Sazuna/UAT_keywords huggingface dataset:
POLAMI Multiwavelength Polarization Study of Active Galactic Nuclei Jets: A Millimeter─Optical Comparison. Millimeter-band polarimetry offers a powerful probe of active galactic nuclei jets, accessing regions less affected by opacity and Faraday rotation than at longer radio wavelengths. As part of the POLAMI program, we have conducted 14 yr of 1 and 3 mm polarization monitoring of a sample of gamma-ray-bright blazars with the IRAM 30 m telescope, complemented here with long-term optical polarimetric observations from multiple facilities. We aim to test whether current models of parsec-scale jet physics are consistent with observed multiband polarization behavior. Using a Bayesian framework, we derive intrinsic mean flux densities and modulation indices for total flux and fractional polarization, and characterize electric vector position angle (EVPA) variability using circular statistics. We then examine how these quantities reflecting variability properties across millimeter and optical bands relate to synchrotron peak frequency, jet orientation, and radio/gamma-ray luminosities. BL Lacertae (BL Lac) objects exhibit, on average, higher fractional polarization and lower EVPA variability than flat-spectrum radio quasars (FSRQs) at all wavelengths. Fractional polarization increases with frequency, consistent with increasingly ordered magnetic fields at shorter wavelengths. BL Lacs also show more frequent alignment of EVPAs between optical and millimeter bands, whereas FSRQs display weaker coherence. EVPA variability correlates positively with radio and gamma-ray luminosities and negatively with synchrotron peak frequency, most strongly in the optical. We further find a positive correlation between EVPA spread and fractional polarization variability, suggesting a direct link between magnetic-field structure and polarization dynamics.

Keywords: BL Lacertae objects, Blazars, Active galaxies, Flat-spectrum radio quasars, Radio continuum emission, Polarimetry
The LIRA─Ising Model: Estimating the Boundaries of Irregularly Shaped X-Ray Sources. Mapping the boundary of an extended source is a key step in the study of its morphology. The background contamination and statistical fluctuations of typical astronomical images make this a challenging statistical task, in particular for X-ray images with low surface brightness. We develop a three-step Bayesian procedure to identify the boundaries of irregularly shaped sources. We first apply a Bayesian multiscale reconstruction algorithm known as LIRA to obtain posterior pixel-wise probability distributions of the source intensity that properly account for known structures, astrophysical background, and the effect of the telescope point-spread function. Next, we adopt an Ising model to group pixels with similar intensities into cohesive regions corresponding to background and source. Finally, the boundary is derived on the basis of the most likely aggregation of pixels into the source region. Because the overall model combines LIRA and the Ising model, we call it LIRA─Ising. We verify the proposed method using a set of simulation studies. We then apply it to the Chandra X-ray Observatory images of two high-redshift quasars, PKS J1421−0643 and 0730+257, to determine the extent and morphology of X-ray jets. Our method shows a uniform X-ray surface brightness of PKS J1421−0643's jet, and it identifies knotty structure in the X-ray jet of 0730+257.

Keywords: Bayesian statistics, Deconvolution, Astrostatistics, Computational methods, Interdisciplinary astronomy, Algorithms
Cold Dust Properties and Submillimeter Excess in 33 Nearby Spiral Galaxies. The origin of submillimeter excess in galaxies remains unclear. We analyze cold dust properties of 33 nearby spiral galaxies, identify a possible 850 μm excess, and explore its environments. Spectral energy distributions are fitted using a hierarchical Bayesian framework with three modified blackbody models: single temperature (SMBB), two temperature (TMBB), and broken emissivity. With a standard value of the cold dust emissivity index (βc = 2), 13 galaxies exhibit 850 μm excess using SMBB and TMBB. With decreasing βc, the submillimeter excess still persists: at βc = 1.8, 10 (SMBB) and nine (TMBB) galaxies retain the submillimeter excess; at βc = 1.5, six galaxies remain in the submillimeter excess. Even when βc is free, some galaxies still show 850 μm excess, suggesting the submillimeter excess arises from intrinsic dust properties rather than modeling artifacts. Submillimeter excess correlates with metallicity, being more likely to occur in low-metal galaxies. A low 160-to-850 μm flux ratio (typically &lt;50─70) may serve as a criteria for selecting candidate galaxies with submillimeter excess. Based on TMBB, cold dust temperature correlates positively with molecular gas fraction ( logMH2/M* ) and specific star formation rate (sSFR). The cold dust emissivity index shows positive correlations with star formation rate, stellar mass, oxygen abundance, and  logMH2/M* , and a negative correlation with atomic gas fraction. Cold dust-to-stellar mass ratio correlates positively with gas fraction and sSFR, and anticorrelates with stellar mass. These results provide constraints on the nature of submillimeter excess and physical properties of cold dust in spiral galaxies.

Keywords: Interstellar dust, Bayesian statistics, Spiral galaxies, Submillimeter astronomy, Hierarchical models
Deep Learning─driven Atmospheric Parameter Prediction for Hot Subdwarf Stars with Synthetic and Observed Spectra. We design a convolutional neural network incorporating channel attention and spatial attention mechanisms to predict atmospheric parameters of hot subdwarfs. The experimental dataset comprises spectra at nine distinct signal-to-noise ratio (SNR) levels, with each SNR level containing 11,396 synthetic spectra and 945 observed spectra. The trained deep learning models achieves mean absolute errors in predicting hot subdwarf atmospheric parameters of 730 K for effective temperature (Teff), 0.09 dex for surface gravity ( logg ), and 0.03 dex for helium abundance ( log(nHe/nH) ), respectively, which reaches the accuracy of traditional spectral fitting methods. Utilizing the trained deep learning models and low-resolution spectra from Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR12, we confirm 1512 hot subdwarfs from the catalog of hot subdwarf candidates, of which 291 are newly identified. Our results demonstrate that the deep learning model not only achieves accuracy comparable to traditional methods in obtaining hot subdwarf atmospheric parameters but also far exceeds them in speed and efficiency, making it particularly suitable for the analysis of large datasets of hot subdwarf spectra.

Keywords: B subdwarf stars
The 2025 Evaluation of Experimental Thermonuclear Reaction Rates (ETR25). This work describes the formalism for estimating thermonuclear reaction rates for astrophysical applications, emphasizing modern statistical approaches such as Monte Carlo sampling and Bayesian models. We discuss related topics including the calculation of resonance energies from nuclear Q values, indirect estimates of particle partial widths, and matching of reaction rates at elevated temperatures to statistical model results. We have evaluated available experimental data on cross sections, resonance energies and strengths, partial widths, lifetimes, spin-parities, and spectroscopic factors. Based on these results, we have estimated numerical values of 78 experimental charged-particle thermonuclear reaction rates for target nuclei in the A = 2─40 mass region, for temperatures ranging from 1 MK to 10 GK. For each reaction, three rate values are provided: low, median, and high, corresponding to the 16th, 50th, and 84th percentiles, respectively, of the cumulative reaction rate probability density distribution. Additionally, we present the factor uncertainty of each rate at each temperature grid point. These results enable users to sample the reaction rate probability density in nucleosynthesis calculations, facilitating uncertainty estimates of nuclidic abundances. The rates presented here refer to their laboratory values. For use in stellar model simulations, these values need to be corrected for the effects of thermal excitations of the interacting nuclei. For each reaction, we include graphs that illustrate the fractional contributions to the overall reaction rate along with the associated uncertainty. These visuals are designed to assist both stellar modelers and nuclear experimentalists by identifying the primary sources of rate uncertainty at specific stellar temperatures. A graphical comparison with earlier Monte Carlo rates is also provided.

Keywords: Nuclear astrophysics
A Novel Method of Estimating Gamma-Ray Burst Peak Energies beyond the Swift/BAT Limit. The Swift Burst Alert Telescope (BAT), operating in the 15─150 keV band, cannot directly measure the peak energy (Ep) for most gamma-ray bursts (GRBs), as typical Ep values of 200─300 keV lie beyond its upper energy limit. In this paper, we develop a method to robustly estimate the lower limit of Ep for GRBs with Ep &gt; 150 keV by exploiting the intrinsic spectral curvature already evident within the BAT energy range. Fitting BAT spectra with a cutoff power-law model and extrapolating the spectral curvature, we estimate the cutoff energy ( Ec' ) beyond 150 keV and the corresponding peak energy ( Ep' ). Applying this method to 17 GRBs, we identify two main groups: Group I (10 bursts) exhibits typical photon indices (−1.20 ≲ α ≲ −0.8) with increasing Ec, while Group II (two bursts) shows typical Ec values (300─500 keV) with varying α. For Ec ≲ 1000 keV, the estimated  Ec'  agrees well with observed values. The reliability of  Ec'  depends on α: harder spectra (α ≳ −2/3) show reduced accuracy, while softer spectra (α ≲ −2/3) yield more precise estimates. We validate this method using Swift/BAT data for nine GRBs with simultaneous Fermi Gamma-ray Burst Monitor detections, successfully recovering  Ec'  consistent with broadband measurements in 89% of cases. In conclusion, this method is therefore well suited for GRB spectra with moderately constrained Ec (Ep) values and photon indices that are not too hard.

Keywords: Gamma-ray bursts
Machine Learning─based Identification of the Solar Disk and Plages in Kodaikanal Solar Observatory Historical Suncharts. Kodaikanal Solar Observatory (KoSO) is one of the oldest solar observatories, possessing an archive of multiwavelength solar observations, including white light, Ca II K, and Hα images spanning over a century. In addition to these observations, KoSO has preserved hand-drawn suncharts (1904─2022), on which various solar features such as sunspots, plages, filaments, and prominences are marked on the Stonyhurst grid with distinct color coding. In this study, we present the first comprehensive result that includes the entire dataset from these suncharts using a supervised machine learning (ML) model called "convolutional neural networks" (CNNs), first to identify the solar disks from the charts (1909─2007) and second to identify the plages, spanning nine solar cycles (1916─2007). We train the CNN with the manually identified solar disk and plages. We first detect the solar limb and the north─south line in the suncharts, which enables the extraction of disk center coordinates, radius, and P angle. Following that, we use a CNN similar architecture to achieve accurate image segmentation for the identification of plages. We compare plage areas derived from the suncharts with those obtained from Ca II K full-disk observations, and find good agreement that demonstrates the potential application of such an ML technique for historical data. The results of this study further demonstrate the potential application of sunchart data to fill the existing data gaps in the KoSO multiwavelength observations and contribute toward constructing a composite series over the last century.

Keywords: Solar cycle, Plages, The Sun, Convolutional neural networks, Solar chromosphere
Diversity in Evolutionary Status and Magnetic Activity among Solar-type Twin Detached Eclipsing Binaries. We present a combined photometric and spectroscopic analysis of four detached eclipsing binaries (KIC 8957954, KIC 10593759, KIC 8302455, and TIC 207398432), all of which exhibit composite G-type spectra and nearly equal mass ratios. Based on survey data and our own observations, we measured radial velocities with the broadening function method, applied the fd3 program for spectral disentangling, and modeled the light curves with the Wilson─Devinney code to determine accurate absolute parameters. The results reveal significant differences in evolutionary stages and magnetic activity despite their nearly equal masses. Both components of KIC 8957954 and KIC 8302455 are on the main sequence; KIC 10593759 has evolved to the subgiant stage; and in TIC 207398432, the secondary has entered the red-giant phase. Stronger magnetic activity is observed in KIC 10593759 and TIC 207398432, characterized by rapid O'Connell effect ratio variations, with the latter also exhibiting multiple superflare events. In addition, the spectral characteristics of TIC 207398432 suggest that it may be part of a hierarchical triple system. This study provides precise absolute parameters for twin binaries and offers important observational evidence for understanding their evolutionary diversity, magnetic activity, and the possible presence of tertiary companions.

Keywords: Eclipsing binary stars, Spectroscopic binary stars, Stellar evolution
SKYSURF. X. A Novel Method for Measuring Integrated Galaxy Light. We describe the drizzling pipeline and contents of the drizzled database for Hubble Space Telescope Cycle 27─29 Archival Legacy project "SKYSURF," the largest archival project ever approved for Hubble. SKYSURF aims to investigate the extragalactic background light using all 143,914 ACSWFC, WFC3UVIS, and WFC3IR images that have been taken by Hubble since its launch in 2002. SKYSURF has produced 38,027 single-visit mosaics and 7893 multivisit mosaics across 28 ACSWFC, WFC3UVIS, and WFC3IR filters using nonstandard drizzling methods, which include preserving the lowest sky-level of each visit/group in the drizzled products, applying wider apertures for cosmic-ray rejection, correcting effects caused by charge transfer efficiency degradation, and removing potential light gradients from input images via sky-map subtraction. We generate source catalogs for all drizzled products with SExtractor and provide updated star─galaxy separation parameters and integrated galaxy light (IGL) estimates for 25 of the 28 SKYSURF filters (wavelength range 0.2─1.7 μm) using a novel IGL fitting method made possible by the vast SKYSURF dataset. We discuss the data processing and data analysis challenges encountered, detail our solutions, and offer suggestions that may facilitate future large-scale IGL investigations with Webb, SPHEREx, and Roman.

Keywords: Large-scale structure of the universe, Astronomy data analysis, Galaxy counts, Extragalactic astronomy, Astronomy image processing
A Catalog of 486 Barium Stars Identified in GALAH DR4. We present a catalog of 486 Ba stars identified in the GALAH DR4 survey using high-resolution spectra and precise abundance measurements. The sample was selected based on s-process enrichment criteria involving the abundances of Ba and La relative to Eu, and further refined using the signed-distance method, resulting in the largest sample of Ba stars to date, including five newly identified Ba dwarfs. Using astrometric and kinematic parameters from Gaia DR3 and StarHorse, we derived the Galactic velocity components for 367 Ba stars and found that most belong to the thin or thick disk, while 18 exhibit halo-like kinematics. Chemical abundance analysis suggests that most Ba stars are of in situ origin, whereas two stars (4077588766331013248 and 6692980582560946304) display signatures of accreted populations. The E─Lz diagram further shows that star 4077588766331013248 lies within the region of substructure ED-8. The observed decline of [Ba/Fe] and [La/Fe] with increasing metallicity implies that s-process elements originate from nucleosynthetic sites distinct from those of iron-peak elements, while the decreasing [hs/ls] ratio toward higher metallicity indicates higher neutron-capture efficiency at lower metallicity. Both giant and dwarf Ba stars—except for 6053735173729807872—are confirmed binaries hosting white dwarf companions. Moreover, we estimated the masses of the former asymptotic giant branch (AGB) companions to these Ba stars based on the good agreement between the FRUITY AGB model predictions and their observed abundance patterns.

Keywords: Barium stars, Chemical abundances, Asymptotic giant branch
Magnetohydrodynamic Guiding Center Particle-in-cell Method for Multiscale Plasma Kinetic Simulations. We present the formulation, algorithm, and numerical tests of the magnetohydrodynamic particle-in-cell (MHD-PIC) method with particles treated under the guiding center approximation, which we term the MHD-gPIC method, and it is implemented in the Athena++ MHD code. The new MHD-gPIC model consists of thermal (cold) fluid and high-energy particles whose dynamics are integrated through guiding center equations including drift motion, with carefully evaluated source terms as particle back-reaction. The code is validated with a series of tests, and it is expected to be primarily applicable to studying particle acceleration and transport in systems where gyroresonance is considered insignificant. We also present preliminary studies of particle acceleration during nonrelativistic magnetic reconnection.

Keywords: Magnetohydrodynamics, Plasma astrophysics, Solar magnetic reconnection, High energy astrophysics
Fundamental Properties of Novae in M31. The peak luminosities and rates of decline for a large sample of novae recently published by Clark et al. have been analyzed using the Yaron et al. nova models to estimate fundamental properties of the M31 nova population. The apparent white dwarf (WD) mass distribution is approximately Gaussian with a mean &lt;MWD&gt; = 1.16 ± 0.14 M⊙. When corrected for recurrence time bias, the mean drops to &lt;MWD&gt; = 1.07 M⊙. The average WD mass of the M31 nova sample is found to be remarkably similar to that found by Shara et al. in their study of 82 Galactic novae but ∼0.15 M⊙ more massive than the mean recently determined by Schaefer in his comprehensive study of more than 300 systems. As expected, the average WD mass for the recurrent novae included in the M31 sample, &lt;MWD&gt; = 1.33 ± 0.08 M⊙, is significantly higher than that for novae generally. Other parameters of interest, such as the accretion rate, velocity of the ejecta, and predicted recurrence time, are characterized by skewed distributions with large spreads about means of  &lt;logṀ(M⊙yr−1)&gt;≃−9.27 ,  &lt;Vmax&gt;≃1690  km s−1, and  &lt;logPrec(yr)&gt;≃4.39 , respectively. The role of hibernation in affecting the  Ṁ  and Prec distributions is briefly discussed. Finally, the nova properties were studied as a function of apparent position (isophotal radius) in M31, with the preponderance of evidence failing to establish any clear dependence on stellar population.

Keywords: Time domain astronomy, Recurrent novae, Cataclysmic variable stars, Andromeda Galaxy, Classical novae
The Hubble Arp Galaxy Survey. The typical galaxy in the local Universe is expected to be in a self-regulated quasi-equilibrium, displaying a settled morphology that falls within the Hubble sequence. The Arp and Arp─Madore catalogs are filled with striking examples of galaxies that defy these expectations, making them useful targets for studying the astrophysics that controls dramatic, but short-lived, episodes of disequilibrium that mark galaxies' evolution. In this paper, we greatly expand the available Hubble Space Telescope imaging of galaxies drawn from the Arp and Arp─Madore catalogs. We present new optical F606W images and point-source photometry for 216 systems, whose sizes are well matched to the Advanced Camera for Surveys' wide field of view. Essentially, none of the samples had been previously observed with Hubble. The resulting images display rich morphologies, revealing a variety of massive stars, H II regions, stellar clusters, dust lanes, tidal tails, backlit galaxies, and occasional chance superpositions. We provide a pedagogical guide for interpreting highly resolved optical galaxy images, which has general application beyond this atlas. The atlas images also provide a superb starting point for more detailed studies with high-resolution imaging in other wavelengths, and spectroscopy to track kinematics and the interstellar medium (ISM). Areas of obvious scientific relevance include feedback and star formation in merging and interacting galaxies, resolved stellar populations at the extremes of stellar density, the properties of young massive stars and stellar clusters, the physics of the cold ISM and dust, and stellar and gas dynamics.

Keywords: Stellar associations, Massive stars, Active galaxies, Star forming regions, Irregular galaxies, Young massive clusters, Dwarf galaxies, Infrared excess galaxies, Star clusters, Interacting galaxies, Early-type galaxies, Low surface brightness galaxies
Active Galactic Nuclei and Star Formation in Nearby Galaxies (AGNSTRONG). II. Results for Jetted Type-I AGNs with Strong Ionized-gas Outflows. We investigate the correlation between ionized-gas outflows, jets, and star formation in a sample of 42 local type-I active galactic nuclei (AGNs) exhibiting significant [O III] outflows. This study uses both new submillimeter observations and archival data from the James Clerk Maxwell Telescope. Our analysis, which includes a correction for jet emission in the submillimeter bands, fitting spectral energy distribution, and analyzing spectra, enables us to derive star formation rates (SFRs) through various methods. By comparing radio power and SFRs, we select a subsample of jetted AGNs of which radio emission is mostly from the jets. We find that jetted AGNs predominantly lie above the main sequence of star-forming galaxies, suggesting a correlation between jet activity and star formation. By comparing dust extinction, we demonstrate that jetted AGNs do not have more dust, which is the fuel of both star formation and AGN activity. Therefore, this correlation is more likely to arise from AGN feedback. We also find that the Eddington ratio does not impact the specific SFRs (sSFRs) of our sample. Additionally, for jetted AGNs, stronger radio emission corresponds to higher sSFRs, suggesting that jet emission may promote star formation, i.e., positive feedback. Our results not only shed light on the feedback mechanisms of AGNs but also underscore the complex interplay between black hole activity and star formation in galaxy evolution.

Keywords: Active galactic nuclei, Star formation, Spectral energy distribution