boxy bulge is still favored by the data. This finding is robust under the variation of various parameters, for example, the excitation temperature of atomic hydrogen, and a number of tests for systematic issues.

Keywords: Galactic center, Dark matter, Gamma-rays
Anatomy of Pulsar XTE J1829-098: Ultramassive SXFT with a Dominant Nondipolar Magnetic Field, or the Third Canonical HMXB Caught at the Bottom of the Corbet Gap?. The X-ray binary pulsar XTE J1829-098 has been observed at extremely low luminosities for its spin period of 7.8448 s. Although its distance is uncertain by a factor of 4, the lowest observed X-ray fluxes may not correspond to its minimal-accretion propeller state or to nonaccreting states occurring at even lower X-ray luminosities, in which case the source has been caught at the bottom of the Corbet gap. We analyze all proposed distances D to the binary and the lowest X-ray fluxes, and we find only two physically acceptable solutions: (a) For D = 4.5 kpc (if the companion is a main-sequence B0 star), the neutron star is canonical with mass 1.41 M ⊙, radius 10.1 km, and a purely dipolar magnetic field as indicated by a cyclotron absorption line detected at 15 keV. In this case, the source has been observed at the bottom of the Corbet gap, the third high-mass X-ray binary pulsar to be caught in this state after the "twins" 4U 0115+63 and V 0332+53 found by Tsygankov et al. (b) For D = 18 kpc (if the companion is a B0.5Ib supergiant), the neutron star is ultramassive with mass 2.62 M ⊙, radius 18.7 km, and a dominant nondipolar magnetic field B mul = 1.26 TG (versus a dipolar component of only B dip = 0.43 TG). In this case, the source has been observed in its propeller state.

Keywords: Stellar accretion disks, X-ray binary stars, Magnetic fields
An 8.56 keV Absorption Line in the Hyperluminous X-Ray Source in NGC 4045: Ultrafast Outflow or Cyclotron Line?. We report on the discovery of an absorption line at $E={8.56}_{-0.11}^{+0.05}$ keV detected with a significance of &gt;3.3σ in the NuSTAR and XMM-Newton spectra of a newly discovered hyperluminous X-ray source (L X &gt; 1041 erg s-1) in the galaxy NGC 4045 at a distance of 32 Mpc. The source was first discovered serendipitously in a Swift/XRT observation of the galaxy, and Swift monitoring reveals a highly variable source changing by over an order of magnitude from maximum to minimum. The origin of the absorption line appears likely to be from highly ionized iron with a blueshift of 0.19c, indicating an ultrafast outflow. However, the large equivalent width of the line ( $\mathrm{EW}=-{0.22}_{-0.09}^{+0.08}$ keV) paired with the lack of other absorption lines detected is difficult to reconcile with models. An alternative explanation is that the line is due to a cyclotron resonance scattering feature produced by the interaction of X-ray photons with the powerful magnetic field of a neutron star.

Keywords: Neutron stars, Black holes, X-ray transient sources, Ultraluminous x-ray sources, X-ray sources
AT2020hur: A Possible Optical Counterpart of FRB 180916B. The physical origin of fast radio bursts (FRBs) remains unclear. Finding multiwavelength counterparts of FRBs can provide a breakthrough for understanding their nature. In this work, we perform a systematic search for astronomical transients whose positions are consistent with FRBs. We find an unclassified optical transient AT2020hur (α = 01h58m00.ˢ750 ± 1″, $\delta =65^\circ {43}^{{\prime} }00\buildrel{\prime\prime}\over{.} 30\pm 1^{\prime\prime} $ ) that is spatially coincident with the repeating FRB 180916B (α = 01h58m00.ˢ7502 ± 2.3 mas, $\delta =65^\circ {43}^{{\prime} }00\buildrel{\prime\prime}\over{.} 3152\pm 2.3$ mas; Marcote et al. 2020). The chance possibility of the AT2020hur-FRB 180916B association is about 0.04%, which corresponds to a significance of 3.5σ. We develop a giant flare (GF) afterglow model to fit AT2020hur. Although the GF afterglow model can interpret the observations of AT2020hur, the derived kinetic energy of such a GF is at least three orders of magnitude larger than that of a typical GF, and a lot of fine-tuning and coincidences are required for this model. Another possible explanation is that AT2020hur might consist of two or more optical flares originating from the FRB source, e.g., fast optical bursts produced by the inverse Compton scattering of FRB emission. Besides, AT2020hur is located in one of the activity windows of FRB 180916B, which provides independent support for the association. This coincidence may be due to the optical counterparts being subject to the same periodic modulation as FRB 180916B, as implied by the prompt FRB counterparts. Future simultaneous observations of FRBs and their optical counterparts may help to reveal their physical origin.

Keywords: Magnetars, Radio bursts, Radio transient sources
An Empirical Representation of a Physical Model for the ISM [C II], CO, and [C I] Emission at Redshift 1 ≤ z ≤ 9. Submillimeter emission lines produced by the interstellar medium (ISM) are strong tracers of star formation and are some of the main targets of line intensity mapping (LIM) surveys. In this work we present an empirical multiline emission model that simultaneously covers the mean, scatter, and correlations of [C II], CO J = 1-0 to J = 5-4, and [C I] lines in the redshift range 1 ≤ z ≤ 9. We assume that the galaxy ISM line emission luminosity versus halo mass relations can be described by double power laws with redshift-dependent lognormal scatter. The model parameters are then derived by fitting to the state-of-the-art semianalytic simulation results that have successfully reproduced multiple submillimeter line observations at 0 ≤ z ≲ 6. We cross-check the line emission statistics predicted by the semianalytic simulation and our empirical model, finding that at z ≥ 1 our model reproduces the simulated line intensities with fractional error less than about 10%. The fractional difference is less than 25% for the power spectra. Grounded on physically motivated and self-consistent galaxy simulations, this computationally efficient model will be helpful in forecasting ISM emission-line statistics for upcoming LIM surveys.

Keywords: Diffuse radiation, Large-scale structure of the universe, Intergalactic medium
The X-Ray Coronae in NuSTAR Bright Active Galactic Nuclei. We present a systematic and uniform analysis of NuSTAR data of a sample of 60 SWIFT BAT-selected AGNs with 10-78 keV signal-to-noise ratio (S/N) &gt; 50, 10 of which are radio loud. We measure their high-energy cutoff E cut or coronal temperature T e using three different spectral models to fit their NuSTAR spectra and show that a threshold in NuSTAR spectral S/N is essential for such measurements. High-energy spectral breaks are detected in the majority of the sample, and for the rest, strong constraints on E cut or T e are obtained. Strikingly, we find extraordinarily large E cut lower limits (&gt;400 keV, up to &gt;800 keV) in 10 radio-quiet sources, whereas we find none in the radio-loud sample. Consequently and surprisingly, we find a significantly larger mean E cut/T e of radio-quiet sources compared with radio-loud ones. The reliability of these measurements is carefully inspected and verified with simulations. We find a strong positive correlation between E cut and photon index Γ, which cannot be attributed to the parameter degeneracy. The strong dependence of E cut on Γ, which could fully account for the discrepancy of the E cut distribution between radio-loud and radio-quiet sources, indicates that the X-ray coronae in AGNs with steeper hard X-ray spectra have on average higher temperature and thus smaller opacity. However, no prominent correlation is found between E cut and λ edd. In the l-Θ diagram, we find a considerable fraction of sources lie beyond the boundaries of forbidden regions due to runaway pair production, posing (stronger) challenges to various (flat) coronal geometries.

Keywords: X-ray active galactic nuclei, Active galactic nuclei
Pressure-Strain Interaction as the Energy Dissipation Estimate in Collisionless Plasma. The dissipative mechanism in weakly collisional plasma is a topic that pervades decades of studies without a consensus solution. We compare several energy dissipation estimates based on energy transfer processes in plasma turbulence and provide justification for the pressure-strain interaction as a direct estimate of the energy dissipation rate. The global and scale-by-scale energy balances are examined in 2.5D and 3D kinetic simulations. We show that the global internal energy increase and the temperature enhancement of each species are directly tracked by the pressure-strain interaction. The incompressive part of the pressure-strain interaction dominates over its compressive part in all simulations considered. The scale-by-scale energy balance is quantified by scale filtered Vlasov-Maxwell equations, a kinetic plasma approach, and the lag dependent von Kármán-Howarth equation, an approach based on fluid models. We find that the energy balance is exactly satisfied across all scales, but the lack of a well-defined inertial range influences the distribution of the energy budget among different terms in the inertial range. Therefore, the widespread use of the Yaglom relation in estimating the dissipation rate is questionable in some cases, especially when the scale separation in the system is not clearly defined. In contrast, the pressure-strain interaction balances exactly the dissipation rate at kinetic scales regardless of the scale separation.

Keywords: Interplanetary turbulence, Solar wind, Plasma astrophysics, Plasma physics
Continuous Habitable Zones: Using Bayesian Methods to Prioritize Characterization of Potentially Habitable Worlds. The number of potentially habitable planets continues to increase, but we lack the time and resources to characterize all of them. With ~30 known potentially habitable planets and an ever-growing number of candidate and confirmed planets, a robust statistical framework for prioritizing characterization of these planets is desirable. Using the ~2 Gyr it took life on Earth to make a detectable impact on the atmosphere as a benchmark, we use a Bayesian statistical method to determine the probability that a given radius around a star has been continuously habitable for 2 Gyr. We perform this analysis on nine potentially habitable exoplanets with planetary radii &lt;1.8 R ⊕ and/or planetary masses &lt;10 M ⊕ around nine low-mass host stars (~0.5-1.1 M ⊙) with measured stellar mass and metallicity, as well as Venus, Earth, and Mars. Ages for the host stars are generated by the analysis. The technique is also used to provide age estimates for 2768 low-mass stars (0.5-1.3 M ⊙) in the TESS Continuous Viewing Zones.

Keywords: Bayesian statistics, Stellar properties, Exoplanets, Stellar ages, Stellar evolutionary models, Astrobiology, Interdisciplinary astronomy, Habitable zone, Stellar evolutionary tracks, Habitable planets, Catalogs, Stellar evolution