Sazuna/UAT_keywords huggingface dataset:
Exploring TeV Candidates of Fermi Blazars through Machine Learning. In this work, we make use of a supervised machine-learning algorithm based on Logistic Regression (LR) to select TeV blazar candidates from the 4FGL-DR2/4LAC-DR2, 3FHL, 3HSP, and 2BIGB catalogs. LR constructs a hyperplane based on a selection of optimal parameters, named features, and hyperparameters whose values control the learning process and determine the values of features that a learning algorithm ends up learning, to discriminate TeV blazars from non-TeV blazars. In addition, it gives the probability (or logistic) that a source may be considered a TeV blazar candidate. Non-TeV blazars with logistics greater than 80% are considered high-confidence TeV candidates. Using this technique, we identify 40 high-confidence TeV candidates from the 4FGL-DR2/4LAC-DR2 blazars and we build the feature hyperplane to distinguish TeV and non-TeV blazars. We also calculate the hyperplanes for the 3FHL, 3HSP, and 2BIGB. Finally, we construct the broadband spectral energy distributions for the 40 candidates, testing for their detectability with various instruments. We find that seven of them are likely to be detected by existing or upcoming IACT observatories, while one could be observed with extensive air shower particle detector arrays.

Keywords: Blazars
Nonthermal Motions and Atmospheric Heating of Cool Stars. The magnetic processes associated with the nonthermal broadening of optically thin emission lines appear to carry enough energy to heat the corona and accelerate the solar wind. We investigate whether nonthermal motions in cool stars exhibit the same behavior as on the Sun by analyzing archival stellar spectra taken by the Hubble Space Telescope, and full-disk Solar spectra taken by the Interface Region Imaging Spectrograph. We determined the nonthermal velocities by measuring the excess broadening in optically thin emission lines formed in the stellar atmosphere; the chromosphere, the transition region, and the corona. Assuming the nonthermal broadening is caused by the presence of Alfvén waves, we also determined the associated wave energy densities. Our results show that with a nonthermal velocity of ~23 km s-1 the Sun-as-a-star results are in very good agreement with values obtained from spatially resolved solar observations. The nonthermal broadening in our sample shows a correlation to stellar rotation, with the strength of the nonthermal velocity decreasing with decreasing rotation rate. Finally, the nonthermal velocity in cool Sun-like stars varies with atmospheric height or temperature of the emission lines, and peaks at transition region temperatures. This points toward a solar-like Alfvén wave-driven heating in stellar atmospheres. However, the peak is at a lower temperature in some cool stars suggesting that other magnetic processes such as flaring events could also dominate.

Keywords: Stellar winds, Stellar atmospheres
Probing the Star Formation Main Sequence Down to 10<SUP>8</SUP> M <SUB>⊙</SUB> at 1.0 &lt; z &lt; 3.0. We investigate the star formation main sequence (MS; SFR-M ⋆) down to 108-9 M ⊙ using a sample of 34,061 newly discovered ultrafaint (27 mag ≲ i ≲ 30 mag) galaxies at 1 &lt; z &lt; 3 detected in the GOODS-N field. Virtually none of these galaxies are contained in previous public catalogs, effectively doubling the number of known sources in the field. The sample was constructed by stacking the optical broadband observations taken by the HST/GOODS-CANDELS surveys, as well as the 25 ultradeep medium-band images gathered by the GTC/SHARDS project. Our sources are faint (average observed magnitudes ~ 28.2 and &lt;H&gt; ~ 27.9 mag), blue (UV slope &lt;β&gt; ~ -1.9), star-forming (rest-frame colors &lt;U - V&gt; ~ 0.10 and &lt;V - J&gt; ~ 0.17 mag) galaxies. These observational characteristics are identified with young (mass-weighted age &lt;t  M-w &gt; ~ 0.014 Gyr) stellar populations subject to low attenuations (&lt;A(V)&gt; ~ 0.30 mag). Our sample allows us to probe the MS down to 108.0 M ⊙ at z = 1 and 108.5 M ⊙ at z = 3, around 0.6 dex deeper than previous analyses. In the low-mass galaxy regime, we find an average value for the slope of 0.97 at 1 &lt; z &lt; 2 and 1.12 at 2 &lt; z &lt; 3. Nearly 60% of our sample presents stellar masses in the range 106-8 M ⊙ at 1 &lt; z &lt;G 3. If the slope of the MS remained constant in this regime, the sources populating the low-mass tail of our sample would qualify as starburst galaxies.

Keywords: Galaxy formation, Catalogs, Dwarf galaxies, Star formation, Galaxy evolution, High-redshift galaxies, Galaxies
Blanco DECam Bulge Survey (BDBS). VI. Extinction Maps Toward Southern Galactic Bulge Globular Clusters. We present wide-field, high resolution maps of the color excess for 14 globular clusters toward the Southern Galactic bulge. The maps were derived using Gaia EDR3 astrometry and stellar photometry from the Blanco DECam Bulge Survey, which is a deep, wide-field ugrizY photometric survey of the southern Galactic bulge. Comparisons with WISE 12 μm images of thermal continuum emission demonstrate that the maps presented here trace interstellar extinction by dust down to 5″ scales. We use the reddening-corrected photometry of proper motion-selected cluster stars to build color-magnitude diagrams for the target globular clusters, which show residual broadening in excess of that expected from the photometric errors alone. This residual broadening is likely to be driven by star-to-star elemental abundance variations.

Keywords: Globular star clusters, Red giant branch, Galactic bulge, Interstellar dust extinction, Broad band photometry
A High Fraction of Heavily X-Ray-obscured Active Galactic Nuclei. We present new estimates on the fraction of heavily X-ray-obscured, Compton-thick (CT) active galactic nuclei (AGNs) out to a redshift of z ≤ 0.8. From a sample of 540 AGNs selected by mid-infrared (MIR) properties in observed X-ray survey fields, we forward model the observed-to-intrinsic X-ray luminosity ratio ( ${R}_{{L}_{{\rm{X}}}}$ ) with a Markov Chain Monte Carlo simulation to estimate the total fraction of CT AGNs (f CT), many of which are missed in typical X-ray observations. We create model N H distributions and convert these to ${R}_{{L}_{{\rm{X}}}}$ using a set of X-ray spectral models. We probe the posterior distribution of our models to infer the population of X-ray-nondetected sources. From our simulation we estimate a CT fraction of f CT = ${0.555}_{-0.032}^{+0.037}$ . We perform an X-ray stacking analysis for sources in Chandra X-ray Observatory fields and find that the expected soft (0.5-2 keV) and hard (2-7 keV) observed fluxes drawn from our model to be within 0.48 and 0.12 dex of our stacked fluxes, respectively. Our results suggests at least 50% of all MIR-selected AGNs, possibly more, are CT (N H ≳ 1024 cm-2), which is in excellent agreement with other recent work using independent methods. This work indicates that the total number of AGNs is higher than can be identified using X-ray observations alone, highlighting the importance of a multiwavelength approach. A high f CT also has implications for black hole (BH) accretion physics and supports models of BH and galaxy coevolution that include periods of heavy obscuration.

Keywords: Surveys, Active galaxies, Active galactic nuclei, X-ray surveys, X-ray active galactic nuclei, Luminous infrared galaxies
Giant Planet Engulfment by Evolved Giant Stars: Light Curves, Asteroseismology, and Survivability. About ten percent of Sun-like (1-2 M ⊙) stars will engulf a 1-10 M J planet as they expand during the red giant branch (RGB) or asymptotic giant branch (AGB) phase of their evolution. Once engulfed, these planets experience a strong drag force in the star's convective envelope and spiral inward, depositing energy and angular momentum. For these mass ratios, the inspiral takes ~10-102 yr (~102-103 orbits); the planet undergoes tidal disruption at a radius of ~1 R ⊙. We use the Modules for Experiments in Stellar Astrophysics (MESA) software instrument to track the stellar response to the energy deposition while simultaneously evolving the planetary orbit. For RGB stars, as well as AGB stars with M p ≲ 5 M J planets, the star responds quasi-statically but still brightens measurably on a timescale of years. In addition, asteroseismic indicators, such as the frequency spacing or rotational splitting, differ before and after engulfment. For AGB stars, engulfment of an M p ≳ 5 M J planet drives supersonic expansion of the envelope, causing a bright, red, dusty eruption similar to a "luminous red nova." Based on the peak luminosity, color, duration, and expected rate of these events, we suggest that engulfment events on the AGB could be a significant fraction of low-luminosity red novae in the Galaxy. We do not find conditions where the envelope is ejected prior to the planet's tidal disruption, complicating the interpretation of short-period giant planets orbiting white dwarfs as survivors of common envelope evolution.

Keywords: Exoplanets, White dwarf stars, Asymptotic giant branch stars, Red giant stars, Star-planet interactions, Common envelope evolution
The Effect of f(R, T) Modified Gravity on the Mass and Radius of Pulsar HerX1. Millisecond pulsars are the perfect testable to examine potential matter-geometry coupling and its physical consequences in the context of the recent Neutron Star Interior Composition Explorer discoveries. We apply the field equations of modified gravity, f(R, T) = R + α T, to a spherically symmetric spacetime, where R is the Ricci scalar, α is a dimensional parameter, and T is the matter of the geometry. Five unknown functions are present in the output system of differential equations, which consists of three equations. To close the system, we make explicit assumptions about the anisotropy and the radial metric potential, g  rr . We then solve the output differential equations and derive the explicit forms of the components of the energy-momentum tensor, i.e., density, radial, and tangential pressures. We look into the possibility that all of the physical parameters in the star can be reexpressed in terms of α and the compactness parameters, C = 2 GM Rc-2. We show that, for a given mass, the size permitted by Einstein's general relativity is less due to the matter-geometry coupling in f(R, T). The validity of the hypothesis was validated by observations from an extra 21 pulsars. To achieve a surface density that is compatible with a neutron core at nuclear saturation density, the mass-radius curve enables masses up to 3.35M ☉. We emphasize that although there is no assumption of an equation of state, the model fits well with a linear behavior. When comparing the surface densities of these 20 pulsars, we divided them into three groups. We show that these three groups are compatible with neutron cores.

Keywords: Gravitation, Star formation
The Effect of Environment on the Properties of the Most Massive Galaxies at 0.5 &lt; z &lt; 2.5 in the COSMOS-DASH Field. How the environment influences the most massive galaxies is still unclear. To explore the effects of the environment on morphology and star formation in the most massive galaxies at high redshift, we select galaxies with stellar mass $\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 11$ at 0.5 &lt; z &lt; 2.5 in the COSMOS-DASH field, which is the largest field with near-infrared photometric observations using HST/WFC3 to date. Combining these with the newly published COSMOS2020 catalog, we estimate the localized galaxy overdensity using a density estimator within the Bayesian probability framework. With the overdensity map, no significant environmental dependence is found in the distributions of Sérsic index and effective radius. When we consider the star formation state, galaxies at a lower density are found to have a higher median specific star formation rate (sSFR) at 0.5 &lt; z &lt; 1.5. But for star-forming galaxies only, sSFR is independent of the environment over the whole redshift range, indicating that the primary effect of the environment might be to control the quiescent fraction. Based on these observations, the possible environmental quenching process for these massive galaxies might be mergers.

Keywords: Galaxy quenching, Galaxy structure, Star formation, Galaxy environments
Bi-Kappa Proton Mirror and Cyclotron Instabilities in the Solar Wind. The charged particles in the solar wind are often observed to possess a nonthermal tail in the velocity distribution function, a feature that can be fitted with the Kappa model. The anisotropic, or bi-Kappa, model of protons, electrons, and other charged particles is thus adopted in the literature for interpreting the data as well as in the context of the analysis of wave-particle interactions. The present paper develops an approximate but efficient theory of the mirror and cyclotron instabilities excited by the bi-Kappa protons in the solar wind. A velocity moment-based quasi-linear theory of these instabilities is also formulated in order to investigate the saturation behavior. Applications of the formalism are made for instabilities close to the marginally unstable state, which is typical of the solar wind near 1 au.

Keywords: Space plasmas, Solar wind, Interplanetary physics, Interstellar plasma
Code Comparison in Galaxy-scale Simulations with Resolved Supernova Feedback: Lagrangian versus Eulerian Methods. We present a suite of high-resolution simulations of an isolated dwarf galaxy using four different hydrodynamical codes: GIZMO, AREPO, GADGET, and RAMSES. All codes adopt the same physical model, which includes radiative cooling, photoelectric heating, star formation, and supernova (SN) feedback. Individual SN explosions are directly resolved without resorting to subgrid models, eliminating one of the major uncertainties in cosmological simulations. We find reasonable agreement on the time-averaged star formation rates as well as the joint density-temperature distributions between all codes. However, the Lagrangian codes show significantly burstier star formation, larger SN-driven bubbles, and stronger galactic outflows compared to the Eulerian code. This is caused by the behavior in the dense, collapsing gas clouds when the Jeans length becomes unresolved: Gas in Lagrangian codes collapses to much higher densities than that in Eulerian codes, as the latter is stabilized by the minimal cell size. Therefore, more of the gas cloud is converted to stars and SNe are much more clustered in the Lagrangian models, amplifying their dynamical impact. The differences between Lagrangian and Eulerian codes can be reduced by adopting a higher star formation efficiency in Eulerian codes, which significantly enhances SN clustering in the latter. Adopting a zero SN delay time reduces burstiness in all codes, resulting in vanishing outflows as SN clustering is suppressed.

Keywords: Hydrodynamical simulations, Galaxy formation, Stellar feedback
New <SUP>26</SUP>P(p, γ)<SUP>27</SUP>S Thermonuclear Reaction Rate and Its Astrophysical Implications in the rp-process. Accurate nuclear reaction rates for 26P(p, γ)27S are pivotal for a comprehensive understanding of the rp-process nucleosynthesis path in the region of proton-rich sulfur and phosphorus isotopes. However, large uncertainties still exist in the current rate of 26P(p, γ)27S because of the lack of nuclear mass and energy level structure information for 27S. We reevaluate this reaction rate using the experimentally constrained 27S mass, together with the shell model predicted level structure. It is found that the 26P(p, γ)27S reaction rate is dominated by a direct capture reaction mechanism despite the presence of three resonances at E = 1.104, 1.597, and 1.777 MeV above the proton threshold in 27S. The new rate is overall smaller than the other previous rates from the Hauser-Feshbach statistical model by at least 1 order of magnitude in the temperature range of X-ray burst interest. In addition, we consistently update the photodisintegration rate using the new 27S mass. The influence of new rates of forward and reverse reaction in the abundances of isotopes produced in the rp-process is explored by postprocessing nucleosynthesis calculations. The final abundance ratio of 27S/26P obtained using the new rates is only 10% of that from the old rate. The abundance flow calculations show that the reaction path 26P(p, γ)27S(β +,ν)27P is not as important as previously thought for producing 27P. The adoption of the new reaction rates for 26P(p, γ)27S only reduces the final production of aluminum by 7.1% and has no discernible impact on the yield of other elements.

Keywords: Explosive nucleosynthesis, Nuclear abundances, Reaction rates, X-ray bursts, Nuclear physics
Subarcminute Localization of 13 Repeating Fast Radio Bursts Detected by CHIME/FRB. We report on improved sky localizations of 13 repeating fast radio bursts (FRBs) discovered by CHIME/FRB via the use of interferometric techniques on channelized voltages from the telescope. These so-called "baseband localizations" improve the localization uncertainty area presented in past studies by more than three orders of magnitude. The improved localization regions are provided for the full sample of FRBs to enable follow-up studies. The localization uncertainties, together with the limits on the source distances from their dispersion measures, allow us to identify likely host galaxies for two of the FRB sources. FRB 20180814A lives in a massive passive red spiral at z ~ 0.068 with very little indication of star formation, while FRB 20190303A resides in a merging pair of spiral galaxies at z ~ 0.064 undergoing significant star formation. These galaxies show very different characteristics, further confirming the presence of FRB progenitors in a variety of environments even among the repeating subclass.

Keywords: Radio transient sources
The GeMS/GSAOI Galactic Globular Cluster Survey (G4CS). II. Characterization of 47 Tuc with Bayesian Statistics. We present a photometric analysis of globular cluster 47 Tuc (NGC 104) using near-IR imaging data from the GeMS/GSAOI Galactic Globular Cluster Survey (G4CS), which is in operation at Gemini-South telescope. Our survey is designed to obtain AO-assisted deep imaging with near diffraction-limited spatial resolution of the central fields of Milky Way globular clusters. The G4CS near-IR photometry was combined with an optical photometry catalog that was obtained from Hubble Space Telescope survey data to produce a high-quality color-magnitude diagram that reaches down to K  s  ≈ 21 Vega mag. We used the software suite BASE-9, which uses an adaptive Metropolis sampling algorithm to perform a Markov chain Monte Carlo Bayesian analysis, and obtained probability distributions and precise estimates for the age, distance, and extinction cluster parameters. Our best estimate for the age of 47 Tuc is ${12.42}_{-0.05}^{+0.05}$ ± 0.08 Gyr and our true distance modulus estimate is (m-M)0 = 13.250 ${}_{-0.003}^{+0.003}$ ± 0.028 mag, which are in tight agreement with previous studies using Gaia DR2 parallax and detached eclipsing binaries.

Keywords: Globular star clusters
Identification and Characterization of a Large Sample of Distant Active Dwarf Galaxies in XMM-SERVS. Active dwarf galaxies are important because they contribute to the evolution of dwarf galaxies and can reveal their hosted massive black holes. However, the sample size of such sources beyond the local universe is still highly limited. In this work, we search for active dwarf galaxies in the recently completed XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS). XMM-SERVS is currently the largest medium-depth X-ray survey covering 13 deg2 in three extragalactic fields, which all have well-characterized multiwavelength information. After considering several factors that may lead to misidentifications, we identify 73 active dwarf galaxies at z &lt; 1, which constitutes the currently largest X-ray-selected sample beyond the local universe. Our sources are generally less obscured than predictions based on the massive-AGN (active galactic nucleus) X-ray luminosity function and have a low radio-excess fraction. We find that our sources reside in environments similar to those of inactive dwarf galaxies. We further quantify the accretion distribution of the dwarf-galaxy population after considering various selection effects and find that it decreases with X-ray luminosity, but redshift evolution cannot be statistically confirmed. Depending on how we define an AGN, the active fraction may or may not show a strong dependence on stellar mass. Their Eddington ratios and X-ray bolometric corrections significantly deviate from the expected relation, which is likely caused by several large underlying systematic biases when estimating the relevant parameters for dwarf galaxies. Throughout this work, we also highlight problems in reliably measuring photometric redshifts and overcoming strong selection effects for distant active dwarf galaxies.

Keywords: Intermediate-mass black holes, Dwarf galaxies, X-ray active galactic nuclei
Progenitor Constraint with Circumstellar Material for the Magnetar-hosting Supernova Remnant RCW 103. Stellar winds blown out from massive stars (≳10 M ☉) contain precious information on the progenitor itself, and in this context the most important elements are carbon (C), nitrogen (N), and oxygen (O), which are produced by the CNO cycle in the H-burning layer. Although their X-ray fluorescence lines are expected to be detected in swept-up shock-heated circumstellar materials in supernova remnants, those of C and N have been particularly difficult to detect so far. Here, we present high-resolution spectroscopy of the young magnetar-hosting supernova remnant RCW 103 with the Reflection Grating Spectrometer on board XMM-Newton and report on the detection of the N VII Lyα (0.50 keV) line for the first time. By comparing the obtained abundance ratio of N to O (N/O = 3.8 ± 0.1) with various stellar evolution models, we show that the progenitor of RCW 103 is likely to have a low mass (10-12 M ☉) and medium rotation velocity (≲100 km s-1). The results also rule out the possibility of dynamo effects in massive (≥35 M ☉) stars as a mechanism for forming the associated magnetar 1E 161348-5055. Our method is useful for estimating various progenitor parameters for future missions with microcalorimeters such as XRISM and Athena.

Keywords: High energy astrophysics, Supernova remnants, Circumstellar matter, X-ray sources, Interstellar medium, Stellar evolution