Sazuna/UAT_keywords huggingface dataset:
The Statistical Analysis of GeV Spectral Breaks in Bright Gamma-Ray Flat-spectrum Radio Quasars. We present the statistical results of GeV spectral breaks of bright gamma-ray flat-spectrum radio quasars (FSRQs) in the energy range of 0.1–10 GeV based on New Pass 8 data of the Large Area Telescope on board Fermi Gamma-Ray Space Telescope. We have fitted the 15 yr average gamma-ray spectra of 755 FSRQs by using both the broken power law (BPL) and logarithmic parabola (LP) models, and obtained 87 bright gamma-ray FSRQs with their integrated photon fluxes greater than 2.16 × 10‑8 cm‑2 s‑1. From our results, the FSRQ population shows similar preferences for both the BPL and LP models in gamma-ray spectral fitting, and the clustering analysis suggests that BPL-preferred and LP-preferred FSRQs belong to the same category. Our results indicate that GeV spectral breaks in bright gamma-ray FSRQs are located at 2.90 ± 1.92 GeV in the rest frame, and the observed change in photon index is Δγ = 0.45 ± 0.19, which is consistent with the expected value for a cooling break of electrons scattering seed photons.

Keywords: Gamma-ray sources, Blazars, Flat-spectrum radio quasars, Active galactic nuclei
An Empirical Sample of Spectra of M-type Stars with Homogeneous Atmospheric-parameter Labels. The discrepancies between theoretical and observed spectra, and the systematic differences between various spectroscopic parameter estimates, complicate the determination of atmospheric parameters of M-type stars. In this work, we present an empirical sample of 5105 M-type star spectra with homogeneous atmospheric parameter labels through stellar-label transfer and sample cleaning. We addressed systematic discrepancies in spectroscopic parameter estimates by adopting recent results for Gaia EDR3 stars as a reference standard. Then, we used a density-based spatial clustering of applications with noise to remove unreliable samples in each subgrid of parameters. To confirm the reliability of the stellar labels, a five-layer neural network was utilized, randomly partitioning the samples into training and testing sets. The standard deviations between the predicted and actual values in the testing set are 14 K for T eff, 0.06 dex for logg, and 0.05 dex for [M/H], respectively. In addition, we conducted an internal cross validation to enhance validation and obtained precisions of 11 K, 0.05 dex, and 0.05 dex for T eff, logg, and [M/H], respectively. A grid of 1365 high-signal-to-noise ratio (S/N) spectra and their labels, selected from the empirical sample, was utilized in the stellar parameter pipeline for M-type stars of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), producing an almost seamless Kiel distribution diagram for LAMOST DR10 and DR11 data. The atmospheric parameters for M-type stars from LAMOST DR11 show improved precision compared to the data from DR9, with improvements (for spectra with S/N higher than 10) from 118 to 67 K in T eff, 0.2 to 0.07 dex in logg, and 0.29 to 0.14 dex in [M/H].

Keywords: Stellar atmospheres
The JCMT Legacy Release: SCUBA-2 850 μm Coadds and Catalogs. We present the James Clerk Maxwell Telescope (JCMT) 850 μm Legacy Release, containing uniformly reduced, coadded tiles, and catalogs of detected emission, for the 850 μm data from all Submillimetre Common User Bolometer Array 2 (SCUBA-2) observations taken between 2011 February 2 and 2020 August 1. This release provides the fastest and easiest way to identify uniformly determined 850 μm detections and calibrated fluxes for any position observed by the JCMT. The coadded observations include 11,722 hr of observing time and cover 1516 square degrees of the sky, with detections of contiguous areas of emission at better than 5σ covering 2.46 square degrees of area. Within these regions 21,059 individual local maxima were detected. Fifteen tiles contain regions with a noise level better than 0.0025 mJy arcsec‑2. The data are gridded onto HEALPix tiles of ≈1° a side, using the HEALPix projection with pixels of size ≈3.″22. The coadds have been calibrated into units of mJy arcsec‑2 using the standard date-varying SCUBA-2 flux-conversion factor (FCF) from Mairs et al. (2021). We then examined the accuracy of this calibration for our data set by calculating self-derived FCF values for our two most-used standard sources, finding a result within the expected errors but with a larger standard deviation of 9%. The coadds and catalogs can be searched and retrieved via the Canadian Astronomy Data Centre (project code: JCMT-LR). Combined catalogs of all detected regions and of all local maxima can be downloaded from the Canadian Advanced Network for Astronomy Research Data Publication Service (doi:10.11570/23.0013), along with masks showing the full area observed in this release and the full area of detected emission.

Keywords: Submillimeter astronomy, Astronomy databases, Catalogs
Bayesian Model Reconstruction Based on Spectral Line Observations. Spectral line observations encode a wealth of information. A key challenge, therefore, lies in the interpretation of these observations in terms of models to derive the physical and chemical properties of the astronomical environments from which they arise. In this paper, we present POMME, an open-source PYTHON package that allows users to retrieve 1D or 3D models of physical properties, such as chemical abundance, velocity, and temperature distributions of (optically thin) astrophysical media, based on spectral line observations. We discuss how prior knowledge, for instance, in the form of a steady-state hydrodynamics model, can be used to guide the retrieval process, and we demonstrate our methods on both synthetic and real observations of cool stellar winds.

Keywords: Radiative transfer simulations, Computational methods, Astronomy software, Rotational spectroscopy
Photon Shells, Black Hole Shadows, and Accretion Toroids. We analyze the properties of the Kerr black hole (BH) photon shell, focusing on the influence of aggregates of corotating and counterrotating toroids (ringed accretion disks, hereafter RAD), orbiting in the BH photon shell (photon shell "obscuration"). The particular case of a corotating accretion disk orbiting in the BH ergoregion is also investigated. We study influence on the BH shadow boundary, fixing the conditions under which it is possible to observe the ergoregion and RAD "imprint" on the shadows boundary. In general, remarkable differences appear between the counterrotating photon components of the boundary with respect to the corotating ones. Various regions of the shadow boundary generated from orbital regions linked to the aggregates of orbiting structures have been analyzed. In particular, we investigate the bound unstable spherical photon orbits in the ergoregion, or at the inversion point, where (toroidal)  , or with the impact parameter ℓ = 0 to characterize the effects of the frame dragging on the boundary. Five main classes of BHs have been identified by distinguishable features of their photon shells (and shadow boundaries) in the context of the orbiting RAD.

Keywords: Supermassive black holes, Black hole physics, Black holes, Retrograde orbit, Kerr black holes, Photon sphere, Rotating black holes, Classical black holes, Ergosphere, Prograde orbit, Relativistic disks, Maximal Kerr black holes
Exploring Unobscured Quasi-stellar Objects in the Southern Hemisphere with KS4. We present a catalog of unobscured quasi-stellar object (QSO) candidates in the Southern Hemisphere from the early interim data of the KMTNet Synoptic Survey of Southern Sky (KS4). The KS4 data covers ∼2500 deg2 sky area, reaching 5σ detection limits of ∼22.1─22.7 AB mag in the BVRI bands. Combining this with available infrared photometric data from the surveys covering the southern sky, we select the unobscured QSO candidates based on their colors and spectral energy distribution fitting results. The final catalog contains 72,964 unobscured QSO candidates, of which only 0.4% are previously identified as QSOs based on spectroscopic observations. Our selection method achieves an 87% recovery rate for spectroscopically confirmed bright QSOs at z &lt; 2 within the KS4 survey area. In addition, the number count of our candidates is comparable to that of spectroscopically confirmed QSOs from the Sloan Digital Sky Survey in the northern sky. These demonstrate that our approach is effective in searching for unobscured QSOs in the southern sky. Future spectrophotometric surveys covering the southern sky will enable us to discern their true nature and enhance our understanding of QSO populations in the Southern Hemisphere.

Keywords: Catalogs, Galaxies, Photometry, Quasars
Keck Infrared Transient Survey. I. Survey Description and Data Release 1. We present the Keck Infrared Transient Survey, a NASA Key Strategic Mission Support program to obtain near-infrared (NIR) spectra of astrophysical transients of all types, and its first data release, consisting of 105 NIR spectra of 50 transients. Such a data set is essential as we enter a new era of IR astronomy with the James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman). NIR spectral templates will be essential to search JWST images for stellar explosions of the first stars and to plan an effective Roman SN Ia cosmology survey, both key science objectives for mission success. Between 2022 February and 2023 July, we systematically obtained 274 NIR spectra of 146 astronomical transients, representing a significant increase in the number of available NIR spectra in the literature. Here, we describe the first release of data from the 2022A semester. We systematically observed three samples: a flux-limited sample that includes all transients &lt;17 mag in a red optical band (usually ZTF r or ATLAS o bands); a volume-limited sample including all transients within redshift z &lt; 0.01 (D ≈ 50 Mpc); and an SN Ia sample targeting objects at phases and light-curve parameters that had scant existing NIR data in the literature. The flux-limited sample is 39% complete (60% excluding SNe Ia), while the volume-limited sample is 54% complete and is 79% complete to z = 0.005. Transient classes observed include common Type Ia and core-collapse supernovae, tidal disruption events, luminous red novae, and the newly categorized hydrogen-free/helium-poor interacting Type Icn supernovae. We describe our observing procedures and data reduction using PypeIt, which requires minimal human interaction to ensure reproducibility.

Keywords: Surveys, Tidal disruption, Transient sources, Infrared astronomy, Type Ia supernovae, Spectroscopy, Supernovae
ESPRESSO Observations of Gaia BH1: High-precision Orbital Constraints and no Evidence for an Inner Binary. We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary. A BH + BH binary is expected in some models where Gaia BH1 formed as a hierarchical triple, which is attractive because they avoid many of the difficulties associated with forming the system through isolated binary evolution. Our observations test the inner binary scenario. We have measured 115 precise RVs of the G star, including 40 from ESPRESSO with a precision of 3─5 m s−1, and 75 from other instruments with a typical precision of 30─100 m s−1. Our observations span 2.33 orbits of the G star and are concentrated near a periastron passage, when perturbations due to an inner binary would be largest. The RVs are well-fit by a Keplerian two-body orbit and show no convincing evidence of an inner binary. Using REBOUND simulations of hierarchical triples with a range of inner periods, mass ratios, eccentricities, and orientations, we show that plausible inner binaries with periods P inner ≳ 1.5 days would have produced larger deviations from a Keplerian orbit than observed. Binaries with P inner ≲ 1.5 days are consistent with the data, but these would merge within a Hubble time and would thus imply fine-tuning. We present updated parameters of Gaia BH1's orbit. The RVs yield a spectroscopic mass function $f\left({M}_{\mathrm{BH}}\right)=3.9358\pm 0.0002\,{M}_{\odot }$ —about 7000σ above the ∼2.5 M ☉ maximum neutron star mass. Including the inclination constraint from Gaia astrometry, this implies a BH mass of M BH = 9.27 ± 0.10 M ☉.

Keywords: Multiple stars, Black holes
Optimal Photometry of Point Sources: Joint Source Flux and Background Determination on Array Detectors-from Theory to Practical Implementation. In this paper we study the joint determination of source and background flux for point sources as observed by digital array detectors. We explicitly compute the two-dimensional Cramér-Rao absolute lower bound (CRLB) as well as the performance bounds for high-dimensional implicit estimators from a generalized Taylor expansion. This later approach allows us to obtain computable prescriptions for the bias and variance of the joint estimators. We compare these prescriptions with empirical results from numerical simulations in the case of the weighted least squares estimator (introducing an improved version, denoted stochastic weighted least-squares) as well as with the maximum likelihood estimator, finding excellent agreement. We demonstrate that these estimators provide quasi-unbiased joint estimations of the flux and background, with a variance that approaches the CRLB very tightly and are, hence, optimal, unlike the case of sequential estimation used commonly in astronomical photometry which is sub-optimal. We compare our predictions with numerical simulations of realistic observations, as well as with observations of a bona fide non-variable stellar source observed with TESS, and compare it to the results from the sequential estimation of background and flux, confirming our theoretical expectations. Our practical estimators can be used as benchmarks for general photometric pipelines, or for applications that require maximum precision and accuracy in absolute photometry.

Keywords: CCD photometry, Bayesian statistics, Minimum chi-squared, Photometry, Maximum likelihood estimation
A Novel Eccentricity Parameterization for Transit-only Models. We present a novel eccentricity parameterization for transit-only fits that allows us to efficiently sample the eccentricity and argument of periastron, while being able to generate a self-consistent model of a planet in a Keplerian orbit around its host star. With simulated fits of 330 randomly generated systems, we demonstrate that typical parameterizations often lead to inaccurate and overly precise determinations of the planetary eccentricity. However, our proposed parameterization allows us to accurately—and often precisely—recover the eccentricity for the simulated planetary systems with only transit data available.

Keywords: Transit photometry, Astronomical models, Orbital elements, Eccentricity
An Algorithm to Mitigate Charge Migration Effects in Data from the Near Infrared Imager and Slitless Spectrograph on the James Webb Space Telescope. We present an algorithm that mitigates the effects of charge migration due to the "brighter-fatter effect" (BFE) that occurs for highly illuminated stars in the Teledyne HAWAII-2RG detectors used in the NIRCam, NIRISS, and NIRSpec science instruments aboard the James Webb Space Telescope (JWST). The impact of this effect is most significant for photometry and spectrophotometry of bright stars in data for which the point-spread function (PSF) is undersampled, which is the case for several observing modes of the NIRISS instrument. The main impact of BFE to NIRISS data is incorrect count rate determinations for pixels in the central regions of PSFs of bright stars due to jump detections that are caused by charge migration from peak pixels to surrounding pixels. The effect is especially significant for bright compact sources in resampled, distortion-free images produced by the drizzle algorithm: quantitatively, apparent flux losses of &gt;50% can occur in such images due to BFE. We describe the algorithm of the "charge_migration" mitigation step that has been implemented in version 10.0 of the operational JWST calibration pipeline as of 2023 December 5. We illustrate the impact of this step in terms of the resulting improvements of the precision of imaging photometry of point sources. The algorithm renders the effects of BFE on photometry and surface brightness measurements to stay within 1%. *This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated with programs #1083, 1093, 1094, and 1096.

Keywords: Astronomy data analysis, Direct imaging, Astronomical instrumentation, Infrared observatories, Infrared photometry
WARP: The Data Reduction Pipeline for the WINERED Spectrograph. We present a data reduction pipeline written in Python for data obtained with the near-infrared cross-dispersed echelle spectrograph, WINERED, which yields a 0.91–1.35 μm spectrum with the resolving power of ${R}_{\max }\equiv \lambda /{\rm{\Delta }}\lambda ={\rm{28,000}}$ or 70,000 depending on the observing mode. The pipeline was developed to efficiently extract the spectrum from the raw data with high quality. It comprises two modes: the calibration and the science mode. The calibration mode automatically produces the flat-fielding image, bad pixel map, echellogram distortion map and the dispersion solution from the set of the calibration data. Using calibration images and parameters, the science data of astronomical objects can be reduced automatically using the science mode. The science mode is also used for the real-time quick look at the data during observations. An example of the spectra reduced with WARP is presented. The effect of the highly inclined slit image on the spectral resolution is discussed.

Keywords: Astronomy data reduction, Spectroscopy, Near infrared astronomy
Median Statistics Estimate of the Distance to M87. de Grijs &amp; Bono compiled 211 independent measurements of the distance to galaxy M87 in the Virgo cluster from 15 different tracers and reported 31.03 ± 0.14 mag as the arithmetic mean of a subset of this compilation as the best estimate of the distance. We compute three different central estimates—the arithmetic mean, weighted mean, and the median—and corresponding statistical uncertainty for the full data set as well as three sub-compilations. We find that for all three central estimates the error distributions show that the data sets are significantly non-Gaussian. As a result, we conclude that the median is the most reliable of the three central estimates, as median statistics do not assume Gaussianity. We use median statistics to determine the systematic error on the distance by analyzing the scatter in the 15 tracer subgroup distances. From the 211 distance measurements, we recommend a summary M87 distance modulus of ${31.08}_{-0.04}^{+0.05}$ (statistical) ${}_{-0.06}^{+0.04}$ (systematic) mag, or combining the two errors in quadrature ${31.08}_{-0.07}^{+0.06}$ mag, rounded to 16.4 ± 0.5 Mpc, all at 68.27% significance.

Keywords: Astrostatistics techniques, Distance measure, Observational cosmology, Astronomy data analysis, Non-Gaussianity
Time Variability of FUV Emission from Cool Stars on Multi-year Timescales. The physical and chemical properties of planetary atmospheres are affected by temporal evolution of ultraviolet (UV) radiation inputs from their host stars at all time scales. While studies of X-ray/UV flare properties and long-term stellar evolution of exoplanet host stars have provided new constraints regarding stellar inputs to exoplanetary systems, the UV temporal variability of cool stars on the timescale of stellar cycles remains largely unexplored. To address this gap in our understanding of the UV temporal variability of cool stars, we analyze far-ultraviolet (FUV) emission lines of ions that trace the chromosphere and transition region of nearby stars (C II, Si III, Si IV, and N V; formation temperatures ∼ 20–150 kK) using data from the Hubble Space Telescope (HST) and International Ultraviolet Explorer (IUE) archives spanning temporal baselines of months to years. We select 33 unique stars of spectral types F-M with observing campaigns spanning over a year, and create ionic light curves to evaluate the characteristic variability of cool stars on such timescales. Screening for large flare events, we observe that the relative variability of FUV light curves decreases with increasing stellar effective temperature, from 30% to 70% variability for M-type stars to &lt;30% variability for F and G-type stars. We also observe a weak trend in the temporal variability with the Ca II ${R}_{\mathrm{HK}}^{{\prime} }$ stellar activity indicator, suggesting that stars with lower Ca II activity exhibit a smaller range of FUV flux variability. Screening for data sets with optimal temporal spread, and a sufficient number of individual observations, we select 5 data sets for further periodicity analysis (HST α Centauri A, HST α Centauri B, IUE α Centauri B, IUE ϵ Eri, IUE ξ Boo). Various periodic structures within the FUV flux were detected, with most significant being a 79 days frequency present within the IUE observations of ξ Boo, with a significance of 6σ, and a periodic signal in the FUV observations of α Centauri B, for both HST and IUE measurements, at ≈210 days frequency with significance of 3σ and 3.7σ, respectively. Our results suggest that extreme ultraviolet flux from cool stars varies by less than a factor of two on decade timescales, significantly smaller than variations on flare or stellar evolutionary timescales.

Keywords: Stellar chromospheres, Ultraviolet telescopes, Stellar activity
No X-Rays or Radio from the Nearest Black Holes and Implications for Future Searches. Astrometry from the Gaia mission was recently used to discover the two nearest known stellar-mass black holes (BHs), Gaia BH1 and Gaia BH2. These objects are among the first stellar-mass BHs not discovered via X-rays or gravitational waves. Both systems contain ∼1 M ☉ stars in wide orbits (a ≈ 1.4 au, 4.96 au) around ∼9 M ☉ BHs, with both stars (solar-type main sequence star, red giant) well within their Roche lobes in Gaia BH1 and BH2, respectively. However, the BHs are still expected to accrete stellar winds, leading to potentially detectable X-ray or radio emission. Here, we report observations of both systems with the Chandra X-ray Observatory, the Very Large Array (for Gaia BH1) and MeerKAT (for Gaia BH2). We did not detect either system, leading to X-ray upper limits of L X &lt; 9.4 × 1028 and L X &lt; 4.0 × 1029 erg s−1 and radio upper limits of L  r  &lt; 1.6 × 1025 and L  r  &lt; 1.0 × 1026 erg s−1 for Gaia BH1 and BH2, respectively. For Gaia BH2, the non-detection implies that the accretion rate near the horizon is much lower than the Bondi rate, consistent with recent models for hot accretion flows. We discuss implications of these non-detections for broader BH searches, concluding that it is unlikely that isolated BHs will be detected via interstellar medium accretion in the near future. We also calculate evolutionary models for the binaries' future evolution using Modules for Experiments in Stellar Astrophysics, and find that Gaia BH1 will be visible as a symbiotic BH X-ray binary for 5─50 Myr. Since no symbiotic BH X-ray binaries are known, this implies either that fewer than ∼104 Gaia BH1-like binaries exist in the Milky Way, or that they are common but have evaded detection.

Keywords: Accretion, X-ray binary stars, Binary stars, Stellar mass black holes