Sazuna/UAT_keywords huggingface dataset:
The Green Chile Project. I. A New Catalog of Low-redshift Extended Emission-line Nebulae. Extended emission-line nebulae (EELN) around galaxies allow us to study their host galaxies and their surrounding environments. EELN can provide insights into the physical properties of the extended gas and, when powered by active galactic nuclei (AGN), they can constrain the ionization history of the central engine as well. Of interest is a sample of low-redshift EELN powered by AGN at z ∼ 0.3 that were discovered in the Sloan Digital Sky Survey (SDSS) through color selection. Colloquially called "Green Beans," due to strong, spatially extended [O III]λ5007 emission dominating the r-band flux, they have been shown to be low-redshift counterparts to higher-redshift Lyα nebulae. However, only 17 Green Bean EELN are known to exist at z ∼ 0.3, and the original color selection was subsequently found to be biased in terms of host galaxy properties. In order to mitigate these biases and expand the known sample, we have developed a new, physically motivated selection approach, based on simulated EELN at z ∼ 0.3, with well-defined physical properties ([O III]λ5007 rest-frame equivalent width and continuum spectral slope). With this improved selection approach, we have generated a new sample of 165 EELN candidates: the "Green Chile" catalog. Of the 13 candidates with existing SDSS/Baryon Oscillation Spectroscopic Survey spectra, we confirm that five are EELN with [O III]λ5007 equivalent widths &gt;200 Å and emission-line ratios indicative of AGN powering.

Keywords: Active galaxies, Emission line galaxies, Active galactic nuclei, Galaxy evolution, Extragalactic astronomy
Signatures of Atmospheric Mass Loss and Planet Migration in the Time Evolution of Short-period Transiting Exoplanets. Comparative studies of young and old exoplanet populations offer a glimpse into how planets may form and evolve with time. We present an occurrence rate study of short-period (&lt;12 days) planets between 1.8 and 10 R⊕ around 1374 FGK stars in nearby (200 pc) young clusters (&lt;1 Gyr), utilizing data from the Transiting Exoplanet Survey Satellite mission. These planets represent a population closer to their primordial state. We find that the occurrence rate of young planets is higher ( %) compared to the Gyr-old population observed by Kepler ( %). Dividing our sample into bins of young (10–100 Myr) and intermediate (100 Myr–1 Gyr) ages, we also find that the occurrence distribution in orbital period remains unchanged, while the distribution in planet radius changes with time. Specifically, the radius distribution steepens with age, indicative of a larger planet population shrinking due to the atmospheric thermal cooling and mass loss. We also find evidence for an increase (1.9σ) in occurrence after 100 Myr, possibly due to tidal migration driving planets inside of 12 days. While evidence suggests that postdisk migration and atmospheric mass loss shape the population of short-period planets, more detections of young planets are needed to improve statistical comparisons with older planets. Detecting long-period young planets and planets &lt;1.8 R⊕ will help us understand these processes better. Additionally, studying young planetary atmospheres provides insights into planet formation and the efficiency of atmospheric mass-loss mechanisms on the evolution of planetary systems.

Keywords: Exoplanet migration, Hot Neptunes, Young star clusters, Exoplanet systems, Exoplanet formation, Exoplanet evolution, Transit photometry
JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO<SUB>2</SUB> in the HR 8799 and 51 Eri Exoplanets' Atmospheres. High-contrast observations with JWST can reveal key composition and vertical mixing dependent absorption features in the spectra of directly imaged planets across the 3─5 μm wavelength range. We present novel coronagraphic images of the HR 8799 and 51 Eri planetary systems using the NIRCam Long Wavelength Bar in an offset "narrow" position. These observations have revealed the four known gas giant planets encircling HR 8799, even at spatial separations challenging for a 6.5 m telescope in the mid-infrared, including the first ever detection of HR 8799 e at 4.6 μm. The chosen filters constrain the strength of CO, CH4, and CO2 absorption in each planet's photosphere. The planets display a diversity of 3─5 μm colors that could be due to differences in composition and ultimately be used to trace their formation history. They also show stronger CO2 absorption than expected from solar metallicity models, indicating that they are metal enriched. We detected 51 Eri b at 4.1 μm and not at longer wavelengths, which, given the planet's temperature, is indicative of out-of-equilibrium carbon chemistry and an enhanced metallicity. Updated orbits fit to the new measurement of 51 Eri b validate previous studies that find a preference for high eccentricities ( ), which likely indicates some dynamical processing in the system's past. These results present an exciting opportunity to model the atmospheres and formation histories of these planets in more detail in the near future, and are complementary to future higher-resolution, continuum-subtracted JWST spectroscopy.

Keywords: High contrast techniques, Coronagraphic imaging, Extrasolar gaseous planets, Exoplanets
Fast Catalog Matching for Improved Posteriors via Constrained Clustering. We propose a novel approximate method for the probabilistic catalog matching problem that provides better solutions than previously used heuristics and scales well for large real-world applications. We also improve probabilistic catalog matching by including a simple but powerful prior and optimizing the posterior instead of just the likelihood as in previous formulations. Our new approach uses constrained clustering, specifically COP-KMeans, to provide near-optimal solutions in a fraction of the time of previous methods. We empirically demonstrate our constrained clustering's efficacy through simulations and data from the Hubble Source Catalog.

Keywords: Bayes factor, Clustering, Photometry, Astronomical methods, Catalogs
Analysis of the Gaia Data Release 3 Parallax Bias at Bright Magnitudes. The combination of visual and spectroscopic orbits in binary systems enables precise distance measurements without additional assumptions, making them ideal for examining the parallax zero-point offset (PZPO) at bright magnitudes (G &lt; 13) in Gaia. We compiled 249 orbital parallaxes from 246 binary systems and used Markov chain Monte Carlo simulations to exclude binaries where orbital motion significantly impacts parallaxes. After removing systems with substantial parallax errors, large discrepancies between orbital and Gaia parallaxes, and selecting systems with orbital periods under 100 days, a final sample of 44 binaries was retained.The weighted mean PZPO for this sample is −38.9 ± 10.3 μas, compared to −58.0 ± 10.1 μas for the remaining systems, suggesting that orbital motion significantly affects parallax measurements. These formal uncertainties of the PZPO appear to be underestimated by a factor of approximately 2.0. For bright stars with independent trigonometric parallaxes from Very Long Baseline Interferometry and Hubble Space Telescope, the weighted mean PZPOs are −14.8 ± 10.6 and −31.9 ± 14.1 μas, respectively. Stars with G ≤ 8 exhibit a more pronounced parallax bias, with some targets showing unusually large deviations, likely due to systematic calibration errors in Gaia for bright stars. The orbital parallaxes dataset compiled in this work serves as a vital resource for validating parallaxes in future Gaia data releases.

Keywords: Parallax, Gaia, Astrometry
An Obliquity Measurement of the Hot Neptune TOI-1694b. We present spectral observations of the multiplanet host TOI-1694 during the transit of TOI-1694b, a 26.1 M⊕ hot Neptune with a 3.77 day orbit. By analyzing radial velocities obtained from the Keck Planet Finder, we modeled the Rossiter─McLaughlin effect and constrained the sky-projected obliquity to  , which is strong evidence for a nearly aligned orbit. TOI-1694b is one of fewer than 10 small planets accompanied by confirmed outer giant planets for which the obliquity has been measured. We consider the significance of the outer planet TOI-1694c, a Jupiter-mass planet with a 1 yr orbit, and its potential role in influencing the orbit of TOI-1694b to its current state. Incorporating our measurement, we discuss the bifurcation in hot Neptune obliquities and present evidence for an independent polar population. The observed polar planets nearly ubiquitously have periods of ≤6 days and mass ratios of 10−4. Early perturbations by outer companions from resonance crossings in the disk-dispersal stage provide the most compelling explanation for this population. Systems which lack the necessary configuration will retain their primordial obliquity, since hot Neptunes lack the angular momentum needed to realign their hosts on relevant timescales.

Keywords: Exoplanet dynamics, Exoplanets
3D MC. II. X-Ray Echoes Reveal a Clumpy Molecular Cloud in the CMZ. X-ray observations collected over the past decades have revealed a strongly variable X-ray signal within the Milky Way's Galactic center, interpreted as X-ray echoes from its supermassive black hole, Sgr A*. These echoes are traced by the strong Fe Kα fluorescent line at 6.4 keV, the intensity of which is proportional to the density of the illuminated molecular gas. Over time, the echo scans through molecular clouds (MCs) in our Galactic center, revealing their 3D structure and highlighting their densest parts. While previous studies have utilized spectral line Doppler shifts along with kinematic models to constrain the geometry of the Central Molecular Zone (CMZ) or to study the structure of individual clouds, these methods have limitations, particularly in the turbulent region of the CMZ. We use archival Chandra X-ray data to construct one of the first 3D representations of one prominent MC, the Stone cloud, located at (ℓ = 0 068, b = –0 076) at a distance of ∼20 pc from Sgr A* in projection. Using the Chandra X-ray Observatory, we followed the X-ray echo in this cloud from 2008 to 2017. We combine these data with 1.3 mm dust continuum emission observed with the Submillimeter Array (SMA) and the Herschel Space Observatory to reconstruct the 3D structure of the cloud and estimate the column densities for each year's observed slice. The analysis of the X-ray echoes, along with velocities from SMA molecular line data, indicates that the structure of the Stone cloud can be described as a very diffuse background with multiple dense clumps throughout.

Keywords: X-ray astronomy, Galactic center, Molecular clouds
Chemical Abundance Gradients in Open Clusters from the Gaia/LAMOST Sample. Based on a large and homogeneous sample of 299 open clusters (OCs) from Gaia DR3 and large sky area multiobject fiber spectroscopic telescope DR11, we studied the abundance gradients of the α-elements Mg and Si, and the iron-peak elements Fe and Ni to explore the chemical evolution of the Galactic disk. A noticeable downward trend in metallicities, with a slope of −0.048 ± 0.008 dex kpc−1, is observed as the Galactocentric distance (RGC) increases. The abundance gradients of both α-elements and iron-peak elements in our sample exhibit no apparent symmetry between the regions above and below the Galactic plane. The metallicities in the sample, scaled to the Galactocentric distance of the Sun, show an age-related increase of 0.017 ± 0.016 dex Gyr−1. [El/H] exhibits distinct downward trends toward the outer Galaxy. In the inner Galaxy, younger OCs have lower [El/H] values than older clusters, whereas in the outer Galaxy, this trend is reversed. For OCs aged between 0.5 and 2.5 Gyr, the number of clusters migrating inward is approximately equal to those migrating outward. However, the outward migration distances are notably greater than the inward ones. Analyzing the impact of kinematic orbits on the radial and vertical abundance gradients of the four elements, we found that kinematic orbits exert minimal influence on the radial abundance gradients for both α-elements and iron-peak elements. In contrast, they have a pronounced effect on the vertical abundance gradients.

Keywords: Open star clusters, Galaxy abundances, Galaxy evolution
Image Preprocessing Framework for Time-domain Astronomy in the Artificial Intelligence Era. The rapid advancement of image analysis methods in time-domain astronomy, particularly those leveraging artificial intelligence (AI) algorithms, has highlighted efficient image preprocessing as a critical bottleneck affecting algorithm performance. Image preprocessing, which involves standardizing images for training or deployment of various AI algorithms, encompasses essential steps such as image quality evaluation, alignment, stacking, background extraction, gray-scale transformation, cropping, source detection, astrometry, and photometry. Historically, these algorithms were developed independently by different research groups, primarily based on central processing unit (CPU) architecture for small-scale data processing. This paper introduces a novel framework for image preprocessing that integrates key algorithms specifically modified for graphics processing unit architecture, enabling large-scale image preprocessing for different algorithms. To prepare for the new algorithm design paradigm in the AI era, we have implemented two operational modes in the framework for different application scenarios: eager mode and pipeline mode. The Eager mode facilitates real-time feedback and flexible adjustments, which could be used for parameter tuning and algorithm development. The pipeline mode is primarily designed for large-scale data processing, which could be used for training or deploying of AI models. We have tested the performance of our framework using simulated and real observation images. Results demonstrate that our framework significantly enhances image preprocessing speed while maintaining accuracy levels comparable to CPU-based algorithms. To promote accessibility and ease of use, a Docker version of our framework is available for download in the PaperData Repository powered by China-VO, compatible with various AI algorithms developed for time-domain astronomy research.

Keywords: GPU computing, Astronomical techniques, Time domain astronomy
Utilizing Machine Learning to Predict Host Stars and the Key Elemental Abundances of Small Planets. Stars and their associated planets originate from the same cloud of gas and dust, making a star's elemental composition a valuable indicator for indirectly studying planetary compositions. While the connection between a star's iron (Fe) abundance and the presence of giant exoplanets is established, the relationship with small planets remains unclear. The elements Mg, Si, and Fe are important in forming small planets. Employing machine learning algorithms like XGBoost, trained on the abundances (e.g., the Hypatia Catalog) of known exoplanet-hosting stars (NASA Exoplanet Archive), allows us to determine significant "features" (abundances or molar ratios) that may indicate the presence of small planets. We test on three groups of exoplanets: (1) all small, RP &lt; 3.5 R⊕; (2) sub-Neptunes, 2.0 R⊕ &lt; RP &lt; 3.5 R⊕; and (3) super-Earths, 1.0 R⊕ &lt; RP&lt; 2.0 R⊕—each subdivided into seven ensembles to test different combinations of features. We created a list of stars with ≥90% probability of hosting small planets across all ensembles and experiments ("overlap stars"). We found abundance trends for stars hosting small planets, possibly indicating star─planet chemical interplay during formation. We also found that Na and V are key features regardless of planetary radii. We expect our results to underscore the importance of elements in exoplanet formation and machine learning's role in target selection for future NASA missions, e.g., the James Webb Space Telescope, the Nancy Grace Roman Space Telescope, and the Habitable Worlds Observatory—all of which are aimed at small-planet detection.

Keywords: Exoplanets, Stellar abundances, Super Earths, Computational methods, Mini Neptunes
Multibeam SETI Observations Toward Nearby M Dwarfs with FAST. The search for extraterrestrial intelligence (SETI) targeted searches aim to observe specific areas and objects to find possible technosignatures. Many SETI researches have focused on nearby stars and their planets in recent years. In this paper, we report a targeted SETI observations using the most sensitive L-band Five-hundred-meter Aperture Spherical radio Telescope toward three nearby M dwarfs, all of which have been discovered exoplanet candidates. The minimum equivalent isotropic radiant power of the lower limit from the three sources we can detect is 6.19 × 108 W, which is well within the reach of current human technology. Applying the multibeam coincidence matching blind search mode, we search for narrowband drifting signals across 1.05–1.45 GHz in each of the two orthogonal linear polarization directions. An unusual signal at 1312.50 MHz detected from the observation toward AD Leo originally piqued our interest. However, we finally eliminate the possibility of an extraterrestrial origin based on much evidence, such as the polarization, frequency, and beam coverage characteristics.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Astrobiology, Exoplanets
The Orbital Period of the Long-period and Colliding-wind Binary WR 146 from Radio Interferometry of the Shock Cone. We report the first measurement of the orbital period of a long-period colliding-wind-binary system Wolf–Rayet (WR) 146, derived by tracing the rotational morphology of its wind-colliding region (WCR) and the relative orientation of the two binary components. This result is based on our imaging observations using the very-long-baseline array (VLBA) and the European Very-long-baseline-interferometry Network (EVN), combined with archival data from VLBA, EVN, the Very Large Array, the enhanced Multi-Element Radio-Linked Interferometer Network arrays, and optical images from the Hubble Space Telescope. We evaluated two methods for determining the binary's orbital period based on the images of the WCR: (i) fitting the shock cone of the WCR and (ii) stacking images using the cross-correlation function. Using these techniques, we find orbital period estimates of 810  yr from method I and 1120  yr from method II, both of which support a long orbital period of approximately 1000 yr. Furthermore, we analyzed archival spectral data of WR 146 to estimate the stellar wind velocities of the binary components, finding no significant orbital phase lag between the binary orientation and the WCR rotation. We also estimate the range of the binary's mass using the currently measured parameters.

Keywords: Orbits, Very long baseline interferometry, Radio continuum emission, Stellar winds, Non-thermal radiation sources, Wolf-Rayet stars, Visual binary stars, Radio interferometry
Census of Blue Straggler Stars in Distant Open Clusters and Maximum Fractional Mass Excess of Open Cluster Blue Straggler Stars. We identified blue straggler stars (BSSs) in 53 open clusters utilizing data from Gaia DR3. Most of these clusters are situated in the outer regions of the Galactic disk, encompassing structures such as the warp and the Outer arm. We analyzed their astrometric parameters and determined that 48 of them demonstrate high reliability in the radial density profile. Furthermore, through manual isochrone fitting and visual inspection, we confirmed 119 BSS candidates and identified 328 additional possible candidates within these clusters. Our results contribute to a 46% increase in the sample size of BSSs in open clusters for regions of the Galactic disk where Rgc &gt; 12 kpc. We observed that the new samples are fainter compared to those identified in the past. Additionally, we investigated the maximum fractional mass excess (Me) of the BSSs in open clusters, including previously published BSS samples. Our findings indicate a strong correlation between the capability to produce highest-Me BSSs and the mass of their host clusters. This observation appears to reinforce a fundamental principle whereby an increase in the mass of a star cluster correlates with a higher likelihood of stellar mergers. In contrast, we observe minimal correlation between maximum-Me and the cluster age. Among clusters containing BSSs, younger clusters (0.5–1 Gyr) display a scarcity of high-Me BSSs. This scarcity may be attributed to the absence of more massive clusters within this age range.

Keywords: Blue straggler stars, Open star clusters
Identify Main-sequence Binaries from the Chinese Space Station Telescope Survey with Machine Learning. II. Based on Gaia and GALEX. The statistical characteristics of double main-sequence (MS) binaries are essential for investigating star formation, binary evolution, and population synthesis. Our previous study proposed a machine learning-based method to identify MS binaries from MS single stars using mock data from the Chinese Space Station Telescope (CSST). We further utilized detection efficiencies and an empirical mass ratio distribution to estimate the binary fraction within the sample. To further validate the effectiveness of this method, we conducted a more realistic sample simulation, incorporating additional factors such as metallicity, extinction, and photometric errors from CSST simulations. The detection efficiency for binaries with mass ratios between 0.2 and 0.7 reached over 80%. We performed a detailed observational validation using the data selected from the Gaia Sky Survey and Galaxy Evolution Explorer. The detection efficiency for MS binaries in the observed sample was 65%. The binary fraction can be inferred with high precision for a set of observed samples, based on accurate empirical mass ratio distribution.

Keywords: Binary stars
Clouds and Hazes in GJ 1214 b's Metal-rich Atmosphere. The sub-Neptune GJ 1214 b has an infamously flat transmission spectrum, likely due to thick aerosols in its atmosphere. A recent JWST/MIRI spectroscopic phase curve of GJ 1214 b added to this picture, suggesting a highly reflective and metal-rich atmosphere. Using a 3D general circulation model with both photochemical hazes and condensate clouds, we characterize how different aerosol types affect the atmospheric structure of GJ 1214 b and manifest in its spectroscopic phase curve. Additionally, we reanalyze the original GJ 1214 b JWST phase curve. The reanalysis shows a hotter nightside, similar dayside temperature, and a lower, but still elevated, Bond albedo (0.42 ± 0.11) in comparison to the original results. We find that a scenario with both clouds and hazes is most consistent with the JWST phase curve. Reflective clouds or hazes are needed to explain the large Bond albedo, and hazes or a supersolar metallicity help account for the several hundred kelvin day─night temperature difference measured by the phase curve.

Keywords: Exoplanet astronomy, Exoplanet atmospheric composition , Exoplanet atmospheric dynamics, Exoplanet atmospheres