Sazuna/UAT_keywords huggingface dataset:
Landscape of Coronal X-Ray Variability and Cycles. Coronal (1–10 MK) X-rays display dramatic variability over the Sun's iconic 11 yr magnetic dynamo cycle: already a factor of 4 in the soft 0.1–2.4 keV "ROSAT band," soaring to more than 100 at harder energies (&gt;10 keV). The high-energy variations impact heliospheric space weather (SW); presumably likewise for host-star analogs. In an effort to better document long-term coronal variability and X-ray cycles of other stars, measurements of 19 late-type F–M dwarfs and subgiants were obtained from archives of the three contemporary long-lived X-ray observatories: Chandra, XMM-Newton, and Swift. The X-ray event lists were time-filtered to suppress transients like flares and telemetry dropouts. A novel scheme, based on empirical coronal models, harmonized flux conversions across the different instruments. The Sun was included based on high-energy irradiance time series. Results generally confirmed previous findings: high-contrast, decadal-class X-ray modulations were found exclusively at low-to-medium LX/LBOL; higher X-ray intensity stars displayed lower-amplitude, faster variations, if cycling at all; whereas the highest activity classes showed stable ("saturated") long-term X-ray trends, but punctuated by persistent flaring. In addition, several variants of "dynamo diagrams" are presented to illustrate possible correlations among key parameters, such as rotation period and cycle duration. Early versions of such diagrams had displayed what appeared to be clear trends, although additional observations in recent years have tended to downplay the previous relationships. The diverse X-ray behaviors hold implications for stellar SW, as well as posing tough challenges for dynamo theory.

Keywords: Solar cycle, Solar dynamo, Solar x-ray emission, Single x-ray stars
Adaptive Detection of Fast-moving Celestial Objects Using a Mixture-of-experts and Physical-inspired Neural Network. Fast-moving celestial objects are characterized by velocities across the celestial sphere that significantly differ from the motions of background stars. In observational images, these objects exhibit distinct shapes, contrasting with the typical appearances of stars. Depending on the observational method employed, these celestial entities may be designated as near-Earth objects or asteroids. Historically, fast-moving celestial objects have been observed using ground-based telescopes, where the relative stability of stars and Earth facilitated effective image differencing techniques alongside traditional fast-moving celestial object detection and classification algorithms. However, the growing prevalence of space-based telescopes, along with their diverse observational modes, produces images with different properties, rendering conventional methods less effective. This paper presents a novel algorithm for detecting fast-moving celestial objects within star fields. Our approach enhances state-of-the-art fast-moving celestial object detection neural networks by transforming them into physical-inspired neural networks. These neural networks leverage the point-spread function of the telescope and the specific observational mode as prior information; they can directly identify fast-moving celestial objects within star fields without requiring additional training, thereby addressing the limitations of traditional techniques. Additionally, all neural networks are integrated using the mixture-of-experts technique, forming a comprehensive fast-moving celestial object detection algorithm. We have evaluated our algorithm using simulated observational data that mimic various observations carried out by space-based telescope scenarios and real observation images. Results demonstrate that our method effectively detects fast-moving celestial objects across different observational modes and telescope configurations.

Keywords: CCD photometry, Convolutional neural networks, Wide-field telescopes
Stellar Population and Energy Feedback in the Supergiant Shell LMC 1. Supergiant shells (SGSs) are the largest interstellar structures in galaxies and inject hot enriched gas into galactic halos. We have studied SGS LMC 1 to determine quantitatively whether stellar energy feedback is adequate to power the formation of an SGS. The Gaia EDR3 photometric data of the OB association LH15 inside SGS LMC 1 are used to construct color─magnitude diagrams, and stellar evolutionary tracks and isochrones are used to assess stellar masses and ages. The observed present-day mass function is compared with the Salpter initial mass function to estimate the number of massive stars that have exploded as supernovae. Their total stellar wind mechanical energy and supernova explosion energy input amounts to (57 ± 12) × 1051 erg. For the gas components of SGS LMC 1, ATCA+Parkes H I data are used to determine the total mass and kinetic energy in the H I shell, MCELS Hα image is used to determine the ionized gas mass and kinetic energy, adopting the H I expansion velocity, and ROSAT X-ray observations are used to estimate the thermal energy in the SGS interior. The sum of the kinetic and thermal energies in the three layers is estimated to be (59 ± 5) × 1051 erg. Thus, the stellar energy feedback from LH15 appears adequate to power the formation of SGS LMC 1. The radial age gradient in LH15 and the young stellar objects along the outer periphery indicate a progression of star formation, which might be a crucial factor for an SGS to grow to its large size.

Keywords: OB associations, Large Magellanic Cloud, Interstellar medium, Magellanic Clouds, Superbubbles
A Neutral Hydrogen Absorption Study of Cold Gas in the Outskirts of the Magellanic Clouds Using the GASKAP-H I Survey. Cold neutral hydrogen (H I) is a crucial precursor for molecular gas formation and can be studied via H I absorption. This study investigates H I absorption in low column density regions of the Small and Large Magellanic Clouds (SMC and LMC) using the Galactic-ASKAP H I (GASKAP-H I) survey, conducted by the Australian Square Kilometer Array Pathfinder (ASKAP). We select 10 SMC directions in the outer regions and 18 LMC directions, with four in the outskirts and 14 within the main disk. Using the radiative transfer method, we decompose the emission and absorption spectra into individual cold neutral medium (CNM) and warm neutral medium (WNM) components. In the SMC, we find H I peak optical depths of 0.09─1.16, spin temperatures of ∼20─50 K, and CNM fractions of 1%─11%. In the LMC, optical depths range from 0.03─3.55, spin temperatures from ∼10─100 K, and CNM fractions from 1%─100%. The SMC's low CNM fractions likely result from its low metallicity and large LOS depth. Additionally, the SMC's outskirts show lower CNM fractions than the main body, potentially due to increased CNM evaporation influenced by the hot Magellanic Corona. Shell motions dominate the kinematics of the majority of CNM clouds in this study and likely supply cold H I to the Magellanic Stream. In the LMC, high CNM fraction clouds are found near supergiant shells, where thermal instability induced by stellar feedback promotes WNM-to-CNM transition. Although no carbon monoxide has been detected, enhanced dust shielding in these areas helps maintain the cold H I.

Keywords: Interstellar absorption, Magellanic Clouds, Interstellar atomic gas
Evolution of Massive Red Galaxies in Clusters from z = 1.0 to z = 0.3. A critical issue in studying the evolution of galaxy clusters is to find ways that enable meaningful comparisons of clusters observed at different redshifts, as well as in various stages of their growth. Studies in the past have typically suffered from uncertainties in cluster mass estimates due to the scatter between cluster observables and mass. Here we propose a novel and general approach that uses the probability distribution function of an observable–cluster mass relation, together with dark matter halo merger trees extracted from numerical simulations, such that one can trace the evolution in a self-contained fashion, for clusters chosen to lie in a specified range in mass and redshift. This method, when applied to clusters of different mass ranges, further allows one to examine the evolution of various observable-cluster mass scaling relations. We illustrate the potential of this method by studying the stellar mass content of red cluster member galaxies, as well as the growth of brightest cluster galaxies, from z = 1.0 to z = 0.3, using a large optically detected cluster sample from the Subaru Hyper Suprime-Cam Survey, finding good agreement with previous studies.

Keywords: Galaxy clusters, Elliptical galaxies, Galaxy evolution, Scaling relations
HST Transmission Spectra of the Hot Neptune HD 219666 b: Detection of Water and the Challenge of Constraining Both Water and Methane. Although Neptunian-sized (2─5 R⊕) planets appear to be extremely common in the Galaxy, many mysteries remain about their overall nature. To date, only 11 Neptunian-sized planets have had their atmospheres spectroscopically characterized, and these observations hint at interesting diversity within this class of planets. Much of our understanding of these worlds and others derive from transmission spectroscopy with the Hubble Space Telescope's Wide Field Camera 3 (HST/WFC3). One key outcome of HST/WFC3 observations has been the consistent detection of water but no methane in Neptunian atmospheres, though recent James Webb Space Telescope (JWST) observations are potentially starting to overturn this "missing methane" paradigm. In this work, we present the transmission spectrum of the hot Neptune HD 219666 b from 1.1 to 1.6 μm from two transit observations using HST/WFC3 G141. Our fiducial atmospheric retrieval detects water at ∼3σ in HD 219666 b's atmosphere and prefers no contribution from methane, similar to these previous observations of other planets. Motivated by recent detections of methane in Neptunian atmospheres by JWST, we explore additional models and find that a methane-only scenario could adequately fit the data, though it is not preferred and likely unphysical. We discuss the impact of this methane detection challenge on our understanding of planetary atmospheres based on HST/WFC3 observations alone, and where JWST observations offer a solution.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheres
JWST/NIRCam Coronagraphic Search for Hidden Planets in the HD 163296 Protoplanetary Disk. HD 163296 is a Herbig Ae/Be star with multiple signposts of ongoing planet formation on its disk, such as prominent rings and gaps, as well as kinematic features as identified by previous Atacama Large Millimeter/submillimeter Array (ALMA) observations. We carried out JWST/NIRCam coronagraphic imaging using the F410M and F200W NIRCam filters, with the goal of detecting the emission from the putative young planets in this system. Our F410M observations did not detect the putative planets at the predicted locations of the ALMA velocity kinks, but they did detect a point-like source candidate at a separation of   and a position angle of   that is unlikely a background star because of the measured flux in the F410M filter and the detection limit in the F200W filter. These data achieved unprecedented contrast levels at ∼4 μm at stellocentric separations  . This allowed us to derive stringent constraints at the outer velocity kink (ΔF410M = 15.2 mag) on the mass of the putative planet with or without a circumplanetary disk, and considering different possible initial entropies for the planet.

Keywords: Exoplanets, Coronagraphic imaging, James Webb Space Telescope, Protoplanetary disks, Planet formation
Four Planets Found through Microlensing Events Involving Faint Source Stars. To conduct a comprehensive demographic study of microlensing planets, it is essential to detect all planetary signals that exceed a predefined threshold through a detailed analysis of survey data. We reanalyzed previous data from the Korea Microlensing Telescope Network survey to search for weak planetary signals in lensing events involving faint source stars. For events with potential short-term anomalies identified in the initial search, we validated the signals using rereduced data and conducted detailed modeling of the anomalous events. This process led to the discovery of four planetary events: KMT-2017-BLG-2197, KMT-2022-BLG-1790, KMT-2022-BLG-2076, and KMT-2023-BLG-2209. For all these events, the modeling resulted in two solutions due to the well-known inner─outer degeneracy. The estimated masses of the planets and their hosts are approximately (Mp/MJ, Mh/M⊙) ∼ (0.36, 7.9) for KMT-2017-BLG-2197L, ∼(0.6, 1.7) for KMT-2022-BLG-1790L, ∼(0.67, 0.9) for KMT-2022-BLG-2076L, and ∼(0.73, 0.8) for KMT-2023-BLG-2209L. The planetary systems KMT-2017-BLG-2197L and KMT-2022-BLG-1790L are likely located in the Galactic bulge, while KMT-2022-BLG-2076L and KMT-2023-BLG-2209L are more likely situated in the disk.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection
A Decentralized Framework for Radio-interferometric Image Reconstruction. The advent of large aperture arrays, such as the ones currently under construction for the SKA project, allows for observing the Universe in the radio-spectrum at unprecedented resolution and sensitivity. To process the enormous amounts of data produced by these telescopes, scalable software pipelines are required. This paper helps address this by proposing a framework that allows for decentralized radio-interferometric image reconstruction, parallelizing by spatial frequency. This is achieved by creating pseudo-full-resolution problems for each node by using the local visibilities together with previous major cycle reconstructed images from the other nodes. We apply the proposed framework to both multiscale CLEAN and sparsity regularized convex reconstruction and compare them to their serial counterparts across four different data sets of varying properties in the context of two visibility partitions. We found that the parallelization framework allows for significantly improved reconstruction times for images of similar quality. This was especially the case for our larger data sets where we were able to achieve close to the optimal 2× speedup.

Keywords: Computational methods, Radio interferometry, Distributed computing, Astronomy image processing
Cooling Process of the High-mass Young Stellar Object G24.33+0.14 Following an Accretion Burst. The high-mass young stellar object G24.33+0.14 (G24), has recently been observed to undergo an accretion burst since 2019 September, lasting approximately two years. By utilizing 1.3 mm observational data from the NOrthern Extended Millimeter Array in 2020 March and the Atacama Large Millimeter/submillimeter Array in 2019 September, we have examined the physical environment changes in gas and dust within G24 region during the decay phase of the accretion burst. Following the burst, the continuum emission in the inner core region of G24 diminished by approximately 20%, while the emission in the outer region exhibited an increase by a factor of ∼30%. This pattern indicates that the heat wave, triggered by the accretion burst, radiated outward from the core's interior to its periphery over the half-year period, with a calculated propagation speed of 0.08–0.38 times the speed of light. Moreover, the methanol emission intensity in this area has experienced a notable decline, with the rate of flux reduction correlating positively with the energy of the upper energy states. This, in conjunction with the analysis of methanol molecular line rotation temperature diagrams for different emitting regions, further substantiates that the core region of G24 cooled down, contrasted with the persistent heating in the outer region following the burst.

Keywords: Interstellar line emission, Young stellar objects, Star formation, Stellar accretion, Radio continuum emission
Distributions and Physical Properties of Molecular Clouds in the G24 Region of the Milky Way. We report the spatial distribution and physical characteristics of molecular clouds in the G24 region, which is located near the intersection of the Milky Way's Galactic bar with the Norma arm and the 3 kpc arm. Utilizing molecular line data from the Milky Way Imaging Scroll Painting project, including 12CO, 13CO and C18O, along with our own observations of the HCO+ line using the Purple Mountain Observatory 13.7 m telescope, we reveal the complex architecture of molecular clouds in the G24 region. Seven giant molecular clouds, each with a mass exceeding 104 M⊙ and a typical H2 column density of 1021 cm−2, have been identified through observations of CO and its isotopes. The conversion factor XCO for the G24 region is estimated to be 8.25 × 1019 cm−2 (K km s−1)−1, aligning with the typical values observed in other regions. Adopting the GaussClumps algorithm, we identify a total of 257, 201, and 110 clumps in 12CO, 13CO and C18O within the G24 region, respectively. The derived physical properties (including effective radius, mass, and virial parameter) indicate that the majority of these clumps are gravitationally bound, with a subset possessing the potential to form massive stars. Examination of gas infall activities within these clumps further suggests ongoing massive star formation. The complex physical and kinematic environment, shaped by the G24 region's unique location within the Milky Way, has limited the clear detection of gas outflows.

Keywords: Interstellar molecules, Star formation, Molecular clouds, CO line emission
Tidally Heated Sub-Neptunes, Refined Planetary Compositions, and Confirmation of a Third Planet in the TOI-1266 System. TOI-1266 is a benchmark system of two temperate (&lt;450 K) sub-Neptune-sized planets orbiting a nearby M dwarf exhibiting a rare inverted architecture with a larger interior planet. In this study, we characterize transit timing variations (TTVs) in the TOI-1266 system using high-precision ground-based follow-up and new TESS data. We confirm the presence of a third exterior nontransiting planet, TOI-1266 d (P = 32.5 days, Md = 3.68 ), and combine the TTVs with archival radial velocity measurements to improve our knowledge of the planetary masses and radii. We find that, consistent with previous studies, TOI-1266 b (Rb = 2.52 ± 0.08 R⊕, Mb = 4.46 ± 0.69 M⊕) has a low bulk density requiring the presence of a hydrogen-rich envelope, while TOI-1266 c (Rc = 1.98 ± 0.10 R⊕, Mc = 3.17 ± 0.76 M⊕) has a higher bulk density that can be matched by either a hydrogen-rich or water-rich envelope. Our new dynamical model reveals that this system is arranged in a rare configuration with the inner and outer planets located near the 3:1 period ratio with a nonresonant planet in between them. Our dynamical fits indicate that the inner and outer planet have significantly nonzero eccentricities ( ), suggesting that TOI-1266 b may have an inflated envelope due to tidal heating. Finally, we explore the corresponding implications for the formation and long-term evolution of the system, which contains two of the most favorable cool (&lt;500 K) sub-Neptunes for atmospheric characterization with JWST.

Keywords: Exoplanet dynamics, M dwarf stars, Transits, Mini Neptunes, Exoplanet tides, Transit timing variation method, Radial velocity
Vintage NPOI: New and Updated Angular Diameters for 145 Stars. We present new or updated angular diameters, physical radii, and effective temperatures for 145 stars from the Navy Precision Optical Interferometer (NPOI) data archive. We used data from 1996 to late 2021, and we describe the differences between early and late data, which hinge upon an update of the beam combiner in 2002. We came across several subcategories of stars of interest: 13 of our stars are promising targets for the Habitable World Observatory and therefore require as much study as possible, and 14 more are asteroseismic targets and have stellar masses after we combined our radii and effective temperatures with frequencies of maximum oscillation power values from the literature. In addition to this, many of the stars here show measurements to the first null in the visibility curve and beyond, which is the gateway to determining second-order effects such as direct measurements of limb darkening. Finally, we consider the stars in the larger context of previous NPOI measurements and find the majority (75%) of the angular diameters in the overall NPOI sample have uncertainties of 2% or less.

Keywords: Fundamental parameters of stars, Stellar astronomy, Optical interferometry, High angular resolution
Asymmetry and Dynamical Constraints in Two-limbs Retrieval of WASP-39 b Inferring from JWST Data. Transmission spectroscopy has provided unprecedented insight into the makeup of exoplanet atmospheres. A transmission spectrum contains contributions from a planet's morning and evening limbs, which can differ in temperature, composition, and aerosol properties due to atmospheric circulation. While high-resolution ground-based observations have identified limb asymmetry in several ultrahot/hot exoplanets, space-based studies of limb asymmetry are still in their early stages. The prevalence of limb asymmetry across a broad range of exoplanets remains largely unexplored. We conduct a comparative analysis of retrievals on transmission spectra, including traditional one-dimensional (1D) approaches and four 2D models that account for limb asymmetry. Two of these 2D models include our newly proposed dynamical constraints derived from shallow-water simulations to provide physically-motivated temperature differences between limbs. Our analysis of WASP-39 b using JWST observations and previous combined data sets (HST, VLT, and Spitzer) strongly favors 2D retrievals over traditional 1D approaches, confirming significant limb asymmetry in this hot Jupiter. Within our 2D framework, unconstrained models recover larger temperature contrasts than dynamically-constrained models, with improved fits to specific spectral features, although Bayesian evidence cannot definitively distinguish between these 2D approaches. Our results support the presence of homogeneous C/O in both the morning and evening atmospheres, but with temperature differences leading to variations in clouds and hazes. Using this treatment, we can study a larger sample of hot Jupiters to gain insights into atmospheric limb asymmetries on these planets.

Keywords: Exoplanet atmospheres
Systematic Reanalysis of KMTNet Microlensing Events. II. Two New Planets in Giant-source Events. In this work, we continue to apply the updated KMTNet tender-love care photometric pipeline to historical microlensing events. We apply the pipeline to a subsample of events from the KMTNet database, which we refer to as the giant source sample. Leveraging the improved photometric data, we conduct a systematic search for anomalies within this sample. The search successfully uncovers four new planet-like anomalies and recovers two previously known planetary signals. After detailed analysis, two of the newly discovered anomalies are confirmed as clear planets: KMT-2019-BLG-0578 and KMT-2021-BLG-0736. Their planet-to-host mass ratios are q ∼ 4 × 10‑3 and q ∼ 1 × 10‑4, respectively. Another event, OGLE-2018-BLG-0421 (KMT-2018-BLG-0831), remains ambiguous. Both a stellar companion and a giant planet in the lens system could potentially explain the observed anomaly. The anomaly signal of the last event, MOA-2022-BLG-038 (KMT-2022-BLG-2342), is attributed to an extra source star. Within this sample, our procedure doubles the number of confirmed planets, demonstrating a significant enhancement in the survey sensitivity.

Keywords: Gravitational microlensing exoplanet detection, Exoplanets, Light curves, Photometry, Gravitational microlensing