Sazuna/UAT_keywords huggingface dataset:
The Ejecta Nebula Around the Wolf–Rayet Star WR 71. We present deep Hα and [O III] images of the ejecta-rich nebulosity associated with the suspected runaway and binary Wolf–Rayet (WR) star WR 71 (HD 143414). In Hα emission, the nebula appears as a crescent shaped, broken ring of clumpy emission some  9'×13'  in angular size centered to the south and west of the WR star. At a Gaia estimated distance of 4.27 kpc, the nebula has physical dimensions of 11 × 16 pc making it one of the larger known ejecta rich WR ring nebulae. Our [O III] image also show considerable surrounding faint nebulosity much of which may be unrelated to the WR star. A comparison of the nebula's optical appearance with that seen in Wide-field Infrared Survey Explorer 22 μm data shows infrared coincidence with the nebula's brightest [O III] emission features. Deep Hα and [O III] images like those presented here suggests that new and substantially deeper imaging reconnaissance of WR stars compared to earlier surveys may lead to additional WR ring nebula detections, thereby enhancing our understanding on the frequency and formation of WR ring nebulae.

Keywords: Wolf-Rayet stars, Ejecta, Emission nebulae, Early-type emission stars
TOI-880 is an Aligned, Coplanar, Multiplanet System. Although many cases of stellar spin–orbit misalignment are known, it is usually unclear whether a single planet's orbit was tilted or if the entire protoplanetary disk was misaligned. Measuring stellar obliquities in multitransiting planetary systems helps to distinguish these possibilities. Here, we present a measurement of the sky-projected spin–orbit angle for TOI-880 c (TOI-880.01), a member of a system of three transiting planets, using the Keck Planet Finder. We found that the host star is a K-type star (Teff = 5050 ± 100 K). Planet b (TOI-880.02) has a radius of 2.19 ± 0.11R⊕ and an orbital period of 2.6 days; planet c (TOI-880.01) is a Neptune-sized planet with 4.95 ± 0.20R⊕ on a 6.4 days orbit; and planet d (TOI-880.03) has a radius of  3.40‑0.21+0.22R⊕  and a period of 14.3 days. By modeling the Rossiter–McLaughlin effect, we found the sky-projected obliquity to be  ∣λc∣=7.4‑7.2+6.8 °, consistent with a prograde, well-aligned orbit. The lack of detectable rotational modulation of the flux of the host star and a low  vsini⋆  (1.6 km s‑1) imply slow rotation and correspondingly slow nodal precession of the planetary orbits and the expectation that the system will remain in this coplanar configuration. TOI-880 joins a growing sample of well-aligned, coplanar, multitransiting systems. Additionally, TOI-880 c is a promising target for James Webb Space Telescope follow-up, with a transmission spectroscopy metric of ∼170. We could not detect clear signs of atmospheric erosion in the Hα line from TOI-880 c, as photoevaporation might have diminished for this mature planet.

Keywords: Exoplanet dynamics, Exoplanet formation, Transits, Exoplanets
An Ultraviolet Study of CO Chemistry in the Magellanic Clouds. How does molecular cloud chemistry change with metallicity? In this work, we study the relation between molecular hydrogen (H2) and carbon monoxide (CO) at 1/2 and 1/5 solar metallicity using ultraviolet absorption spectroscopy obtained as part of the UV Legacy Library of Young Stars as Essential Standards Hubble Space Telescope program. We determine CO column densities or upper limits for a sample of 50 lines of sight through the Large and Small Magellanic Clouds (LMC and SMC). 12CO is detected along eight lines of sight and 13CO is detected along two. Combining our new CO column densities with  NH2  measurements from the literature, we find that the evolution of  NCO(NH2)  from the Milky Way to the LMC and SMC is a relatively shallow function of metallicity. Taking NCO &gt; 3 × 1015 cm−2 as a threshold value above which CO emission is likely to be detectable at the distance of the Magellanic Clouds, the  log10NH2  at which a sightline has a 50% probability of having NCO above this threshold is 20.8 in the Milky Way, 20.9 in the LMC, and 21.1 in the SMC. This is an 0.3 dex change in threshold  log10NH2  over an 0.7 dex change in metallicity. We compare our measurements with  NCO(NH2)  relations from literature chemical models and find that the measured relations agree best with models in which the dynamical timescale is longer than the chemical timescale for H2 but shorter than the chemical timescale for CO.

Keywords: Interstellar molecules, Interstellar absorption, Ultraviolet spectroscopy, Interstellar medium
Metallicities of M Dwarf Planet Host Stars from Kepler, K2, and TESS Observed by APOGEE: Trends with Exoplanetary Radii and Orbital Periods. One important property in studying the exoplanet population is the host star metallicity ([M/H]). In this study, we derived stellar metallicities and oxygen abundances for 48 M dwarf stars using the near-infrared high-resolution spectra from the SDSS APOGEE survey and synthetic spectra computed in LTE. We also investigated the exoplanetary radii distribution for a larger sample of 246 exoplanets orbiting 188 M dwarf stars. The [M/H] versus [O/M] distribution obtained indicates that our sample is composed mainly of thin disk stars, which follow the behavior of the low-alpha sequence in the Milky Way thin disk. Small planets with radii smaller than 3R⊕ were found around stars with a range of metallicities (‑0.6 &lt; [M/H] &lt; +0.3), while larger planets of the sample orbit only stars with [M/H]≥ 0.0. These results indicate that while small planets can form in different environments, larger planets preferentially form in metal-rich protoplanetary disks. Exoplanets with Porb &lt; 4.3 days orbit on average more metal-rich stars than planets with longer periods. This threshold is smaller than that found for FGK stars (8–10 days) and might be related to M dwarfs having a smaller dust sublimation radius. The distribution of exoplanets with Rp &gt; 4R⊕ shows a concentration at orbital periods between 2 and 5 days, which may result from inward orbital migration. There is also a different behavior between single-detected exoplanets and planets from multiplanetary systems, with the latter being found on average around more metal-poor stars, and with planetary radii roughly up to 3 R⊕.

Keywords: M dwarf stars, Exoplanet evolution, Planet hosting stars, Metallicity, Near infrared astronomy
The HUSTLE Program: The UV to Near-IR Transmission Spectrum of the Hot Jupiter KELT-7b. The ultraviolet and optical wavelength ranges have proven to be a key addition to infrared observations of exoplanet atmospheres because they offer unique insights into the properties of clouds and hazes and are sensitive to signatures of disequilibrium chemistry. Here, we present the 0.2─0.8 μm transmission spectrum of the T eq = 2000 K Jupiter KELT-7b, acquired with Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3)/UVIS G280 as part of the HUSTLE Treasury program. We combined this new spectrum with the previously published HST WFC3/IR G141 (1.1─1.7 μm) spectrum and Spitzer photometric points at 3.6 and 4.5 μm, to reveal a generally featureless transmission spectrum between 0.2 and 1.7 μm, with a slight downward slope toward bluer wavelengths, and an asymmetric water feature in the 1.1─1.7 μm band. Retrieval models conclude that the 0.2─1.7 μm spectrum is primarily explained by a high H− abundance (∼10−5), significantly above the equilibrium chemistry prediction (∼10−12), suggesting disequilibrium in KELT-7b's upper atmosphere. Our retrievals also suggest the presence of bright inhomogeneities in the stellar surface, and tentative evidence of CO2 at the Spitzer wavelengths. We demonstrate that with the UV─optical coverage provided by WFC3 UVIS/G280, we are able to confirm the presence and constrain the abundance of H−, and obtain evidence for bright stellar inhomogeneities that would have been overlooked using infrared data alone. Observations redward of 1 μm with JWST should be able to further constrain the abundance of H−, as well as confirm the presence of CO2 inferred by the two Spitzer data points.

Keywords: Hot Jupiters, Exoplanet atmospheres, Exoplanets
Searching for Low-mass Exoplanets amid Stellar Variability with a Fixed Effects Linear Model of Line-by-line Shape Changes. The radial velocity (RV) method, also known as Doppler spectroscopy, is a powerful technique for exoplanet discovery and characterization. In recent years, progress has been made thanks to the improvements in the quality of spectra from new extreme-precision RV spectrometers. However, detecting the RV signals of Earth-like exoplanets remains challenging, as the spectroscopic signatures of low-mass planets can be obscured or confused with intrinsic stellar variability. Changes in the shapes of spectral lines across time can provide valuable information for disentangling stellar activity from true Doppler shifts caused by low-mass exoplanets. In this work, we present a fixed effects linear model to estimate RV signals that controls for changes in line shapes by aggregating information from hundreds of spectral lines. Our methodology is fast and flexible, allowing us to use cross validation to evaluate model performance on unseen data. We evaluate the model's ability to remove stellar activity using solar observations from the NEID spectrograph, as the Sun's true center-of-mass motion is precisely known. Including line shape-change covariates reduces the RV rms errors by approximately 76% (from 1.722 to 0.403 m s−1) relative to using only the line-by-line Doppler shifts. The magnitude of the residuals is significantly less than that from traditional cross-correlation function-based RV estimators and comparable to other state-of-the-art methods for mitigating stellar variability.

Keywords: The Sun, Radial velocity, Astronomy data analysis, Astrostatistics, Stellar activity, Spectroscopy, Solar activity, Exoplanet detection methods
Terrestrial Planet Formation from Two Source Reservoirs. This work describes new dynamical simulations of terrestrial planet formation. The simulations started at the protoplanetary disk stage, when planetesimals formed and accreted into protoplanets, and continued past the late stage of giant impacts. We explored the effect of different parameters, such as the initial radial distribution of planetesimals and Type-I migration of protoplanets, on the final results. In each case, a thousand simulations were completed to characterize the stochastic nature of the accretion process. In the model best able to satisfy various constraints, Mercury, Venus, and Earth accreted from planetesimals that formed early near the silicate sublimation line at ≃0.5 au and migrated by disk torques. For Venus and Earth to end up at 0.7–1 au, Type-I migration had to be directed outward, for example, as the magnetically driven winds reduced the surface gas density in the inner part of the disk. Mercury was left behind near the original ring location. We suggest that Mars and multiple Mars-sized protoplanets grew from a distinct outer source of planetesimals at 1.5–2 au. While many migrated inward to accrete onto the proto-Earth, our Mars was the lone survivor. This model explains: (1) the masses and orbits of the terrestrial planets, (2) the chemical composition of the Earth, where ∼70% and ∼30% come from reduced inner-ring and more-oxidized outer-ring materials, and (3) the isotopic differences of the Earth and Mars. It suggests that the Moon-forming impactor Theia plausibly shared a similar isotopic composition and accretion history with that of the proto-Earth.

Keywords: Cosmochemistry, Planet formation, Solar system terrestrial planets, Planetary migration, Earth-moon system
The California Legacy Survey. VI. The Fate of Activity Cycles in Sun-like Stars. We analyze the spectra of 91 solar-type G- and K-type main-sequence dwarfs in the solar neighborhood to assess activity trends with stellar properties. As a follow-on work to our studies of the decoupling of rotation from age, we use chromospheric activity time series data to probe changes in stellar activity cycles as further evidence of differences in magnetic dynamos. We present evidence that the average chromospheric activity remains nearly constant while the variation in a star's activity decreases by an order of magnitude. Measurable changes to the stellar dynamo are suggested that are not strongly correlated with the average stellar activity, but instead correlated with the amplitude of activity variations for stars beyond the age of the Sun. In contrast, while the activity cycle period is strongly correlated with effective temperature for stars aged between 2 and 4 Gyr, we find no such correlation for stars older than the Sun or otherwise low-activity stars beyond  log(RHK')  = ‑4.90. By quantifying the Ca II H and K activity variation over the timescales of stellar cycles, we suggest that age dating of mature-age solar-type stars requires knowledge of activity variability in addition to the average activity.

Keywords: Stellar rotation, Stellar chromospheres, Stellar ages, Stellar activity
An Aligned Sub-Neptune Revealed with MAROON-X and a Tendency Toward Alignment for Small Planets. We present the Rossiter─McLaughlin measurement of the sub-Neptune TOI-1759A b with MAROON-X. A joint analysis with MuSCAT3 photometry and nine additional TESS transits produces a sky-projected obliquity of ∣λ∣ = 4° ± 18°. We also derive a true obliquity of ψ = 24° ± 12° making this planet consistent with full alignment albeit to &lt;1σ. With a period of 18.85 days and an a/R* of 40, TOI-1759A b is the longest period single sub-Neptune to have a measured obliquity. It joins a growing number of smaller planets which have had this measurement made and, along with K2-25 b, is the only single, aligned sub-Neptune known to date. We also provide an overview of the emerging distribution of obliquity measurements for planets with R &lt; 8 R⊕. We find that these types of planets tend toward alignment, especially the sub-Neptunes and super-Earths, implying a dynamically cool formation history. The majority of misaligned planets in this category have 4 &lt; R ≤ 8 R⊕ and are more likely to be isolated than planets rather than in compact systems. We find this result to be significant at the 3σ level, consistent with previous studies. In addition, we conduct injection and recovery testing on available archival radial velocity data to put limits on the presence of massive companions in these systems. Current archival data is insufficient for most systems to have detected a giant planet.

Keywords: M dwarf stars, Exoplanet systems, Mini Neptunes, Exoplanet astronomy, Radial velocity, Transit photometry
Scaling K2. VIII. Short-period Sub-Neptune Occurrence Rates Peak Around Early-type M Dwarfs. We uniformly combined data from the NASA Kepler and K2 missions to compute planet occurrence rates across the entire FGK and M-dwarf stellar range. The K2 mission, driven by targets selected by guest observers, monitored nine times more M dwarfs than the Kepler mission. Combined, Kepler and K2 observed 130 short-period (P = 1–40 days) Earth to Neptune-sized candidate planets orbiting M dwarfs. K2 observed 3.5 times more of these planets than Kepler for host stars below 3700 K. Our planet occurrence rates show that short-period sub-Neptunes peak at  3750‑97+153  K and drop for cooler M dwarfs. A peak near this location was predicted by pebble accretion planet formation models and confirmed here by observations for the first time. Super-Earths continue to increase in occurrence toward cooler stars and show no clear evidence of a peak in the host star range considered here (3200–6900 K). Our observations provide critical input to further refine planet formation models. We strongly recommend further study of mid-to-late M dwarfs with TESS and soon the Nancy Grace Roman Space Telescope and PLATO to identify additional small planet trends.

Keywords: Fundamental parameters of stars, Exoplanet systems, Exoplanets
TESS Photometry and LAMOST Spectroscopy of 10 Detached Eclipsing Binaries. This study presents a thorough analysis of 10 detached eclipsing binaries that contain main-sequence stars. We have utilized a multifaceted approach, incorporating data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), TESS photometry, and broadband photometric spectral energy distributions, to determine the atmospheric parameters, radii, and masses of the component stars with high precision. The integration of these diverse data sets allows for the cross verification of results, thereby enhancing the accuracy and trustworthiness of our findings. Our investigation reveals consistent atmospheric parameters and stellar radii across the three methodologies, with exceptions like TIC 369605666 and 54759992, where the effective temperatures determined by the spectra differ from those calculated using the light-curve orbital solution. We explored possible reasons for the discrepancies in parameter estimation among the different methods for specific sources. Utilizing precise stellar parameters, determined and validated by multiple means, we compared them with PARSEC models to assess these samples' evolutionary states and infer their ages. Regarding the determination of binary ages, the components of most sources are in agreement. However, for two targets with eccentric orbits, where the component stars' ages diverge, we explored the potential causes.

Keywords: Eclipsing binary stars, Binary stars, Detached binary stars
CU-JADE: A Method for Traversing Extinction Jumps Along the Line of Sight. Although interstellar dust extinction serves as a powerful distance estimator, the solar system's location within the Galactic plane complicates distance determinations, especially for molecular clouds (MCs) at varying distances along the line of sight (LoS). The presence of complex extinction patterns along the LoS introduces degeneracies, resulting in less accurate distance measurements to overlapping MCs in crowded regions of the Galactic plane. In this study, we develop the CUSUM-based Jump-point Analysis for Distance Estimation (CU-JADE), a novel method designed to help mitigate these observational challenges. The key strengths of CU-JADE include: (1) sensitivity to detect abrupt jumps in Distance–Aλ (D–A) data sets, (2) minimal systematic errors as demonstrated on both mock and observed data, and (3) the ability to combine CUSUM analysis with multiwavelength data to improve the completeness of distance measurements for nearby gas structures, even for extinction values as low as ΔAV ≳ 0.15 mag. By combining CO survey data with a large sample of stars characterized by high-precision parallaxes and extinctions, we uncovered the multilayered molecular gas distribution in the high-latitude Cepheus region. We also determined accurate distances to MCs beyond the Cygnus Rift by analyzing the intricate structure of gas and extinction within the Galactic plane. Additionally, we constructed a full-sky 3D extinction map extending to 4 kpc, which provides critical insights into dense interstellar medium components dominated by molecular hydrogen. These results advance our understanding of the spatial distribution and physical properties of MCs across the Milky Way.

Keywords: Distance measure, Molecular clouds, Interstellar medium, Interstellar extinction
TESSELLATE: Piecing Together the Variable Sky with TESS. We present TESSELLATE, a dedicated pipeline for performing an untargeted search documenting all variable phenomena captured by the TESS space telescope. Building on the TESSreduce difference imaging pipeline, TESSELLATE extracts calibrated and reduced photometric data for every full frame image in the TESS archive. Using this data, we systematically identify transient, variable, and nonsidereal signals across timescales ranging from minutes to weeks. The high cadence and wide field of view of TESS enables us to conduct a comprehensive search of the entire sky to a depth of ∼17 mi. Based on the volumetric rates for known fast transients, we expect there to be numerous fast blue optical transients and gamma-ray burst afterglows present in the existing TESS data set. Beyond transients, TESSELLATE can also identify new variable stars and exoplanet candidates and recover known asteroids. We classify events using machine learning techniques and the work of citizen scientists via the Zooniverse Cosmic Cataclysms project. Finally, we introduce the TESSELLATE Sky Survey: a complete, open catalog of the variable sky observed by TESS.

Keywords: Gamma-ray bursts, Sky surveys, Transient sources, Time domain astronomy, Cataclysmic variable stars
Detecting Asteroids in TESS Full-frame Images Using a Gradient-based Iterative Algorithm. The shift-stacking method is commonly used to detect asteroids in astronomical multiframe image data. However, the computation required for the traditional shift-stacking method is substantial. In this study, we observed a relation between velocity hypotheses and signal intensities in the stacked images. Based on this observation, we propose a gradient-based iterative algorithm to detect asteroids. The time complexity for detecting faint moving objects can be drastically reduced by avoiding calculations throughout the entire velocity space. A series of preprocessing steps were implemented to increase the effectiveness of the algorithm. We used the Transiting Exoplanet Survey Satellite full-frame image data consisting of 128 frames and covering a 12° × 12° area to demonstrate the performance of our pipeline. Within the data, 3143 independent detections were returned, of which 2266 are correlated to known asteroids. The completeness for asteroids brighter than 20 and 21 mag is 82.7% and 71.6%, respectively, and the detectability limit using our pipeline is estimated to be a visual magnitude of 21.8.

Keywords: Detection, Algorithms, Asteroids
A Nest of Diffuse Interstellar Bands—Likely of Common Origin. Diffuse interstellar bands (DIBs) have been proposed to cluster into distinct "families" each potentially linked to a single carrier molecule. In our study, we focus on identifying such a family within the spectral range of approximately 4945─4990 Å, which encompasses a closely spaced group of diffuse bands, most of which are extremely weak. Notably, the relative intensities of these bands remain consistent across various interstellar sightlines, strongly indicating a common origin. The potential members of this "nest" of diffuse bands, include numerous weak features within the specified wavelength range, as well as moderately strong diffuse bands at 4964, 4969, 4980, and 4985 Å, and possibly some other DIBs located slightly apart, such as those at 5062 and 5418 Å.

Keywords: Interstellar absorption, Interstellar medium
The RR Lyrae Luminosity Metallicity Relation Revisited. We utilize a set of internally consistent absolute ages for a sample of ten Galactic globular clusters to determine the variation of the slope with the zero point of the MV(RR) ∼ [Fe/H] relation for RR Lyrae variables. Our formalism relies on numerical modeling of the main sequence turnoff magnitude in the V band as a function of age, [Fe/H] and [α/Fe] using two different sets of theoretical isochrones. These are then combined with the aforementioned absolute cluster ages and observed values of the magnitude difference between the main-sequence turnoff and the horizontal branch (i.e., ΔV(TO ‑ HB)) for each cluster to calculate relations between the slope and zero point of the MV(RR) ∼ [Fe/H] relation within this paradigm. Based on this analysis, our preferred relation is of the form MV(RR) = 0.20[Fe/H] + 0.81 as presented in this work.

Keywords: RR Lyrae variable stars, Pulsating variable stars