Sazuna/UAT_keywords huggingface dataset:
Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN-CH-NH Photometry. VII. Metal-poor Populations in 47 Tucanae (NGC 104). We present new large field-of-view (~1°×1°) Ca-CN photometry of the prototypical metal-rich globular cluster 47 Tucanae (NGC 104). Our results are the following. (1) The populational number ratios of the red giant branch (RGB) and red horizontal branch (RHB) are in excellent agreement: n(CN-w):n(CN-s) = 30:70 (±1-2), where the CN-w and CN-s stand for the CN-weak and CN-strong populations, respectively. Both the CN-s RGB and RHB populations are more centrally concentrated than those of CN-w populations are. (2) Our photometric metallicities of individual RGB stars in each population can be well described by bimodal distributions with two metallicity peaks, [Fe/H] ~-0.72 and -0.92 dex, where the metal-poor components occupy ~13% of the total RGB stars. The metal-poor populations are more significantly centrally concentrated than the metal-rich populations, showing a similar result that we found in M3. (3) The RGB bump V magnitudes of individual populations indicate that there is no difference in the helium abundance between the two metal-poor populations, while the helium enhancement of ΔY ~0.02-0.03 is required between the the two metal-rich populations. (4) The RHB morphology of 47 Tuc appears to support our idea of the bimodal metallicity distribution of the cluster. We suggest that 47 Tuc could be another example of merger remnants of two globular clusters, similar to M3 and M22. * Based on observations made with the Cerro Tololo Inter-American Observatory (CTIO) 1 m telescope, which is operated by the SMARTS consortium. †This work presents results from the European Space Agency space mission Gaia. Gaia data are being processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia MultiLateral Agreement. The Gaia mission website is https://www.cosmos.esa.int/gaia. The Gaia archive website is https://archives.esac.esa.int/gaia.

Keywords: Globular star clusters, Horizontal branch stars, Hertzsprung Russell diagram, Red giant branch, Stellar populations, Chemical abundances, Population II stars, Red giant bump, Stellar evolution
Accelerating Spherical Harmonic Transforms for a Large Number of Sky Maps. The spherical harmonic transform is a powerful tool in the analysis of spherical data sets, such as cosmic microwave background data. In this work, we present a new scheme for spherical harmonic transforms that supports both CPU and GPU computations, which is especially efficient on a large number of sky maps. By comparing our implementation with the standard Libsharp-HEALPix program, we demonstrate a 2-10 times speedup for the CPU implementation, and an up to 30 times speedup when a state-of-the-art GPU is employed. This new scheme's software package is available via an open-source GitHub repository.

Keywords: GPU computing, Cosmic microwave background radiation, Astronomy data analysis
Statistical Study and Live Catalog of Multispacecraft <SUP>3</SUP>He-rich Time Periods over Solar Cycles 23, 24, and 25. Using ion measurements from Ultra-Low-Energy Isotope Spectrometer observations on board Advanced Composition Explorer and Solar Isotope Spectrometer observations on board the Solar Terrestrial Observatory (STEREO)-A and STEREO-B spacecraft, we have identified 854 3He-rich time periods between 1997 September and 2021 March. We include all event types with observed 3He enhancements such as corotating interaction regions, gradual solar energetic particle (SEP) events, interplanetary shocks, and impulsive SEP events. We employ two different mass separation techniques to obtain 3He, 4He, Fe, and O fluences for each event, and we determine the 3He/4He and Fe/O abundance ratios between 0.32-0.45 and 0.64-1.28 MeV nucleon-1. We find a clear correlation in the 3He/4He and Fe/O abundance ratios between both energy ranges. We find two distinct trends in the 3He/4He versus Fe/O relation. For low 3He/4He values, there is a positive linear correlation between 3He/4He and Fe/O. However, at 3He/4He ~ 0.3, Fe/O appears to reach a limit and the correlation weakens significantly. We provide a live catalog of 3He-rich time periods that includes the robust determination of the onset and end times of the 3He enhancements in SEP-associated periods for different types of events observed by multiple spacecraft. This catalog is available for public use. New releases will follow after major additions such as adding new periods from new missions (e.g., Parker Solar Probe and Solar Orbiter), identifying event types (impulsive SEP events, etc.), or adding new parameters such as remote observations detailing characteristics of the events' active regions.

Keywords: Solar atmosphere, Heliosphere, Solar energetic particles, Active sun, Solar abundances, Solar observatories, Active solar corona
LSST Survey Strategies and Brown Dwarf Parallaxes. The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) has the potential to measure parallaxes for thousands of nearby ultracool dwarfs, enabling improved measurements of the brown dwarf luminosity function. We develop a simple model to estimate the number of L dwarfs and T dwarfs with parallaxes with signal-to-noise ratio greater than 10 in the baseline LSST survey. High-quality astrometry imposes scheduling constraints. We assess different possible observing strategies using quantitative metrics and make recommendations as part of the LSST community input process. We find that the new substellar parallax sample will represent a nearly order-of-magnitude increase on existing samples, with ~50-100 objects per spectral type bin for late-L to mid-T dwarfs. The sample size is robust (±5% or less) against most survey strategy changes under consideration, although we do identify areas of tension with other uses of twilight time that could have a larger impact.

Keywords: Brown dwarfs, Sky surveys, Parallax, L dwarfs, T dwarfs
The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope: Data Release 3. An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 yr of E &gt; 50 MeV gamma-ray data, where the spectral parameters, spectral energy distributions (SEDs), yearly light curves, and associations have been updated for all sources. The new reported AGNs include 587 blazar candidates and four radio galaxies. We describe the properties of the new sample and outline changes affecting the previously published one. We also introduce two new parameters in this release, namely the peak energy of the SED high-energy component and the corresponding flux. These parameters allow an assessment of the Compton dominance, the ratio of the inverse-Compton to the synchrotron-peak luminosities, without relying on X-ray data.

Keywords: BL Lacertae objects, Blazars, Flat-spectrum radio quasars, Active galactic nuclei, Spectral energy distribution, Gamma-ray astronomy
Improving the Spatial Resolution of Solar Images Based on an Improved Conditional Denoising Diffusion Probability Model. The quality of solar images plays an important role in the analysis of small events in solar physics. Therefore, the improvement of image resolution based on super-resolution (SR) reconstruction technology has aroused the interest of many researchers. In this paper, an improved conditional denoising diffusion probability model (ICDDPM) based on the Markov chain is proposed for the SR reconstruction of solar images. This method reconstructs high-resolution (HR) images from low-resolution images by learning a reverse process that adds noise to HR images. To verify the effectiveness of the method, images from the Goode Solar Telescope at the Big Bear Solar Observatory and the Helioseismic and Magnetic Imager (HMI) on the Solar Dynamics Observatory are used to train a network, and the spatial resolution of reconstructed images is 4 times that of the original HMI images. The experimental results show that the performance based on ICDDPM is better than the previous work in subject judgment and object evaluation indexes. The reconstructed images of this method have higher subjective vision quality and better consistency with the HMI images. And the structural similarity and rms index results are also higher than the compared method, demonstrating the success of the resolution improvement using ICDDPM.

Keywords: Solar active regions, Solar photosphere, Neural networks
H-AMR: A New GPU-accelerated GRMHD Code for Exascale Computing with 3D Adaptive Mesh Refinement and Local Adaptive Time Stepping. General relativistic magnetohydrodynamic (GRMHD) simulations have revolutionized our understanding of black hole accretion. Here, we present a GPU-accelerated GRMHD code H-AMR with multifaceted optimizations that, collectively, accelerate computation by 2-5 orders of magnitude for a wide range of applications. First, it introduces a spherical grid with 3D adaptive mesh refinement that operates in each of the three dimensions independently. This allows us to circumvent the Courant condition near the polar singularity, which otherwise cripples high-resolution computational performance. Second, we demonstrate that local adaptive time stepping on a logarithmic spherical-polar grid accelerates computation by a factor of ≲10 compared to traditional hierarchical time-stepping approaches. Jointly, these unique features lead to an effective speed of ~109 zone cycles per second per node on 5400 NVIDIA V100 GPUs (i.e., 900 nodes of the OLCF Summit supercomputer). We illustrate H-AMR's computational performance by presenting the first GRMHD simulation of a tilted thin accretion disk threaded by a toroidal magnetic field around a rapidly spinning black hole. With an effective resolution of 13,440 × 4608 × 8092 cells and a total of ≲22 billion cells and ~0.65 × 108 time steps, it is among the largest astrophysical simulations ever performed. We find that frame dragging by the black hole tears up the disk into two independently precessing subdisks. The innermost subdisk rotation axis intermittently aligns with the black hole spin, demonstrating for the first time that such long-sought alignment is possible in the absence of large-scale poloidal magnetic fields.

Keywords: Black hole physics, High energy astrophysics, Magnetohydrodynamical simulations
Second Data Release of the COSMOS Lyα Mapping and Tomography Observations: The First 3D Maps of the Detailed Cosmic Web at 2.05 &lt; z &lt; 2.55. We present the second data release of the COSMOS Lyα Mapping And Tomography Observations Survey conducted with the Low Resolution Imaging Spectrometer on the Keck I telescope. This project used Lyα forest absorption in the spectra of faint star-forming galaxies and quasars at z ~ 2-3 to trace neutral hydrogen in the intergalactic medium. In particular, we use 320 objects over a footprint of ~0.2 deg2 to reconstruct the absorption field at 2.05 &lt; z &lt; 2.55 at ~2 h -1 Mpc resolution. We apply a Wiener filtering technique to the observed data to reconstruct three-dimensional (3D) maps of the field over a volume of 4.1 × 105 h -3 Mpc3. In addition to the filtered flux maps, for the first time we infer the underlying dark matter field through a forward-modeling framework from a joint likelihood of galaxy and Lyα forest data, finding clear examples of the detailed cosmic web consisting of cosmic voids, sheets, filaments, and nodes. In addition to traditional figures, we present a number of interactive 3D models to allow exploration of the data and qualitative comparisons to known galaxy surveys. We find that our inferred overdensities are consistent with those found from galaxy fields. We will make all our reduced spectra, extracted Lyα forest pixel data, and reconstructed tomographic maps publicly available upon publication.

Keywords: Galaxy clusters, High-redshift galaxy clusters, Lyman alpha forest, Surveys, Hubble Space Telescope, Intergalactic gas, Voids, Spectroscopy, Intergalactic medium, Extragalactic astronomy, Redshift surveys, Intergalactic filaments
Solar Flare Index Prediction Using SDO/HMI Vector Magnetic Data Products with Statistical and Machine-learning Methods. Solar flares, especially the M- and X-class flares, are often associated with coronal mass ejections. They are the most important sources of space weather effects, which can severely impact the near-Earth environment. Thus it is essential to forecast flares (especially the M- and X-class ones) to mitigate their destructive and hazardous consequences. Here, we introduce several statistical and machine-learning approaches to the prediction of an active region's (AR) flare index (FI) that quantifies the flare productivity of an AR by taking into account the number of different class flares within a certain time interval. Specifically, our sample includes 563 ARs that appeared on the solar disk from 2010 May to 2017 December. The 25 magnetic parameters, provided by the Space-weather HMI Active Region Patches (SHARP) from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, characterize coronal magnetic energy stored in ARs by proxy and are used as the predictors. We investigate the relationship between these SHARP parameters and the FI of ARs with a machine-learning algorithm (spline regression) and the resampling method (Synthetic Minority Oversampling Technique for Regression with Gaussian Noise). Based on the established relationship, we are able to predict the value of FIs for a given AR within the next 1 day period. Compared with other four popular machine-learning algorithms, our methods improve the accuracy of FI prediction, especially for a large FI. In addition, we sort the importance of SHARP parameters by the Borda count method calculated from the ranks that are rendered by nine different machine-learning methods.

Keywords: Solar activity, Solar physics, Solar flares
Stellar Loci. VI. An Updated Catalog of the Best and Brightest Metal-poor Stars. We employ Gaia, Two Micron All Sky Survey, and ALLWISE photometry, as well as astrometric data from Gaia, to search for relatively bright very metal-poor (VMP; [Fe/H] &lt; -2.0) giant star candidates using three different criteria: (1) the derived Gaia photometric metallicities from Xu et al., (2) the lack of stellar molecular absorption near 4.6 μm, and (3) their high tangential velocities. With different combinations of these criteria, we have identified six samples of candidates with G &lt; 15: the Gold sample (24,304 candidates), the Silver GW sample (40,157 candidates), the Silver GK sample (120,452 candidates), the Bronze G sample (291,690 candidates), the Bronze WK sample (68,526 candidates), and the Low-b sample (4645 candidates). The Low-b sample applies to sources with low Galactic latitude, ∣b∣ &lt; 10°, while the others are for sources with ∣b∣ &gt; 10°. By crossmatching with results derived from medium-resolution spectroscopy (R ~ 1800) from LAMOST DR8, we establish that the success rate for identifying VMP stars is 60.1% for the Gold sample, 39.2% for the Silver GW sample, 41.3% for the Silver GK sample, 15.4% for the Bronze G sample, 31.7% for the Bronze WK sample, and 16.6% for the Low-b sample, respectively. An additional strict cut on the quality parameter RUWE &lt; 1.1 can further increase the success rate of the Silver GW, Silver GK, and Bronze G samples to 46.9%, 51.6%, and 29.3%, respectively. Our samples provide valuable targets for high-resolution follow-up spectroscopic observations and are made publicly available.

Keywords: Population II stars, Milky Way stellar halo, Stellar abundances
Stellar Flyby Analysis for Spiral Arm Hosts with Gaia DR3. Scattered-light imaging studies have detected nearly two dozen spiral arm systems in circumstellar disks, yet the formation mechanisms for most of them are still under debate. Although existing studies can use motion measurements to distinguish leading mechanisms such as planet-disk interaction and disk self-gravity, close-in stellar flybys can induce short-lived spirals and even excite arm-driving planets into highly eccentric orbits. With unprecedented stellar location and proper-motion measurements from Gaia Data Release 3 (DR3), here we study for known spiral arm systems their flyby history with their stellar neighbors by formulating an analytical on-sky flyby framework. For stellar neighbors currently located within 10 pc of the spiral hosts, we restrict the flyby time to within the past 104 yr and the flyby distance to within 10 times the disk extent in scattered light. Among a total of 12,570 neighbors that are identified in Gaia DR3 for 20 spiral systems, we do not identify credible flyby candidates for isolated systems. Our analysis suggests that a close-in recent flyby is not the dominant formation mechanism for isolated spiral systems in scattered light.

Keywords: Planetary system formation, Coronagraphic imaging, Protoplanetary disks
SADHANA: A Doubly Linked List-based Multidimensional Adaptive Mesh Refinement Framework for Solving Hyperbolic Conservation Laws with Application to Astrophysical Hydrodynamics and Magnetohydrodynamics. We report the development of a nested block-structured adaptive mesh framework to solve multidimensional, time-dependent hyperbolic equations encountered in astrophysics. An approach based on a tabular list is used to construct variants of Hilbert space-filling curves in an iterative fashion to maintain the connectivity of locally refined mesh configurations using a doubly linked list. Modifications are made to conventional boundaries of computational blocks to aid the adaptive mesh. We also describe a well-defined, computationally efficient data structure to hold self-similar mesh units for this purpose. The flexibility of this code is demonstrated by the performance of various Riemann solvers implemented in this computational framework.

Keywords: Magnetohydrodynamics, Hydrodynamics, Computational methods, Astrophysical fluid dynamics, Algorithms
An Early Catalog of Planet-hosting Multiple-star Systems of Order Three and Higher. We present a catalog (status 2022 July 1) of triple and higher-order systems identified containing exoplanets based on data from the literature, including various analyses. We explore statistical properties of the systems with a focus on both the stars and the planets. So far, about 30 triple systems and one to three quadruple systems, including (mildly) controversial cases, have been found. The total number of planets is close to 40. All planet-hosting triple-star systems are highly hierarchic, consisting of a quasi-binary complemented by a distant stellar component, which is in orbit about the common center of mass. Furthermore, the quadruple systems are in fact pairs of close binaries ("double-doubles"), with one binary harboring a planet. For the different types of star-planet systems, we introduce a template for the classifications of planetary orbital configurations in correspondence to the hierarchy of the system and the planetary host. The data show that almost all stars are main-sequence stars, as expected. However, the stellar primaries tend to be more massive (i.e., corresponding to spectral types A, F, and G) than expected from single-star statistics, a finding also valid for stellar secondaries but less pronounced. Tertiary stellar components are almost exclusively low-mass stars of spectral type M. Almost all planets have been discovered based on either the Radial Velocity method or the Transit method. Both gas giants (the dominant type) and terrestrial planets (including super-Earths) have been identified. We anticipate the expansion of this database in the light of future planetary search missions.

Keywords: Exoplanet catalogs, Interstellar dynamics, Exoplanets, Exoplanet systems, Exoplanet astronomy, Stellar astronomy, Stellar physics, Stellar types, Catalogs
Detection of δ Scuti Pulsators in the Eclipsing Binaries Observed by TESS. Based on 2 minute cadence TESS data from sectors 1-50, we report the results of the systematic extraction of δ Scuti-type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period P dom, orbital period P orb, and effective temperature T eff. As a consequence, 216 targets are likely δ Scuti stars (123 new), 11 likely γ Doradus-δ Scuti hybrid stars (8 new), 5 likely β Cephei stars (4 new), 4 likely δ Scuti-γ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the six new δ Scuti pulsators in eclipsing binaries with P orb &lt; 0.65 days, we found that three of them significantly exceed the upper limits of the P dom/P orb ratio. This may indicate that P dom and P orb are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 δ Scuti stars in eclipsing binaries. Those stars concentrate around 225 μHz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass-transfer process.

Keywords: Stellar oscillations, Asteroseismology, Delta Scuti variable stars, Pulsating variable stars
R-matrix Electron-impact Excitation Data for the H- and He-like Ions with Z = 6-30. Plasma models built on extensive atomic data are essential to interpreting observed cosmic spectra. H-like Lyman series and He-like triplets observable in the X-ray band are powerful diagnostic lines to measure the physical properties of various types of astrophysical plasmas. Electron-impact excitation is a fundamental atomic process for the formation of H-like and He-like key diagnostic lines. Electron-impact excitation data adopted by the widely used plasma codes (AtomDB, CHIANTI, and SPEX) do not necessarily agree with each other. Here we present a systematic calculation of electron-impact excitation data of H-like and He-like ions with the atomic number Z = 6-30 (i.e., C to Zn). A radiation-damped R-matrix intermediate-coupling frame transformation calculation was performed for each ion with configurations up to n = 6. We compare the present work with the above three plasma codes and the literature to assess the quality of the new data, which are relevant for current and future high-resolution X-ray spectrometers.

Keywords: X-ray astronomy, Atomic spectroscopy, Atomic physics