Sazuna/UAT_keywords huggingface dataset:
BALNet: Deep-learning-based Detection and Measurement of Broad Absorption Lines in Quasar Spectra. Broad absorption line (BAL) quasars serve as critical probes for understanding outflows from active galactic nuclei, black hole accretion, and cosmic evolution. To address the limitations of manual classification in large-scale spectroscopic surveys—where the number of quasar spectra is growing exponentially—we propose BALNet, a deep learning approach consisting of a one-dimensional convolutional neural network and bidirectional long short-term memory networks to automatically detect BAL troughs in quasar spectra. BALNet enables both the identification of BAL quasars and the measurement of their BAL troughs. We construct a simulated dataset for training and testing by combining non-BAL quasar spectra and BAL troughs, both derived from Sloan Digital Sky Survey (SDSS) DR16 observations. Experimental results in the testing set show that: (1) BAL trough detection achieves 83.0% completeness, 90.7% purity, and an F1-score of 86.7%; (2) BAL quasar classification achieves 90.8% completeness and 94.4% purity; (3) the predicted BAL velocities agree closely with simulated ground-truth labels, confirming BALNet's robustness and accuracy. When applied to the SDSS DR16 data within the redshift range 1.5 &lt; z &lt; 5.7, at least one BAL trough is detected in 20.4% of spectra. Notably, more than a quarter of these are newly identified sources with significant absorption, 8.8% correspond to redshifted systems, and some narrow/weak absorption features were missed. BALNet greatly improves the efficiency of large-scale BAL trough detection and enables more effective scientific analysis of quasar spectra.

Keywords: Neural networks, Broad-absorption line quasar, Quasars, Active galaxies, Astronomy data analysis
Optimizing Long-term Variability of Active Galactic Nucleus Light Curves. I. A Case Study with ZTF Observations in the EGS Field. Optical variability is a key observational probe for studying the accretion dynamics and central engine physics of active galactic nuclei (AGNs). The quality and completeness of light curves have a direct impact on variability studies, particularly for faint AGNs and high-redshift AGNs. To improve the quality of long-term light curves for AGNs, we bin and stack multiepoch images balancing the image depths and temporal resolution. As a case study, we apply this method to Zwicky Transient Facility (ZTF) observations in the Extended Groth Strip (EGS) field, where the overlapping region covers an area of about 370 arcmin2 and includes g-band and r-band data taken from 2018 March to 2024 December. The coadded images are approximately 2.0─2.5 mag deeper than the ZTF single-epoch images. With coadded images, we construct light curves for 73 AGNs in the EGS field. Compared to the traditional ZTF light curves, our light curves maintain consistent long-term variability trends but with higher photometric precision. Furthermore, this method can help detect AGNs with weak variability, which are missed from the traditional ZTF data due to the noisy light curves or being below the detection limit in ZTF's single-epoch exposure. Among the 73 AGNs, the majority exhibit a bluer-when-brighter trend on long-term timescales, which is consistent with previous studies. This work offers insights for optimizing AGN light curves in both current and upcoming all-sky time-domain surveys.

Keywords: Light curves, Active galactic nuclei, Time domain astronomy
Stellar Characterization, Magnesium Abundances, and Chromospheric Activity Analysis of Stars with Confirmed Exoplanets from the K2 Mission. We present a homogeneous spectroscopic analysis of confirmed Kepler's extended mission (K2) exoplanet-hosting stars, comprising 301 targets with high-resolution optical spectra from HIRES and TRES taken from ExoFOP. We derived effective temperatures, surface gravities, and iron and magnesium abundances in local thermodynamic equilibrium by measuring the equivalent widths of Fe I, Fe II, and Mg I lines. Three estimates of stellar masses and radii were obtained via the Stefan─Boltzmann and isochrone methods using the codes PARAM and isochrones. These were used to derive exoplanetary radii reaching internal precisions of 2.5%, 2.6%, and 6.6%, respectively, and the radius gap was consistently detected near 1.9R⊕. We measured chromospheric activity from the Ca II H and K and Hα lines. Within the low-activity range ( logR'HK&lt;−4.75 ), stellar activity appears to decrease with increasing planetary radius from super-Earths, sub-Neptunes, sub-Saturns, into the Jupiter regime. According to the [Mg/Fe] measurements, most of our K2 planet hosts belong to the Galactic thin disk, but our sample has a population from the thick disk (high-alpha sequence). Most stars show consistent chemodynamical behavior. We find that the [Mg/Fe] ratios are indistinguishable between systems containing large or small exoplanets, as well as single- or multi-exoplanetary systems. Both the [Fe/H] and [Mg/H] distributions reveal that stars hosting large planets are more iron and magnesium enhanced than those having only small planets, further confirming the link between stellar abundances and exoplanetary size, but no significant differences are found between the single- versus multi-exoplanetary systems.

Keywords: Parallax, Fundamental parameters of stars, Exoplanet systems, Chemical abundances, Stellar activity, Spectroscopy
HELIOS: A Visualization Tool to Decipher the Locations and Dynamical Properties of Expanding Small Magnetic Flux Ropes in the Corona. On 2024 December 24, Parker Solar Probe made its closest approach to the Sun, reaching a 9.86 R⊙ heliocentric distance and capturing high-resolution observations of the solar corona. During this and other perihelia, the Wide-field Imager for Solar Probe (WISPR) imaged numerous small "blobs" propagating near the heliospheric current sheet (HCS). In this study, we analyze five such features observed during encounters 20 and 22 and introduce Helio-Environment Localization and Interpretation of OutflowS (HELIOS), a new visualization tool. HELIOS projects the 3D HCS geometry, derived from potential field extrapolations, on the WISPR images to provide the magnetic context for the observations. We compare the HELIOS output with a tracking technique to constrain the 3D position, speed, and acceleration of each blob. The blobs exhibit speeds ranging from 100 to 510 km s−1 and accelerations of 3─21 m s−2. The HELIOS-based localization validates the independent fitting method with an accuracy ranging from 1° to 13°, with a mean of 7°. All blobs exhibit non-self-similar accelerating expansion, likely driven by internal magnetic pressure. Some blobs show strong growth, while others display acceleration following initially weak expansion rates. HELIOS offers a powerful and versatile means to visualize and interpret the scene in WISPR and validate other analysis techniques.

Keywords: Solar magnetic reconnection, Heliosphere, Solar magnetic fields, Solar corona, Active solar corona
Artificial-intelligence-based Reconstruction of Solar Farside Vector Magnetograms from Multispacecraft Extreme-ultraviolet Data. In this study, we generate full-disk vector magnetic field data of the solar farside, as viewed from the Solar Terrestrial Relations Observatory-Ahead (STEREO-A), Solar Terrestrial Relations Observatory-Behind (STEREO-B), and Solar Orbiter (SolO), using a deep learning model based on the Pix2PixCC architecture. Our model takes extreme-ultraviolet (EUV) 304 and 171 Å images, together with reference magnetic field data from a surface flux transport (SFT) model, as inputs. To train and evaluate the model, we use EUV images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly and SFT-predicted magnetic field data from one solar rotation earlier as inputs, and we use vector magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI) as targets. For frontside test datasets covering Solar Cycles 24 and 25, our model successfully generates all three vector magnetic field components consistent with those from SDO/HMI, showing improved performance compared with previous studies. We then generate vector magnetic field data by applying the trained model to EUV observations from STEREO-A and SolO. For the first time, we compare the artificial intelligence (AI)-generated results with corresponding SDO/HMI data obtained when STEREO-A and SolO were near inferior conjunction with SDO in 2023 and 2022, respectively. We also track active-region magnetic fields and derive vector magnetic parameters using AI-generated farside data from STEREO-A, STEREO-B, and SolO, along with frontside SDO/HMI data. These results demonstrate the potential for continuous monitoring of solar vector magnetic fields and derived parameters from the farside to the frontside using AI-generated and SDO/HMI data.

Keywords: The Sun, Convolutional neural networks, Astronomy data analysis, Solar magnetic fields
Mining Young Stellar Objects in unTimely: Probing Variability and Physical Properties. We present a comprehensive analysis of variability in young stellar objects (YSOs) using a decade-long mid-infrared photometric dataset from the unTimely catalog. With its enhanced sensitivity and extended temporal coverage compared to previous surveys like NEOWISE, the catalog enables the detection of subtle variability patterns and long-term brightness fluctuations in YSOs. We characterize their variability using 12 statistical features and identify 17,795 variable YSOs in the W2 band. Through spectral energy distribution fitting, key physical properties such as mass, age, and luminosity are derived, revealing evolutionary trends. The YSOs are classified into six types of variability: linear (0.4%), curved (16.2%), periodic (2.0%), burst (3.0%), drop (1.0%), and irregular (42.9%), with 15.7% exhibiting combined secular and irregular behaviors. The extended observational baseline significantly improves the detection of stochastic phenomena (e.g., bursts and drops) and complex light-curve morphologies. Our analysis confirms that the mass─luminosity relation of our sample is broadly consistent with Padova and Trieste Stellar Evolution Code pre-main-sequence isochrones; only a small number of low-mass objects deviate at &gt;3σ, likely reflecting measurement and modeling uncertainties. Combined with the observed correlation between variability types and evolutionary stages, these results advance our understanding of the mechanisms driving the observed brightness changes.

Keywords: Light curve classification , Stellar properties, Light curves, Young stellar objects, Pre-main sequence stars, Stellar physics, Time domain astronomy, Time series analysis
A Catalog of 45,206 Hα Emission-line Stars from LAMOST MRS DR7. Stars that exhibit prominent emission lines in their spectra are referred to as emission-line stars, encompassing a wide range of stellar types and indicative of intriguing physical properties. The Large Sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) has released millions of spectra from its Medium-Resolution Survey (MRS). A small fraction of these spectra exhibit emission lines, yet they remain undiscovered and unanalyzed due to being buried in the vast dataset. We have developed a method based on derivative spectroscopy, which provides a novel approach for detecting and identifying emission-line stars by extracting signals from complex backgrounds and estimating spectral line profiles. Applying this method to the Hα spectral line profiles from the LAMOST-MRS Data Release 7, we compiled a catalog of emission-line stars using the second- and third-derivative spectra for automated peak detection. This approach also facilitates the classification of Hα emission-line morphologies through a simplified scheme. The catalog comprises 56,649 spectra with relatively prominent Hα emission lines from 45,206 unique stars, with each emission-line component accompanied by approximate estimates of its wavelength, amplitude, and width. All Hα spectral lines were classified into three morphological classes under a unified classification scheme: single emission peak (83.0%), double emission peaks (5.6%), and P Cygni-type profiles (11.5%), which encompass both P Cygni and inverse P Cygni features. Through cross-referencing with SIMBAD, 39,497 stars represent new emission-line sources discovered in our research.

Keywords: Stellar spectral lines, Classification systems, Emission line stars, Catalogs
H I-detected Dwarf Galaxies in the FASHI Survey: Insights from Single- and Double-peaked Emission-line Samples. We present a sample of low H I mass (MH I &lt; 108 M⊙) dwarf galaxies detected by The FAST All Sky H I Survey (FASHI) project. Due to the faint and irregular morphology of these galaxies, the default photometry is often inaccurate. Therefore, we utilized The Dark Energy Camera Legacy Survey data to perform careful photometric measurements, and find that the low H I mass galaxies have similar stellar mass densities to dwarf elliptical galaxies. Compared to other dwarf galaxy populations, the H I-selected dwarfs exhibit higher stellar mass densities than ultradiffuse galaxies, and similar densities to H I-selected low-surface-brightness galaxies, albeit with lower stellar masses, suggesting a possible evolutionary connection among these populations. By classifying the galaxies according to their H I spectral-line profiles, we show that the double-peaked sources conform closely to the Tully─Fisher relation, whereas the single-peaked sources follow the Faber─Jackson relation but with large scatter. This indicates that the single-peaked systems are likely dispersion dominated and that the relationship between stellar mass and halo mass in such systems may remain consistent across both low- and high-mass regimes. These findings suggest that H I-selected dwarf galaxies with single-peaked H I profiles may share a similar dynamical state with massive ellipticals, offering new insights into their structural evolution and the diversity of formation pathways for low-mass galaxies.

Keywords: Radio spectroscopy, Galaxy dark matter halos, Galaxy formation, Dwarf galaxies, Dwarf elliptical galaxies, Cold neutral medium
Linear Mode Conversion Theory of Radio Emission from Turbulent Solar Wind Plasmas. This work presents a new theoretical and numerical model describing all possible linear interactions between upper-hybrid wave turbulence and random density fluctuations in a weakly magnetized solar wind plasma. Not only linear processes, such as wave reflection, refraction, scattering, tunneling, trapping, or mode conversion at constant frequency, are taken into account, but so are linear wave coupling, interferences between scattered waves, etc. Compact equations describing the radiation of electromagnetic waves in the  O -,  X -, and  Z -modes by the current resulting from the transformations of upper-hybrid waves on density fluctuations are determined analytically and solved numerically, providing the time variations of electromagnetic energies and the corresponding radiation rates. Jointly, on the basis of these numerical results, which validate the model's hypotheses, analytical calculations are conducted under the framework of weak turbulence theory extended to randomly inhomogeneous plasmas, which recover the main physical conclusions stated when using the model. The dependencies of radiation rates on plasma parameters, such as magnetization, electron temperature, and average level of random density fluctuations, are determined in the form of scaling laws. This work opens a new way to analyze the efficiency of electromagnetic emissions at plasma frequency by realistic wave and density turbulence spectra interacting in solar wind plasmas.

Keywords: Space plasmas, Solar wind, Radio bursts, Solar electromagnetic emission, Radio sources
COSMOS-Web: Unraveling the Evolution of Galaxy Size and Related Properties at 2 &lt; z &lt; 10. We measure galaxy sizes from 2 &lt; z &lt; 10 using COSMOS-Web, the largest-area JWST imaging survey to date, covering ∼0.54 deg2. We analyze the rest-frame optical (∼5000 Å) size evolution and its scaling relation with stellar mass ( Re∝M*α ) for star-forming and quiescent galaxies. For star-forming galaxies, the slope α remains approximately 0.20 at 2 &lt; z &lt; 8, showing no significant evolution over this redshift range. At higher redshifts, the slopes are −0.13 ± 0.15 and 0.37 ± 0.36 for 8 &lt; z &lt; 9 and 9 &lt; z &lt; 10, respectively. At fixed galaxy mass, the size evolution for star-forming galaxies follows Re ∝ (1 + z)−1.21±0.05. For quiescent galaxies, the size─mass relation is steeper with α ∼ 0.5─0.8 at 2 &lt; z &lt; 5, and size evolves as Re ∝ (1 + z)−0.81±0.26. We find that the size−mass relation is consistent between UV and optical at z &lt; 8 for star-forming galaxies. However, we observe a decrease in the slope from UV to optical at z &gt; 8, with a tentative negative slope in the optical at 8 &lt; z &lt; 9, suggesting a complex interplay between intrinsic galaxy properties and observational effects such as dust attenuation. We discuss the ratio between galaxies' half-light radius and underlying halos' virial radius, Rvir, and find the median value of Re/Rvir = 2.7%. The star formation rate surface density evolves as  log(ΣSFR/(M⊙/yr/kpc2))=  (0.20 ± 0.08)z + (−0.65 ± 0.51), and the ΣSFR─M* relation remains flat at 2 &lt; z &lt; 10. Lastly, we identify a threshold in stellar mass surface density  log(Σe/(M⊙/kpc2))∼9.5−10  marking the transition to compact, quenched galaxies from extended, star-forming progenitors. In summary, our findings show that the extensive COSMOS-Web dataset at z &gt; 3 provides new insights into galaxy size and related properties in the rest-frame optical.

Keywords: Galaxy structure, Galaxy evolution
SHORES: Serendipitous H-ATLAS-fields Observations of Radio Extragalactic Sources with the ATCA. I. Catalog Generation and Analysis. We introduce the Serendipitous H-ATLAS-fields Observations of Radio Extragalactic Sources (SHORES) multiple pencil beam survey that observed at 2.1 GHz with the Australia Telescope Compact Array (ATCA) 29 fields in total intensity and polarization within the Herschel-ATLAS Southern Galactic Field. This paper presents the observations, calibration and analysis of the 27 shallow fields that cover an overall area of ∼26 square degree with increasing sensitivity towards the phase centers of each pointing according to the ATCA 22 m dish response function, down to σ ≲ 33 μJy. Two additional (deep) fields have been observed to even higher sensitivity. All the SHORES observations have been calibrated to account also for linear polarization. Polarization and deeper field analysis will be presented in future papers. The SHORES shallow-field sample considered in the present paper counts 2294 sources detected with BLOBCAT to signal-to-noise ratio SNR ≳ 4.5. Simulations determined that our procedure and final catalog is 95% reliable above 497.5 μJy and 95% complete to the SNR ≳ 4.5 significance level. By exploiting ATCA E–W 6 km configuration we reached resolutions of 3 2 × 7 2, to which level 81% of our sources are unresolved. We determined source counts down to the 150 μJy level. For the sources with a counterpart in H-ATLAS, the FIR-radio correlation is calculated and discussed.

Keywords: Surveys, Extragalactic radio sources, Radio interferometry, Radio source catalogs
Cataclysmic Variables and AM CVn Binaries in SRG/eROSITA + Gaia: Volume Limited Samples, X-Ray Luminosity Functions, and Space Densities. We present volume-limited samples of cataclysmic variables (CVs) and AM CVn binaries jointly selected from SRG/eROSITA eRASS1 and Gaia DR3 using an X-ray + optical color–color diagram (the "X-ray Main Sequence"). This tool identifies all CV subtypes, including magnetic and low-accretion rate systems, in contrast to most previous surveys. We find 23 CVs, 3 of which are AM CVns, out to 150 pc in the Western Galactic Hemisphere. Our 150 pc sample is spectroscopically verified and complete down to LX = 1.3 × 1029 erg s‑1 in the 0.2–2.3 keV band, and we also present CV candidates out to 300 pc and 1000 pc. We discovered two previously unknown systems in our 150 pc sample: the third nearest AM CVn and a magnetic period bouncer. We find the mean LX of CVs to be &lt;LX&gt; ≈ 4.6 × 1030 erg s‑1, in contrast to previous surveys which yielded &lt;LX&gt; ∼ 1031‑1032 erg s‑1. We construct X-ray luminosity functions that, for the first time, flatten out at LX ∼ 1030 erg s‑1. We infer average number, mass, and luminosity densities of ρN,CV = (3.7 ± 0.7) × 10‑6pc‑3,  , and  , respectively, in the solar neighborhood. Our uniform selection method also allows us to place meaningful estimates on the space density of AM CVns, ρN,AM CVn = (5.5 ± 3.7) × 10‑7 pc‑3. Magnetic CVs and period bouncers make up 35% and 25% of our sample, respectively. This work, through a novel discovery technique, shows that the observed number densities of CVs and AM CVns, as well as the fraction of period bouncers, are still in tension with population synthesis estimates.

Keywords: X-ray astronomy, Stellar populations, AM Canum Venaticorum stars, Time domain astronomy, X-ray surveys, Cataclysmic variable stars
Digitization and Evaluation of Spectrograms from ϵ Aurigae's 1928–1930 Eclipse. We have digitized 24 spectrograms from the 1928 to 1930 eclipse of ϵ Aurigae, a binary system that has generated extensive investigation due to its long 27.1 yr period and enigmatic secondary, which is completely obscured. The spectrograms that we have digitized comprise the earliest campaign undertaken by the Yerkes Observatory astronomers to record an eclipse of ϵ Aurigae. In this article, we describe our methods of digitization and compare our data with more contemporary spectrogram digitizations. This work demonstrates the quality of scientific data extracted from historical analog material to expand the range of time-domain astronomy. The calibrated spectra are made available via OCHRE, a comprehensive research database, for public use.

Keywords: Eclipsing binary stars, Spectroscopy
Commissioning of the MIRAC-5 Mid-infrared Instrument on the MMT. We present results from commissioning observations of the mid-IR instrument, MIRAC-5, on the 6.5 m MMT telescope. MIRAC-5 is a novel ground-based instrument that utilizes a state-of-the-art GeoSnap (2–13 µm) HgCdTe detector with adaptive optics support from MAPS to study protoplanetary disks, wide-orbit brown dwarfs, planetary companions in the contrast-limit, and a wide range of other astrophysical objects. We have used MIRAC-5 on six engineering observing runs, improving its performance and defining operating procedures. We characterize key aspects of MIRAC-5's performance, including verification that the total telescope, atmosphere, instrument, and detector throughput is approximately 10%. Following a planned dichroic upgrade, the system will have a throughput of 20% and background limiting magnitudes (for SNR = 5 and 8 hr exposure times) of 18.0, 15.6, and 12.6 for the L', M', and N' filters, respectively. The detector pixels experience 1/f noise but, if the astrophysical scene is properly modulated via chopping and nodding sequences, it is less than 10% the Poisson noise from the observed background in an 85 Hz frame. We achieve close to diffraction-limited performance in the N-band and all bands are expected to reach diffraction-limited performance following the adaptive optics system commissioning. We also present an exposure time calculator calibrated to the on-sky results. In its current state, MIRAC-5 will be capable of achieving several scientific objectives including the observation of warm wide-orbit companions. Once the adaptive optics is commissioned and a coronagraph installed in 2025, MIRAC-5 will have contrast-limited performance comparable to JWST, opening new and complementary science investigations for close-in companions.

Keywords: Infrared astronomy, Exoplanets, Astronomical instrumentation, Telescopes