Sazuna/UAT_keywords huggingface dataset:
The Behavior of Bp He-weak Stars in the Far UV-Paper VII: HD 144334. The analysis of 14 spectra of the B8 He-weak Si star HD 144334 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution shortwards of 1600 Å over a time interval of about five days in 1994 October. In contrast, the level of the mid-UV flux did not vary between phases of FUV flux maximum and minimum which suggests that changes of the silicon continuous and line opacity play an important role in the variations.

Keywords: Helium-weak stars, Chemically peculiar stars
Formation of an Ultra Diffuse Satellite Galaxy. The formation of ultra diffuse satellite galaxies (UDSGs) within Λ CDM cosmology is a key area of study in theoretical galaxy formation because current models struggle to produce low-mass galaxies with a wide variety of morphologies. We identified 16 UDSGs around 8 Milky Way-mass hosts in the FIRE-2 simulations based on their large sizes in comparison to typical satellites. We selected an analogue of the observed Milky Way UDSG Antlia II in the stellar mass range 106-6.5 M ⊙ for further study. The analogue likely underwent a tidal shock near its first pericenter passage as it came within &lt;10 kpc of its host. The analogue galaxy subsequently experienced significant tidal stripping of its dark matter and puffing up of its stellar distribution, causing it to transform into an UDSG.

Keywords: Galaxy formation, Astronomical simulations, Low surface brightness galaxies
Hidden Companions to Intermediate-mass Stars. VI. Discovery of a 0.50M <SUB>⊙</SUB>, 6 au Companion to HIP 74696. A-type stars with a large long-term proper motion change and without a known companion to cause it are candidates for being Sirius analogues. However, in most cases the culprit is expected to be a hitherto unknown low mass companion rather than a white dwarf. Here we report the discovery of a 0.50M ⊙ companion to the nearby 1.64M ⊙ star HIP 74696 at a projected separation ρ = 118.9 mas ↔ 6.2 au based on a VLTI/GRAVITY observation. This companion explains the Gaia-Hipparcos proper motion change of the primary. Together with the wide 660 au companion that was found by Gaia DR3 to be a 0.70M ⊙ + 0.20M ⊙ 1.5 au binary, this makes HIP 74696 a quadruple and part of the growing class of high multiplicity systems with an A-type star primary. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Keywords: Optical interferometry, Multiple stars, A stars
Unprecedented X-Ray Emission from the Fast Blue Optical Transient AT2022tsd. We present the X-ray monitoring campaign of AT2022tsd in the time range δ t rest = 23-116 days rest-frame since discovery. With an initial 0.3-10 keV X-ray luminosity of L x ≈ 1044 erg s-1 at δ t rest ≈ 23 days, AT2022tsd is the most luminous FBOT to date and rivals the most luminous GRBs. We find no statistical evidence for spectral evolution. The average X-ray spectrum is well-described by an absorbed simple power-law spectral model with best-fitting photon index ${\rm{\Gamma }}={1.89}_{-0.08}^{+0.09}$ and marginal evidence at the 3σ confidence level for intrinsic absorption NHint ≈ 4 × 1019 cm-2. The X-ray light-curve can be either interpreted as a power-law decay L x ∝ t  α  with α ≈ - 2 and superimposed X-ray variability, or as a broken power-law with a steeper post-break decay as observed in other FBOTs such as AT2018cow. We briefly compare these results to accretion models of TDEs and GRB afterglow models.

Keywords: Transient sources, X-ray transient sources, Supernovae, High energy astrophysics
Extratidal Members of Segue 3 are Rare and Difficult to Confirm. We simulate extratidal members of Segue 3, a sparse, faint, and small, ~2.6 Gyr halo cluster, and investigate their observational detectability. Using the Gala package to simulate Segue 3's potential tidal tails, we find that the tails are narrow, linear, and around 4°-6° in length: the tails' position angles and width are most sensitive to the uncertainties in the cluster's distance and mean proper motion. Post-processing the synthetic tail particles to assign realistic observational properties, we infer that Segue 3 would have close to 25 extra-tidal members with G ≤ 23, concentrated ≲1.°33 from the center of the cluster. The 11 candidate extratidal members identified by Fadely and collaborators are comparable in number, but significantly closer to the cluster center (d ~ 4') than these simulations predict. This analysis demonstrates the difficulty of identifying extratidal stars in the Milky Way's halo clusters, even in deep photometric surveys.

Keywords: Globular star clusters, Open star clusters, Star clusters
X-Ray Observations of Type Ia Supernova 2018cqj. I report on Chandra X-ray observations of SN 2018cqj, a low luminosity Type Ia supernova that showed an Hα line in its optical spectrum. No X-ray emission was detected at the location of the SN, with an upper limit to the X-ray luminosity of 2 × 1039 erg s-1.

Keywords: Circumstellar matter, Type Ia supernovae, Supernovae, X-ray sources
G0.481-0.037, an Isolated Compact H II Region in Sgr B1. We present a near-infrared spectrum of the isolated compact H II region G0.481-0.037 taken with SpeX on the Infrared Telescope Facility. This spectrum shows strong lines of hydrogen Brγ, Brδ, Pα, and He I 2.059 μm. The radial velocity observed from the strongest line, Brγ, is V LSR = 77 ± 6 km s-1, significantly larger than the velocities of other ionized components of Sgr B1. We modeled the observed He I 2.059/Brγ ratio, 0.353 ± 0.075, with Cloudy C22.01 using model stellar atmospheres representing both dwarfs and giants. Our model ratios agree with the observed ratio for stellar effective temperatures of ~34,500 K for dwarfs and ~33,000 K for giants, from which we estimate late O spectral types for both luminosity classes. These values are consistent with the observed radio fluxes, given that the ionizing star of G0.481-0.037 is probably no longer embedded in its natal molecular cloud.

Keywords: Compact H II region, Galactic center, H II regions
The Behavior of Bp He-weak Stars in the far-UV-Paper VIII: HD 131120. The analysis of four spectra of the B8 He-weak star HD 131120 recorded by the SWP camera on board the International Ultraviolet Explorer reveals low amplitude variations of the far-ultraviolet spectral energy distribution shortwards of 1500 Å over about half its rotational period in 1984. Silicon must be distributed in a non uniform manner over the surface of HD 131120 so as to modulate the FUV flux over the rotational period. This confirms the results of earlier investigations based on phase resolved high resolution optical spectra.

Keywords: Helium-weak stars, Chemically peculiar stars
On the Most Reliable Value of the Galactic Aberration Constant. Galactic aberration (GA) is a small effect in proper motions of celestial objects with an amplitude of about 5 μas yr-1 already noticeable in highly accurate astrometric observations such as VLBI and Gaia. However accurate accounting for this effect faces difficulty caused by the uncertainty in the GA amplitude (GA constant). Its estimates derived from VLBI and Gaia data processing differ significantly, so it would be very desirable to involve another independent method to solve the problem of inconsistency between these two methods. Such a method, that I consider in this paper, is using determination of the Galactic rotation parameters by methods of stellar astronomy. The result obtained in this study showed that the GA constant estimate obtained from stellar astronomy is closer to the estimate obtained from Gaia.

Keywords: Milky Way rotation, Astrometry
2023 Recovery Observations and Characterization of the Active Centaur P/2010 TO20 (LINEAR-Grauer). We report the recovery of the Centaur P/2010 TO20 (LINEAR-Grauer) on CCD imaging data from three separate dates in 2023 April, May, and June from the 8.1 m Gemini South Telescope, representing its first known detections since 2012. The recovery observations display a compact coma and tail, consistent with ongoing activity after its recent 2022 November 27 perihelion passage. We estimate a nucleus radius upper-limit of r  n  ≤ 2.7 km. Due to the current uncertainty inherent in the nucleus' true size, we report a plausible range for the dust production of 2.7 cm ≤ Af ρ ≤ 14.5 cm after subtraction of an assumed nucleus flux based on radii of 2.7 km and 0.5 km, respectively. P/2010 TO20 experienced a recent and well-defined orbital change and associated change in thermal environment, making it an exciting target through which to study Centaur activity drivers and their evolution as their orbits change in real-time.

Keywords: Short period comets, Centaur group
Super-Earth GJ 667Cc: Age and XUV Irradiances of the Temperate-zone Planet with Potential for Advanced Life. GJ 667Cc is a nearby (23.6 lt-yr) super-Earth that orbits within the habitable zone (HZ) of its ~M2V host star and has Earth-like properties: (M- $\sin (i)\sim 4.1\,{M}_{\oplus };$ R ~ 1.7 R ⊕; T eq (A = 0.3) ~ 277 K). The age of the star/planet is poorly constrained at 2 ≳ Gyr. Age is crucial in evaluating the potential for complex life. We determine an age of ~6.10 ± 2.2 Gyr from our recent Age-Rotation relations. This is compatible with its low metallicity ([Fe/H] ~ -0.59 ± 0.1 dex), weak coronal/chromospheric X-ray/FUV emissions, and space motions. We also determine the photodissociating/photoionizing X-ray-UV irradiances from Chandra and ROSAT X-ray and HST/FUV observations. Like most HZ-planets hosted by M-dwarfs, these irradiances are much higher than Earth's and are detrimental to the planet's atmosphere retention, water inventories, and habitability. A strong geomagnetic field could mitigate atmospheric erosion, permitting life to develop.

Keywords: M dwarf stars, Late-type stars, Stellar ages, Exoplanets, Super Earths, Late-type dwarf stars, Habitable planets
An Observational Upper Limit on the Rate of Gamma-Ray Bursts with Neutron Star-Black Hole Merger Progenitors. Compact-object binary mergers consisting of one neutron star and one black hole (NSBHs) have long been considered promising progenitors for gamma-ray bursts, whose central engine remains poorly understood. Using gravitational-wave constraints on the population-level NSBH mass and spin distributions we find that at most 20 Gpc-3 yr-1 of gamma-ray bursts in the local universe can have NSBH progenitors.

Keywords: Neutron stars, Gamma-ray bursts, Black holes, Gravitational wave sources
An Astrometric Mass Estimate for (624) Hektor. Jupiter Trojans are remnants of the early solar system. In this research note I present and discuss the mass and the bulk density of the largest Jovian Trojan (624) Hektor, obtained from its gravitational interaction with (437759) 2014 GG47.

Keywords: Small Solar System bodies, Asteroids, Asteroid dynamics, Jupiter trojans, Trojan asteroids
Hidden Companions to Intermediate-mass Stars. VII. Discovery of a 0.76 M <SUB>⊙</SUB>, 39 au Companion to the Ap Star HIP 88866 = π Pavonis. HIP 88866 = π Pavonis is a nearby chemically peculiar Ap star. Here we report the discovery of a companion with an H band contrast ΔH = 3.63 at a projected separation ρ = 959 mas ↔ 39 au based on the acquisition camera image of a VLTI/GRAVITY observation. Isochrone fitting yields masses M  A  = 1.80 M ⊙ and M  B  = 0.76 M ⊙ and an age of 1.4 Gyr. However, even for a face-on orbit the companion cannot fully account for the GaiaDR3-Hipparcos proper motion change of π Pav. We present constraints on the nature and location of a putative additional closer companion based on the lack of its detection in the interferometric data. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Keywords: Optical interferometry, Multiple stars, Ap stars
The Behavior of Bp He-weak Stars in the Far UV-Paper IX: HD 142990. The analysis of eighteen spectra of the B6 He-weak star HD 142990 recorded by the SWP camera on board the International Ultraviolet Explorer reveals variations of the far-ultraviolet spectral energy distribution shortwards of 1700 Å over about 6 hr, ie. about 25% of the rotational period. Several Si II, Si III and Si IV vary consistently. Silicon must be distributed in a non uniform manner over the surface of HD 142990 so as to modulate the FUV flux over the rotational period. The low resolution spectra also confirm this variability.

Keywords: Helium-weak stars, Chemically peculiar stars
VVV-VIVACE ID 533558 (=OGLE RRLYR-09505): The Half-day Period as a Challenge for the Automatic Searches for Variable Stars. Searches for periodic variable stars are susceptible to seasonal aliases caused by sampling. Nightly observations from ground based telescopes produce a large number of false detections at the integer multiples of day-1 frequency. Here we discuss the case of VISTA Variables in the Vía Láctea-VIrac VAriable Classification Ensemble (VVV-VIVACE) ID 533558, classified by the VIVACE using machine learning as an EA/EB binary with a period of P = 0.6659 day, in contradiction with a previous classification as an AB-type RR Lyrae with period P = 0.4992 day by the OGLE survey. We discuss the problem of phase coverage causing the misclassification with a wrong period by the VVV, in spite of a robust set of 652 data points over six years of observations. As automatic light-curve classifications of large data sets become more popular, this is a problem that cannot be overlooked.

Keywords: Surveys, RR Lyrae variable stars, Variable stars, Eclipsing binary stars, Milky Way Galaxy
Photometry of Type II Supernova SN 2023ixf with a Worldwide Citizen Science Network. We present highly sampled photometry of the supernova (SN) 2023ixf, a Type II SN in M101, beginning 2 days before its first known detection. To gather these data, we enlisted the global Unistellar Network of citizen scientists. These 252 observations from 115 telescopes show the SN's rising brightness associated with shock emergence followed by gradual decay. We measure a peak M  V  = - 18.18 ± 0.09 mag at 2023 May 25 21:37 UTC in agreement with previously published analyses.

Keywords: Type II supernovae, Supernovae, Core-collapse supernovae
Cosmic Dark Dawn. Could self-interacting dark matter dominate most of the cosmic dawn at redshifts between z of 1000 and of 50?

Keywords: Dark matter density, Black hole physics
Modeling the Free Inclinations of the Classical Kuiper Belt with the von Mises-Fisher Distribution. The orientations of orbital planes of minor planets are directional random variables. Their free inclination is the deviation of the orbit plane from the plane forced by the major planets. We construct a model of the distribution of free inclinations of classical Kuiper Belt objects (CKBOs) based on the von Mises-Fisher (vMF) distribution function, the analog of the normal distribution for directional statistics. The CKBOs are known to have a "cold" component of orbit planes concentrated near the forced plane and a more widely dispersed "hot" component. Adopting a model with a linear combination of two vMF functions, we find that the cold and hot components account for 57% and 43%, characterized by widths of 1.°7 and 12.°9, respectively. This model improves upon previous models based on smaller observational samples and empirical choices of functional forms for inclination distributions.

Keywords: Small Solar System bodies, Kuiper belt, Classical Kuiper belt objects, Trans-Neptunian objects
Scarlet Spectra: Two Red L Dwarfs Revealed by SOAR. We present the analysis of two unusually red L dwarfs, CWISE J075554.14-325956.3 (W0755-3259) and CWISE J165909.91-351108.5 (W1659-3511), confirmed by their newly obtained near-infrared spectra collected with the TripleSpec4 spectrograph on the Southern Astrophysical Research Telescope. We classify W0755-3259 as an L7 very low-gravity dwarf, exhibiting extreme redness with a characteristic peaked H-band and spectral indices typical of low-gravity late-type L dwarfs. We classify W1659-3511 as a red L7 field-gravity dwarf, with a more rounded H-band peak and spectral indices that support a normal gravity designation. W1659-3511 is noticeably fainter than W0755-3259, and the rounded H-band of W1659-3511 may be evidence of CH4 absorption.

Keywords: Brown dwarfs, L dwarfs, Spectroscopy, Near infrared astronomy
The "Super-Active" Accretion Phase of T CrB has Ended. The symbiotic recurrent nova T CrB erupted for the second and last recorded time in 1946. Following the outburst, the accretion rate onto its WD has remained rather low with only occasional and minor flaring episodes, until in late 2014 it entered a "super-active" phase (SAP) that peaked in 2016 April: the flux radiated by Balmer lines increased by two orders of magnitude, accompanied by the appearance of strong He I, He II, and many other emission lines. Following the sharp maximum, the intensity of the emission lines has been steadily decreasing, reaching back to pre-SAP levels by mid-2023. The end of SAP is also confirmed by the drop of B-band brightness to pre-SAP conditions and the simultaneous re-appearance of a large-amplitude flickering. This suggests that the accretion disk has emptied from the extra material that has driven the "super active" state and has completed its transfer onto the WD, setting the stage for a new and probably imminent nova eruption.

Keywords: Stellar accretion disks, Symbiotic binary stars, Recurrent novae
A Jupiter-family Comet Discovery via Citizen Science: 2005 XR132. We report the discovery of cometary activity associated with minor planet 2005 XR132, a finding facilitated by our NASA Partner program Active Asteroids, hosted on the Zooniverse online Citizen Science platform. Volunteers identified activity in a Dark Energy Camera image of 2005 XR132 from UT 2021 March 26, and our own investigation uncovered additional images of activity in Zwicky Transient Facility data spanning UT 2021 January 3 through March 31. 2005 XR132 has a semimajor axis a = 3.760 au, eccentricity e = 0.432, inclination i = 14.°474, and a Tisserand parameter with respect to Jupiter of T J = 2.869, and thus is dynamically classified as a Jupiter-family comet.

Keywords: Comet tails, Short period comets, Asteroids
New Dimming Events in Southern R Coronae Borealis Stars. This paper reports on photometry of dimming events for three Southern R Coronae Borealis (RCB) stars. Two of these stars have recently entered a dimming phase (IO Nor and V653 Sco), while the other (GU Sgr) is emerging from a dimming event. Low resolution spectra of one of the targets indicates blueshifted Na I D lines, and hydrogen alpha emission. As the number of known RCBs grows, the need to monitor them and detect dimming events at an early stage increases.

Keywords: R Coronae Borealis variable stars, Johnson photometry, Spectroscopy
Assessing the Accuracy of TESS Asteroseismology with APOGEE. The recent NASA TESS mission has the potential to increase the available asteroseismic sample dramatically, but its precision and accuracy have yet to be confirmed. To date, NASA's Kepler mission has been considered the gold standard for asteroseismic samples, despite data only being available for a small portion of the sky. TESSs observations cover the whole sky, and previous work has identified 158,000 potential red giant oscillators. Using APOGEE, which is calibrated to the asteroseismic scale of the Kepler data, we show that seismology from TESS is calibrated to the Kepler scale to better than 5% for about 90% of red giants, and has only slight trends with mass, metallicity, and surface gravity. We therefore conclude that current TESS seismic results can already be used for galactic archeology, and future results are likely to be highly transformational to our understanding.

Keywords: Red giant stars
Spectroscopic Follow-up of Two Star-forming Objects in the M101 Field. We present the spectra of two faint star-forming objects originally identified in our deep narrowband survey of the M101 Group. One is an isolated H II region near the M101 Group galaxy NGC 5474, and the other is projected close to the background galaxy NGC 5486. Both are spectroscopically confirmed to be physically associated with their nearby host. We estimate the oxygen abundances for each system using strong-line methods. For the source near NGC 5474, we use GALEX UV photometry to estimate an age of ~200 Myr and suggest a connection to the M101-NGC 5474 interaction. *Based on observations obtained with the Hobby-Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen.

Keywords: Star forming regions, Chemical abundances, Spectroscopy
Evolution of Circumstellar Disks around T Tauri Stars as a Function of Stellar Age. We analyzed the distribution of surface gravities, $\mathrm{log}\,g$ , of a sample of classical T Tauri stars in Taurus to examine the relationship between stellar ages and circumstellar disk evolution. This is critical to understanding the timescales for planet formation. Given the uncertainties in $\mathrm{log}\,g$ , we find no distinction between the ages of stars with and without disks beyond that identified previously. This approach, while avoiding the contamination that plagues young star luminosity measurements, will require precisions in $\mathrm{log}\,g$ of 0.05 dex or better to be effective.

Keywords: Pre-main sequence stars, Early stellar evolution
Bias in Polarization CLEAN Imaging. Various deconvolution algorithms, such as Hogbom CLEAN, have been developed to construct radio images of the sky. The algorithms used for synthesis imaging in CASA are sub-optimal for polarimetric imaging of sources with nonzero rotation measures. This method focuses on linear polarization in Stokes Q and U and the bias introduced in cleaning linearly polarized sources. We propose a hybrid method of cleaning based on QU fitting to reduce this bias. This method acquires a fit for a source's spectral index, polarization angle, Stokes I amplitude, polarized fraction, and rotation measure from a dirty image and uses these parameters to form a model that is fed into CASA for cleaning. Preliminary results show that this method cleans faster than the existing CASA task but introduces some degeneracies that need to be resolved prior to polarimetric imaging.

Keywords: Radio astronomy, Algorithms, Astronomy image processing
Optical and Near-infrared Atmospheric Extinction Coefficients at La Silla. We used observations obtained at the Rapid Eye Mount (REM) at the La Silla Observatory between 2016 June 7 UT to determine the extinction coefficients of the REM filters currently in use. The observations were obtain on 6 nights, spanning 2016 June UT through 2016 July 4 UT, over a wide range of airmass values, to determine the mean atmospheric extinction coefficients at the La Silla Observatory site. Coefficients in the REM filter sets-Sloan g', r', i', z', and J, H and K were determined, where the REM infrared filters closely match those of the J, H, and Ks filters of the 2MASS All-Sky Survey.

Keywords: Atmospheric extinction