Sazuna/UAT_keywords huggingface dataset:
Observational Constraints on Close Binary Star Evolution. II. Extreme Mass Ratios. W UMa systems become tidally unstable when their mass ratios (q ≡ M2/M1) dip below some minimum value ( qmin ) used for identifying stellar merger candidates. Recent fitting of photometric lightcurves (LCs) has identified dozens of putative extreme-q systems (q &lt; 0.15). In this paper, we combine high-resolution echelle spectroscopy (R ∼ 31,000) with high-precision Kepler and TESS photometry to examine 18 putative low-q and extreme-q systems, most notably V857 Her, V1187 Her, and NSVS 2569022. The spectroscopic mass ratios are consistently larger than previously published photometric values, sometimes dramatically. In particular, we find large, previously unidentified third light (l3) in V1187 Her, NSVS 2569022, and VSX J082700.8+462850, yielding revised mass ratios q &gt; 0.12. We demonstrate that photometry alone cannot reliably determine q, even for totally eclipsing systems; constraints on l3 are needed. The mass ratios, which range from q = 0.063 to q = 0.234, violate several flat  qmin  predictions, but are consistent with newer  qmin  predictions that are based on modeling the interior of the primary star. The RV profiles of at least five of the systems show significant departures from the conventional model for CBs. The clear anticorrelation between  logf  and  logq  for CBs remains largely unexplained, but an emerging W UMa evolutionary framework may help explain the data. More than half of close detached binaries (P &lt; 2 days) in our extended sample are Algols, exhibiting evidence of prior mass-ratio reversal.

Keywords: Multiple star evolution, Close binary stars, W Ursae Majoris variable stars, Algol variable stars, Stellar evolutionary models, Ellipsoidal variable stars, Contact binary stars
A Link between Rocky Planet Density and Host Star Chemistry. Planets and their host stars form from the same cloud of gas and dust, so we assume that their chemical compositions are linked. However, a clear correlation between rocky planet interior properties and host star chemistry remains elusive for planets around FGK dwarfs, and nonexistent for planets around M dwarfs because cool stars frequently lack detailed chemical information. Here, we investigate the relationship between small (RP ≤ 1.8 R⊕) planet densities and host star elemental abundances. We use the Sloan Digital Sky Survey-V/Milky Way Mapper and an accompanying data-driven framework to obtain abundances for FGK and M dwarf hosts of 22 rocky planets. We find that planet densities exhibit a strong, inverse relationship to [Mg/Fe] abundances of FGK hosts (p = 0.001). This correlation becomes more significant with the addition of M dwarf hosts (p = 0.0005). If we assume that rocky planets have terrestrial-like compositions, this suggests that low [Mg/Fe] environments form planets with larger Fe-rich cores and thus higher densities. The thick disk planets in our sample help anchor this trend, illustrating the importance of sampling exoplanet properties across a range of host star populations. This finding highlights the connection between Galactic chemical evolution and rocky planet formation, and indicates that Earth-like planet compositions may vary significantly across different regions of the Galaxy.

Keywords: Extrasolar rocky planets, Stellar abundances
FAST Search for Circumstellar Atomic Hydrogen. IV. Bubbles Associated with Planetary Nebulae. Investigating the bubbles generated by the interaction between asymptotic giant branch stellar outflows and the interstellar medium (ISM) is pivotal for elucidating the mechanism by which evolved low- to intermediate-mass stars enrich the ISM with heavy elements. Using archival data sets from the Galactic Plane Pulsar Snapshot survey and the Galactic Arecibo L-Band Array H I survey, we have identified 14 bubbles within interstellar atomic hydrogen (H I) maps, each showing evidence of potential association with planetary nebulae (PNe). We pursue two primary objectives centered on the identified ISM bubbles and their association with PNe. First, leveraging the calibrated distance measurements of PNe from Gaia Data Release 3, we utilize these ISM bubbles as observational tracers to investigate and constrain the Galactic rotation curve. Second, we note that distance determinations for some PNe remain unreliable, partly because their central stars are obscured by extended nebular envelopes or are misidentified. Therefore, we develop a novel methodological framework to derive kinematic distances for PNe by leveraging the velocities of their associated ISM bubbles and constraints from the Galactic rotation curve.

Keywords: Stellar-interstellar interactions, Interstellar atomic gas, Distance measure, Planetary nebulae, Interstellar medium
On the Detection of Exorings in Reflected Light with JWST NIRCam. When directly imaging a cold-giant exoplanet hosting a ring system, the reflected light from the rings can outshine the planet's thermal emission and reflected light in the near-infrared. Consequently, an exoring may be detectable at a significantly lower contrasts than is required to image the exoplanet itself. Here we investigate the detectability of exorings in near-infrared reflected light using NIRCam coronagraphy PanCAKE simulations of two nearby mature stars, Proxima Centauri and Tau Ceti. Under the most favorable assumptions, we find JWST 2 μm NIRCam coronagraphy (F200W + MASK335R) is capable of detecting an exoring system with a radius of 2.8 times that of Saturn's A-ring for planets on an orbit with a = 1.3─1.9 au. Broader simulations indicate that NIRCam can probe large planetary ring systems around mature exoplanets comparable in size to circumplanetary disks, which can reach up to 1000 times the radius of Saturn's A-ring. These results suggest that NIRCam F200W coronagraphy could serendipitously detect large exorings in reflected light under the right conditions. A combined analysis of F200W coronagraphic observations of confirmed exoplanets could provide the first empirical constraints on the occurrence rate of large exorings. Confirming the existence and frequency of exorings spanning the scale between circumplanetary disks and the rings of the solar system giant planet could offer new insight into the formation, evolution, and architecture of planetary systems.

Keywords: Exoplanet rings, Direct imaging, James Webb Space Telescope
Optimized Asteroid Rotation and Shape Modeling through an Integrated Shape-from-silhouette and Optical Flow Approach. Asteroids offer valuable insights into the formation and evolution of the solar system. Understanding their rotation and shape is essential for studying asteroid collision histories and geological processes, as well as for planning exploration missions. The conventional shape-from-silhouette (SFS) method reconstructs an asteroid's rotation and shape using multiple resolved silhouette images captured at different rotational states. However, this method relies solely on silhouette information and is affected by the inherent shape symmetries, leading to ambiguities in rotation and shape model inversion. This paper presents an approach that integrates SFS and optical flow techniques for optimized asteroid rotation and shape modeling. In our approach, an optical flow method revealing information on asteroid motion and structure is integrated with the SFS technique to realize effective optimization. Additionally, a swarm intelligence-based strategy relying on parallel exploration and dynamic step adjustment is used to enhance global optimization. Experiments based on data from two typical asteroids, Itokawa (asymmetric shape) and Bennu (symmetric shape), demonstrate the promising performance of the proposed method. The results show that the approach achieves unique and accurate pole estimations from distances of several hundred kilometers, even under varying illumination conditions. Additionally, it can generate unique and precise shape models when favorable illumination conditions are present. For the asymmetric asteroid Itokawa, the maximum distance that allows for pole and shape inversion is approximately twice that of the symmetric asteroid Bennu. The proposed method can support scientific research on asteroids, such as their dynamics and morphology, as well as asteroid exploration missions.

Keywords: Near-Earth objects, Asteroid rotation, Asteroids
High-pass Filtering and Gaussian Process Regularization: Stellar Activity Characterization Techniques Applied to the 55 Cancri Planetary System. Doppler planet searches are complicated by stellar activity, through which cyclical changes in the host star's photosphere and chromosphere can mask or mimic planetary signals. A popular technique for modeling stellar activity is to apply a quasiperiodic Gaussian process (GP) kernel, which provides a flexible model with rigorous error propagation. However, observers must guard against overfitting, as a GP may be flexible enough to subsume other signals besides the one it is intended to model. To counteract overfitting, we introduce a curvature-penalizing objective function for fitting GP models to long-term magnetic activity cycles. We also demonstrate that a Gaussian filter can be an effective method of detrending radial velocities (RVs) so that shorter-period signals can be extracted even in the absence of a mathematical model of the long-term trend. We apply our methods to the heavily studied 55 Cancri system, fitting Keplerian orbits plus the GP activity-cycle model. We show that a four-Keplerian model that includes planets b, c, e, and f combined with a GP for the activity cycle performs at least as well as the widely agreed upon five-planet system with its own GP activity model. Our results suggest that the existence of planet d cannot be established from the RVs alone; additional data are required for confirmation.

Keywords: Radial velocity, Stellar activity, Period search , Gaussian Processes regression, Exoplanet detection methods
ExoMiner++: Enhanced Transit Classification and a New Vetting Catalog for 2-minute TESS Data. We present ExoMiner++, an enhanced deep learning model that builds on the success of ExoMiner to improve transit signal classification in 2-minute TESS data. ExoMiner++ incorporates additional diagnostic inputs, including periodogram, flux trend, difference image, unfolded flux, and spacecraft attitude control data, all of which are crucial for effectively distinguishing transit signals from more challenging sources of false positives (FPs). To further enhance performance, we leverage multisource training by combining high-quality labeled data from the Kepler space telescope with TESS data. This approach mitigates the impact of TESS's noisier and more ambiguous labels. ExoMiner++ achieves high accuracy across various classification and ranking metrics, significantly narrowing the search space for follow-up investigations to confirm new planets. To serve the exoplanet community, we introduce a new TESS catalog containing ExoMiner++ classifications and confidence scores for each transit signal. Among the 147,568 unlabeled TCEs, ExoMiner++ identifies 7330 as planet candidates (PCs), with the remainder classified as FPs. These 7330 PCs correspond to 1868 existing TESS Objects of Interest (TOIs), 69 Community TESS Objects of Interest (CTOIs), and 50 newly introduced CTOIs. 1797 out of the 2506 TOIs previously labeled as PCs in ExoFOP are classified as PCs by ExoMiner++. This reduction in plausible candidates, combined with the excellent ranking quality of ExoMiner++, allows the follow-up efforts to be focused on the most likely candidates, increasing the overall planet yield.

Keywords: Exoplanet astronomy, Exoplanet catalogs, Exoplanets
The MiMO Catalog: Physical Parameters and Stellar Mass Functions of 1232 Open Clusters from Gaia DR3. We present a homogeneous catalog of 1232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color─magnitude diagram. By explicitly accounting for field-star contamination as a model component, MiMO removes the conventional need for stringent membership preselection, allowing for a more complete inclusion of member stars, and thereby enhancing both precision and robustness. Our results broadly agree with existing catalogs but offer improved precision. For each cluster, we provide the best-fit age, metallicity, distance, extinction, and MF slope, along with their full likelihood chains and photometric membership probabilities for individual stars. We further identify an "MF Prime" subsample of 163 clusters with high-quality data, for which the MF estimates are considered most reliable. The catalog and an open-source implementation of MiMO are made publicly available to the community.

Keywords: Hertzsprung Russell diagram, Bayesian statistics, Binary stars, Stellar ages, Open star clusters, Stellar mass functions, Mixture model
Characterizing the Time Variability of 2M1207 A + b with JWST NIRSpec/PRISM. We present JWST NIRSpec/PRISM integral field unit time-resolved observations of 2M1207 A and b (TWA 27), an ∼10 Myr binary system consisting of an ∼2500 K substellar primary hosting an ∼1300 K companion. Our data provide 20 time-resolved spectra over an observation spanning 12.56 hr. We provide an empirical characterization for the spectra of both objects across time. For 2M1207 A, nonlinear trend models are statistically favored within the ranges 0.6─2.3 μm and 3.8─5.3 μm. However, most of the periods constrained from sinusoidal models exceed the observing window, setting a lower limit of 12.56 hr. We find the data at Hα and beyond 4.35 μm show a moderate time correlation, as well as a pair of light curves at 0.73─0.80 μm and 3.36─3.38 μm. For 2M1207 b, light curves integrated across 0.86─1.77 μm and 3.29─4.34 μm support linear trend models. Following the interpretation of Z. Zhang et al., we model the 2M1207 b data with two 1D atmospheric components, both with silicate and iron condensates. The model of time variability due to changes in the cloud filling factor shows broad consistency with the variability amplitudes derived from our data. Our amplitudes, however, disagree with the models at ≍0.86─1 μm. While an additional model component such as rainout chemistry may be considered here, our analysis is limited by low signal-to-noise ratio. Our results demonstrate the capability of JWST to simultaneously monitor the spectral variability of a planetary-mass companion and host at low contrast.

Keywords: Brown dwarfs, Exoplanet atmospheric variability, James Webb Space Telescope, Extrasolar gaseous planets, Direct imaging
The Effect of Offsets from True Orbital Parameters on Exoplanet High-resolution Transmission Spectra. High-resolution spectroscopy (HRS) plays a crucial role in characterizing exoplanet atmospheres, revealing detailed information about their chemical composition, temperatures, and dynamics. However, inaccuracies in orbital parameters can affect the result of HRS analyses. In this paper, we simulated HRS observations of an exoplanet's transit to model the effects of an offset in transit midpoint or eccentricity on the resulting spectra. We derived analytical equations to relate an offset in transit midpoint or eccentricity to shifted velocities, and compared it with velocities measured from simulated HRS observations. Additionally, we compared velocity shifts in the spectrum of the ultra-hot-Jupiter WASP-76b using previously reported and newly measured transit times. We found that transit midpoint offsets on the order of minutes, combined with eccentricity offsets of approximately 0.1, lead to significant shifts in velocities, yielding measurements on the order of several kilometers per second. Thus, such uncertainties could obfuscate derived wind measurements.

Keywords: High resolution spectroscopy, Optical observation, Exoplanets, Keplerian orbit, Exoplanet atmospheres
A Scatter of Light from a Polarized World. Many known exoplanets harbor clouds, which lead to degeneracies in spectroscopic models between particle composition and size. Polarimetry, however, provides independent assessment. Here we report the 7.2σ discovery of linearly polarized, scattered light from the hot Jupiter HD 189733b in B band (390─475 nm) peaking near quarter phase with ∆p = 40.9 ± 7.1 ppm. Polarization measurements, obtained with the POLISH2 polarimeter at both Gemini North and the Lick Observatory 3 m, are best explained by silicate (SiO2 or MgSiO3) particles with effective radius  reff=0.038−0.023+0.047  μm (90% confidence). This is broadly consistent with results from both Hubble transmission spectroscopy and JWST secondary eclipse spectroscopy suggesting small, SiO2 scattering particles. It is difficult to reconcile large polarization and moderate Hubble secondary eclipse depth via pure Rayleigh, silicate, or MnS scatterers. The measured polarization of HD 189733b is detected with such high confidence that we place a 2σ lower limit on its B-band geometric albedo of Ag &gt; 0.26 with a preferred value of Ag = 0.6. This is larger than the prior estimate of Ag = 0.226 ± 0.091 from Hubble secondary eclipse photometry, and it presents HD 189733b as one of the most reflective known exoplanets in B band. It also validates Rayleigh scattering from the exoplanet, as opposed to starspot contamination, as the cause of HD 189733's blue optical slope in transmission spectroscopy. Assuming other known exoplanets harbor atmospheres like HD 189733b, we model dozens to be detectable with at least 5σ confidence after one week of Gemini time each.

Keywords: High contrast techniques, Exoplanet atmospheric composition , Hot Jupiters, Calibration, Ground-based astronomy, Exoplanet detection methods, Albedo, Polarimetry
JWST-TST DREAMS: Sulfur Dioxide in the Atmosphere of the Neptune-mass Planet HAT-P-26 b from NIRSpec G395H Transmission Spectroscopy. We present the James Webb Space Telescope (JWST) transmission spectrum of the exoplanet HAT-P-26 b (18.6 M⊕, 6.33 R⊕), based on a single transit observed with the JWST NIRSpec G395H grating. We detect water vapor ( lnB  = 4.1), carbon dioxide ( lnB  = 85.6), and sulfur dioxide ( lnB  = 13.5) with high confidence, along with marginal indications for hydrogen sulfide and carbon monoxide ( lnB&lt;  0.5). The detection of SO2 in a warm super-Neptune-sized exoplanet (RP ∼ 6 R⊕) bridges the gap between previous detections in hot Jupiters and sub-Neptunes, highlighting the role of disequilibrium photochemistry across a broad range of exoplanet atmospheres, including those cooler than 1000 K. Our precise measurements of carbon, oxygen, and sulfur indicate an atmospheric metallicity of ∼10× solar and a subsolar C/O ratio. Retrieved molecular abundances are consistent within 2σ with predictions from self-consistent models including photochemistry. The elevated CO2 abundance and possible H2S signal may also reflect sensitivities to the thermal structure, cloud properties, or additional disequilibrium processes such as vertical mixing. We compare the SO2 abundance in HAT-P-26 b with that of 10 other JWST-observed giant exoplanets, and find a correlation with atmospheric metallicity. The trend is consistent with the prediction from I. J. M. Crossfield, showing a steep rise in SO2 abundance at low metallicities, and a more gradual increase beyond 30× solar. This work is part of a series of studies by our JWST Telescope Scientist Team (JWST-TST), in which we use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).

Keywords: Exoplanet atmospheric composition , Exoplanets, Hot Neptunes, Exoplanet systems, Exoplanet astronomy, Exoplanet atmospheres
HWO Target Stars and Systems: A Survey of Archival UV and X-Ray Data. We assess archival high-energy data for key stars on the Habitable Worlds Observatory (HWO) Target Stars and Systems 2025 list, as stellar radiation is critical to shaping and interpreting planetary atmospheres. Using a sample of 98 nearby stars (HWO Tier 1 targets), we compile and evaluate X-ray and ultraviolet (UV) data from archival eROSITA, Chandra, XMM-Newton, RÖentgen SATellite, Extreme-Ultraviolet Explorer, Swift, Far Ultraviolet Spectroscopic Explorer, International Ultraviolet Explorer (IUE), Galaxy Evolution Explorer, and Hubble Space Telescope (HST). We examine spectral and temporal coverage, assess data quality, and identify major gaps. UV data are moderately available, with most coverage coming from near-UV spectra from IUE. Far fewer stars have far-UV spectra, especially from HST. In the X-ray regime, some stars have high-quality spectra, while others are limited to shallow detections or broadband photometry. A small fraction of the sample has both X-ray and UV spectra of sufficient quality to support full spectral energy distribution modeling. Truly comprehensive coverage across X-ray, extreme-UV, and both UV bands remains extremely rare. Most data sets are single-epoch, limiting assessments of variability and flares—key factors in atmospheric photochemistry and escape. Moreover, the lack of simultaneous or contemporaneous observations across bands adds further uncertainty. Our findings underscore the need for new space-based missions and coordinated multiwavelength campaigns, ideally with overlapping coverage, to improve stellar characterization for HWO. As several key observatories age and face potential decommissioning, there is a narrow window of opportunity to secure these critical data. Investing in this effort now will directly support the science goals of HWO and enhance future studies of planetary habitability.

Keywords: X-ray astronomy, Catalogs, Stellar chromospheres, Astronomical reference materials, Ultraviolet astronomy, Stellar astronomy, Stellar coronae, Stellar atmospheres
DELVE-ing into the Milky Way's Globular Clusters: Assessing Extratidal Features in NGC 5897, NGC 7492, and Testing Detectability with Deeper Photometry. Extratidal features around globular clusters (GCs) are tracers of their disruption, stellar stream formation, and their host's gravitational potential. However, these features remain challenging to detect due to their low surface brightness. We conduct a systematic search for such features around 19 GCs in the DECam Local Volume Exploration (DELVE) survey Data Release 2, discovering a new extra-tidal envelope around NGC 5897 and find tentative evidence for an extended envelope surrounding NGC 7492. Through a combination of dynamical modeling and analyzing synthetic stellar populations, we demonstrate these envelopes may have formed through tidal disruption. We use these models to explore the detectability of these features in the upcoming Legacy Survey of Space and Time (LSST), finding that while LSST's deeper photometry will enhance detection significance, additional methods for foreground removal like proper motions or metallicities may be important for robust stream detection. Our results both add to the sample of globular clusters with extratidal features and provide insights on interpreting similar features in current and upcoming data.

Keywords: Globular star clusters, Tidal disruption, Milky Way Galaxy