Sazuna/UAT_keywords huggingface dataset:
Identification of New Classical Be Stars from the LAMOST Medium Resolution Survey. Be stars are B-type main-sequence stars that display broad Balmer emission lines in their spectra. Identification of the Be population is essential to further examine the formation and evolutionary models. We report the detection of classical Be (CBe) stars from observations with the Large sky Area Multi-Object fiber Spectroscopic Telescope Medium Resolution Survey Data Release 7 (LAMOST MRS DR7). We used a deep convolutional neural network, ResNet, with an 18 layer module to examine the morphology of the Hα profile. We identified 1162 candidate Be stars from the collection of 2,260,387 spectra for 789,918 stars in the database. The ResNet network achieves a Be-star classification accuracy of 99.5%. Among the detections, 151 of these are prior known Be stars crossmatched from the literature. By applying a three-step test, we identified 183 new CBe stars. We find that 41 CBe stars are members of known open clusters. Based on an investigation of the kinematics of the identified CBe stars from the Gaia EDR3 astrometric solutions, we identified 16 new runaways. These new identifications will provide a reference for future follow-ups to further investigate their physical properties.

Keywords: Surveys, Early-type stars, Be stars
Can We Detect Coronal Mass Ejections through Asymmetries of Sun-as-a-star Extreme-ultraviolet Spectral Line Profiles?. Coronal mass ejections (CMEs) are the largest-scale eruptive phenomena in the solar system. Associated with enormous plasma ejections and energy releases, CMEs have an important impact on the solar-terrestrial environment. Accurate predictions of the arrival times of CMEs at the Earth depend on precise measurements of their 3D velocities, which can be achieved by using simultaneous line-of-sight (LOS) and plane-of-sky (POS) observations. Besides the POS information from routine coronagraph and extreme-ultraviolet (EUV) imaging observations, spectroscopic observations could unveil the physical properties of CMEs, including their LOS velocities. We propose that spectral line asymmetries measured by Sun-as-a-star spectrographs can be used for routine detections of CMEs and estimations of their LOS velocities during their early propagation phases. Such observations can also provide important clues for the detection of CMEs on other solar-like stars. However, few studies have concentrated on whether we can detect CME signals and accurately diagnose CME properties through Sun-as-a-star spectral observations. In this work, we construct a geometric CME model and derive the analytical expressions for full disk-integrated EUV line profiles during CMEs. For different CME properties and instrumental configurations, the full disk-integrated line profiles are synthesized. We further evaluate the detectability and diagnostic potential of CMEs from the synthetic line profiles. Our investigations provide important constraints on the future design of Sun-as-a-star spectrographs for CME detections through EUV line asymmetries.

Keywords: Solar corona, Solar coronal mass ejections, Spectroscopy, Stellar coronal mass ejections
Vacuum Ultraviolet Fourier-transform Spectroscopy of <SUP>16</SUP>O and <SUP>18</SUP>O. A spectroscopic study of atomic oxygen (O I) is performed using the Fourier-transform vacuum ultraviolet (VUV) spectrometer at the Dichroïsme Et Spectroscopie par Interaction avec le Rayonnement Synchrotron beamline of the SOLEIL synchrotron. Transition frequencies of O I lines in the range between 76,000 and 151,000 cm-1, corresponding to wavelengths between 665 and 1306 Å, are presented. In the wavelength window a data set of 208 lines is obtained for which line centers were determined at an accuracy of ≤0.035 cm-1, verified through a comparison with previous VUV-laser spectroscopy at an accuracy of 0.008 cm-1. Transitions to upper states belonging to several ns and nd Rydberg series that converge to the 4S3/2, 2D, and 2P ionization limits are presented. Besides studies on the main 16O isotope, measurements of the 18O isotope are also performed, for which an enriched sample of 18O2 gas is used. A least-squares optimization analysis is performed after merging the present new data set with some relevant accurate literature data to extract a list of level energies at high accuracy. When comparing with the database of the National Institute of Standards and Technology, good agreement is found for levels with low principal quantum numbers n ≤ 7 or below excitation energies of 108,000 cm-1; however, significant deviations were found for levels with n &gt; 7. The main result of the present study is the realization of an improved data set of transition frequencies and level energies for O I, with its usefulness demonstrated in a comparison with high-resolution astronomical spectra showing absorption in the line of sight to distant quasars.

Keywords: Atomic spectroscopy
Variability of the Sun's Luminosity Places Constraints on the Thermal Equilibrium of the Convection Zone. Luminosity, which is the total amount of radiant energy emitted by an object, is one of the most critical quantities in astrophysics for characterizing stars. Equally important is the temporal evolution of a star's luminosity because of its intimate connection with the stellar energy budget, large-scale convective motion, and heat storage in the stellar interior. The Sun's luminosity and its variation have not been measured to date because current observations of the solar radiative output have been restricted to vantage points near the Earth. Here, we model the solar luminosity by extending a semiempirical total solar irradiance (TSI) model that uses solar-surface magnetism to reconstruct solar irradiance over the entire 4π solid angle around the Sun. This model was constrained by comparing its output to the irradiance in the Earth's direction with the measured TSI. Comparing the solar luminosity to the TSI on timescales from days to solar cycles for cycles 23 and 24, we find poor agreement on short timescales (&lt;solar rotation). This is not unexpected due to the Earth-centric viewing geometry and short-term irradiance dependence on surface features on the Earth-facing solar disk. On longer timescales, however, we find good agreement between the luminosity model and the TSI, which suggests that the extrapolation of luminosities to multicycle timescales based on TSI reconstructions may be possible. We show that the solar luminosity is not constant but varies in phase with the solar cycle. This variation has an amplitude of 0.14% from minimum to maximum for Solar Cycle 23. Considering the energetics in the solar convection zone, it is therefore obvious that a steady-state input from the radiative zone at the solar minimum level would lead to a gradual reduction in the energy content in the convection zone over multicentury timescales. We show that the luminosity at the base of the convection zone should be approximately 0.032% higher than that at the solar surface during solar minimum to maintain net energy equilibrium through the solar cycle. These different energy-input scenarios place constraints on the long-term evolution of the TSI and its impact on the solar forcing of climate variability. These results highlight the convection zone's role as an energy reservoir on solar-cycle timescales and set constraints for dynamo models intending to understand the long-term evolution of the Sun and solar analogs.

Keywords: Solar cycle, Stellar convective zones, Stellar luminosities, Solar magnetic flux emergence, Solar convective zone, Solar spectral irradiance, Solar dynamo
Long-term Multiband Near-infrared Variability of the Blazar OJ 287 during 2007-2021. We present the most extensive and well-sampled long-term multiband near-infrared (NIR) temporal and spectral variability study of OJ 287, considered to be the best candidate binary supermassive black hole blazar. These observations were made between 2007 December and 2021 November. The source underwent ~2-2.5 mag variations in the J, H, and Ks NIR bands. Over these long-term timescales there were no systematic trends in either flux or spectral evolution with time or with the source's flux states. However, on shorter timescales, there are significant variations in flux and spectra indicative of strong changes during different activity states. The NIR spectral energy distributions show diverse facets at each flux state, from the lowest to the highest. The spectra are, in general, consistent with a power-law spectral profile (within 10%) and many of them indicate minor changes (observationally insignificant) in the shift of the peak. The NIR spectra generally steepen during bright phases. We briefly discuss these behaviors in the context of blazar emission scenarios/mechanisms, OJ 287's well-known traditional behavior, and implications for models of the source central engine invoked for its long-term optical semiperiodic variations.

Keywords: BL Lacertae objects, Galaxies
Improved Background Model for the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat. We present an improved background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on board AstroSat. Because of the large collecting area and high pressure, the LAXPC instrument has a large background count rate, which varies during the orbit. Apart from the variation with latitude and longitude during the orbit there is a prominent quasi-diurnal variation which has not been previously modeled. Using over 5 yr of background observations, we determined the period of the quasi-diurnal variation to be 84,495 s and using this period it is possible to account for the variation and also identify time intervals where the fit is not good. These lead to a significant improvement in the background model. The quasi-diurnal variation can be ascribed to the changes in charged particle flux in the near-Earth orbit.

Keywords: Space vehicle instruments
Dust Extinction Law in Nearby Star-resolved Galaxies. II. M33 Traced by Supergiants. The dust extinction curves toward individual sight lines in M33 are derived for the first time with a sample of reddened O-type and B-type supergiants obtained from the Local Group Galaxies Survey (LGGS). The observed photometric data are obtained from the LGGS, PS1 Survey, UKIRT, PHATTER Survey, Galaxy Evolution Explorer, Swift/UVOT, and XMM-SUSS. We combine the intrinsic spectral energy distributions (SEDs) obtained from the ATLAS9 and Tlusty stellar model atmosphere extinguished by the model extinction curves from the silicate-graphite dust model to construct model SEDs. The extinction traces are distributed along the arms in M33, and the derived extinction curves cover a wide range of shapes (R  V  ≈ 2-6), indicating the complexity of the interstellar environment and the inhomogeneous distribution of interstellar dust in M33. The average extinction curve with R  V  ≈ 3.39 and dust size distribution ${dn}/{da}\sim {a}^{-3.45}\exp (-a/0.25)$ is similar to that of the Milky Way but with a weaker 2175 Å bump and a slightly steeper rise in the far-UV band. The extinction in the V band of M33 is up to 2 mag, with a median value of A  V  ≈ 0.43 mag. The multiband extinction values from the UV to IR bands are also predicted for M33, which will provide extinction corrections for future works. The method adopted in this work is also applied to other star-resolved galaxies (NGC 6822 and WLM), but only a few extinction curves can be derived because of the limited observations.

Keywords: Interstellar dust, OB supergiant stars, Interstellar dust extinction, Triangulum Galaxy, Supergiant stars
The Diffuse X-Ray Background of the Insight-HXMT/LE Telescope in the Galactic Plane. Accurately estimating of diffuse X-ray background (DXB) is essential for the investigation of sources in the Galactic plane observed with Insight-HXMT/LE, which is a collimated telescope in the soft X-ray energy band with a relatively large field of view. In the high-Galactic-latitude region, DXB is dominated by the cosmic X-ray background, which is almost uniform, but DXB in the Galactic plane region is more complex due to the Galactic H I absorption and the contribution of the Galactic ridge X-ray emission. This study, as a part of background estimation of LE, focuses on estimating the contribution of DXB in the Galactic plane to Insight-HXMT/LE observations. We calculate DXB confined in a region of 0° &lt; l &lt; 360° and ∣b∣ &lt; 10°, where l and b denote Galactic longitude and latitude, respectively, with the first 3 yr of Galactic-plane-scanning survey data of Insight-HXMT/LE. The Galactic plane is divided into 360 × 20 small pixels (1° × 1° per pixel), and a DXB spectrum is obtained for each pixel. An indirect method is developed for the pixels of the bright source regions, which brings a systematic error of ~10%. The systematic error brought by the satellite attitude is ~7% on average for all the pixels in the Galactic plane. The LE DXB spectrum obtained in this study is consistent with that reported by RXTE's Proportional Counter Array.

Keywords: X-ray detectors, Astronomy data analysis, Milky Way disk, Diffuse x-ray background, Telescopes
MSWIM2D: Two-dimensional Outer Heliosphere Solar Wind Modeling. The vast size of the Sun's heliosphere, combined with sparse spacecraft measurements over that large domain, makes numerical modeling a critical tool to predict solar wind conditions where there are no measurements. This study models the solar wind propagation in 2D using the BATSRUS MHD solver to form the MSWIM2D data set of solar wind in the outer heliosphere. Representing the solar wind from 1 to 75 au in the ecliptic plane, a continuous model run from 1995-present has been performed. The results are available for free at http://csem.engin.umich.edu/mswim2d/. The web interface extracts output at desired locations and times. In addition to solar wind ions, the model includes neutrals coming from the interstellar medium to reproduce the slowing of the solar wind in the outer heliosphere and to extend the utility of the model to larger radial distances. The inclusion of neutral hydrogen is critical to recreating the solar wind accurately outside of ~4 au. The inner boundary is filled by interpolating and time-shifting in situ observations from L1 and STEREO spacecraft when available. Using multiple spacecraft provides a more accurate boundary condition than a single spacecraft with time shifting alone. Validations of MSWIM2D are performed using MAVEN and New Horizons observations. The results demonstrate the efficacy of this model to propagate the solar wind to large distances and obtain practical, useful solar wind predictions. For example, the rms error of solar wind speed prediction at Mars is only 66 km s-1 and at Pluto is a mere 25 km s-1.

Keywords: Magnetohydrodynamics, Heliosphere, Mars, Solar wind, Pluto
Scalar Quadratic Maximum-likelihood Estimators for the CMB Cross-power Spectrum. Estimating the cross-correlation power spectra of the cosmic microwave background, in particular, the TB and EB spectra, is important for testing parity symmetry in cosmology and diagnosing insidious instrumental systematics. The quadratic maximum-likelihood (QML) estimator provides optimal estimates of the power spectra, but it is computationally very expensive. The hybrid pseudo-C  ℓ  estimator is computationally fast but performs poorly on large scales. As a natural extension of previous work, in this article, we present a new unbiased estimator based on the Smith-Zaldarriaga (SZ) approach of E-B separation and the scalar QML approach to reconstruct the cross-correlation power spectrum, called the QML-SZ estimator. Our new estimator relies on the ability to construct scalar maps, which allows us to use a scalar QML estimator to obtain the cross-correlation power spectrum. By reducing the pixel number and algorithm complexity, the computational cost is nearly one order of magnitude smaller and the running time is nearly two orders of magnitude faster in the test situations.

Keywords: Cosmic microwave background radiation
Stellar Atmospheric Parameters of M-type Stars from LAMOST DR8. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low Resolution Spectroscopic Survey (LRS) provides massive spectroscopic data on M-type stars, and the derived stellar parameters could bring vital help to various studies. We adopt the ULySS package to perform χ 2 minimization with model spectra generated from the MILES interpolator and determine the stellar atmospheric parameters for the M-type stars from LAMOST LRS Data Release 8. Comparison with the stellar parameters from the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP) suggests that most of our results have good consistency. For M dwarfs, we achieve dispersions better than 74 K, 0.19 dex, and 0.16 dex for T eff, $\mathrm{log}g$ , and [Fe/H], while for M giants, the internal uncertainties are 58 K, 0.32 dex, and 0.26 dex, respectively. Compared to ASPCAP we also find a systematic underestimation of ΔT eff = -176 K for M dwarfs and a systematic overestimation of ${\rm{\Delta }}\mathrm{log}g$ = 0.30 dex for M giants. However, such differences are less significant when we make a comparison with common stars from other literature, which indicates that systematic biases exist in the difference between ASPCAP and other measurements. A catalog of 763,136 spectra corresponding to 616,314 M-type stars with derived stellar parameters is presented. We determine the stellar parameters for stars with T eff higher than 2900 K, with $\mathrm{log}g$ from -0.24 dex to 5.9 dex. The typical precisions are 45 K, 0.25 dex, and 0.22 dex, for T eff, $\mathrm{log}g$ , and [Fe/H], respectively, which are estimated from duplicate observations of the same stars.

Keywords: Late-type stars, Sky surveys, Catalogs, M stars, Atomic spectroscopy, Stellar physics, Spectroscopy, Stellar atmospheres
The OGLE Collection of Variable Stars: Nearly 66,000 Mira Stars in the Milky Way. We present a collection of 65,981 Mira-type variable stars found in the Optical Gravitational Lensing Experiment (OGLE) project database. Two-thirds of our sample (40,356 objects) are located in the Galactic bulge fields, whereas 25,625 stars are in the Galactic disk. The vast majority of the collection (47,532 objects) comprises new discoveries. We provide basic observational parameters of the Mira variables: equatorial coordinates, pulsation periods, I-band and V-band mean magnitudes, I-band brightness amplitudes, and identifications in other catalogs of variable stars. We also provide the I-band and V-band time-series photometry collected since 1997 during the OGLE-II, OGLE-III, and OGLE-IV phases. The classical selection process, i.e., being mostly based on the visual inspection of light curves by experienced astronomers, has led to the high purity of the catalog. As a result, this collection can be used as a training set for machine-learning classification algorithms. Using overlapping areas of adjacent OGLE fields, we estimate the completeness of the catalog to be about 96%. We compare and discuss the statistical features of Miras located in different regions of the Milky Way. We show examples of stars that change their type over time, from a semiregular variable to Mira and vice versa. This data set is perfectly suited to studying the three-dimensional structure of the Milky Way, and it may help to explain the puzzle of the X-shaped bulge.

Keywords: Astrographic catalogs, Sky surveys, Galactic center, Catalogs, Carbon stars, Galactic bulge, Asymptotic giant branch stars, Mira variable stars, Milky Way disk, Long period variable stars, Milky Way Galaxy, Time series analysis
Long-term Optical Monitoring of the TeV BL Lacertae Object 1ES 2344 + 514. Variability is one of the main observational characteristics of blazars. Studying variability is an efficient method to reveal the nature of active galactic nuclei. In the present work, we report optical R-band photometry observations of a TeV blazar, 1ES 2344 + 514, carried out with a 70 cm telescope in the period of 1998 July-2017 November at Abastumani Observatory, Georgia. Based on the optical R-band observations, the optical variation behaviors on both short timescales and long timescales are investigated. Three methods (Jurkevich, discrete correlation function, and power spectrum analysis) are used to investigate periodicity in the light curve. In addition, combined with multiwavelength data, the jet physical properties are discussed. The following conclusions are drawn: (1) A variability of ΔR = 0.155 mag (15.356 - 15.201 mag) over a timescale of ΔT = 12.99 minutes is detected during our 628 days of monitoring. (2) According to the Kelvin-Helmholtz thermal instability, if the magnetic field intensity (B) for the source is greater than a critical value (B  c ), it will reduce the incidence of intraday variations in the light curves. (3) The physical parameters of the dissipation region are obtained by fitting the spectral energy distribution with a one-zone synchrotron self-Compton model for the average and flare states. (4) The three methods show that there are periods of P = 2.72 ± 0.47 yr, P = 1.61 ± 0.18 yr, P = 1.31 ± 0.17 yr, and P = 1.05 ± 0.07 yr. When a binary black hole system is adopted with a period of P = 2.72 ± 0.41 yr, we obtain the orbital parameters for the binary black hole system as follows: M = 8.08 × 109 M ⊙, the sum of the semiaxes is r = 7.18 × 1016 cm, and the lifetime of the binary black hole is τ merge = 6.24 × 102 yr.

Keywords: CCD photometry, Active galactic nuclei, Quasars
Exploring γ-Ray Flares in the Long-term Light Curves of CTA 102 at GeV Energies. Blazar CTA 102 experienced an intense multiwavelength activity phase from 2015 to 2018; in particular, an unprecedented outburst was observed from 2016 October to 2017 February. In this work, we extract a 7 day binned γ-ray light curve from 2008 August to 2018 March in the energy range 0.1-300 GeV and identify three main outbursts. We study in detail the short-timescale variability of these three outbursts via an exponential function with parameterized rise and decay timescales. The obtained shortest rise and decay timescales are 0.70 ± 0.05 hr and 0.79 ± 0.27 hr, respectively. Based on these variability timescales, the physical parameters of the flaring region (e.g., the minimum Doppler factor and the emission region size) are constrained. The short-timescale flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the light-crossing timescale or by disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that the best-fitting form of the γ-ray spectra during the flare period is a power law with an exponential cutoff. The derived jet parameters from the spectral behavior and the temporal characteristics of the individual flares suggest that the γ-ray emission region is located upstream of the radio core. The extreme γ-ray flare of CTA 102 is likely to have been caused by magnetic reconnection.

Keywords: Blazars, Relativistic jets, Active galactic nuclei, Gamma-rays