Sazuna/UAT_keywords huggingface dataset:
A Search for the O'Connell Effect in Contact Binaries in the Era of Big Sky Surveys. I.. Asymmetries between the two maxima of the light curves of contact binaries, known as the O'Connell effect, have been identified using the All Sky Automated Survey, All-Sky Automated Survey for Supernovae, Northern Sky Variability Survey, Optical Gravitational Lensing Experiment, and Optical Monitoring Camera sky surveys. The morphology of the mean light curve has been analyzed for a total of 43,659 objects already classified as contact binaries. After applying several filters and criteria, we present a sample of 797 systems representing the largest sample to date of maxima asymmetries of EW-type binaries with ∣∆m∣ up to 0.13 mag. We also added information on distance and temperature from Gaia DR3 and The Large Sky Area Multi-Object Fiber Spectroscopic Telescope. We investigated the statistical distributions of periods, temperatures, signs of maximum asymmetry, O'Connell effect ratio and light-curve asymmetry indices of asymmetry, and their correlations. While starspots could explain the different maxima asymmetries in stars with convection zones and differential rotations, the discovery of sizeable asymmetric maxima in 161 early-type systems above the upper limit of the Kraft break (T &gt; 6700 K) may indicate a different mechanism. We also report systems with peculiar unequal maxima.

Keywords: Astronomy databases, Close binary stars, W Ursae Majoris variable stars, Light curves, Astronomy data analysis, Eclipsing binary stars
Gas-phase Formation of Large, Astronomically Relevant Polycyclic Aromatic Hydrocarbon Clusters. As one class of important carbon reservoirs in interstellar clouds, large polycyclic aromatic hydrocarbons (PAHs) and their derivative species play an important role in the formation and evolution of interstellar carbonaceous compounds. To understand these chemical routes, the gas-phase ion–molecular collision reaction between large, astronomically relevant PAH (dicoronylene, DC, C48H20) cations and smaller neutral superhydrogenated PAHs (2, 3–benzofluorene, C17H12) are investigated. Series of large DC/2, 3–benzofluorene cluster cations (e.g., [(C17H12)6C48H14]+, 236 atoms, and [(C17H12)5C48]+, 193 atoms) are efficiently formed by gas-phase condensation under laser irradiation conditions. With theoretical calculations, the structure of newly formed DC/2, 3-benzofluorene cluster cations and the bonding energy for these formation reactions are obtained. Moreover, the IR spectra of DC/2, 3-benzofluorene cluster cations are also calculated. The gas-phase reactions between large PAH species occur relatively easily, resulting in a very large number of reactions and very complex molecular clusters. The adduct processes and the formed molecular structure relatively depend on the carbon reaction sites. The carbon edge sites have different chemical reactivity, which may affect the abundance of these relevant interstellar substances. Furthermore, intermolecular hydrogen transfer plays an important role in cluster formation processes, which can lead the newly formed clusters to become more stable. We infer that small superhydrogenated PAH molecules (e.g., 2, 3-benzofluorene) can effectively aggregate on the large PAH molecules (e.g., dehydrogenated DC cations or carbon clusters) in the gas phase, which provides proposed chemical-evolution routes (ion–molecular reaction pathways) for the formation of the nanometer-sized dust grains in a bottom-up process (in building block pathways) in the interstellar medium.

Keywords: Interstellar molecules, Interstellar dust, Polycyclic aromatic hydrocarbons, Laboratory astrophysics, Astrochemistry
Investigations of MWISP Filaments. I. Filament Identification and Analysis Algorithms, and Source Catalog. Filaments play a crucial role in providing the necessary environmental conditions for star formation, actively participating in the process. To facilitate the identification and analysis of filaments, we introduce Directional and Positional Consistency between Clumps and Filaments (DPConCFil), a suite of algorithms comprising one identification method and two analysis methods. The first method, the consistency-based identification approach, uses directional and positional consistency among neighboring clumps and local filament axes to identify filaments in the position–position–velocity data cube. The second method employs a graph-based skeletonization technique to extract the filament intensity skeletons. The third method, a graph-based substructuring approach, allows the decomposition of complex filaments into simpler subfilaments. We demonstrate the effectiveness of DPConCFil by applying the identification method to the clumps detected in the Milky Way Imaging Scroll Painting survey data set by FacetClumps, successfully identifying a batch of filaments across various scales within 10° ≤ l ≤ 20°, ‑5 25 ≤ b ≤ 5 25, and ‑200 km s‑1 ≤v ≤ 200 km s‑1. Subsequently, we apply the analysis methods to the identified filaments, presenting a catalog with basic parameters and conducting statistics of their galactic distribution and properties. DPConCFil is openly available on GitHub (https://github.com/JiangYuTS/DPConCFil), accompanied by a manual.

Keywords: Interstellar molecules, Stellar structures, Interstellar filaments, Radio source catalogs, Astronomical techniques, Astronomical methods, Diffuse interstellar clouds
Research on F10.7 Index Prediction Based on Factor Decomposition and Feature Enhancement. The F10.7 index is crucial for assessing solar activity, significantly impacting communication, navigation, and satellite operations. The intrinsic complexity and variability of solar activity often result in sudden perturbations in the F10.7 index, compromising the accuracy and stability of forecasts. To address this challenge, we propose a novel prediction strategy that separately forecasts fundamental trends driven by the medium-to-long-term evolution of the solar cycle and the 27 day rotational modulation, along with transient disturbances caused by solar flares and the rapid evolution of active regions. These forecasts are then integrated to enhance overall prediction accuracy. We incorporate additional features such as the soft X-ray flare index (FISXR), magnetic type of the active region (new_Mag), and X-ray background flux (XBF) to enhance the understanding of the underlying physical processes of solar activity. Our experiments, conducted using advanced forecasting models on the SG-F10.7-All data set, validate the efficacy of our proposed strategy. Notably, the iTransformer model demonstrates superior performance in both short-term and medium-term forecasting scenarios. The inclusion of FISXR, new_Mag, and XBF significantly improves forecasting accuracy, highlighting their importance in improving the F10.7 index predictions. Our method outperforms international models from the Space Weather Prediction Center, British Geological Survey, and Collecte Localisation Satellites, exhibiting greater accuracy and adaptability across various solar activity phases. This finding provides a novel approach for precise forecasting of the F10.7 index.

Keywords: Solar radio emission
Ultraviolet Photometry and Habitable Zones of over 2700 Planet-hosting Stars. The ongoing discovery of exoplanets has sparked significant interest in finding suitable worlds that could potentially support life. Stellar ultraviolet (UV; 100─3000 Å) radiation may play a crucial role in determining the habitability of their planets. In this paper, we conducted a detailed analysis of the UV photometry of over 2700 host stars with confirmed planets, using observational data from the Galaxy Evolution Explorer and Swift Ultraviolet/Optical Telescope missions. We performed aperture photometry on single-exposure images and provided photometric catalogs that can be used to explore a wide range of scientific questions, such as stellar UV activity and planet habitability. By calculating the circumstellar habitable zone and UV habitable zone, we found that fewer than 100 exoplanets fall within both of these zones, with the majority being gas giants. We also examined stellar activity based on their far-UV (FUV) and near-UV (NUV) emissions. We found the FUV−NUV color more effectively represents stellar activity compared to the   and   indices. The Sun's low FUV emission and moderate NUV emission highlight its uniqueness among (solar-like) stars.

Keywords: Catalogs, Habitable zone, Ultraviolet photometry, Stellar activity
Polarization Reconstruction Study of Wide Field-of-view Photoelectric Polarimeter for POLAR-2/LPD. The Low-Energy X-ray Polarization Detector (LPD) is one of the payloads in the POLAR-2 experiment, which is planned as an external payload for deployment on the China Space Station in 2026. The LPD is specifically designed to observe the polarization of gamma-ray burst prompt emissions in the energy range of 2–10 keV, with a preliminary design featuring a wide field-of-view (FOV) of ±45°. This observation is achieved using an array of X-ray photoelectric polarimeters. Because of the wide FOV design of the detector, nearly all photons impinge on the detector off-axis. This paper investigates the polarization reconstruction of a photoelectric polarimeter for off-axis photons. It was found that the reconstruction of the emission azimuthal angles of photoelectron tracks is the main factor affecting the shape of the modulation function for off-axis radiation. Therefore, a modulation function correction method based on Monte Carlo (MC) simulation is proposed. This MC simulation-based method is applied to both simulated and experimental data to correct the modulation function for off-axis radiation. The reconstruction results demonstrate that this method can accurately determine the polarization degree and polarization angle of photons under different conditions. While we tested up to 45° off-axis angles due to our ±45° FOV, the method is theoretically applicable to off-axis angles up to ∼90°.

Keywords: Polarimeters, Gamma-ray bursts, Astronomical instrumentation
Simons Observatory: Predeployment Performance of a Large Aperture Telescope Optics Tube in the 90 and 150 GHz Spectral Bands. The Simons Observatory will map the temperature and polarization over half of the sky at millimeter wavelengths in six spectral bands from the Atacama Desert in Chile. These data will provide new insights into the genesis, content, and history of our Universe, the astrophysics of galaxies and galaxy clusters, objects in our solar system, and time-varying astrophysical phenomena. This ambitious new instrument suite, initially comprising three 0.5 m diameter small aperture telescopes and one 6 m diameter large aperture telescope, is designed using a common combination of new technologies and new implementations to realize an observatory significantly more sensitive than the previous generation. In this paper, we present the predeployment performance of the first mid-frequency "optics tube," which will be fielded on the large aperture telescope with sensitivity to the 90 and 150 GHz spectral bands. This optics tube contains lenses, filters, detectors, and readout components, all of which operate at cryogenic temperatures. It is one of seven that form the core of the large aperture telescope receiver in its initial deployment. We describe this optics tube, including details of comprehensive testing methods, new techniques for beam and passband characterization, and its measured performance. The performance metrics include beams, optical efficiency, passbands, and forecasts for the on-sky performance of the system. We forecast a sensitivity that exceeds the requirements of the large aperture telescope with greater than 30% margin in each spectral band and predict that the instrument will realize diffraction-limited performance and the expected detector passbands.

Keywords: Observatories, Observational cosmology, Cosmic microwave background radiation, CMBR detectors, Astronomical instrumentation, Polarimeters, Ground telescopes
Improved Particle Spray Algorithm for Modeling Globular Cluster Streams. Stellar streams that emerge from globular clusters (GCs) are thin stellar structures spread along the orbits of progenitor clusters. Numerical modeling of these streams is essential for understanding their interaction with the host galaxy's mass distribution. Traditional methods are either computationally expensive or oversimplified, motivating us to develop a fast and accurate approach using a particle spray algorithm. By conducting a series of N-body simulations of GCs orbiting a host galaxy, we find that the position and velocity distributions of newly escaped stream particles are consistent across various GC masses and orbital parameters. Based on these distributions, we develop a new algorithm that avoids computing the detailed internal cluster dynamics by directly drawing tracer particles from these distributions. This algorithm correctly reproduces the action space distribution of stream particles and achieves a 10% accuracy in stream morphology and velocities compared to N-body simulations. To facilitate broader use, we have implemented this algorithm in galactic dynamics codes agama, gala, galax, and galpy.

Keywords: Globular star clusters, Computational astronomy, Stellar streams, Galaxy dynamics, Galaxy structure, N-body simulations
Expanded Generalized Needlet Internal Linear Combination (eGNILC) Framework for the 21 cm Foreground Removal. The Generalized Needlet Internal Linear Combination (GNILC) method is a nonparametric component separation algorithm to remove the foreground contamination of the 21 cm intensity mapping data. In this work, we perform the discrete cosine transform along the frequency axis in the expanded GNILC framework (denoted eGNILC), which helps reduce the power loss in low multipoles, and further demonstrates its performance. We also calculate the eGNILC bias to modify the criterion for determining the degrees of freedom (dof) of the foreground, and embed the robust principal component analysis in mixing matrix computation to obtain a blind component separation method. We find that the eGNILC bias is related to the averaged domain size and the dof of the foreground but not the underlying 21 cm signal. In the case of no beam effect, the eGNILC bias is negligible for simple power-law foregrounds outside the Galactic plane. We also examine the eGNILC performance in the SKA Phase-I in mid-frequency (SKA-MID) and Baryon Acoustic Oscillations from Integrated Neutral Gas Observations (BINGO) simulations. We show that if the adjacent frequency channels are not highly correlated, eGNILC can recover the underlying 21 cm signal with good accuracy. With the varying Airy-disk beam applied to both SKA-MID and BINGO, the power spectra of 21 cm can be effectively recovered at the multipoles ℓ ∈ [20, 250] and [20, 300], respectively. With no instrumental noise, the SKA-MID exhibits ≲20% power loss, and BINGO exhibits ~10% power loss. The varying Airy-disk beam only causes significant errors at large multipoles.

Keywords: Radio astronomy, H I line emission
The Spatial Distribution of Globular Cluster Systems in Early-type Galaxies: Estimation Procedure and Catalog of Properties for Globular Cluster Systems Observed with Deep Imaging Surveys. We present an analysis of the spatial distribution of globular cluster (GC) systems of 118 nearby early-type galaxies in the Next Generation Virgo Cluster Survey and Mass Assembly of early-Type GaLAxies with their fine Structures survey programs, which both used MegaCam on the Canada─France─Hawaii Telescope. We describe the procedure used to select GC candidates and fit the spatial distributions of GCs to a two-dimensional Sérsic function, which provides effective radii (half number radii) and Sérsic indices, and estimate background contamination by adding a constant term to the Sérsic function. In cases where a neighboring galaxy affects the estimation of the GC spatial distribution in the target galaxy, we fit two two-dimensional Sérsic functions, simultaneously. We also investigate the color distributions of GCs in our sample by using Gaussian mixture modeling. For GC systems with bimodal color distributions, we divide the GCs into blue and red subgroups and fit their respective spatial distributions with Sérsic functions. Finally, we measure the total number of GCs based on our fitted Sérsic function, and calculate the GC specific frequency.

Keywords: Globular star clusters, Virgo Cluster, Galaxy evolution, Field galaxies, Early-type galaxies
Performance-portable Binary Neutron Star Mergers with AthenaK. We introduce an extension to the AthenaK code for general-relativistic magnetohydrodynamics (GRMHD) in dynamical spacetimes using a 3+1 conservative Eulerian formulation. Like the fixed-spacetime GRMHD solver, we use standard finite-volume methods to evolve the fluid and a constrained-transport scheme to preserve the divergence-free constraint for the magnetic field. We also utilize a first-order flux correction (FOFC) scheme to reduce the need for an artificial atmosphere and optionally enforce a maximum principle to improve robustness. We demonstrate the accuracy of AthenaK using a set of standard tests in flat and curved spacetimes. Using a SANE accretion disk around a Kerr black hole, we compare the new solver to the existing solver for stationary spacetimes using the so-called "HARM-like" formulation. We find that both formulations converge to similar results. We also include the first published binary neutron star (BNS) mergers performed on graphical processing units (GPUs). Thanks to the FOFC scheme, our BNS mergers maintain a relative error of   or better in baryon mass conservation up to collapse. Finally, we perform scaling tests of AthenaK on OLCF Frontier, where we show excellent weak scaling of ≥80% efficiency up to 32,768 GPUs and 74% up to 65,536 GPUs for a GRMHD problem in dynamical spacetimes with six levels of mesh refinement. AthenaK achieves an order-of-magnitude speedup using GPUs compared to CPUs, demonstrating that it is suitable for performing numerical relativity problems on modern exascale resources.

Keywords: Neutron stars, Relativistic binary stars, Computational methods, General relativity, Compact objects, GPU computing, Magnetohydrodynamical simulations
UPdec-Webb: A Data Set for Coaddition of JWST NIRCam Images. We present the application of the image coaddition algorithm, upsampling and point-spread function (PSF) deconvolution coaddition (UPDC), for stacking multiple exposure images captured by the James Webb Space Telescope (JWST) Near-Infrared Camera. By addressing the PSF effect, UPDC provides visually enhanced and sharper images. Furthermore, the antialiasing and superresolution capabilities of UPDC make it easier to deblend sources overlapped on images, yielding a higher accuracy of aperture photometry. We apply this algorithm to the SMACS J0723 imaging data. Comparative analysis with the Drizzle algorithm demonstrates significant improvements in detecting faint sources, achieving accurate photometry, and effectively deblending (superresolution) closely packed sources. As a result, we have newly detected a pair of close binary stars that were previously unresolvable in the original exposures or the Drizzled image. These improvements significantly benefit various scientific projects conducted by JWST. The resulting data set, named "UPdec-Webb," can be accessed through the official website of the Chinese Virtual Observatory.

Keywords: Galaxy clusters, Deconvolution, Space observatories, High angular resolution, Near infrared astronomy
Deep Learning for Identification and Characterization of Ca II Absorption Lines: A Multitask Convolutional Neural Network Approach. Quasar absorption lines are a powerful tool for studying the Universe, enabling us to probe distant gas, dust, and galaxy formation and evolution. However, detecting these lines, particularly Ca II absorption lines, is a time-consuming and laborious process. Existing deep learning methods are prone to false positives and still require extensive manual verification and parameter measurement. This work presents three multitask convolutional neural network models and identifies the ResNet-CBAM model, which incorporates residual learning and an attention mechanism as the most effective. The results show that the ResNet-CBAM model achieves an accuracy of 99.7% in detecting Ca II absorbers and excels in predicting critical parameters such as equivalent width and full width at half-maximum, with average correlation coefficients of 0.98 and 0.85, respectively. Furthermore, its remarkable generalization ability significantly improves detection precision on unseen data, rising from 20.3% of the cutting-edge model to 92.6%. In addition, with our numerous optimizations, our method can directly search for nonnormalized data, still achieving an accuracy of 98.6%. This translates to a dramatic reduction in manual inspection workload, paving the way for efficient and automated Ca II absorber identification. In real-world applications on the Sloan Digital Sky Survey DR7 and DR12, our model successfully rediscovered 321 known Ca II absorbers while identifying potential candidates in an additional 381 spectra. The codes used in this paper are available on Zenodo at doi:10.5281/zenodo.13953656.

Keywords: Detection, Computational astronomy, Quasar absorption line spectroscopy, Astrostatistics techniques, Astronomy data analysis
The Radio Fundamental Catalog. I. Astrometry. We present an all-sky catalog of absolute positions and estimates of correlated flux density of 21,942 compact radio sources determined from processing interferometric visibility data of virtually all very long baseline interferometry (VLBI) observing sessions at 2–23 GHz from 72 programs suitable for absolute astrometry collected for 30 yr. We used a novel technique of generation of a data set of fused observables that allowed us to incorporate all available data in our analysis. The catalog is the most complete and most precise to date. It forms the foundation and reference for positional astronomy, space geodesy, space navigation, and population analysis of active galactic nuclei (AGNs), and provides calibrators for phase referencing for differential astrometry and VLBI astrophysical observations. Its accuracy was evaluated through a detailed accounting of systematic errors, rigorous decimation tests, comparison of different data sets, and comparison with other catalogs. The catalog preferentially samples AGNs with strong contemporary parsec-scale synchrotron emission. Its milliarcsecond-level positional accuracy allows association of these AGNs with detections in a wide range of the electromagnetic spectrum from low-frequency radio to γ rays and high-energy neutrinos. We describe the innovative data processing and calibration technique in full detail, report the in depth analysis of random and systematic positional errors, and provide a list of associations with large surveys at different wavelengths.

Keywords: Very long baseline interferometry, Active galactic nuclei, Astrometry