Sazuna/UAT_keywords huggingface dataset:
Star-crossed Lovers DI Tau A and B: Orbit Characterization and Physical Properties Determination. The stellar companion to the weak-line T Tauri star DI Tau A was first discovered by the lunar occultation technique in 1989 and was subsequently confirmed by a speckle imaging observation in 1991. It has not been detected since, despite being targeted by five different studies that used a variety of methods and spanned more than 20 yr. Here, we report the serendipitous rediscovery of DI Tau B during our Young Exoplanets Spectroscopic Survey (YESS). Using radial velocity data from YESS spanning 17 yr, new adaptive optics observations from Keck II, and a variety of other data from the literature, we derive a preliminary orbital solution for the system that effectively explains the detection and (almost all of the) non-detection history of DI Tau B. We estimate the dynamical masses of both components, finding that the large mass difference (q ~ 0.17) and long orbital period (≳35 yr) make the DI Tau system a noteworthy and valuable addition to studies of stellar evolution and pre-main-sequence models. With a long orbital period and a small flux ratio (f2/f1) between DI Tau A and B, additional measurements are needed for a better comparison between these observational results and pre-main-sequence models. Finally, we report an average surface magnetic field strength ( $\bar{B}$ ) for DI Tau A, of ~0.55 kG, which is unusually low in the context of young active stars.

Keywords: Binary stars, Fundamental parameters of stars, Pre-main sequence stars, Radial velocity, Visual binary stars, High angular resolution
New Chondritic Bodies Identified in Eight Oxygen-bearing White Dwarfs. We present observations and analyses of eight white dwarf stars (WDs) that have accreted rocky material from their surrounding planetary systems. The spectra of these helium-atmosphere WDs contain detectable optical lines of all four major rock-forming elements (O, Mg, Si, and Fe). This work increases the sample of oxygen-bearing WDs with parent body composition analyses by roughly 33%. To first order, the parent bodies that have been accreted by the eight WDs are similar to those of chondritic meteorites in relative elemental abundances and oxidation states. Seventy-five percent of the WDs in this study have observed oxygen excesses implying volatiles in the parent bodies with abundances similar to those of chondritic meteorites. Three WDs have oxidation states that imply more reduced material than found in CI chondrites, indicating the possible detection of Mercury-like parent bodies, but are less constrained. These results contribute to the recurring conclusion that extrasolar rocky bodies closely resemble those in our solar system, and do not, as a whole, yield unusual or unique compositions.

Keywords: Exoplanet astronomy, White dwarf stars, DB stars, Exoplanets
Cosmic Sands: The Origin of Dusty, Star-forming Galaxies in the Epoch of Reionization. We present the Cosmic Sands suite of cosmological zoom-in simulations based on the SIMBA galaxy formation model in order to study the buildup of the first massive and dusty galaxies in the early universe. Residing in the most massive halos, we find that the compact proto-massive galaxies undergo nearly continuous mergers with smaller subhalos, boosting star formation rates (SFRs) and the buildup of stellar mass. The galaxies are already appreciably chemically evolved by z = 7, with modeled dust masses comparable to those inferred from observations in the same epoch, except for the most extreme systems. We track gas accretion onto the galaxies to understand how extreme SFRs can be sustained by these early systems. We find that smooth gas accretion can maintain SFRs above 250 M ⊙ yr-1, but to achieve SFRs that boost galaxies well above the main sequence, a larger perturbation like a gas-rich major merger is necessary to trigger a starburst episode. Post-processing the Cosmic Sands simulations with dust RT, we find that, while the infrared luminosities of the most-dust-rich galaxies are comparable to local ULIRGs, they are substantially dimmer than classical z = 2 submillimeter galaxies. We end with a discussion on the possible reasons for this discrepancy at the highest masses and the future work we intend to carry out to study the chemical enrichment of the earliest dusty galaxies.

Keywords: Hydrodynamical simulations, Ultraluminous infrared galaxies, Starburst galaxies, Galaxies
Gemini Near Infrared Spectrograph-Distant Quasar Survey: Augmented Spectroscopic Catalog and a Prescription for Correcting UV-based Quasar Redshifts. Quasars at z ≳ 1 most often have redshifts measured from rest-frame ultraviolet emission lines. One of the most common such lines, C IV λ1549, shows blueshifts up to ≈5000 km s-1 and in rare cases even higher. This blueshifting results in highly uncertain redshifts when compared to redshift determinations from rest-frame optical emission lines, e.g., from the narrow [O III] λ5007 feature. We present spectroscopic measurements for 260 sources at 1.55 ≲ z ≲ 3.50 having -28.0 ≲ M  i  ≲ - 30.0 mag from the Gemini Near Infrared Spectrograph-Distant Quasar Survey (GNIRS-DQS) catalog, augmenting the previous iteration, which contained 226 of the 260 sources whose measurements are improved upon in this work. We obtain reliable systemic redshifts based on [O III] λ5007 for a subset of 121 sources, which we use to calibrate prescriptions for correcting UV-based redshifts. These prescriptions are based on a regression analysis involving C IV full-width-at-half-maximum intensity and equivalent width, along with the UV continuum luminosity at a rest-frame wavelength of 1350 Å. Applying these corrections can improve the accuracy and the precision in the C IV-based redshift by up to ~850 km s-1 and ~150 km s-1, respectively, which correspond to ~8.5 and ~1.5 Mpc in comoving distance at z = 2.5. Our prescriptions also improve the accuracy of the best available multifeature redshift determination algorithm by ~100 km s-1, indicating that the spectroscopic properties of the C IV emission line can provide robust redshift estimates for high-redshift quasars. We discuss the prospects of our prescriptions for cosmological and quasar studies utilizing upcoming large spectroscopic surveys.

Keywords: Surveys, Active galactic nuclei, Quasars
Gemini Near Infrared Spectrograph-Distant Quasar Survey: Prescriptions for Calibrating UV-based Estimates of Supermassive Black Hole Masses in High-redshift Quasars. The most reliable single-epoch supermassive black hole mass (M BH) estimates in quasars are obtained by using the velocity widths of low-ionization emission lines, typically the Hβ λ4861 line. Unfortunately, this line is redshifted out of the optical band at z ≈ 1, leaving M BH estimates to rely on proxy rest-frame ultraviolet (UV) emission lines, such as C IV λ1549 or Mg II λ2800, which contain intrinsic challenges when measuring, resulting in uncertain M BH estimates. In this work, we aim at correcting M BH estimates derived from the C IV and Mg II emission lines based on estimates derived from the Hβ emission line. We find that employing the equivalent width of C IV in deriving M BH estimates based on Mg II and C IV provides values that are closest to those obtained from Hβ. We also provide prescriptions to estimate M BH values when only C IV, only Mg II, and both C IV and Mg II are measurable. We find that utilizing both emission lines, where available, reduces the scatter of UV-based M BH estimates by ~15% when compared to previous studies. Lastly, we discuss the potential of our prescriptions to provide more accurate and precise estimates of M BH given a much larger sample of quasars at 3.20 ≲ z ≲ 3.50, where both Mg II and Hβ can be measured in the same near-infrared spectrum.

Keywords: Surveys, Supermassive black holes, Active galactic nuclei, Quasars
Shedding New Light on Weak Emission-line Quasars in the C IV-Hβ Parameter Space. Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Lyα + N V λ1240 and/or C IV λ1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 "ordinary" type 1 quasars and 18 WLQs at z &lt; 0.5 and 1.5 &lt; z &lt; 3.5 that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the Hβ-based black hole mass (M BH) estimates of these quasars using the strength of the optical Fe II emission. We confirm previous findings that WLQs' M BH values are overestimated by up to an order of magnitude using the traditional broad-emission-line region size-luminosity relation. With this M BH correction, we find a significant correlation between Hβ-based Eddington luminosity ratios and a combination of the rest-frame C IV equivalent width and C IV blueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional C IV parameter space can serve as an indicator of accretion rate in all type 1 quasars across a wide range of spectral properties.

Keywords: Supermassive black holes, Active galactic nuclei, Quasars
Radiation Pressure Acting on the Neutral He Atoms in the Heliosphere. Interstellar neutral helium (ISN He) is an important source of information on the physical state of the local interstellar medium. Radiation pressure acting on the neutral helium atoms in the heliosphere has always been neglected; its effect has been considered insignificant compared to gravitational force. The most advanced numerical models of ISN He take into account more and more subtle effects; therefore, it is important to check if the effect of radiation pressure is still negligible. In this paper, we use the most up-to-date version of the Warsaw Test Particle Model (WTPM) to calculate the expected helium distribution in the heliosphere and simulate the flux of the ISN He observed by the Interstellar Boundary Explorer (IBEX) and in the future by the Interstellar Mapping and Acceleration Probe (IMAP). We compare results calculated with and without radiation pressure during low and high solar activity. The results show that in the analysis of IBEX-Lo observations, the radiation pressure acting on typical helium causes flux differences at a level of 1%-4% and is comparable to the observational errors. For the more sensitive IMAP-Lo instrument, there are some regions in the considered observation configurations where radiation pressure causes potentially statistically significant changes in the calculated fluxes. The effect can be up to 9% for the indirect beam and is likely to be higher than the estimated errors. Therefore, we claim that in the future analysis of the IMAP-Lo observations, radiation pressure acting on ISN He should be considered.

Keywords: Solar extreme ultraviolet emission, Heliosphere
An Eclipsing Binary Comprising Two Active Red Stragglers of Identical Mass and Synchronized Rotation: A Post-mass-transfer System or Just Born That Way?. We report the discovery of 2M0056-08 as an equal-mass eclipsing binary (EB), comprising two red straggler stars (RSSs) with an orbital period of 33.9 days. Both stars have masses of ≈1.419 M ☉, identical to within 0.2%. Both stars appear to be in the early red-giant phase of evolution; however, they are far displaced to cooler temperatures and lower luminosities compared to standard stellar models. The broadband spectral energy distribution shows NUV excess and X-ray emission, which is consistent with chromospheric and coronal emission from magnetically active stars. Indeed, the stars rotate more rapidly than typical red giants and they evince light-curve modulations due to spots. These modulations also reveal the stars to be rotating synchronously with one another. There is evidence for excess FUV emission and long-term modulations in radial velocities, although it is not clear if they are also attributable to magnetic activity or if they reveal a tertiary companion. Stellar evolution models that are modified to account for the effects of spots can reproduce the observed radii and temperatures of the RSSs. If the system possesses a white dwarf tertiary, then mass-transfer scenarios could explain the manner by which the stars came to possess such remarkably identical masses and by which they came to be synchronized. However, if the stars are presumed to have been formed as identical twins and they then managed to become tidally synchronized as they evolved toward the red-giant branch, then all of the features of the system can be explained via activity effects without requiring a complex dynamical history.

Keywords: Fundamental parameters of stars, Stellar activity, Eclipsing binary stars, Red straggler stars, Stellar evolution
Solar Filament Eruptions in H<SUB> α </SUB> Doppler Velocity. We use observations taken with a novel solar telescope spectroheliograph to investigate the association between the early filament rise and coronal mass ejections (CMEs). The instrument allows the H α  full line profile to be registered in each pixel of the solar disk with a time cadence of about 1 minute. We analyze observations of three eruptive filaments in 2021 and show that patrol telescope measurements of the H α  line profile with a spectral resolution R = 40,000 can be used to detect precursors of filament eruptions with an advance of several hours and to estimate the initial acceleration of CMEs. Our limited case study also suggests that while detecting an early filament rise may serve as an indicator of a possible eruption, the filament ascent alone is not a definite sign of a CME.

Keywords: Astronomical instrumentation, Solar filaments, Solar filament eruptions, Solar instruments
JWST-TST Proper Motions. I. High-precision NIRISS Calibration and Large Magellanic Cloud Kinematics. We develop and disseminate effective point-spread functions and geometric-distortion solutions for high-precision astrometry and photometry with the JWST NIRISS instrument. We correct field dependencies and detector effects, and assess the quality and the temporal stability of the calibrations. As a scientific application and validation, we study the proper motion (PM) kinematics of stars in the JWST calibration field near the Large Magellanic Cloud (LMC) center, comparing to a first-epoch Hubble Space Telescope (HST) archival catalog with a 16 yr baseline. For stars with G ∼ 20, the median PM uncertainty is ∼13 μas yr‑1 (3.1 km s‑1), better than Gaia DR3 typically achieves for its very best-measured stars. We kinematically detect the known star cluster OGLE-CL LMC 407, measure its absolute PM for the first time, and show how this differs from other LMC populations. The inferred cluster dispersion sets an upper limit of 24 μas yr‑1 (5.6 km s‑1) on systematic uncertainties. Red-giant-branch stars have a velocity dispersion of 33.8 ± 0.6 km s‑1, while younger blue populations have a narrower velocity distribution, but with a significant kinematical substructure. We discuss how this relates to the larger velocity dispersions inferred from Gaia DR3. These results establish JWST as capable of state-of-the-art astrometry, building on the extensive legacy of HST. This is the first paper in a series by our JWST Telescope Scientist Team, in which we will use Guaranteed Time Observations to study the PM kinematics of various stellar systems in the Local Group.

Keywords: Large Magellanic Cloud, Astrometry, Photometry, Proper motions, Star clusters
Searching for Spectroscopic Signatures of Ongoing Quenching in SDSS Galaxies. In this paper, we estimate the "star formation change parameter," SFR79, which characterizes the current SFR relative to the average during the last 800 Myr, for ~300,000 galaxies selected from the Sloan Digital Sky Survey (SDSS). The goals are to examine, in a much larger and independent sample, the trends previously reported in a sample of star-forming (SF) MaNGA galaxies and also to search for spectroscopic signatures of ongoing quenching in the so-called "Green Valley," which is generally believed to contain galaxies that are migrating from the SF population to the quenched population of galaxies. Measuring SFR79 for our large sample of SDSS galaxies, we first confirm the basic results of SF galaxies published by Wang &amp; Lilly. We then discuss in detail the calibration and meaning of SFR79 for galaxies that are well below the SFMS and establish the expected statistical signature of systematic ongoing quenching from modeling the z ~ 0 quenching rate of the SF population. We conclude that it is not possible at present to establish unambiguous observational evidence for systematic ongoing quenching processes, due to limitations both in the noise of the observational data, in particular in the measurements of Hδ absorption, and in the calibration of SFR79, as well as biases introduced by the necessity of selecting objects with significant Hα emission. We do however see plausible indications of ongoing quenching, which are quantitatively consistent with expectations from "growth+quenching" models of galaxy evolution and a typical e-folding timescale for quenching of ~500 Myr.

Keywords: Green valley galaxies, Star formation, Galaxy evolution, Galaxy quenching, Galaxy spectroscopy, Galaxies
Sparse Logistic Regression for RR Lyrae versus Binaries Classification. RR Lyrae (RRL) stars are old, low-mass, radially pulsating variable stars in their core helium burning phase. They are popular stellar tracers and primary distance indicators since they obey well-defined period-luminosity relations in the near-infrared regime. Their photometric identification is not trivial; indeed, RRL star samples can be contaminated by eclipsing binaries, especially in large data sets produced by fully automatic pipelines. Interpretable machine-learning approaches for separating eclipsing binaries from RRL stars are thus needed. Ideally, they should be able to achieve high precision in identifying RRL stars while generalizing new data from different instruments. In this paper, we train a simple logistic regression classifier on Catalina Sky Survey (CSS) light curves. It achieves a precision of 87% at 78% recall for the RRL star class on unseen CSS light curves. It generalizes on out-of-sample data (ASAS/ASAS-SN light curves) with a precision of 85% at 96% recall. We also considered a L1-regularized version of our classifier, which reaches 90% sparsity in the light-curve features with a limited trade-off in accuracy on our CSS validation set and-remarkably-also on the ASAS/ASAS-SN light-curve test set. Logistic regression is natively interpretable, and regularization allows us to point out the parts of the light curves that matter the most in classification. We thus achieved both good generalization and full interpretability.

Keywords: Periodic variable stars, Pulsating variable stars, Astrostatistics, Short period variable stars, Stellar classification, RRc variable stars, RR Lyrae variable stars, Gaussian Processes regression, Eclipsing binary stars, Intrinsic variable stars
Internal Calibration of LAMOST and Gaia DR3 GSP-Spec Stellar Abundances. Stellar chemical abundances are crucial and fundamental in astrophysics. However, they could suffer from substantial systematic errors according to several investigations but still lack calibrations in bulk. By using Gaia wide binaries, we find the temperature-dependent bias between the two binary components for [Fe/H] and [α/Fe] measurements from the LAMOST low-resolution spectra and Gaia RVS spectra. At T eff = 4000 K, the LAMOST [Fe/H] is significantly underestimated by approximately 0.4 dex when compared with its typical uncertainty of 0.1 dex. Its [α/Fe] is overestimated by about 0.2 dex. For Gaia, the underestimation of [M/H] and overestimation of [α/Fe] becomes pronounced near 7000 K with smaller magnitudes. We perform an internal calibration by minimizing the differences between the binary components and provide the correction curves. After corrections, the standard deviations of the residuals compared to the PASTEL catalog decrease from about 0.045/0.1 to 0.02/0.043 for LAMOST and Gaia, respectively. The chemical homogeneity of the open cluster M 44 is also improved by a factor of two. We stress that the underestimation of [Fe/H] could lead to an overestimation of binary fractions when selecting binary stars by the excess of luminosity. The method of this work could be applied to other data sets in the future. Our results will benefit statistic studies that use LAMOST and Gaia samples with a wide temperature range.

Keywords: Wide binary stars, Stellar abundances
Detecting and Characterizing Young Quasars. III. The Impact of Gravitational Lensing Magnification. We test the impact of gravitational lensing on the lifetime estimates of seven high-redshift quasars at redshift z ≳ 6. The targeted quasars are identified by their small observed proximity zone sizes, which indicate extremely short quasar lifetimes (t  Q  ≲ 105yr). However, these estimates of quasar lifetimes rely on the assumption that the observed luminosities of the quasars are intrinsic and not magnified by gravitational lensing, which would bias the lifetime estimates toward younger ages. In order to test the possible effects of gravitational lensing, we obtain high-resolution images of the seven quasars with the Hubble Space Telescope and look for signs of strong lensing. We do not find any evidence of strong lensing, i.e., all quasars are well described by point sources, and no foreground lensing galaxy is detected. We estimate that the strong-lensing probabilities for these quasars are extremely small (~1.4 × 10-5) and show that weak lensing changes the estimated quasar lifetimes by only ≲0.2 dex. We thus confirm that the short lifetimes of these quasars are intrinsic. The existence of young quasars indicates a high obscured fraction, radiatively inefficient accretion, and/or flickering lightcurves for high-redshift quasars. We further discuss the impact of lensing magnification on measurements of black hole masses and Eddington ratios of quasars.

Keywords: Supermassive black holes, Quasars
Steep Balmer Decrement in Weak AGNs May Not Be Caused by Dust Extinction: Clues from Low-luminosity AGNs and Changing-look AGNs. The hydrogen Balmer decrement (e.g., Hα/Hβ) is widely adopted as an indicator of the internal reddening of active galactic nuclei (AGNs). This is challenged by some low-luminosity AGNs and changing-look AGNs (CLAGNs), which have steep Balmer decrement but without strong evidence for absorption. We compile a sample of normal AGNs and CLAGNs with a wider distribution of bolometric Eddington ratio (λ Edd = L bol/L Edd) and find a strong negative correlation between Hα/Hβ and λ Edd, which suggests that the Balmer decrement is also accretion-rate dependent. We further explore the Balmer decrement based on the photoionization model using the Cloudy code by considering spectral energy distribution from the accretion disk with different accretion rates (e.g., disk/corona and truncated disk at high and low Eddington ratios, respectively). Both the standard disk and truncated disk predict a negative correlation of Hα/Hβ-λ Edd, where the relation is steeper in the case of the truncated disk. The negative correlations are also explored in two single CLAGNs. The measured negative correlation of Hα/Hβ-λ Edd is mainly caused by the lower responsivity $(d\mathrm{log}{L}_{\mathrm{line}}/d\mathrm{log}{L}_{\mathrm{cont}})$ in Hα relative to that in Hβ due to the larger optical depth in the former. We propose that the steep Balmer decrements in low Eddington ratio AGNs (e.g., some Seyferts 1.5-1.9 and CLAGNs) are not simply caused by absorption but mainly caused by the relatively low flux of ionizing photons.

Keywords: Accretion, Supermassive black holes, Seyfert galaxies, Active galactic nuclei, Line intensities