Sazuna/UAT_keywords huggingface dataset:
Thick Disks Around White Dwarfs Viewed "Edge-off": Effects on Transit Properties and Infrared Excess. A significant fraction of white dwarfs (WDs) host dust/debris disks formed from the tidal disruption of asteroids and planetesimals. Several studies indicate that the disks can attain significant vertical heights through a collisional cascade. In this work, I model the effects of geometrically thick disks on two primary observables: photometric transits by the disk when viewed at high inclinations and infrared dust emission. Specifically, I consider disks with a Gaussian vertical profile with scale heights comparable to or larger than the WD radius. I primarily focus on inclinations ≳87° ("edge-off"), which can produce significant transits with moderate disk thickness. Both the transit depth and color become strong functions of inclination, and I explore their dependence on the disk parameters. I show that such a setup can produce the recently discovered reddening in the transit of WD J1013−0427. Moving to infrared emission, I show that the contribution from the heated inner rim can be substantial even at high inclinations. It can potentially explain the infrared excess observed in two transiting debris systems, WD 1145+017 and WD 1232+563, consistently with the transits. The other two important radiation components are the optically thin dust emission from the disk's outer layers and the optically thick emission from the backwarmed disk interior. Extending my analysis to G29-38 shows that the former can adequately produce the silicate emission feature with an optically thin dust mass of &gt;1017 g. The inner dense layers, on the other hand, allow the disk to contain orders of magnitude larger net dust mass. Overall, I show that thick disk effects can be significant and should be taken into account. I motivate detailed studies to quantify the effects accurately.

Keywords: Transits, White dwarf stars, Infrared excess, Variable stars, Circumstellar dust, Debris disks
A Spectral Library and Census of Near-infrared Stellar Large-amplitude Variables from Palomar Gattini-IR. We present a near-infrared census of stellar large-amplitude variables (LAVs) observed by the Palomar Gattini-IR (PGIR) surveyor from 2019─2021. Over the three-year time period, PGIR performed a brightness-limited survey of the Northern sky (∼18,000 deg2) to J-band AB magnitudes ∼13 within and ∼15 outside the Galactic plane. From ∼70 million stars detected in PGIR reference images, we provide a spectral and photometric library of the 128 largest amplitude stellar variables detected to median SNR &gt; 10 for more than 50 epochs with more than 5 high-amplitude detections, peak-to-peak magnitudes ≥2, and von Neumann ratios ≤0.2. We obtained medium-resolution near-infrared spectra with TripleSpec on the 200 inch Hale Telescope at Palomar Observatory and SpeX at NASA's Infrared Telescope Facility. The spectral census consists of 82 evolved and dust-obscured Asymptotic Giant Branch stars, 16 R Coronae Borealis stars, 13 young-stellar or pre-main-sequence objects, 8 symbiotic binaries, 7 erratic carbon- and oxygen-rich giants, and 2 RV Tauri supergiants. The spectral and photometric dataset serves as an atlas of near-infrared LAVs and a repository of evolved stars, eruptive variables, and binary systems for future deeper infrared surveys.

Keywords: Sky surveys, Carbon stars, R Coronae Borealis variable stars, Young stellar objects, Infrared telescopes, Variable stars, Late-type giant stars, Symbiotic binary stars, Near infrared astronomy
Reassessing the Relationship between Stellar X-Ray Luminosity and Age with eROSITA Data Release 1. Accurate stellar dating provides crucial information about the formation and development of planetary systems. Existing age-dating techniques are limited in terms of both the spectral type and age range they can accurately probe, and many are unreliable for stars older than 1 Gyr. Recent studies have suggested that a star's X-ray luminosity correlates strongly with stellar age and shows a steep fall-off at ages older than 1 Gyr. In this work, we present X-ray luminosity relationship values from eROSITA for four previously unassessed stars. Additionally, we reassess the X-ray luminosity/age relationship present in 24 main-sequence stars older than a gigayear. We confirm that a correlation does appear to exist between stellar age and X-ray luminosity at ages older than 1 Gyr. However, we measure a shallower slope with age than previous research for older stars, similar to what was found for younger stars. We also find evidence for significant astrophysical variability in a star's X-ray luminosity, which will likely limit the precision with which X-ray measurements can yield age estimates. We also find weak evidence for mass dependence in the X-ray luminosity/age relationship. These results suggest that although X-ray luminosity correlates with stellar age, it may not serve as a reliable standalone age indicator and is better used as part of a broader suite of age-dating methods.

Keywords: X-ray astronomy, Stellar ages, Stellar activity, Planet hosting stars
Characterizing the Host Galaxies and Delay Times of Ca-rich Gap Transients versus 91bg-like SNe and Normal Type Ia SNe. Calcium-rich gap transients are a faint, fast-evolving class of supernovae that show strong nebular Ca emission lines. Their progenitor systems are uncertain, but they are often associated with old and quiescent host galaxies. In this work, we compare the properties of the hosts of hydrogen-poor Ca-rich gap transients to the hosts of 3 other classes of supernova (SNe): normal Type Ia, 91bg-like, and Type II. We use data from the Zwicky Transient Facility Census of the Local Universe (CLU) experiment to build up our 4 SNe samples and identify the host galaxies. A combination of precomputed host properties from the CLU catalog and those derived from spectral energy distribution fitting are used to characterize each host's stellar mass, star formation rate, and specific star formation rate (sSFR). We find that the hosts of Ca-rich gap transients and 91bg-like SNe occupy a similar parameter space of mass and sSFR, and are more massive and quiescent compared to the hosts of Type Ia and Type II SNe. Additionally, we construct delay time distributions (DTDs) for our 4 samples, finding that Ca-rich gap transients and 91bg-like SNe have the longest peak delay times ∼104 Myr, compared to the peak delay times of Type Ia SNe (∼103 Myr) and Type II SNe (∼10 Myr). The similarity of host environment and DTDs for Ca-rich gap transients and 91bg-like SNe motivates further analysis of the relationship of these two transient classes.

Keywords: Galaxy stellar content, Supernovae, Star formation, Transient sources
A Bow-Shock Nebula Around the Z Camelopardalis-type Cataclysmic Variable FY Vulpeculae. We present deep images of the faint nebulosity StDr 90, which we have discovered surrounds the cataclysmic variable (CV) star FY Vulpeculae. Archival photometric and spectroscopic observations, and a new optical spectrum, confirm that FY Vul belongs to the Z Camelopardalis subclass of CVs. Our imagery, obtained by accumulating long exposures with amateur telescopes equipped with CMOS cameras, shows a prominent bow shock in the light of [O III] λ5007, collisionally excited in front of the star as it passes through a relatively dense region in the surrounding interstellar medium (ISM). FY Vul also lies near the edge of an extended faint Hα-emitting nebula, which we interpret as a "recombination wake," i.e., a Strömgren zone recombining after being photoionized by the star's ultraviolet radiation. FY Vul joins five other CVs known to be associated with optical bow shocks and off-center nebulae. All of them are characterized by luminous accretion disks, which drive fast winds into the ISM that produce the bow shocks. ∗Based in part on observations obtained with the Hobby-Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universität München, and Georg-August Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

Keywords: Stellar bow shocks, Z Camelopardalis stars, Nebulae, Nova-like variable stars, Cataclysmic variable stars
Limits of Standard Tidal Models at Quaoar: Matching Weywot's Orbit, Missing the Spin. Weywot, Quaoar's small satellite, follows a nearly circular orbit at a distance of 12.9 times Quaoar's diameter and coexists with a compact ring system. Nevertheless, Quaoar's flattening of 0.16, slow 17.7 hr rotation and Weywot's low mass are difficult to reconcile with conventional tidal-evolution theory. We assess whether standard tides can reproduce the present-day architecture of the Quaoar─Weywot system and identify the initial conditions required. Orbit-averaged integrations spanning 4.5 Gyr were carried out with two formalisms: (i) a constant phase-lag and (ii) an Andrade creep-tide framework. With the nominal Weywot mass, both tidal prescriptions converge on Weywot's observed orbital distance for a wide range of initial orbital distances and eccentricities; eccentricity is damped and present-day tidal torques are negligible, rendering the orbit quasi-stationary. Quaoar's spin, however, remains essentially unchanged from its inferred primordial period based on its present-day flattening, and does not reproduce the observed value. A match is possible only if Weywot is ≳5─10× more massive than current estimates and if its initial eccentricity is finely tuned; such scenarios are inconsistent with occultation-derived masses and imply an implausibly dense satellite. Based on the best fitting viscoelastic parameters, the most plausible composition for Quaoar is found to be a partially differentiated dwarf planet containing roughly equal masses of silicate rock and H2O-dominated warm (150─180 K) ices. Standard tidal models reproduce Weywot's semimajor axis but cannot account for Quaoar's slow 17.7 hr rotation without invoking an unrealistically massive satellite or external torques, suggesting that non-tidal processes—such as a largely primordial spin, early satellite loss, or a retrograde secondary giant impact—must have influenced Quaoar's rotational evolution.

Keywords: Tidal interaction, Dwarf planets, Asteroid satellites, Trans-Neptunian objects
Investigating the Formation of Planets Interior to In Situ Hot Jupiters. The population of hot Jupiters with adjacent planetary companions is small but growing, and inner companions appear to be a nearly ubiquitous outcome within this subset of the exoplanet census. While most hot Jupiters are believed to form via tidal migration, the presence of adjacent companions is not easily explained by this formation mechanism, requiring consideration of additional formation mechanisms such as disk migration and in situ formation. In this work, we explore the possibility of in situ formation for both hot Jupiters and their interior companions. Using numerical simulations performed with the N-body integrator REBOUND, we investigate the growth of interior companions under various assumptions about disk conditions and hot Jupiter final orbital positions. Our results show that if a sufficiently high density of planetary embryos is transported to short orbital radii, it is feasible for both hot Jupiters and their interior companions to form in situ, providing a viable explanation for a subset of observed planetary architectures.

Keywords: Planet formation, Exoplanet migration, Hot Jupiters, Exoplanets
Surface Correction Values for the Outbursts of Comet 29P/Schwassmann─Wachmann. We present a new method for calculating the surface correction, defined as the ratio of the surface area of the nucleus that was altered during the outburst to the total surface area of the cometary nucleus. The proposed approach is based on the flux-nuclear mechanism, which describes the interaction between the sublimation flux and the porous structure of the cometary nucleus. Calculations were performed for nine observed outbursts of comet 29P/Schwassmann─Wachmann, recorded between 2021 September 19 and December 28. The obtained surface correction value is in the range from 0.003% to 0.626%. The two primary factors influencing the surface correction are both the outburst amplitude and the fraction of the nucleus surface that is active during the quiet sublimation phase. For the two extreme outburst amplitudes, the ratio of the corresponding surface corrections is approximately 10, assuming constant porosity of the agglomerates responsible for scattering incident sunlight. This indicates that greater outburst amplitudes correspond to larger surface corrections. The surface correction thus serves as a physical indicator of the brightness change during cometary outbursts and reflects the combined effects of outburst amplitude, surface porosity, and pre-existing sublimation activity on the evolution of the cometary surface.

Keywords: Comet nuclei, Comets, Coma dust
Searching for Exoplanets Born Outside the Milky Way: VOYAGERS Survey Design. Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milky Way counterparts. VOYAGERS (Views Of Yore—Ancient Gaia-enceladus Exoplanet Revealing Survey) is a radial velocity (RV) search using precision spectrographs to discover exoplanets orbiting very low metallicity (−2.8 &lt; [Fe/H] ≤ −0.8) stars born in the dwarf galaxy Enceladus, which merged with the Milky Way galaxy about 10 Gyr ago. A sample of 22 candidates have been screened from a catalog of Gaia─Enceladus─Sausage (GES) members using a combination of stellar properties and reconnaissance observations from the TRES spectrograph. Precision RV measurements have been initiated using the NEID, HARPS-N, and CARMENES spectrographs. We plan to focus most upcoming observations on 10 main sequence targets. Data collection is well underway, with 778 observations on 22 candidates (385 of which are on 10 focus targets), but far from complete. This survey is designed to be sensitive to sub-Neptune mass planets with periods up to hundreds of days. We note that the RV analysis gives mass multiplied by  sin(inclination)  or the minimum mass for exoplanets. The expected survey yield is three planets, assuming that occurrence rates are similar to those in the Milky Way and taking into account the degeneracy with inclination in our yield models. Our survey is designed to detect at least one exoplanet if occurrence rates are similar to known Milky Way exoplanets or, if no exoplanets are discovered, to rule out a Milky Way-like planet population in GES with 95% confidence level.

Keywords: Exoplanet detection methods, Dwarf galaxies, Radial velocity
Slitless Spectroscopy Source Detection Using YOLO Deep Neural Network. Slitless spectroscopy eliminates the need for slits, allowing light to pass directly through a prism or grism to generate a spectral dispersion image that encompasses all celestial objects within a specified area. This technique enables highly efficient spectral acquisition. However, when processing China Space Station Telescope (CSST) slitless spectroscopy data, the unique design of its focal plane introduces a challenge: photometric and slitless spectroscopic images do not have a one-to-one correspondence. As a result, it becomes essential to first identify and count the sources in the slitless spectroscopic images before extracting spectra. To address this challenge, we employed the You Only Look Once object detection algorithm to develop a model for detecting targets in slitless spectroscopy images. This model was trained on 1560 simulated CSST slitless spectroscopic images. These simulations were generated from the CSST Cycle 6 and Cycle 9 main survey data products, representing the Galactic and nearby galaxy regions and the high galactic latitude regions, respectively. On the validation set, the model achieved a precision of 88.6% and recall of 90.4% for spectral lines, and 87.0% and 80.8% for zeroth-order images. In testing, it maintained a detection rate &gt;80% for targets brighter than 21 mag (medium-density regions) and 20 mag (low-density regions) in the Galactic and nearby galaxies regions, and &gt;70% for targets brighter than 18 mag in high galactic latitude regions.

Keywords: Astronomical techniques, Astronomy data modeling, Astronomy data analysis
Deconvolution for Large Astronomical Surveys: A Study of the Scaled Gradient Projection Method on Zwicky Transient Facility Data. Ground-based astronomical observations will continue to produce resolution-limited images due to atmospheric seeing. Deconvolution reverses such effects and thus can benefit extracted science in multifaceted ways. We apply the Scaled Gradient Projection algorithm for the single-band deconvolution of several observed images from the Zwicky Transient Facility and mainly discuss the performance on stellar sources. The method shows good photometric flux preservation, which deteriorates for fainter sources but significantly reduces flux uncertainties even for the faintest sources. Deconvolved sources have a well-defined Full-Width-at-Half-Maximum of roughly one pixel (one arcsecond for ZTF) regardless of the observed seeing. Detection after deconvolution results in catalogs with ≳99.6% completeness relative to detections in the observed images. A few observed sources that could not be detected in the deconvolved image are found near saturated sources, whereas for others, the deconvolved counterparts are detected when slightly different detection parameters are used. The deconvolution reveals new faint sources previously undetectable, which are confirmed by crossmatching with the deeper DESI Legacy DR10 and with Pan-STARRS1 through forced photometry. The method could identify examples of serendipitous potential deblends that exceeded SExtractor's deblending capabilities, with as extreme as ∆m ≍ 3 and separations as small as one arcsecond between the deblended components. Our survey-agnostic approach is better and eight times faster than Richardson─Lucy deconvolution and could be a reliable method for incorporation into survey pipelines.

Keywords: Maximum likelihood estimation, Sky surveys, Algorithms, Deconvolution
Order-by-order Modeling of Exoplanet Radial Velocity Data. Precise radial velocity (RV) measurements are a crucial tool for exoplanet discovery and characterization. Today, the majority of these measurements are derived from Echelle spectra in the optical wavelength region using cross-correlation techniques. Although for certain stars these approaches can produce RVs with sub-1 m s−1 measurement errors, for many others, we are now in a regime where instrumental precision is fundamentally below the intrinsic RV variations of the star that result from astrophysical processes that can be correlated in both time and wavelength. We explore new methods for measuring exoplanet orbital parameters that take advantage of the fact that RV data sets are fundamentally multi-wavelength. By analyzing NEID extremely precise radial velocity (EPRV) data of three known exoplanet systems, we show that fitting a single Keplerian model to multi-wavelength RVs can produce a factor of 1.5─6.8 better  Mpsini  uncertainties compared to fitting RVs that are derived from a weighted average across wavelength.

Keywords: Radial velocity, Exoplanets, Astrostatistics strategies
DiffuSRBsD: Improvement Method for Solar Radio Burst Long-tailed Detection Using Probabilistic Diffusion Generative Models. Solar radio burst (SRB) detection plays a crucial role in solar physics research and space weather warning. However, multi-class SRB detection suffers from a long-tailed distribution, where the number of samples in most classes (long-tailed classes) is extremely small, while a few classes (head classes) dominate the dataset. To address this issue, we propose a diffusion model for SRBs detection (DiffuSRBsD) model, a generative augmentation method employing diffusion model for long-tailed class enhancement. DiffuSRBsD introduces a mask-conditioned generation strategy to control SRB morphology in spectrograms and employs textual inversion to embed multiple SRB features into a unified semantic representation. Furthermore, we develop a memory structural similarity index measure, a generative image filter specifically for SRBs. Extensive experiments on a benchmark Dataset of SRBs demonstrate that DiffuSRBsD significantly improves the performance of representative detection models, achieving gains of 9.9%, 41.4%, 31.7%, and 11.8% in mAP@50 for the most long-tailed Type IV SRBs. These results validate the effectiveness of our approach and offer a novel perspective for enhancing SRB detection, providing robust data processing support for space weather prediction. The dataset and code are publicly available at https://github.com/onewangqianqian/DiffuSRBsD.git.

Keywords: Detection, Astronomy data modeling, Astronomy data analysis, Radio bursts, Solar activity
Radio Stars in the Era of New Observatories. An international conference Radio Stars in the Era of New Observatories was held at the Massachusetts Institute of Technology Haystack Observatory on 2024 April 17─19. The conference brought together more than 60 researchers from around the world, united by an interest in using radio wavelength observations to explore the physical processes that operate in stars (including the Sun), how stars evolve and interact with their environments, and the role of radio stars as probes of our Galaxy. Topics discussed at the meeting included radio emission from cool and ultracool dwarfs, extrasolar space weather, stellar masers, thermal radio emission from evolved stars, circumstellar chemistry, low frequency observations of the Sun, radio emission from hot stars, applications of very long baseline interferometry techniques to stellar astrophysics, stellar explosive events, the detection of radio stars in the latest generation of widefield sky surveys, the importance of radio stars for understanding the structure and evolution of the Milky Way, and the anticipated applications for stellar astrophysics of future radio observatories on the ground and in space. This article summarizes research topics and results featured at the conference, along with some background and contextual information. It also highlights key outstanding questions in stellar astrophysics where new insights are anticipated from the next generation of observational facilities operating at meter through submillimeter wavelengths.

Keywords: Circumstellar envelopes, Galaxy structure, Stellar activity, Stellar winds, Solar radio emission, Astrophysical masers, Variable stars, Radio astronomy, Stellar evolution