Sazuna/UAT_keywords huggingface dataset:
Estimation of Stellar Ages and Masses Using Gaussian Process Regression. Stellar ages play a crucial role in understanding the formation and evolution of stars and Galaxies, which pose many challenges while determining in practice. In this paper, we have introduced a new machine-learning method, Gaussian process regression (GPR), to estimate the stellar ages, which is different from the traditional isochrone fitting method, which fully utilizes the information provided by previous studies. To demonstrate the performance of our method, we have applied it to the field stars of two important phases of evolution, main-sequence turn-off (MSTO) stars and giants, whose ages and masses are available in the literature. Also, GPR is applied to the red giants of open clusters (e.g., M67). Results showed that the ages given by GPR are in better agreement with those given by isochrone fitting methods. The ages are also estimated from various other machine-learning methods (e.g., support vector regression, neural networks, and random forest) and are compared with GPR, which resulted in GPR outperforming others. In addition to ages, we have applied GPR to estimate the masses of the MSTO stars and red giants and found that the masses predicted by GPR for the red giants are within acceptable uncertainties of masses derived from the asteroseismic scaling relation. We have provided the constraints on the input parameters to GPR, which decides the accuracy of the output ages and masses. Results conclude that the newly introduced GPR is promising to provide a novel approach to estimate stellar ages and masses in the era of big data sets. As a supplement, masses and ages for the MSTO stars and red giants estimated from GPR are provided as a catalog that could be used as a training set for upcoming large data sets with spectroscopic parameters.

Keywords: Astronomical methods, Stellar ages, Astronomy data analysis, Red giant stars
Credit Lost: Two Decades of Software Citation in Astronomy. Software has been a crucial contributor to scientific progress in astronomy for decades, but practices that enable machine-actionable citations have not been consistently applied to software itself. Instead, software citation behaviors developed independently from standard publication mechanisms and policies, resulting in human-readable citations that remain hidden over time and that cannot represent the influence software has had in the field. These historical software citation behaviors need to be understood in order to improve software citation guidance and develop relevant publishing practices that fully support the astronomy community. To this end, a 23 year retrospective analysis of software citation practices in astronomy was developed. Astronomy publications were mined for 410 aliases associated with nine software packages and analyzed to identify past practices and trends that prevent software citations from benefiting software authors.

Keywords: Astronomy software
The Thermal Equilibrium Mass-loss Model and Its Applications in Binary Evolution. Binary evolution is indispensable in stellar evolution to understand the formation and evolution of most peculiar and energetic objects, such as binary compact objects, Type Ia supernovae, X-ray binaries, cataclysmic variables, blue stragglers, hot subdwarfs, and central binaries in planetary nebulae. Mass transfer in binary stars can change the evolutionary path and fate of the components compared to what is expected from single stellar evolution. The critical mass ratio at which unstable mass transfer occurs is an unsolved fundamental problem in binary evolution. To resolve this issue, we construct the thermal equilibrium mass-loss model and derive critical mass ratios for both thermal-timescale mass transfer and unstable mass transfer, the latter of which occurs when the outer Lagrangian point, L2, is overfilled. Using several 3.2 M⊙ stellar models as examples, we study the stellar response to thermal equilibrium mass loss and present the thresholds for thermal-timescale mass transfer. We study the possible mass-transfer channels of binary systems containing a 3.2 M⊙ donor star, taking into account thermal-timescale mass transfer, unstable mass transfer through L2, and dynamical-timescale mass transfer. We repeat this simulation for a grid of donor stars with different masses (from 0.1 to 100 M⊙ with Z = 0.02) and at different evolutionary stages, and present our results. The results show that unstable mass transfer due to the overfilling of the outer Lagrangian point may also play an essential role in the formation of common envelopes for late red giant branch and asymptotic giant branch donors.

Keywords: Stellar interiors, Stellar structures, Close binary stars, Stellar mass loss, Common envelope evolution, Stellar evolution
Extending the FOTE Method to Three-dimensional Plasma Flow Fields. In this study, we examine whether the First-Order Taylor Expansion (FOTE) method can be applied to steady-state plasma flow fields in space. We particularly examine whether this method (termed FOTE-V) can be used to identify the flow critical points (including both stagnation point and vortex center) and reconstruct the flow patterns around these points. Quantitatively, we test the accuracy of this method using 3D kinetic simulation data, and find the FOTE-V method can give accurate reconstruction results within an area about 2 times the size of the spacecraft tetrahedron, particularly when there are no clear nonlinear flow structures in the simulation box. With simulation data, we also reveal the ability of the FOTE-V method on reconstructing 3D flow field topology of both radial-type null and spiral-type nulls. We further test the accuracy of this method using measurements from NASA's Magnetospheric Multi-scale (MMS) mission. In a current sheet crossing event, the FOTE-V method successfully identifies the spiral-type nulls in the reconnection exhaust region. In an EDR crossing event, the FOTE-V method detects the stagnation point near the reconnection center. We find these 3D flow structures are quasi-linear at the MMS separation scale. Utilizing the continuity equation of the steady flow, we define a parameter, $\alpha =\tfrac{{\rm{\nabla }}\cdot \left(n{\boldsymbol{V}}\right)}{{\rm{\nabla }}\times \left(n{\boldsymbol{V}}\right)}$ , to quantify the error of this method—the smaller this parameter the better the results. This study demonstrates that the plasma flows at small scale are indeed linear, and thus the FOTE-V method can be applied to such flow fields. In particular, this method will be useful to study stagnation points and electron vortices in space plasmas.

Keywords: Space plasmas, Magnetohydrodynamics, Solar magnetic reconnection, Solar wind, Astronomy data analysis
A New Comprehensive Data Set of Solar Filaments of 100 yr Interval. I.. Filaments are very common physical phenomena on the Sun and are often taken as important proxies of solar magnetic activities. The study of filaments has become a hot topic in the space weather research. For a more comprehensive understanding of filaments, especially for an understanding of solar activities of multiple solar cycles, it is necessary to perform a combined multifeature analysis by constructing a data set of multiple solar cycle data. To achieve this goal, we constructed a centennial data set that covers the Hα data from five observatories around the world. During the data set construction, we encountered varieties of problems, such as data fusion, accurate determination of the solar edge, classifying data by quality, dynamic threshold, and so on, which arose mainly due to multiple sources and a large time span of data. But fortunately, these problems were well solved. The data set includes seven types of data products and eight types of feature parameters with which we can implement the functions of data searching and statistical analyses. It has the characteristics of better continuity and highly complementary to space observation data, especially in the wavelengths not covered by space observations, and covers many solar cycles (including more than 60 yr of high-cadence data). We expect that this new comprehensive data set as well as the tools will help researchers to significantly speed up their search for features or events of interest, for either statistical or case study purposes, and possibly help them get a better and more comprehensive understanding of solar filament mechanisms.

Keywords: Astronomy databases, Astronomy data analysis, Solar filaments, Solar chromosphere, Astronomy data visualization
Identification of Single Spectral Lines through Supervised Machine Learning in a Large HST Survey (WISP): A Pilot Study for Euclid and WFIRST. Future surveys focusing on understanding the nature of dark energy (e.g., Euclid and WFIRST) will cover large fractions of the extragalactic sky in near-IR slitless spectroscopy. These surveys will detect a large number of galaxies that will have only one emission line in the covered spectral range. In order to maximize the scientific return of these missions, it is imperative that single emission lines are correctly identified. Using a supervised machine-learning approach, we classified a sample of single emission lines extracted from the WFC3 IR Spectroscopic Parallel survey, one of the closest existing analogs to future slitless surveys. Our automatic software integrates a spectral energy distribution (SED)-fitting strategy with additional independent sources of information. We calibrated it and tested it on a "gold" sample of securely identified objects with multiple lines detected. The algorithm correctly classifies real emission lines with an accuracy of 82.6%, whereas the accuracy of the SED-fitting technique alone is low (∼50%) due to the limited amount of photometric data available (≤6 bands). While not specifically designed for the Euclid and WFIRST surveys, the algorithm represents an important precursor of similar algorithms to be used in these future missions.

Keywords: Algorithms, Spectral line identification, Spectroscopy, Maximum likelihood estimation, Redshift surveys
Electromagnetic Ion Cyclotron Waves Pattern Recognition Based on a Deep Learning Technique: Bag-of-Features Algorithm Applied to Spectrograms. Several studies have shown the importance of electromagnetic ion cyclotron (EMIC) waves to the pitch angle scattering of energetic particles in the radiation belt, especially relativistic electrons, thus contributing to their net loss from the outer radiation belt to the upper atmosphere. The huge amount of data collected thus far provides us with the opportunity to use a deep learning technique referred to as the Bag-of-Features (BoF). When applied to images of magnetic field spectrograms in the frequency range of EMIC waves, the BoF allows us to distinguish, in a semi-automated way, several patterns in these spectrograms that can be relevant to describe physical aspects of EMIC waves. Each spectrogram image provided as an input to the BoF corresponds to the windowed Fourier transform of a ∼40 minutes to 1 hour interval of Van Allen Probes' high time-resolution vector magnetic field observations. Our data set spans the 2012 September 8 to 2016 December 31 period and is at geocentric distances larger than 3 Earth radii. A total of 66,204 spectrogram images are acquired in this interval, and about 45% of them, i.e., 30,190 images, are visually inspected to validate the BoF technique. The BoF's performance in identifying spectrograms with likely EMIC wave signatures is comparable to the visual inspection method, with the enormous advantage that the BoF technique greatly expedites the analysis by accomplishing the task in just a few minutes.

Keywords: Space plasmas, Classification, Neural networks, Van Allen radiation belts, pp waves, Planetary magnetospheres, Support vector machine
Parkes Transient Events. I. Database of Single Pulses, Initial Results, and Missing Fast Radio Bursts. A large number of observations from the Parkes 64 m diameter radio telescope, recorded with high time resolution, are publicly available. We have reprocessed all of the observations obtained during the first four years (from 1997-2001) of the Parkes Multibeam Receiver system in order to identify transient events, and have built a database that records the 568,736,756 pulse candidates generated during this search. We have discovered a new fast radio burst (FRB), FRB 010305, with a dispersion measure (DM) of 350 ± 5 cm-3 pc and explored why so few FRBs have been discovered in data prior to 2001. After accounting for the dispersion smearing across the channel bandwidth and the sky regions surveyed, the number of FRBs is found to be consistent with model predictions. We also present five single pulse candidates from unknown sources, but with Galactic DMs. We extract a diverse range of sources from the database, which can be used, for example, as a training set of data for new software being developed to search for FRBs in the presence of radio frequency interference.

Keywords: Radio bursts, Astronomy databases, Radio transient sources
HST/COS Observations of Quasar Outflows in the 500-1050 ŠRest Frame. VII. Distances and Energetics for 11 Outflows in Five Quasars. From Hubble Space Telescope/Cosmic Origins Spectrograph spectra of five quasars, 16 outflows are detected. For 11 outflows, we are able to constrain their distances to the central source (R) and their energetics. In instances of multiple electron number density determinations (used in the calculation of R) for the same outflow, the values are consistent within errors. For the 11 outflows, eight have measurements for R (between 10 and 1000 pc), one has a lower limit, another has an upper limit, and the last has a range in R. There are two outflows that have enough kinetic luminosity to be major contributors to active galactic nucleus feedback. The outflowing mass is found primarily in a very high-ionization phase, which is probed using troughs from, e.g., Ne VIII, Na IX, Mg X, and Si XII. Such ions connect the physical conditions of these ultraviolet outflows to the X-ray warm absorber outflows seen in nearby Seyfert galaxies. The ion Cl VII and several new transitions from Ne V have been detected for the first time. * Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

Keywords: Quasar absorption line spectroscopy, Broad-absorption line quasar, Quasars, Active galaxies, Interstellar absorption, Galaxy kinematics, Active galactic nuclei
Microlensing Optical Depth and Event Rate in the OGLE-IV Galactic Plane Fields. Searches for gravitational microlensing events are traditionally concentrated on the central regions of the Galactic bulge but many microlensing events are expected to occur in the Galactic plane, far from the Galactic Center. Owing to the difficulty in conducting high-cadence observations of the Galactic plane over its vast area, which are necessary for the detection of microlensing events, their global properties were hitherto unknown. Here, we present results of the first comprehensive search for microlensing events in the Galactic plane. We searched an area of almost 3000 square degrees along the Galactic plane ( $| b| \lt 7^\circ $ , 0° &lt; l &lt; 50°, 190° &lt; l &lt; 360°) observed by the Optical Gravitational Lensing Experiment (OGLE) during 2013-2019 and detected 630 events. We demonstrate that the mean Einstein timescales of Galactic plane microlensing events are on average three times longer than those of Galactic bulge events, with little dependence on the Galactic longitude. We also measure the microlensing optical depth and event rate as a function of Galactic longitude and demonstrate that they exponentially decrease with the angular distance from the Galactic Center (with the characteristic angular scale length of 32°). The average optical depth decreases from 0.5 × 10-6 at l = 10° to 1.5 × 10-8 in the Galactic anticenter. We also find that the optical depth in the longitude range 240° &lt; l &lt; 330° is asymmetric about the Galactic equator, which we interpret as a signature of the Galactic warp.

Keywords: Microlensing optical depth, Milky Way disk, Gravitational microlensing, Microlensing event rate, Milky Way Galaxy
Spectral Properties of Quasars from Sloan Digital Sky Survey Data Release 14: The Catalog. We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have a continuum signal-to-noise ratio &gt; 3 pixel-1, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog. We performed a careful and homogeneous analysis of the SDSS spectra of these sources to estimate the continuum and line properties of several emission lines such as Hα, Hβ, Hγ, Mg II, C III], C IV, and Lyα. From the derived emission line parameters, we estimated single-epoch virial black hole masses (MBH) for the sample using Hβ, Mg II, and C IV emission lines. The sample covers a wide range in bolometric luminosity ( $\mathrm{log}{L}_{\mathrm{bol}};$ erg s-1) between 44.4 and 47.3 and $\mathrm{log}{M}_{\mathrm{BH}}$ between 7.1 and 9.9 M⊙. Using the ratio of Lbol to the Eddington luminosity as a measure of the accretion rate, the logarithm of the accretion rate is found to be in the range between -2.06 and 0.43. We performed several correlation analyses between different emission line parameters and found them to match the correlation known earlier using smaller samples. We note that strong Fe II sources with a large Balmer line width and highly accreting sources with large MBH are rare in our sample. We make an extended and complete catalog available online that contains various spectral properties of 526,265 quasars derived in this work along with other properties culled from the SDSS-DR14 quasar catalog.

Keywords: Supermassive black holes, Spectroscopy, Quasars
The Zwicky Transient Facility Catalog of Periodic Variable Stars. The number of known periodic variables has grown rapidly in recent years. Thanks to its large field of view and faint limiting magnitude, the Zwicky Transient Facility (ZTF) offers a unique opportunity to detect variable stars in the northern sky. Here, we exploit ZTF Data Release 2 (DR2) to search for and classify variables down to r ∼ 20.6 mag. We classify 781,602 periodic variables into 11 main types using an improved classification method. Comparison with previously published catalogs shows that 621,702 objects (79.5%) are newly discovered or newly classified, including ∼700 Cepheids, ∼5000 RR Lyrae stars, ∼15,000 δ Scuti variables, ∼350,000 eclipsing binaries, ∼100,000 long-period variables, and about 150,000 rotational variables. The typical misclassification rate and period accuracy are on the order of 2% and 99%, respectively. 74% of our variables are located at Galactic latitudes, $| b| \lt 10^\circ $ . This large sample of Cepheids, RR Lyrae, δ Scuti stars, and contact (EW-type) eclipsing binaries is helpful to investigate the Galaxy's disk structure and evolution with an improved completeness, areal coverage, and age resolution. Specifically, the northern warp and the disk's edge at distances of 15-20 kpc are significantly better covered than previously. Among rotational variables, RS Canum Venaticorum and BY Draconis-type variables can be separated easily. Our knowledge of stellar chromospheric activity would benefit greatly from a statistical analysis of these types of variables.

Keywords: Periodic variable stars, Delta Scuti variable stars, Pulsating variable stars, Galaxy structure, Distance indicators, RR Lyrae variable stars, Cepheid variable stars, Mira variable stars, Long period variable stars, Eclipsing binary stars
The Sejong Suite: Cosmological Hydrodynamical Simulations with Massive Neutrinos, Dark Radiation, and Warm Dark Matter. We present the Sejong Suite, an extensive collection of state-of-the-art high-resolution cosmological hydrodynamical simulations spanning a variety of cosmological and astrophysical parameters, primarily developed for modeling the Lyα forest. The suite is organized into three main categories (Grid Suite, Supporting Suite, and Systematics Suite), addressing different science targets. Adopting a particle-based implementation, we follow the evolution of gas, dark matter (cold and warm), massive neutrinos, and dark radiation, and consider several combinations of box sizes and number of particles. With additional enhancing techniques, we are able to reach an equivalent resolution up to 3 × 33283 = 110 billion particles in a (100h-1 Mpc)3 box size, ideal for current and future surveys (e.g., Extended Baryon Oscillation Spectroscopic Survey and Dark Energy Spectroscopic Instrument). Noticeably, for the first time, we simulate extended mixed scenarios describing the combined effects of warm dark matter, neutrinos, and dark radiation, modeled consistently by taking into account the neutrino mass splitting. In addition to providing multicomponent snapshots from z = 5.0 to z = 2.0 in intervals of Δz = 0.2 for all of the models considered, we produced over 288 million Lyα skewers in the same z-range and extended parameter space. The skewers are well suited for Lyα forest science studies, for mapping the high-z cosmic web and the matter-to-flux relation and bias, and for quantifying the critical role of baryons at small scales. We also present a first analysis of the suite focused on the matter and flux statistics, and show that we are able to accurately reproduce the 1D flux power spectrum down to scales $k=0.06\,{(\mathrm{km}{{\rm{s}}}^{-1})}^{-1}$ as mapped by recent high-resolution quasar data, as well as the thermal history of the intergalactic medium. The simulations and products described here will be progressively made available.

Keywords: Cosmology, Warm dark matter, Hydrodynamical simulations, Large-scale structure of the universe, Redshift surveys, Computational methods, Cosmological neutrinos, N-body simulations, Dark matter, Particle astrophysics
A Catalog of Solar Flare Events Observed by the SOHO/EIT. We have compiled a catalog of solar flares (SFs) as observed by the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) spacecraft and the Geostationary Operational Environmental Satellites (GOES) spacecraft over a span from 1997 to 2010. During mid-1998, the cadence of EIT images was revised from two images per day to 12 minutes. However, the low temporal resolution causes significant data gaps in capturing much of the flaring phenomenon. Therefore, we monitor possible errors in flare detection by flare parameters such as temporal overlap, observational wavelength, and considering full field-of-view images. We consider the GOES flare catalog as the primary source. We describe the technique used to enhance the GOES detected flares using the extreme ultraviolet image captured by the EIT telescope. In order to detect brightenings, we subtract the images with a maximum cadence of 25 minutes. We have downloaded and analyzed the EIT data via the Virtual Solar Observatory. This flare data set from the SOHO/EIT period proves indispensable to the process of the SF predictions as the instrument has covered most of Solar Cycle 23.

Keywords: Solar physics, Solar flares, Catalogs