Sazuna/UAT_keywords huggingface dataset:
Magnetic Activity in M-type Stars Based on LAMOST DR11 and TESS Observations. We have used 898,351 M-type stellar spectra released by Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR11 to calculate the equivalent width of the Ca II infrared triplet (IRT) lines, the residual chromospheric emission, and the parameter  R8542' , which is defined as the ratio of the luminosity of the 8542 Å line to the stellar bolometric luminosity. The chromospheric activity of M dwarfs reaches its maximum around an effective temperature of 3700 K, corresponding to a spectral type of approximately M6. The stellar photospheric activity begins to become significant at around 3800 K, and the trend gradually becomes weaker when approaching 3200 K, which may be due to the influence of the magnetic activity saturation zone. Furthermore, metallicity also influences the intensity of the chromospheric activity. We found that chromospheric and photospheric activity in M dwarfs are correlated, and that both types of activity are influenced by stellar rotation. Additionally, we crossmatched our catalog with the Transiting Exoplanet Survey Satellite and identified 23,079 flare events from 3280 stars. Our results show that the majority of the M dwarf flare radiation energy is below 1036 erg, and the flare duration and energy of nearly all spectral types follow a power-law distribution, i.e.,  dNdE∝E−a  with α = 2. For the cumulative flare frequency distribution's power-law index, we found the range to be between 1.44 and 2. We found that the power-law index α for fully convective M-type stars is approximately 1.61 ± 0.08, while for non─fully convective M-type stars, it is around 1.78 ± 0.11.

Keywords: Stellar chromospheres, Stellar activity, M stars
The Consequences of Rubin Observatory Time-domain Survey Design and Host-galaxy Contamination on the Identification of Binary Supermassive Black Holes. Binary supermassive black holes (SMBHs) are consequences of galaxy mergers and dominate the low-frequency gravitational-wave background. Finding binary SMBHs in existing time-domain observations has proven difficult, as their periodic, electromagnetic signals can be confused with the natural variability of single quasars. In this work, we investigate the effects of host-galaxy contamination and survey design (cadence and duration) on the detectability of binary SMBHs with the upcoming Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate millions of LSST light curves of single and binary quasars, with a distribution of quasar and host-galaxy properties motivated by empirical observations and the anticipated LSST detection space. We then apply simple sinusoidal curve fits as a potential computationally inexpensive detection method. We find that host-galaxy contamination will increase false-positive rates and decrease binary parameter recovery rates. Lower-mass, lower-luminosity binary systems are most likely to be negatively affected by host-galaxy contamination. We also find that monitoring duration affects binary detection more than survey effective cadence for this detection method. As the light-curve duration increases, false-positive rates are suppressed and binary parameter recovery rates, especially for binary periods, are improved. Increasing the light-curve duration from 5 to 10 yr shows the most dramatic improvement for successful binary detection and false-positive rejection, with additional improvement from extending the light-curve duration to 20 yr. The observation duration increase is especially critical for recovering binary periods that are longer than a decade.

Keywords: Supermassive black holes, Quasars, Surveys, Astronomy data analysis, Gravitational wave sources, Active galactic nuclei, Time domain astronomy
Statistical Issues Often Overlooked when Analyzing Astronomical Data. The main topics covered in this paper are (1) controlling significance levels when applying the same hypothesis test to many (possibly millions) of datasets; (2) dealing with the fact that for very large datasets hypotheses are rejected for trivially small departures from the null; (3) in the presence of noise, extreme values selected from samples for follow-up studies are often biased; (4) inference conducted on models fitted to data routinely underestimate the parameter standard errors if the selected model was informed by the observations; (5) obtaining overall least-mean-squared error estimates of a group of observations (e.g. a collection of star cluster masses); and (6) the effects of the violation of mathematical regularity conditions on model selection statistics.

Keywords: Astrostatistics techniques, Astrostatistics
PyEMILI: A New Generation Computer-aided Spectral-line Identifier. II. Emission-line Identification and Plasma Diagnostics of a Sample of Gaseous Nebulae. In order to test the robustness and reliability of the new generation spectral-line identifier PyEMILI, as initially introduced in Paper I, in line identification and establish a reference/benchmark dataset for future spectroscopic studies, we run the code on the line lists of a selected sample of emission-line nebulae, including planetary nebulae (PNe), H II regions, and Herbig─Haro objects with deep high-dispersion spectroscopic observations published over the past two decades. The automated line identifications by PyEMILI demonstrate significant improvements in both completeness and accuracy compared to the previous manual identifications in the literature. Since our last report of PyEMILI, the atomic transition database used by the code has been further expanded by crossmatching the Kurucz line lists. Moreover, to aid the PyEMILI identification of numerous faint optical recombination lines (ORLs) of C II, N II, O II, and Ne II, we compiled a new dataset of effective recombination coefficients for these nebular lines, and created a new subroutine in the code to generate theoretical spectra of heavy-element ORLs at various electron temperature and density cases; these theoretical spectra can be used to fit the observed recombination spectrum of a PN to obtain the electron temperature, density, and ionic abundances using the Markov Chain Monte Carlo (MCMC) method. We present MCMC-derived parameters for a sample of PNe. This work establishes PyEMILI as a robust and versatile tool for both line identification and plasma diagnostics in deep spectroscopy of gaseous nebulae.

Keywords: High resolution spectroscopy, Spectral line lists, Astronomy software, Atomic physics, Spectral line identification, Gaseous nebulae, Planetary nebulae, H II regions
Covariant Energy Density Functionals for Modeling the Equation of State of Neutron Star Matter: Cross-comparison Analysis Using CompactObject. This study analyzes and contrasts different phenomenological methods used to model the nuclear equation of state (EOS) for neutron star matter based on covariant energy density functionals (CEDFs). Using two complementary methodologies, we seek to capture a comprehensive picture of the potential behaviors of ultradense nucleonic matter and identify the most plausible models based on current observational and experimental constraints. Observational data from radio pulsar timing, gravitational-wave detection of GW170817, and X-ray timing provide critical benchmarks for testing the models. We have derived the EOS posteriors for various CEDF models within the CompactObject package, utilizing recent observational data on neutron stars, state-of-the-art theoretical constraints from calculations in chiral effective field theory for pure neutron matter at low densities, and pQCD-derived constraints. Our analysis has demonstrated that while all considered CEDF models broadly reproduce current astrophysical and theoretical constraints, subtle yet important differences persist among them, with each framework exhibiting distinct characteristics at supranuclear density. This is particularly true for the proton fraction inside neutron stars, but is also supported by the models' behavior with respect to the pure neutron matter EOS and the density dependence of the speed of sound. Our study highlights the sensitivity of predictions for dense matter to the underlying EOS parameterizations and the priors considered.

Keywords: Neutron stars, Nuclear astrophysics, Compact objects
A Pan-galaxy Study of Synthetic Giant Molecular Filaments: A Turbulence-dominated Life Cycle. Recent surveys of the Galactic plane have revealed dozens of giant molecular filaments (GMFs), with lengths ranging from tens to hundreds of parsecs, yet their origins and life cycles remain debated. In this work, we analyze over 700 GMFs identified from synthetic CO emission maps of a high-resolution magnetohydrodynamic simulation of a Milky Way─like galaxy, whose lengths range from ∼10 to ∼300 pc. We find that turbulent shock from galactic shear and stellar feedback are the primary drivers of GMF formation. Magnetized turbulence dominates their internal dynamics, supporting the filaments against global collapse while simultaneously inducing fragmentation into dense clumps. This fragmentation follows the turbulence-driven sausage instability model, rather than pure Jeans instability, and triggers efficient star formation along the filaments. Cloud─cloud collisions are frequent, affecting more than 70% of GMFs, and often disrupt or reshape their morphology. The typical filamentary lifetime is  tfil=14−5+2  Myr, comparable to the crossing time of giant molecular clouds (GMCs). The molecular gas half-life is ∼7 Myr, similar to that of GMCs, indicating that GMFs are transient but dynamically important structures.

Keywords: Star formation, Interstellar clouds, Interstellar filaments
Hunting Very High-energy-emitting (&gt;100 GeV) High-synchrotron-peaked Blazars. Very high-energy (VHE; &gt;100 GeV) γ-ray emission originates via some of the most extreme particle acceleration processes in the Universe. Considering beamed active galactic nuclei, i.e., blazars, only a small fraction, mainly high-synchrotron-peaked BL Lacertae (BL Lac) objects, have been detected in the VHE band with ground-based Cherenkov telescopes. We utilized ∼16 yr of Fermi Large Area Telescope (LAT) observations in the 0.1−2 TeV energy range to systematically search for potential VHE emitters in a sample of high-synchrotron-peaked ( νsynpeak&gt;1015  Hz) BL Lac sources. We identified, for the first time, 92 VHE-emitting blazars at a ≥5σ confidence level. A significant VHE emission was also detected from 52 sources previously reported as VHE blazars. Comparing with the general blazar population, these VHE-emitting blazars are found to be located at low redshifts (mean z = 0.2 ± 0.1) and exhibit bright synchrotron emission ( logFsynpeak=−11.2±0.4 , in erg cm−2 s−1). We also investigated the coincidence of VHE photon arrivals with the source activity states and found that Fermi-LAT has detected VHE photons during both quiescent and elevated activity epochs. These VHE-emitting blazars represent promising targets for current and next-generation ground-based Cherenkov telescopes, and provide powerful laboratories for probing particle acceleration in relativistic jets, testing multimessenger connections, and constraining extragalactic background light models.

Keywords: Supermassive black holes, BL Lacertae objects, High energy astrophysics, Blazars, Relativistic jets, Catalogs
Stray Light Correction for the Helioseismic and Magnetic Imager. We report a point-spread function (PSF) and deconvolution procedure to remove stray light from the Helioseismic and Magnetic Imager (HMI) data. Prelaunch calibration observations, postlaunch Venus transit, and lunar transit data were used to develop the PSF and evaluate how well it reproduced the observed scattering. The PSF reported differs from previous stray light removal efforts since we do not use Gaussians as the central mathematical component. Instead, we use a Lorenztian convolved with an Airy function. In 2018, the HMI team began providing full-disk, stray-light-corrected data daily. Intensity, Doppler, magnetogram, and vector magnetic field data are provided. The deconvolution uses a Richardson─Lucy algorithm and takes less than 1 s per full-disk image. The results, on average, show decreases in umbral continuum intensity, a doubling of the granulation intensity contrast, increases in the total field strength, most notably in plage by ∼1.4─2.5 times the original value, and a partial correction for the convective blueshift. Local helioseismology analyses using corrected data yield results that are consistent with those from uncorrected data, with only negligible differences, except in sunspot regions. The new data are found in JSOC with names similar to the original but with the qualifying term "_dcon" or "_dconS" appended, denoting whether the deconvolution was applied to the filtergrams or Stokes images. The HMI team recommends using the corrected data for improved visual clarity, more accurate irradiance reconstruction, better coalignment with high-resolution data, reduced errors in tracking algorithms, and improved magnetic field strengths.

Keywords: Spectropolarimetry, Helioseismology, Sunspots, Solar instruments, Polarimetry
JWST Exoplanetary Worlds and Elemental Survey (JEWELS). I. High-precision Chemical Abundances of 20 FGK Planet-hosting Stars from JWST Cycle 2. We present high-precision chemical abundances for 20 FGK stars hosting planets observed in JWST Cycle 2 GO programs. Using high-resolution, high-signal-to-noise ratio spectra from the ESO and Keck archives, we perform a strict line-by-line differential analysis relative to the Sun to derive stellar parameters and abundances of 19 elements from C to Zn. The stars span effective temperatures of 4500─6500 K and metallicities from −0.57 to +0.50 dex. The sample includes hosts of both gas giants and terrestrial planets, allowing direct comparison between stellar composition and planetary properties. Several of the giant planets orbit metal-rich stars. The detailed abundance patterns show clear chemical diversity, including carbon-enhanced but mildly metal-poor stars (TOI-824, TOI-561, TOI-1130, GJ 9827) and α-enhanced metal-poor stars (TOI-561, GJ 9827, TOI-824). These variations trace differences in protoplanetary disk composition and may influence planetary interiors and atmospheric chemistry. The planet hosts show a range of [C/O] ratios, and the diverse [Mg/Si] ratios may suggest varied interior compositions for their rocky planets. This homogeneous stellar abundance, together with future uniform JWST planetary atmosphere measurements, provides a foundation for exploring the planet mass─metallicity relation and the connection between stellar chemistry and planetary formation pathways. These results constitute the first step in a larger survey spanning multiple JWST cycles to systematically examine how host star composition shapes exoplanetary systems.

Keywords: Exoplanet atmospheric composition , Chemical abundances, Exoplanet astronomy, James Webb Space Telescope, Planet hosting stars, Star-planet interactions
QHSC: The Quasar Candidate Catalog for the Hyper Suprime-Cam Subaru Strategic Program. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a deep wide-field multiband imaging survey consisting of three layers (Wide, Deep, and UltraDeep), with the Wide layer covering ∼1470 deg2 to a depth of i ∼ 26 mag. We present the QHSC catalog, a machine learning─selected sample of quasar candidates with photometric redshifts in the Wide layer of the HSC-SSP survey (Public Data Release 3). The full QHSC catalog contains four distinct samples: a Master Sample with HSC-only photometry, an HSC+WISE sample, and two samples including near-infrared data from UKIDSS and VISTA surveys, denoted as GoldenU and GoldenV. For each sample, an XGBoost classifier is trained and evaluated using independent spectroscopic test sets from HETDEX, VVDS, and zCOSMOS-bright. The numbers of quasar candidates in the QHSC catalog are 1,184,574 (Master), 371,777 (HSC+WISE), 87,460 (GoldenU), and 120,572 (GoldenV), with respective completeness values of 85.3%, 92.7%, 89.8%, and 91.3%. We develop ensemble photometric redshift estimators based on bootstrap aggregating (bagging) of multiple XGBoost regressors, achieving outlier fractions of 21.7%, 13.1%, 9.5%, and 10.7% for these samples. The catalog provides quasar classification probabilities (pQSO), enabling construction of purer subsamples via thresholding. This work offers a valuable resource for studies of quasars and cosmology, and highlights the effectiveness of machine learning for quasar selection in future wide and deep imaging surveys. The catalog is publicly available at doi:10.5281/zenodo.17515028.

Keywords: Classification, Quasars, Astrostatistics techniques, Active galactic nuclei, Redshift surveys, Catalogs
Deep Andromeda JCMT SCUBA-2 Observations. The Submillimeter Maps and Giant Molecular Clouds. We have carried out unprecedentedly deep, nearly confusion-limited JCMT SCUBA-2 mapping observations on the nearest spiral galaxy, M31 (Andromeda). The 850 μm image with a ∼50 pc resolution yields a comprehensive catalog of 383 giant molecular clouds (GMCs) that are associated with the spiral arms. In addition, it unveiled a population of 189 compact interarm GMCs in M31, which are mostly unresolved or marginally resolved. The masses of all these GMCs are in the range of 2 × 104─6 × 106 M⊙; the sizes are in the range of 30─130 pc. They follow a mass─size correlation, M ∝ Rc2.5. The interarm GMCs are systematically less massive, more diffuse, colder, and have lower star formation efficiency (SFE) than on-arm GMCs. Moreover, within individual spatially resolved on-arm and off-arm M31 GMCs, the SFE is considerably lower than the SFE in molecular clouds in main-sequence and green valley galaxies. Follow-up investigations on M31 GMCs may provide clues for how star formation may be quenched in galactic environments. Finally, we reconstrained the dust opacity spectral index β in the M31 galaxy by combining our new JCMT observations with archival Herschel and Planck data and found that the radial variation in β may not be as large as has been proposed by previous studies.

Keywords: Interstellar dust, Galaxy structure, Giant molecular clouds, Interstellar medium, Andromeda Galaxy
Vz-GAL: Probing Cold Molecular Gas in Dusty Star-forming Galaxies at z = 1─6. We present the first results of Vz-GAL, a high-redshift CO(J = 1─0) large survey with the Karl G. Jansky Very Large Array, targeting 92 Herschel-selected, infrared-luminous, dusty star-forming galaxies at redshifts 1─6. These sources are selected based on having redshifts and mid-/high-J CO transitions from the NOrthern Extended Millimeter Array z─GAL survey. We successfully detect CO(J = 1─0) emission in 90/92 galaxies at the expected positions and redshifts, including nine tentative detections at 2σ─3σ significance, and CO(J = 2─1) emission in 10 of these galaxies. The CO(J = 1─0) luminosities suggest apparent gas masses in the range  μMH2  = (2─20) × 1011 (αCO/4.0) M⊙, which implies gas depletion times of 50─600 Myr. These timescales show similar spread as local ULIRGs, suggesting a self-regulatory mechanism that maintains a consistent star formation rate per unit gas mass in starbursts across redshifts. To quantify the contribution of "excitation correction" factors to gas mass estimates, we calculate median CO line brightness temperature ratios of r21 = 0.88 ± 0.25, r31 = 0.61 ± 0.22, r41 = 0.49 ± 0.15, r51 = 0.47 ± 0.13, and r61 = 0.28 ± 0.13. Accounting for these corrections results in a reduced scatter in "gas mass─star formation rate" relations. We also find a median log( L'[CI](3P1−3P0)/L'CO(J=1−0))=−0.71±0.12  for a subsample of 23 sources, consistent with the ratios derived for local star-forming galaxies. Together, our findings are in agreement with common conditions in the cold gas reservoirs among star-forming galaxies over a broad range in star formation modes, efficiencies, and scales.

Keywords: Starburst galaxies, Molecular gas, Star formation, Galaxy evolution, Interstellar medium, CO line emission, High-redshift galaxies
A New Way to Discover Strong Gravitational Lenses: Pairwise Spectroscopic Search from DESI DR1. We present a new method to search for strong gravitational-lensing systems by pairing spectra that are close together on the sky in a spectroscopic survey. We visually inspect 26,621 spectra in the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 that are selected in this way. We further inspect the 11,848 images corresponding to these spectra in the DESI Legacy Imaging Surveys Data Release 10, and obtain 2046 conventional strong gravitational lens candidates, of which 1906 are new. This constitutes the largest sample of lens candidates identified to date in spectroscopic data. Besides the conventional candidates, we identify a new class of systems that we term "dimple lenses." These systems have a low-mass foreground galaxy as a lens, typically smaller in angular extent and fainter compared with the lensed background source galaxy, producing subtle surface brightness indentations in the latter. We report the discovery of 318 of these "dimple lens" candidates. We suspect that these represent dwarf galaxy lensing. With follow-up observations, they could offer a new avenue to test the cold dark matter model by probing their mass profiles, stellar mass─halo mass relation, and halo mass function for MHalo ≲ 1013 M⊙. Thus, in total, we report 2164 new lens candidates. Our method demonstrates the power of pairwise spectroscopic analysis and provides a pathway complementary to imaging-based and single-spectrum lens searches.

Keywords: Sky surveys, Strong gravitational lensing, Dwarf galaxies, Gravitational lensing, Galaxy spectroscopy, Redshift surveys
Constraining the nHz Gravitational-wave Background with an X-Ray Pulsar-timing Array from NICER Observations. We present constraints on the nHz gravitational-wave background (GWB) using X-ray pulsar-timing data from the Neutron Star Interior Composition Explorer (NICER). By analyzing six millisecond pulsars over a 6 yr observational baseline, we employed a Bayesian framework to model noise components and search for a common red signal consistent with a GWB from supermassive black hole binaries (assuming a spectral index γgwb = 13/3). Our results show no significant evidence for a GWB, yielding a 95% upper limit of  log10(Agwb)&lt;−13.4 . Weak evidence for Hellings─Downs spatial correlations was found (S = 2.5), though the signal remains statistically inconclusive. Compared to radio and γ-ray pulsar-timing arrays, the NICER constraint is currently less stringent but demonstrates the feasibility of X-ray timing with NICER for GWB studies and highlights the potential for improved sensitivity with future X-ray missions.

Keywords: X-ray astronomy, Neutron stars, Bayesian statistics, Pulsars, Gravitational waves, Astrophysical black holes
A Comprehensive Model of the K-coronal Spectrum for the Inference of Electron Temperature and Bulk Flow Velocity in the Corona. The electron temperature of the corona is one of the key physical parameters which reflect the complexity of coronal-heating processes. L. E. Cram was the first to show that the K-coronal spectrum, produced by the scattering of the photospheric spectrum from free streaming coronal electrons, could be used to infer the coronal temperature with an uncertainty of 0.2 MK. This study revisits Cram's original work by introducing a robust mathematical model which enables the exploration of a broad range of plasma parameters, most importantly the electron velocity distribution, in its implementation. While the inference of electron temperature is well established, the model results show that the velocity of the electrons in the inner corona can also be inferred.

Keywords: Solar wind, Solar K corona, Solar corona