Sazuna/UAT_keywords huggingface dataset:
A New Search Pipeline for Short Gamma-Ray Bursts in Fermi/GBM Data—A 50% Increase in the Number of Detections. In this paper, we present the development and the results of a new search pipeline for short gamma-ray bursts (sGRBs) in the publicly available data from the Gamma-Ray Burst Monitor (GBM) on board the Fermi satellite. This pipeline uses rigorous statistical methods that are designed to maximize the information extracted from the Fermi/GBM detectors. Our approach differs substantially from existing search efforts in several aspects: the pipeline includes the construction of template banks, Poisson matched filtering, background estimation, background misestimation correction, automatic routines to filter contaminants, statistical estimation of the signal location, and a quantitative estimator of the signal probability of being of cosmological, terrestrial, or solar origin. Our analysis also includes operating the pipeline on "time-slid" copies of the data, which allows exact significance assessment and pastro computation, akin to the state-of-the-art gravitational-wave (GW) data analysis pipelines. Depending on the spectral properties of the bursts, our pipeline achieves a signal-to-noise ratio improvement by a factor of 2─15 over the onboard GBM triggering algorithm. This enhancement increases the detectable volume for sGRBs and results in an approximately 50% increase in sGRB detections in the 2014 GBM data set. As a further consequence of the sensitivity increase, we detect hundreds of soft gamma-ray flares of Galactic origin. This improved sensitivity enhances the chances of detecting fainter, off-axis gamma-ray bursts that would likely fall below the standard triggering thresholds. Applying this pipeline to the full GBM archive is expected to expand further the joint sGRB─GW detection volume.

Keywords: Gamma-ray bursts, Astronomy data analysis
Physical Parameters and Activity Properties of K-type Stars Based on the LAMOST Spectral Survey. K-type stars are important objects of our Galaxy. It is interesting to determine the stellar physical parameters and magnetic activity properties of K-type stars. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR10 provides more than 1 million spectra of K-type stars. We have used spectra with a signal-to-noise ratio greater than 10 as our objects in the large amount of spectral data that we have analyzed. We used the spectral subtraction method to reduce the observational spectra by utilizing the iSpec program. We have determined the chromospheric activity of K-type stars using the Hα line. Among more than 1.33 million spectra associated with about 1.06 million stars, there are a total of 150,000 stellar spectra that have excess chromospheric activity. For K stars with rotation periods above 6.20 days, the chromospheric activity decreases rapidly as the period increases. We calculated the solar Rossby number  ROSun=1.85 , and conclude that when the Rossby number  RO/ROSun&lt;0.07 ,  RHα'  remains stable; when  RO/ROSun≥0.07 ,  RHα'  decreases as  RO/ROSun  increases. By crossmatching with the Gaia survey, we also determined their distances and found that the active fraction decreases as the distance above the Galactic disk increases.

Keywords: Stellar chromospheres, K stars, Stellar activity
Discovering Cataclysmic Variables from the Rubin Observatory LSST. The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will provide a windfall of new transients and variable sources. Here we have performed mock observation simulations to understand LSST's expected detection rates for cataclysmic variables (CVs) with known large-amplitude variations. Under the thin-disk approximation for the distribution of CVs in our Galaxy, we found that only 20% of WZ Sge─type dwarf novae systems, representing the most energetic disk-driven outbursts in CVs, will be detected during outbursts by the LSST. Given their large amplitude (7─9 mag), only those brighter than 17.5 mag at outburst maximum are expected to have an r-band quiescence counterpart in individual scans. Thanks to the planned cadence of the LSST toward the Galactic center, ≍70% of the simulated outbursts will be detected twice or more on the discovery night, and two-thirds will be observed in different bands. CVs of the polar class, which display luminosity changes up to 4 mag, can be unbiasedly recovered to 22.5 mag with more than 100 detections over 10 yr of the LSST operation. Finally, we attempt to characterize the detection rate of micronovae bursts, and find that about 2.6% of the simulated sample will be observed as a ≥0.4 mag amplitude and ≤1 day duration spike in the long-term light curve. Overall, our results consolidate LSST's capability to studying time-domain phenomena in CVs, and inform on how to plan and organize follow-up observation strategies on transients discovered by LSST.

Keywords: Optical astronomy, Dwarf novae, Transient detection, Magnetic variable stars, Cataclysmic variable stars
Distinguishing Tidal Disruption Events and Changing-look Active Galactic Nuclei via Variation in Mid-infrared Color. In this work, we propose that the time variation in mid-infrared (MIR) color is a promising probe to distinguish between MIR outbursts induced by tidal disruption events (TDEs) and changing-look active galactic nuclei (CLAGNs). With an optically selected sample containing TDEs, ambiguous nuclear transients (ANTs), and CLAGNs, we studied the variation in MIR color (W1 − W2) after subtracting the quiescent fluxes using NEOWISE-R data. The MIR color of TDEs and ANTs turns red faster than CLAGNs during the rising phase, as the color variation rate (CVR) of TDEs and ANTs is generally ≳0.2 mag yr−1, whereas that of CLAGNs is generally ≲0.3 mag yr−1. This may be caused by the difference between the ultraviolet light curves of TDEs/ANTs and CLAGNs, or be related to no or weak underlying AGN in TDEs/ANTs. In addition, TDEs have a redder color than ANTs at the earliest phase. Based on CVR, we selected high-probability TDE, ANT, and CLAGN candidates from MIR outbursts in samples of Jiang et al. and Masterson et al. We found that both samples are mixtures of TDEs/ANTs and CLAGNs. For MIR outbursts whose hosts are not Seyfert galaxies, we estimated that ∼50%─80% are TDEs and inferred a rate of infrared TDEs of 1.5─2.8 × 10−5 galaxy−1 yr−1, comparable with that of optical TDEs; the rest are CLAGNs, suggesting the presence of weak AGNs that cannot be identified using common diagnoses. Our work opens a new door for future classification of infrared-selected transients based on only photometric data.

Keywords: Infrared astronomy, Transient sources, High energy astrophysics
FAST Observations of the Microstructure in Interpulse Pulsars. In this study, we investigate the microstructure properties of four pulsars (PSRs J0953+0755 (B0950+08), J0627+0706, J0826+2637 (B0823+26), and J1946+1805 (B1944+17)) using the Five-hundred-meter Aperture Spherical radio Telescope, with particular emphasis on identifying microstructure within the interpulse (IP). Through the application of autocorrelation function analysis and fast Fourier transform techniques, we have systematically examined the periodicity of microstructure in these pulsars. Our findings represent the first successful detection of microstructure within the IP. Furthermore, we conducted a comprehensive statistical analysis comparing the characteristic timescales (τμ) and the characteristic periods Pμ of quasiperiodic microstructure between the main pulse (MP) and the IP, and our results indicate that the τμ and Pμ of microstructure across components appear consistent within measurement errors for PSR J0627+0706, but the microstructure in the IP is relatively smaller than that in the MP for PSR J0953+0755. Furthermore, the relationship between Pμ of microstructure and the rotation period in neutron star populations was reconfirmed: Pμ (ms) = (1.337 ± 0.114) × P(s)(1.063±0.038).

Keywords: Pulsars
The Molecular Inventory of TMC-1 with GOTHAM Observations. Spectral line surveys of the Taurus Molecular Cloud-1 (TMC-1) have led to the detection of more than 100 new molecular species, making it the most prolific source of interstellar molecular discoveries. These wide-band, high-sensitivity line surveys have been enabled by advances in telescope and receiver technology, particularly at centimeter and millimeter wavelengths. In this work, we present a statistical analysis of the molecular inventory of TMC-1 as probed by the GOTHAM large program survey from 3.9 to 36.4 GHz. To fully unlock the potential of the ∼29 GHz spectral bandwidth, we developed an automated pipeline for data reduction and calibration. We applied a Bayesian approach with Markov Chain Monte Carlo fitting to the calibrated spectra and constrained column densities for 102 molecular species detected in TMC-1, including 75 main isotopic species, 20 carbon-13 substituted species, and seven deuterium-substituted species. This list of the detected gas-phase molecules is populated by unsaturated hydrocarbons, in stark contrast to the oxygen-rich organics found in sublimated ices around protostars. Of note, 10 individual aromatic molecules were identified in the GOTHAM observations, contributing 0.011% of the gas-phase carbon budget probed by detected molecules when including CO and 6% when excluding CO. This work provides a reference set of observed gas-phase molecular abundances for interstellar clouds, offering a new benchmark for astrochemical theoretical models.

Keywords: Interstellar molecules, Spectral line identification, Astrochemistry, Single-dish antennas, Dark interstellar clouds
The SPHEREx Sky Simulator: Science Data Modeling for the First All-sky Near-infrared Spectral Survey. We describe the SPHEREx Sky Simulator (henceforth the Simulator), a software tool designed to model science data for NASA's SPHEREx mission that will carry out a series of all-sky spectrophotometric surveys at ∼6″ spatial resolution in 102 spectral channels spanning 0.75─5 μm. The Simulator software implements models for astrophysical emission, instrument characteristics, and survey strategy to generate realistic infrared sky scenes as they will be observed by SPHEREx. The simulated data include a variety of realistic noise and systematic effects that are estimated using up-to-date astrophysical measurements and information from prelaunch instrument characterization campaigns. Through the preflight mission phases, the Simulator has been critical in predicting the impact of various effects on SPHEREx science performance and has played an important role in guiding the development of the SPHEREx data analysis pipeline. In this paper, we describe the Simulator architecture, preflight instrument, and sky models, and summarize high-level predictions from the Simulator, including a prelaunch prediction for the 5σ point source sensitivity of SPHEREx, which we estimate to be mAB 18.5─19 from 0.75 to 3.8 μm and mAB 16.6─18 from 3.8 to 5 μm, with the sensitivity limited by the zodiacal light background at all wavelengths. In the future, on-orbit data will be used to improve the Simulator, which will form the basis of a variety of forward-modeling tools that will be used to model myriad instrumental and astrophysical processes to characterize their systematic effects on our final data products and analyses.

Keywords: Sky surveys, Infrared spectroscopy, Astronomical instrumentation, Space telescopes, Astronomical simulations
Joint Inference of Population, Cosmology, and Neutron Star Equation of State from Gravitational Waves of Dark Binary Neutron Stars. Gravitational waves (GWs) from binary neutron stars (BNSs) are expected to be accompanied by electromagnetic (EM) emissions, which help identify the host galaxy. Since GWs directly measure their luminosity distances, joint GW─EM observations from BNSs help with the study of cosmology, particularly the Hubble constant, unaffected by cosmic distance ladder systematics. However, detecting the EM emissions is not always possible. Additionally, the tidal deformability of neutron stars (NSs), combined with the knowledge of the NS equation of state (EoS), can break the degeneracy between mass parameters and redshift, allowing for the inference of the Hubble constant. While several studies have aimed to infer the Hubble constant using dark BNSs (without EM counterparts), none have consistently combined the uncertainties of population, cosmology, and NS EoS within a Bayesian framework. In this study, we propose a novel Bayesian analysis to jointly constrain the NS EoS, population, and cosmological parameters using a population of dark BNSs detected through GW observations. We demonstrate the statistical robustness of our method using 50 simulated BNS events following Gaussian and double Gaussian mass distributions, detected by Advanced LIGO and Advanced Virgo detectors operating at O5 sensitivity. We show that such measurements can constrain the Hubble constant with a precision of ≲35% (90% credible interval). This level of precision is unattainable without incorporating NS EoS, especially when observing BNS mergers without EM counterpart information. We also report the Hubble constant measurements obtained from a more realistic set of five simulated BNS events.

Keywords: Neutron stars, Cosmology, Binary stars, Bayesian statistics, Gravitational wave sources, Gravitational wave astronomy, Gravitational waves, Compact objects
Detection of Kink Oscillations in Solar Coronal Loops by a Convolutional Neural Network─Long Short-term Memory Neural Network. A hybrid machine learning model, which combines a shallow convolutional neural network and a long short-term memory (CNN-LSTM) network, has been developed to automate the detection of kink oscillations in coronal plasma loops within large volumes of high-cadence sequences of imaging data. The network was trained on a set of 10,000 synthetic data cubes designed to mimic sequences of coronal images, achieving an accuracy greater than 98% on this synthetic data set. The model was then applied to detect kink oscillations in real data cubes of coronal active regions observed with Solar Dynamics Observatory/Atmospheric Imaging Assembly in the 171 Å channel. This data set consisted of 50 samples with visually detected kink oscillations and 128 samples without. Each sample covered an area of 260 × 260 pixels in the spatial domain and a duration of 30 minutes with a 12 s cadence in the time domain. Both off-limb and on-disk regions of interest were used. The data were preprocessed by median filtering in the time domain, and Gaussian smoothing and contrast-limited adaptive histogram equalization in the spatial domain. In the real data set, the performance of the model was 83.7%. The model is fully available in open access. We regard the CNN-LSTM model developed as a first step toward creating robust tools for routine solar coronal data mining in the context of coronal oscillation studies.

Keywords: Solar coronal loops, Solar coronal waves, Neural networks
Evolution of Stellar Activity and Habitable Zone. I. Ultraviolet Emission of Dwarfs in Open Clusters and Field Stars. Near-ultraviolet (NUV) radiation from dwarf stars plays a critical role in shaping the habitability of planetary systems, yet its long-term evolution across different spectral types remains poorly investigated. Based on Galaxy Evolution Explorer NUV observations, we study the evolution of stellar NUV emission for a sample of 386,500 A- to M-type dwarfs spanning ages from 3 Myr to 10 Gyr, drawn from both open clusters and the field. The normalized NUV emission (fNUV/fJ) is used to trace the evolutionary trends. Our results reveal distinct evolutionary pathways after considering the distance completeness: A and early-F dwarfs show a weak decline in NUV emission during the main-sequence phase; late-F to G dwarfs exhibit a clear decrease, consistent with continuous spin-down driven by magnetic braking; late-K and M dwarfs undergo a rapid decline in NUV emission when they evolve from young stellar objects to main-sequence stars. Furthermore, we construct the evolutionary tracks of the stellar ultraviolet habitable zone (UHZ). By comparing stellar circumstellar habitable zone and UHZ, we find that G- and K-type stars offer the most stable overlap between thermal and UV habitability over long-term evolution.

Keywords: Ultraviolet photometry, Habitable zone, Catalogs, Stellar activity
Validating DIRECD: Statistical Evaluation of Coronal Mass Ejection Direction Estimates from Coronal Dimmings. Coronal mass ejections (CMEs) are among the most energetic phenomena in our solar system, with significant implications for space weather. Understanding their early dynamics remains challenging due to observational limitations in the low corona. We present a statistical evaluation of the Dimming InfeRred Estimation of CME Direction (DIRECD) method, which provides a novel approach to determining initial CME propagation directions using coronal dimmings. We analyze 33 coronal-dimming events well observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly and validate our DIRECD results with 3D reconstructions from the graduated cylindrical shell (GCS) model. We find generally good agreement between the DIRECD-derived inclinations and the GCS model. In the meridional plane (north─south direction), the mean difference in inclinations is 0 .° 3 ± 7 .° 8. In the equatorial plane (east─west direction), the mean difference is −2 .° 9 ± 18 .° 9. In 3D, the inclinations show a mean difference of 1 .° 2 ± 10 .° 4. We further visually compare our method by projecting the DIRECD cones onto Large Angle and Spectrometric Coronagraph/C2 observations, and verify the model's ability to capture both the primary CME structure and associated secondary dimming regions. This work establishes DIRECD as a powerful, observationally grounded technique for determining the initial CME direction, offering new insights that complement existing reconstruction methods. The technique's unique capability to determine early CME direction in the low corona using coronal dimmings observed in extreme ultraviolet images makes it particularly valuable for improving space weather forecasting models.

Keywords: Solar corona, Stellar coronal dimming, Solar coronal mass ejections, Active sun
Three-step Acceleration of the Radiation Belt Relativistic Electrons by Interplanetary Shocks. Inward radial diffusion driven by ultra-low-frequency (ULF) waves is one of the dominant acceleration mechanisms of relativistic (&gt;1.0 MeV) electrons in the Earth's outer radiation belt. However, the role of interplanetary (IP) shocks in the ULF-wave-driven acceleration remains inadequately understood. Here we report the rapid acceleration events caused by IP shocks on 2013 January 17 and 18. Based on simultaneous observations, we propose a three-step physical process for the acceleration of relativistic electrons. Our results indicate that IP shocks not only excite ULF waves and provide source populations for the ULF-wave-driven acceleration, but also contribute to establishing a significant phase-space density radial gradient of relativistic electrons in the outer boundary. These can lead to rapid enhancements of relativistic electrons in the outer radiation belt.

Keywords: Space plasmas, Interplanetary shocks, Van Allen radiation belts, Space weather, Solar-planetary interactions, Solar-terrestrial interactions
Voyager VLISM Electron Density Dataset. This paper is a companion to an electron density dataset submitted to both the Planetary Data System and the Space Physics Data Facility for measurements by the Voyager Plasma Wave Science (PWS) instrument in the very local interstellar medium. It describes the methodology of determining the electron density from two features in the PWS electric field spectrum: the frequency of electron plasma oscillations and the frequency of the quasi-thermal noise line. We provide estimates of the uncertainty in the resulting electron densities. Further, the format of the dataset is described.

Keywords: Astrospheres, Interstellar medium wind, Astrosphere interstellar medium interactions, Interstellar plasma
Observational Properties of β Cephei Stars: 88 New Samples Discovered Based on TESS and Gaia Data. We present a systematic investigation of β Cephei (BCEP) stars by integrating photometric data from the Transiting Exoplanet Survey Satellite (TESS) with astrometric parameters from Gaia Data Release 3. Utilizing TESS's short-cadence (SC) and full-frame image (FFI) photometry, along with Gaia parallaxes and temperatures derived from the Extended Stellar Parametrizer for Hot Stars pipeline, we identify 88 new BCEP stars and candidates—85 from SC data and three from SPOC-processed FFI observations. These targets exhibit visual magnitudes ranging from 8.0 to 12.0 mag, parallaxes between 0.11 and 1.74 mas, effective temperatures of 18,000─30,000 K, and luminosities from 1500─38,000 L⊙, consistent with previously cataloged BCEP populations, thereby demonstrating the robustness of our classification criteria. Key findings include: (1) a significant detection disparity between SC and FFI datasets, with 30% of SC targets exceeding 18,000 K compared to only 0.7% in FFI, reflecting observational biases toward high-luminosity, hotter stars in SC data; (2) four samples near the red edge of the theoretical instability strip, exhibiting sparse pulsation modes that are important samples for testing pulsation models under low-mass, low-temperature conditions; and (3) spatial clustering within the Galactic disk (∣b∣ &lt; 20°), with two high-latitude outliers likely representing runaway stars ejected from disk environments. Our analysis underscores the critical role of space-based photometry in detecting low-amplitude pulsators and the transformative potential of multisurvey integration in the era of time-domain astronomy. These results provide new samples to constrain stellar pulsation theories of massive stars and to study Galactic dynamics.

Keywords: Massive stars, Pulsating variable stars
The Atlas of Massive Galactic O-type Spectral Standards (MaGOSS) in the Near-infrared. Spectral morphological analysis is crucial for determining the fundamental physical properties of stars, particularly for rare and astrophysically important O-type stars. Due to heavy interstellar extinction in the optical range, most Galactic O stars remain obscured, making near-infrared (NIR) spectroscopy the only viable approach to achieve a reasonably complete sample of this stellar population and to extend current classification schemes. Our aim is to build a comprehensive spectral classification atlas of O-type stars in the NIR, providing robust morphological criteria to support and enhance future research on massive stars in heavily obscured environments. To this end, we obtained high-resolution (R ∼ 4000─11,000) NIR spectra for the majority of standard stars from the latest installment of the Galactic O-Star Spectroscopic Survey, using spectrographs at Gemini North and Las Campanas Observatory to ensure broad spectral coverage and high data quality. We present an atlas featuring spectral sequences for nine dwarfs (O4 to B0), nine giants (O3.5 to O9.5), and 20 supergiants (O2 to B0), systematically organised and accompanied by clear morphological criteria for subtype classification across the Y, J, H, and K bands (0.930─1.115, 1.160─1.290, 1.460─1.760, and 2.050─2.200 μm, respectively). This atlas provides a unified framework for reliable NIR classification of O-type stars and paves the way for detailed studies of massive stars in regions heavily affected by extinction.

Keywords: Massive stars, Early-type stars, Star atlases