Sazuna/UAT_keywords huggingface dataset:
Size and Shape of Jupiter Trojan (2207) Antenor from Stellar Occultations. Librating around the Lagrange L5, the Jupiter's Trojan (2207) Antenor has been observed in recent years and its rotational light curve suggests it to be a very likely binary asteroid candidate. From stellar occultations, we report results from three events from Europe and North America to estimate the 2D apparent size and shape of Jupiter's Trojan (2207) Antenor. For the best-fitted ellipse in the sky-plane, we determined that Antenor has a 2D apparent equatorial radius of 54.30 ± 0.99 km at the moment of the occultations, with an apparent oblateness of 0.144 ± 0.051. We highlight the positive detection from 2021 June 12, which shows an intriguing feature that can be interpreted as a very large topographical feature (of about 11 km) of the body or that can provide further evidence that this object is, in fact, a close or contact binary. We also determine astrometric positions, with uncertainties of a few milliarcseconds (mas) for our preferred solutions.

Keywords: Asteroids, Stellar occultation, Small Solar System bodies, Jupiter trojans
Heartbeat Stars Recognition Based on Recurrent Neural Networks: Method and Validation. Since the variety of their light curve morphologies, the vast majority of the known heartbeat stars (HBSs) have been discovered by manual inspection. Machine learning, which has already been successfully applied to the classification of variable stars based on light curves, offers another possibility for the automatic detection of HBSs. We propose a novel feature extraction approach for HBSs. First, the orbital frequencies are calculated automatically according to the Fourier spectra of the light curves. Then, the amplitudes of the first 100 harmonics are extracted. Finally, these harmonics are normalized as feature vectors of the light curve. A training data set of synthetic light curves is constructed using ELLC, and their features are fed into recurrent neural networks (RNNs) for supervised learning, with the expected output being the eccentricity of these light curves. The performance of the RNNs is evaluated using a test data set of synthetic light curves, achieving 95% accuracy. When applied to known HBSs from the Optical Gravitational Lensing Experiment, Kepler, and Transiting Exoplanet Survey Satellite surveys, the networks achieve an average accuracy of 86%. This method successfully identifies four new HBSs within the eclipsing binary catalog of Kirk et al. The use of orbital harmonics as features for HBSs proves to be a practical approach that significantly reduces the computational cost of neural networks. RNNs show excellent performance in recognizing this type of time series data. This method not only allows efficient identification of HBSs but can also be extended to recognize other types of periodic variable stars.

Keywords: Stellar oscillations, Elliptical orbits, Binary stars, Neural networks
Searching for Helium Escape and a Low-density Atmosphere Around the 120 Myr Old Sub-Neptune HIP94235b Using CRIRES+. Atmospheric mass loss is thought to induce the bimodality in the small planet population as we observe it today. Observationally, active mass loss can be traced by excess absorption in spectral lines of lighter species, such as the hydrogen Lyα line and the metastable helium triplet. We search for helium escape from the young (120 Myr old) sub-Neptune (3 R⊕) HIP94235b. We obtained two transit observations of HIP94235b using the CRyogenic InfraRed Echelle Spectrograph on the Very Large Telescope. We find no evidence for escaping helium across both visits, allowing us to place a mass loss rate upper limit of 1011 g s−1, based on 1D Parker wind models. Additionally, we search for molecular spectral features in the planet's transmission spectrum, and cross correlate our observations with high-resolution template spectra for H2O, the dominating molecule in the Y band. We detect no significant absorption. We demonstrate that some atmosphere models at 10× solar metallicity would have been retrievable if present. Through the null detection of neutral hydrogen and helium escape, we conclude the atmosphere of HIP94235b likely lacks a large hydrogen-helium envelope. This is consistent with the expectation of small planet photoevaporation models, which suggest most planets lose their primordial hydrogen-helium envelopes within 100 Myr of evolution.

Keywords: Observational astronomy, Exoplanet astronomy, Exoplanet atmospheres, Exoplanet atmospheric evolution
Probing Periodic Trends in the TESS Light Curves of the Seventeen Known Double White Dwarf Systems. There is a relatively large population of known double white dwarfs (DWDs) that were mostly discovered through spectroscopic observations and by measuring their radial velocity variations. Photometric observations from these systems give us additional information about their faint components by manifesting eclipsing or lensing signals or periodic trends such as ellipsoidal variations or Doppler boosting. To find these signals and trends we probe the public photometric data collected by the Transiting Exoplanet Survey Satellite (TESS) telescope from 17 known DWD systems. We use the singular spectrum analysis technique to denoise their light curves. For DWD systems J1717+6757, J1557+2823, LP400‑22, J1449+1717, J2132+0754, and J2151+1614, we find regular and periodic trends in their TESS light curves. The periodic trend in light curve J1449+1717 is caused by the blending effect due to a variable and bright star close to it which are unresolvable in the TESS observations. The discovered periodic trend for J1717+6757 was recovered by the TESS data. The periodic trends in light curves of J1557+2823 and J2151+1614 have false alarm probability values ≃14.8%, 36.5%. So, their detected trends are likely noises with nonorbital origins. Periods of trends in light curves of LP400‑22 and J2132+0754 are the same as and half of orbital periods, respectively. We evaluate possible ranges for Doppler boosting and ellipsoidal variation amplitudes for these targets. This study highlights the importance of TESS data for identifying periodic trends such as ellipsoidal or intrinsic variations rather than short eclipsing/lensing signals in DWD light curves, especially bright targets with ignorable blending.

Keywords: White dwarf stars, Astronomy data analysis, Ellipsoidal variable stars, Optical telescopes, Compact objects, Space telescopes, Intrinsic variable stars, Doppler shift
A Comprehensive Study of Czernik 41 and NGC 1342 Using CCD UBV and Gaia DR3 Data. In this study, the structural, astrophysical, kinematic, and Galactic orbital parameters of the open clusters Czernik 41 and NGC 1342, as well as their dynamical evolution, are investigated using CCD UBV photometry and Gaia data. By applying the UPMASK algorithm to Gaia astrometric data for the estimation of cluster membership probabilities, we have determined that 382 stars in Czernik 41 and 111 stars in NGC 1342 exhibit the highest statistical likelihood of being cluster members. Fundamental parameters (including reddening, metallicity, distance, and age) were derived using both classical methods, where parameters are determined separately, and Markov Chain Monte Carlo methods, where parameters are estimated simultaneously. The results obtained from both approaches are in agreement, confirming the reliability of the derived parameters and demonstrating their robustness against potential degeneracies. The distances to Czernik 41 and NGC 1342 were determined as 2485 ± 151 pc and 645 ± 42 pc, respectively, while their ages were estimated to be 69 ± 10 Myr and 1000 ± 50 Myr. The metallicity values ([Fe/H]) were found to be 0.07 ± 0.09 dex for Czernik 41 and ‑0.14 ± 0.07 dex for NGC 1342. The stellar mass functions for both clusters were derived, yielding slopes of Γ = 1.67 ± 0.23 for Czernik 41 and Γ = 1.56 ± 0.41 for NGC 1342. A kinematic orbit analysis indicates that Czernik 41 originated within the solar circle, whereas NGC 1342 formed outside it.

Keywords: Galaxy disks, Open star clusters, Hertzsprung Russell diagram, Galaxy kinematics
A Metal-poor Atmosphere with a Hot Interior for a Young Sub-Neptune Progenitor: JWST/NIRSpec Transmission Spectrum of V1298 Tau b. We present the JWST/NIRSpec G395H transmission spectrum of the young (10–30 Myr) transiting planet V1298 Tau b (9.85 ± 0.35 R⊕, Teq = 670 K). Combined Hubble Space Telescope and JWST observations reveal a haze-free, H/He-dominated atmosphere with a large scale height (∼1500 km), allowing detection of CO2 (35σ), H2O (30σ), CO (10σ), CH4 (6σ), SO2 (4σ), and OCS (3.5σ). Our observations probe several scale heights (∼4.4 in the CO2 4.3 μm band and ∼3 in the 2.7 μm water band). The planet's mass, inferred from atmospheric scale height using free retrieval and grid modeling, is 12 ± 1 M⊕ and 15 ± 1.7 M⊕, respectively, which is significantly lower than previous radial velocity estimates and confirms it as "gas-dwarf" sub-Neptune progenitor. We find an atmospheric metallicity (log Z = 0.6 ‑0.6+0.4×  solar) and subsolar C/O ratio (0.22 ‑0.05+0.06 ). The atmospheric metallicity is low compared to mature sub-Neptunes by an order of magnitude. The CH4 abundance ([CH4] = ‑6.2 ‑0.5+0.3 ]) is ∼7σ lower than the equilibrium chemistry prediction. To adjust for the low methane abundance, the self-consistent grids favor a high internal temperature (∼500 K) and vertical mixing (Kzz ∼ 107‑108 cm2 s–1). These internal temperatures are inconsistent with predictions from evolutionary models, which expect ∼100–200 K at the current system age. We estimate a gas-to-core mass fraction between 0.1% and 8%, with a core mass of 11–12 M⊕, consistent with in-situ gas-dwarf formation. A deep atmospheric metallicity gradient may explain both the high internal temperature and low observable metallicity. Over time, mass loss from such an atmosphere could enhance its metallicity, potentially reconciling V1298 Tau b with mature sub-Neptunes.

Keywords: Exoplanet atmospheric composition , Exoplanet evolution, Exoplanet atmospheric structure, Exoplanet formation, Exoplanet atmospheres, Exoplanet atmospheric evolution
easyspec: An Open-source Python Package for Long-slit Spectroscopy. In modern-day astronomy, near-infrared, optical, and ultraviolet spectroscopy are indispensable for studying a wide range of phenomena, from measuring black hole masses to analyzing chemical abundances in stellar atmospheres. However, spectroscopic data reduction is often performed using instrument-specific pipelines or legacy software well-established and robust within the community that are often challenging to implement and script in modern astrophysical workflows. In this work, we introduce easyspec, a new Python package designed for long-slit spectroscopy, capable of reducing, extracting, and analyzing spectra from a wide range of instruments—provided they deliver raw FITS files, the standard format for most optical telescopes worldwide. This package is built upon the well-established long-slit spectroscopy routines of the Image Reduction and Analysis Facility (IRAF), integrating modern coding techniques and advanced fitting algorithms based on Markov chain Monte Carlo simulations. We present a user-friendly open-source Python package that can be easily incorporated into customized pipelines for more complex analyses. To validate its capabilities, we apply easyspec to the active galactic nucleus G4Jy 1709, observed with the DOLORES spectrograph at the Telescopio Nazionale Galileo, measuring its redshift and estimating its supermassive black hole mass. Finally, we compare our results with a previous IRAF-based study.

Keywords: Astronomy image processing, Active galactic nuclei, Astronomy data analysis, Spectroscopy
Binary Analysis and Period Study of the Long-period, High-mass-ratio Contact Binary KIC 7766185. We present an in-depth photometric and spectroscopic study of the contact binary KIC 7766185. Spectroscopic observations were conducted on the Mayall 4 m telescope at Kitt Peak National Observatory and used to extract radial velocities. Using the radial velocity measurements, Kepler photometry, and Gaia multicolor photometry, binary analysis was performed in PHOEBE to determine orbital and stellar parameters. The results classify KIC 7766185 as an A-type W UMa system and reveal one of the largest and most massive secondary stars in the sample of well studied W UMa systems. The two stars are in a shallow contact state, with a small fillout factor of 0.029 ± 0.002. Along with the binary analysis, we conduct a period study that reveals evidence for a cyclic variation in the eclipse timings.

Keywords: Eclipsing binary stars, W Ursae Majoris variable stars, Stellar properties, Contact binary stars
Rotation Periods of Candidate Single Late-M Dwarfs in TESS. Recent studies suggest that the angular momentum evolution of late-M and brown dwarfs differs from the well-known spin-down evolution of hotter stars. Characterizing the distribution of rotation periods of these objects in the solar neighborhood can help elucidate this evolutionary pathway just above, at, and below the hydrogen-burning limit. In this paper, we examine 399 candidate single late-M dwarfs with G ‑ GRP ≥ 1.4 mag (≳M6) using Transiting Exoplanet Survey Satellite (TESS) light curves. To determine rotation periods, we employed Lomb–Scargle periodograms to provide a first estimate of the period, then refined them with a Gaussian process approach, requiring multisector confirmation when available. We found 133 rotation periods, ranging from 2 hr to 6 days, and amplitudes between 0.08% and 2.71%. We find that the observed variability fraction in late-M dwarfs rises with the number of available TESS sectors, approaching an apparent ceiling of ∼50%. This likely reflects a detection limit determined by viewing geometry and supports the idea that spot-induced variability is common across the late-M and brown dwarf population. In our comparison with previously published late-M dwarf rotation periods reported, we found consistent results, confirming or updating 31 periods. Our findings expand the number of previously known late-M dwarf periods under 1 day by 76%. Combined with published rotation periods for a broader range of spectral types, we find a lower envelope on the rotation period decreasing from 5 hr at early-M dwarfs to 1 hr at L, T, and Y dwarfs.

Keywords: M dwarf stars, Periodic variable stars, Observational astronomy, Stellar rotation
Photometric Mapping of Carbonaceous/Siliceous Dust and Water Ice in the ISM with JWST: Applications to the Dense Sightlines. We introduce a new photometric mapping method for the James Webb Space Telescope (JWST) to measure the spatial distribution of carbonaceous dust, siliceous dust, and water ice by using absorption features arising from the grains in the dense interstellar medium (ISM). Employing NIRCam and MIRI imaging filters, low-resolution spectroscopic data can be obtained to measure the optical depths of the 3.0 μm water ice –OH feature, the 3.4 μm aliphatic hydrocarbon –CH feature, and the 10 μm silicate –SiO feature for large fields of view. This method provides extensive statistical data of the grains across wide fields in the ISM at minimal observing cost. In this study, we present its application on observational data from the literature to validate the measured optical depths and simulations to assess the accuracy of the method under various conditions. We showed that the photometric method can be employed to obtain reasonably accurate measurements of optical depth. We demonstrate that JWST optical depth maps enable the independent exploration of abundance distributions of major grain components across a wide spatial coverage in the ISM.

Keywords: Interstellar medium, Interstellar absorption, Infrared photometry
Disentangling Metallicity Effects in Hot Jupiter Occurrence across Galactic Birth Radius and Phase-space Density. We explore how the correlation between host star metallicity and giant planets shapes hot Jupiter occurrence as a function of Galactic birth radius (Rbirth) and phase-space density in the Milky Way disk. Using the Galactic Archaeology with HERMES (GALAH) and Apache Point Observatory Galactic Evolution Experiment (APOGEE) surveys and a galaxy from the NIHAO simulation suite, we inject hot Jupiters around stars based on metallicity power laws, reflecting the trend that giant planets preferentially form around metal-rich stars. For Rbirth ≥ 5 kpc, hot Jupiter occurrence decreases with Rbirth by ∼ ‑0.1% per kpc; this is driven by the Galaxy's chemical evolution, where the inner regions of the disk are more metal-rich. Differences in GALAH occurrence rates versus APOGEE's and the simulation's at Rbirth &lt; 5 kpc arise from survey selection effects. APOGEE and the NIHAO simulation have more high-α sequence stars than GALAH, resulting in average differences in metallicity (0.2–0.4 dex), α-process element enrichment (0.2 dex), and vertical velocities (7–14 km s‑1) at each Rbirth bin. Additionally, we replicate the result of A. J. Winter et al., which showed that over 92% of hot Jupiters are associated with stars in phase-space overdensities, or "clustered environments." However, our findings suggest that this clustering effect is primarily driven by chemical and kinematic differences between low and high-α sequence star properties. Our results support stellar characteristics, particularly metallicity, being the primary drivers of hot Jupiter formation, which serves as the "null hypothesis" for interpreting planet demographics. This underscores the need to disentangle planetary and stellar properties from Galactic-scale effects in future planet demographics studies.

Keywords: Stellar kinematics, Stellar abundances, Galactic archaeology, Hot Jupiters
SpecDis: Value Added Distance Catalog for 4 Million Stars from DESI Year-1 Data. We present the SPECDIS value-added stellar distance catalog accompanying DESI Data Release 1. SPECDIS trains a feed-forward neural network (NN) with Gaia parallaxes and gets the distance estimates. To build up an unbiased training sample, we do not apply selections on parallax error or signal-to-noise (S/N) of the stellar spectra, and instead, we incorporate parallax error into the loss function. Moreover, we employ principal component analysis to reduce the noise and dimensionality of stellar spectra. Validated by independent external samples of member stars with precise distances from globular clusters, dwarf galaxies, stellar streams, combined with blue horizontal branch stars, we demonstrate that our distance measurements show no significant bias up to 100 kpc, and are much more precise than Gaia parallax beyond 7 kpc. The median distance uncertainties are 23%, 19%, 11%, and 7% for S/N &lt; 20, 20≤ S/N &lt; 60, 60 ≤ S/N &lt; 100, and S/N ≥ 100. Selecting stars with  logg&lt;3.8  and distance uncertainties smaller than 25%, we have more than 74,000 giant candidates within 50 kpc of the Galactic center and 1500 candidates beyond this distance. Additionally, we develop a Gaussian mixture model to identify unresolvable equal-mass binaries by modeling the discrepancy between the NN-predicted and the geometric absolute magnitudes from Gaia parallaxes and identify 120,000 equal-mass binary candidates. Our final catalog provides distances and distance uncertainties for &gt;4 million stars, offering a valuable resource for Galactic astronomy.

Keywords: Redshift surveys, Stellar distance, Astronomy data analysis
Identification of Outer Galaxy Cluster Members Using Gaia DR3 and Multidimensional Simulation. The outer Galaxy presents a distinctive environment for investigating star formation. This study develops a novel approach to identify true cluster members based on unsupervised clustering using astrometry with significant uncertainties. As a proof of concept, we analyze three outer Galactic young stellar object (YSO) clusters at different distances and densities within 65∘ &lt; l &lt; 265∘, each known to contain &gt;100 members based on the Star Formation in Outer Galaxy (SFOG; E. Winston et al. 2020) catalog. The 618 YSO clusters in the SFOG data set were based on 2D clustering. In this contribution, we apply the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN*) algorithm to the precise Gaia DR3 astrometry to assign YSO cluster membership. A Monte Carlo simulation coupled with the HDBSCAN* (HDBSCAN-MC algorithm) addresses YSO astrometric uncertainties through 5D clustering. We introduce the Generation Of cLuster anD FIeld STar (GOLDFIST) simulation to enable robust membership determination, performing an unsupervised clustering analysis in higher-dimensional feature space while accommodating measurement errors. In this study, we extended our approach to distant outer galaxy YSOs and clusters with larger astrometric uncertainties. The results include the discovery of new members in the previously identified clusters. We also analyze the known stars in the clusters and confirm their membership. The derived membership probabilities are included in the provided cluster catalogs. The more accurately predicted simulation distance estimates closely agree, within uncertainty limits, with the median distance estimates derived from Gaia data, and are compared with the kinematic distances from the Wide-field Infrared Survey Explorer H II survey.

Keywords: Computational astronomy, Star forming regions, Young star clusters, Young stellar objects, Clustering, Astrometry
The Galactic Bulge Exploration. VI. Gaia Enceladus/Sausage RR Lyrae Stars in the Inner-central Stellar Halo of the Milky Way. We present a view of the stellar halo in the inner-central regions of the Milky Way (R ≲ 10 kpc) mapped by RR Lyrae stars. The combined BRAVA-RR/APOGEE RR Lyrae catalog is used to obtain a sample of 281 RR Lyrae stars located in the bulge region of the Galaxy, but with orbits indicating they belong to the inner-central halo. The RR Lyrae stars in the halo are more metal-poor than the bulge RR Lyrae stars and have pulsation properties more consistent with an accreted population. We use the Milky Way-like zoom-in cosmological simulation Auriga to compare the properties of the RR Lyrae stars to those expected from the "Gaia-Enceladus-Sausage" (GES) merger. The integrals of motions and eccentricities of the RR Lyrae stars are consistent with a small fraction of 6–9% ± 2% of the inner-central halo RR Lyrae population having originated from GES. This fraction, lower than what is seen in the solar neighborhood, is consistent with trends seen in the Auriga simulation, where a GES-like merger would have a decreasing fraction of GES stars at small Galactocentric radii compared to other accreted populations. Very few of the Auriga inner Galaxy GES-18 particles have properties consistent with belonging to a bulge population with (zmax &lt; 1.1 kpc), indicating that no (or very few) RR Lyrae stars with bulge orbits should have originated from GES.

Keywords: Milky Way formation, Galaxy dynamics, Milky Way dynamics, Galactic bulge, RR Lyrae variable stars, Milky Way stellar halo, Galaxy mergers, Halo stars