Sazuna/UAT_keywords huggingface dataset:
The Investigation of 84 TESS Totally Eclipsing Contact Binaries. Based on the eclipsing binary catalog provided by A. Prša et al., 84 totally eclipsing contact binaries with stable light curves were selected. The Transiting Exoplanet Survey Satellite light curves of these 84 targets were studied using the Physics Of Eclipsing Binaries code. The results indicate that there are 18 deep contact binaries, 39 moderate contact binaries, and 27 shallow contact binaries. Among them, 43 targets exhibit the O'Connell effect, which is attributed to the presence of star spot on the component's surface. 15 targets are low-mass ratio deep contact binaries and may be contact binary merging candidates. Based on the relationship between the period and semimajor axis of contact binaries, their absolute physical parameters such as mass, radius, and luminosity were derived. The evolutionary status of these 84 targets was studied using the mass–luminosity and mass–radius relation diagrams. Their initial masses were also estimated. Our results are compared with those of targets that have been historically studied. Among the 84 targets, 44 targets have been studied before, and 21 of these have mass ratios q that are consistent with historical values within a 10% difference. For the inconsistent targets, we conducted a detailed investigation and found that the main reasons are poor quality of historical data, or the fact that the machine learning methods used in historical studies might not accurately determine the physical parameters for individual targets.

Keywords: Close binary stars, Mass ratio, Eclipsing binary stars, Contact binary stars, Stellar evolution
On-axis Polarization Calibration of the FAST L-band 19-beam Receiver. We present the polarization calibration of the 19-beam receiver at 1420 MHz within the full illumination of the Five-hundred-meter Aperture Spherical radio Telescope from 2018 October to 2023 March. We perform spider observations to characterize the on-axis Mueller matrix of the central beam. The calibrated polarization percentage and polarization angle of a source with strong linear polarization emission are about 0.2% and 0 .° 5, respectively. Several parameters of the central-beam Mueller matrix show time variability from months to years, suggesting that relatively frequent polarization calibrations are needed. We obtain the Mueller matrix parameters of the 18 off-center beams with a combination of on-the-fly observations and spider observations. The polarization calibration provides consistent fractional Stokes parameters of the 19 beams, although the Mueller matrix parameters of the off-center beams are not as accurate as those of the central beam. The Mueller matrix parameters of the central beam do not show a strong dependence on the reflector surface. However, we notice different off-center Mueller matrix parameters between the eastern and western sides of the reflector surface. We provide average parameters of the 19-beam Mueller matrices that should be applicable to observations from 2020 to 2022, with several caveats. After applying the average parameters, on-axis fractional linear polarization measurements ≳10% and on-axis fractional circular polarization measurements ≳1.5% can be considered high-confidence detections. For sources with weak polarization, timely polarization calibrations using spider observations are required.

Keywords: Single-dish antennas, Calibration, Polarimetry, Astronomical instrumentation
Secular Resonances in Planet-hosting Binary Stars. I. General Theory. Motivated by the diversity of circumstellar planets in binary stars and the strong effects of the secular resonances of Jupiter and Saturn on the formation and architecture of the inner solar system, we have launched an expansive project on studying the effects of secular resonances on the formation of terrestrial planets around a star of a moderately close binary. As the first phase of our project, we present here the general theory of secular resonances in dual-star systems where the primary hosts two giant planets. Using the concept of generalized disturbing function, we derive the formula for the locations of secular resonances and show that in systems where the perturbation of the secondary star is stronger, the locations of secular resonances are farther way from the primary and closer to the giant planets. The latter implies that in such systems, terrestrial planet formation has a larger area to proceed with more of the protoplanetary disk being available to it. To demonstrate the validity of our theoretical results, we simulated the evolution of a protoplanetary disk interior to the inner giant planet. Results, in addition to confirming our theoretical predictions, pointed to an important finding: In binary stars, the perturbation of the secondary suppresses the secular resonances of giant planets. Simulations also show that as the disk loses material, secular resonances move inward, scattering objects out of the disk and/or facilitating their collisional growth. We present results of our study and discuss their implications for the simulations of terrestrial planet formation.

Keywords: Celestial mechanics, Perturbation methods, Orbital resonances
Exploring the Wolf Approach to Constraining NIR Extinction Laws in the Corona Australis Molecular Cloud. The viability of the star count (Wolf) method is assessed as a means of constraining the near-infrared (NIR) extinction law toward the Corona Australis molecular cloud. Using deep JHKS photometry from the VISIONS survey, extinction maps with 1' spatial resolution are constructed. The derived extinction ratios are AJ/AH = 1.73 ± 0.07,  AH/AKS=1.70±0.11 , and  AJ/AKS=3.02±0.22 , which are consistent with Galactic literature means. Assuming a power-law form (Aλ ∝ λ−α) for the NIR extinction law, we derive indices of α ≍ 2.0 across all wavelength combinations, with no statistically significant wavelength dependence throughout the NIR wavelength range. While spatial variations in extinction properties are tentatively observed across the cloud, concerns persist regarding the impact of photometric completeness, and the role of reference field selection. Continued research is required to refine the approach, and scrutinize the veracity of potential extinction law variations over a more expansive region of sky.

Keywords: Interstellar extinction, Interstellar dust, Dense interstellar clouds, Reddening law
Stellar Ancestry Unlocked: Chemical and Orbital Clues Link Metal-poor Stars to Globular Clusters and the Galaxy's Thick Disk. This study presents a detailed chemical, kinematic, and orbital dynamic analysis of five metal-poor stars in the solar neighborhood: HD 2665, HD 5916, HD 122956, HD 189349, and HD 218857. Using high-resolution spectroscopic data from the ELODIE and ESPaDOnS instruments, we derived elemental abundances for 29 species (25 elements: C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Sm) via LTE-based analysis with ATLAS9 model atmospheres. Notably, we report first-time detections of Ce and Nd in HD 2665; Al, V, Sm, and Mn in HD 5916; Al in HD 122956; and C, O, S, Sc, Mn, Co, Cu, Zn, Sr, Zr, Nd, and Sm in HD 189349. Dynamical and chemical diagnostics reveal distinct origins: HD 2665 shows strong orbital and chemical similarity to GC NGC 5139 (ω Cen), while HD 218857 exhibits chemodynamic signatures consistent with NGC 5634. HD 122956 aligns with NGC 6864 (M75), though intriguingly shares age, metallicity ([Fe/H]), and [Mg/Fe] ratios with NGC 6517—a cluster whose reported abundances are derived solely from one star with APOGEE H-band spectroscopic measurements, as no optical spectroscopic data exist for its members. In contrast, HD 5916 and HD 189349 exhibit kinematic and chemical properties consistent with the field-star population and are classified as thick disk members.

Keywords: Stellar kinematics, Stellar abundances, Solar neighborhood, Stellar dynamics
Exoplanet Classification Through Vision Transformers with Temporal Image Analysis. The classification of exoplanets has been a longstanding challenge in astronomy, requiring significant computational and observational resources. Traditional methods demand substantial effort, time, and cost, highlighting the need for advanced machine learning techniques to enhance classification efficiency. In this study, we propose a methodology that transforms raw light curve data from NASA's Kepler mission into Gramian angular fields (GAFs) and recurrence plots (RPs) using the Gramian angular difference field and RP techniques. These transformed images serve as inputs to the vision transformer (ViT) model, leveraging its ability to capture intricate temporal dependencies. We assess the performance of the model through recall, precision, and F1 score metrics, using a five-fold cross-validation approach to obtain a robust estimate of the model's performance and reduce evaluation bias. Our comparative analysis reveals that RPs outperform GAFs, with the ViT model achieving an 89.46% recall and an 85.09% precision rate, demonstrating its significant ability to accurately identify exoplanetary transits. Despite using undersampling techniques to address class imbalance, data set size reduction remains a limitation. This study underscores the importance of further research into optimizing model architectures to enhance automation, performance, and generalization of the model.

Keywords: Light curve classification , Keplerian telescopes, Light curves, Convolutional neural networks, Exoplanet astronomy, Transit photometry, Astronomy data visualization
IRAS 16475─4609: A Young Compact H II Region Sculpting its Molecular Environment. We present a near-infrared spectroscopic and imaging analysis of the star-forming region IRAS 16475−4609, based on TripleSpec/SOAR spectroscopy and NEWFIRM/CTIO imaging, complemented by archival radio and submillimeter data. Our spectroscopic analysis indicates that the central source is an early B-type star (B0─B0.7 V) powering a compact H II region characterized by strong H I and He I recombination lines, and molecular H2 emission. We derive a distance of 3.51 ± 0.74 kpc, consistent with the position of the Scutum─Crux near arm at a Galactic longitude of ∼340∘. At this distance, the ionized gas traced by Brγ emission has a radius of 0.27 ± 0.06 pc, placing the source in a transition phase between ultracompact and compact H II regions. From radio data, we estimate an ionizing photon flux of NLy = (2.3 ± 0.3) × 1047 photons s−1, and an electron temperature of Te = (5.4 ± 0.2) × 103 K for the ionized gas. The analysis also reveals an obscured high-density molecular clump SW of the H II region, coincident with an ATLASGAL submillimeter peak, indicating a potential site of ongoing and triggered star formation as the ionization front advances into the surrounding molecular material. These results suggest that IRAS 16475−4609 is a young high-mass star-forming region with stellar feedback actively shaping its environment, offering valuable insight into the early evolution of compact H II regions.

Keywords: Massive stars, Interstellar medium, Spectroscopy, Stellar distance, H II regions
Apache Point Observatory Follow-up of ACcelerating Candidate ExopLanet Host Stars (APO ACCELS): Ages for 166 Accelerating Stars in the Northern Hemisphere. Directly imaged substellar companions with well-constrained ages and masses serve as vital empirical benchmarks for planet formation and evolution models. Potential benchmark companions can be identified from astrometric accelerations of their host stars. We use Gaia DR3 and Hipparcos astrometry to identify 166 northern hemisphere stars with astrometric accelerations consistent with a substellar companion between 0 .″ 5 and 1″. For this accelerating sample we identify young stars using Apache Point Observatory/ARCES spectra and TESS light curves. From spectroscopic screening of the sample, we measure ages for 24 stars with detectable amounts of lithium, place lower age limits on 135 stars with lithium nondetections, and measure ages from  RHK'  for 34 stars. A total of 129 stars have TESS light curves, from which we measure ages for 20 stars with rotation rates &lt;15 days, and we identify three eclipsing binaries. We present median ages and confidence intervals of age posteriors for the entire sample and discuss how the overall age distribution of our sample compares to a uniform star formation rate in the solar neighborhood. We identify 47 stars with median ages &lt;2 Gyr, 31 stars with median ages &lt;1 Gyr, and 14 stars with median ages &lt;0.5 Gyr, making them high-priority targets for direct imaging follow-up.

Keywords: Brown dwarfs, Stellar ages, Exoplanet astronomy, Direct imaging, Planet hosting stars, Exoplanet detection methods
Metal-polluted White Dwarfs with 21 μm IR Excesses from JWST/MIRI: Planets or Dust?. White dwarfs with metal pollution are caused by the accretion of rocky dust from tidally disrupted minor bodies and are signposts for planetary systems. These minor bodies are perturbed by planets that have survived post-main-sequence evolution. Open questions exist as to the typical mass of the perturbers and the specific planetary architectures that cause metal pollution. JWST's sensitivity in the mid-IR has opened new doors to deciphering polluted white dwarfs. We present JWST Cycle 1 mid-infrared instrument imaging of four nearby metal-polluted white dwarfs with the goal of detecting and characterizing planetary companions. With deep mid-IR imaging we are sensitive to cold Jupiter-mass planet analogs. In addition to finding two candidate planetary companions, for the first time we detect significant excesses above the expected photospheric emission at 21 μm for two of our targets, WD 2149+021 and WD 2105‑820. WD 2105‑820 has a candidate planetary companion at a projected separation of 34 au and an IR excess—if both candidates are confirmed, it would represent the first WD multiplanet system. We investigate whether these excesses could be caused by very low luminosity warm dust disks or planets. While both are likely, we argue that the most likely explanation for the excesses is that they are the thermal emission from Jovian-mass planets in orbits with semimajor axes &lt;10 au, using a combination of observational constraints. If most of the candidate planets presented here are confirmed, it would suggest that metal-polluted white dwarfs are frequently orbited by at least one giant planet.

Keywords: Exoplanets, White dwarf stars, James Webb Space Telescope, Circumstellar disks, Debris disks
Simulating Intermediate Black Hole Mass Measurements for a Sample of Galaxies with Nuclear Star Clusters Using ELT/HARMONI High Spatial Resolution Integral-field Stellar Kinematics. Understanding the demographics of intermediate-mass black holes (IMBHs, MBH ≈ 102–105 M⊙) in low-mass galaxies is key to constraining black hole seed formation models, but detecting them is challenging due to their small gravitational sphere of influence (SOI). The upcoming Extremely Large Telescope (ELT) High Angular Resolution Monolithic Optical and Near-infrared Integral Field Spectrograph (HARMONI) instrument, with its high angular resolution, offers a promising solution. We present simulations assessing HARMONI's ability to measure IMBH masses in nuclear star clusters (NSCs) of nearby dwarf galaxies. We selected a sample of 44 candidates within 10 Mpc. For two representative targets, NGC 300 and NGC 3115 dw01, we generated mock HARMONI integral-field data cubes using realistic inputs derived from Hubble Space Telescope imaging, stellar population models, and Jeans anisotropic models (JAM), assuming IMBH masses up to 1% of the NSC mass. We simulated observations across six near-infrared gratings at 10 mas resolution. Analyzing the mock data with standard kinematic extraction and JAM models in a Bayesian framework, we demonstrate that HARMONI can resolve the IMBH SOI and accurately recover masses down to ≈0.5% of the NSC mass within feasible exposure times. These results highlight HARMONI's potential to revolutionize IMBH studies.

Keywords: Astronomy data modeling, Galaxy dynamics, Galaxy nuclei, Galaxy kinematics, Galaxy spectroscopy, Astrophysical black holes
Submillimeter and Mid-infrared Variability of Young Stellar Objects in the M17 H II Region. We conducted a comprehensive analysis of young stellar object (YSO) variability at submillimeter and mid-infrared (mid-IR) wavelengths for the M17 H II region using 3.5 yr monitoring data from the James Clerk Maxwell Telescope (JCMT) Transient Survey at 450 and 850 μm and 9 yr mid-IR monitoring data from the NEOWISE mission. Our study encompasses observations of 198 and 164 bright submillimeter peaks identified within the deep JCMT coadded maps at 450 and 850 μm, and 66 YSOs seen by NEOWISE W2 that were previously identified in mid-IR observations. We find one robust linear submillimeter variable, an intermediate mass protostar, with a 4% peak flux change in 3.5 yr of JCMT monitoring that sets a lower limit of 16% luminosity increase for the source. At mid-IR wavelengths, our analysis reveals secular and stochastic variability in 22 YSOs, with the highest fraction of secular variability occurring at the earliest evolutionary stage. This mid-IR fractional variability as a function of evolutionary stage result is similar to what has previously been found for YSO variability within the Gould Belt and the intermediate-mass star formation region M17 SWex, though overall less variability is detected in M17 in submillimeter and mid-IR. We suspect that this lower detection of YSO variability is due to both the greater distance to M17 and the strong feedback from the H II region. Our findings showcase the utility of multiwavelength observations to better capture the complex variability phenomena inherent to star formation processes and demonstrate the importance of years-long monitoring of a diverse selection of star-forming environments.

Keywords: Submillimeter astronomy, Infrared astronomy, Young stellar objects, Time domain astronomy, Variable stars, Protostars
Detailed Analysis of Six Contact Binaries and their Possible Origin. A photometric investigation of six binary systems of the W Ursae Majoris (W UMa)-type is presented. We extracted primary and secondary minima from the Transiting Exoplanet Survey Satellite observations of these systems. Using observations previously reported in the literature, linear fits in the O – C diagrams were carried out, and new ephemerides were determined. Light curve solutions were obtained using the legacy version of PHysics Of Eclipsing BinariEs and revealed that five of these systems required cold starspots, implying the presence of the O'Connell effect. The absolute parameters for all of these systems were estimated, and it is shown that they are all consistent with the properties of W UMa-type stars. Finally, we show that the progenitors of these binaries were likely low-mass, short-period, primordial binaries (total mass ≲2 M⊙). We find that mass transfer can be arbitrarily nonconservative and still produce short-period contact binaries. Other formation scenarios are also briefly examined.

Keywords: Contact binary stars
Spectroscopy of Free-floating Planetary-mass Objects and Their Disks with JWST. Free-floating planetary-mass objects (FFPMOs) are known to harbor disks at young ages. Here, we present 1–13 μm spectra for eight young FFPMOs with masses of 5–10 MJup (at ages of 1–5 Myr), using the NIRSpec and MIRI instruments on the James Webb Space Telescope. We derive fundamental properties of these targets, and find spectral types of M9.5 to L4, with effective temperatures of 1600–1900 K. The photospheric spectra of our targets show a clear diversity at similar temperatures, especially in the 3–5 μm range, unaccounted for by existing atmospheric models. We find a silicate absorption feature in the photosphere of one of our targets, the first such detection in very young FFPMOs, indicating silicate clouds in their cool atmospheres. Six of our objects show mid-infrared excess emission above the photosphere, as well as silicate emission features, demonstrating the presence of disks. The shape and strength of the latter features constitute strong evidence of grain growth and crystallization, similar to what is seen in more massive brown dwarfs and stars. We also detect emission lines from hydrocarbon molecules in the disks of several targets. These are the lowest-mass isolated objects found so far with silicate and hydrocarbon emission features arising in their disks. The presence of disks and their characteristics point to the potential for the formation of rocky companions around free-floating planetary-mass objects.

Keywords: Infrared spectroscopy, Infrared excess, Free floating planets, James Webb Space Telescope, Protoplanetary disks
Exoplanet Atmospheric Refraction Effects in the Kepler Sample. We present an analysis on the detection viability of refraction effects in Kepler's exoplanet atmospheres using binning techniques for their light curves in order to compare against simulated refraction effects. We split the Kepler exoplanets into subpopulations according to orbital period and planetary radius, then search for out-of-transit changes in the relative flux associated with atmospheric refraction of starlight. The presence of refraction effects—or lack thereof—may be used to measure and set limits on the bulk properties of an atmosphere, including mean molecular weight or the presence of hazes. In this work, we use the presence of refraction effects to test whether exoplanets above the period–radius valley have H/He atmospheres, which high levels of stellar radiation could evaporate away, in turn leaving rocky cores below the valley. We find strong observational evidence of refraction effects for exoplanets above the period–radius valley based on Kepler photometry; however, those related to optically thin H/He atmospheres are not common in the observed planetary population. This result may be attributed to signal dampening caused by clouds and hazes, consistent with the optically thick and intrinsically hotter atmospheres of Kepler exoplanets caused by relatively close host star proximity.

Keywords: Exoplanet atmospheric composition , Exoplanets, Super Earths, Mini Neptunes, Exoplanet atmospheres
FAST Search for Circumstellar Atomic Hydrogen. III. Planetary Nebulae at Galactic Latitudes ∣b∣ ≥ 10°. The detection of circumstellar atomic hydrogen (H I) via the 21 cm line remains a persistent challenge in planetary nebula (PN) studies, primarily due to contamination from ubiquitous interstellar H I 21 cm emission. In this paper, we report the results of a H I survey of 12 high surface brightness PNe located at Galactic latitudes ∣b∣ ≥ 10°, performed with the Five-hundred-meter Aperture Spherical radio Telescope, which is currently the most sensitive telescope in the L band. Although the contamination from interstellar emission is still severe, we detect or tentatively detect circumstellar H I 21 cm absorption associated with two PNe: NGC 6905 and NGC 7662. H I exhibits a comparatively high detection frequency in bipolar PNe. We estimate the H I masses of the two PNe to range from 0.01 to 0.14 M⊙, resulting in atomic-to-ionized hydrogen ratios of 0.02–0.3. The H I shells have dynamical ages of 2100–2400 yr. Our measurements confirm previous findings that the optical depth of H I decreases with increasing linear radius of the nebula. The mass loss rates traced by the H I absorption are larger than 10‑5 M⊙ yr‑1, indicating that they originate from the superwind phase at the tip of the asymptotic giant branch.

Keywords: Circumstellar envelopes, Planetary nebulae, Single-dish antennas, Stellar mass loss