Sazuna/UAT_keywords huggingface dataset:
An Updated Ephemeris for K2-138 d. K2-138 d (EPIC 245950175 d) is one of five planets in a chain of 3:2 mean motion resonances discovered by Christiansen et al. in K2 Campaign 12. An additional planet, confirmed with the Spitzer Space Telescope by Hardegree-Ullman et al., is not in the resonant chain. The near first-order resonances, coupled with the planets being locked in a set of three-body Laplace resonances, make this system a unique target to study for transit timing variations (TTVs). As the predicted transit timing amplitude (~7 minutes) was below the typical transit timing uncertainty (~10 minutes) of the K2 data, Christiansen et al. were unable to detect TTVs for K2-138 d in the K2 time series. Here, we describe new observations that allow us to refine the ephemeris for K2-138 d and perform a brief search for TTVs. Our efforts result in a refined orbital period that is 19 times more precise than previously available measurements, but our data are insufficient to confirm a TTV signal for K2-138 d.

Keywords: Exoplanets, Exoplanet systems, Exoplanet astronomy, Transit timing variation method, Exoplanet detection methods
Spurious Radial Migration from Relativistic Effects in the Milky Way Disk. The gradient of the gravitational redshift in the potential of the Milky Way induces an apparent spurious radial migration. I show that this effect is simply related to the local acceleration, which was measured recently by Gaia eDR3, implying a spectroscopic shift of -2.4 × 10-2(r/8 kpc)-1 km s-1 kpc-1. The transverse Doppler effect yields a comparable contribution. The spurious radial velocity from both relativistic effects amounts to crossing a major portion of the Milky Way disk during the age of the universe, and must be corrected for in any future measurement of the actual radial migration of stars.

Keywords: Milky Way dynamics
Applying Random Forest Classification to Ultracool Dwarf Discovery in Deep Surveys. I. Color Classification with SDSS, UKIDSS, and WISE Photometry. In this first of two studies, we apply a random forest model to classify ultracool dwarfs from broadband color information. Using the Skrzypek et al. ultracool dwarf sample and a set of background sources, we trained a random forest classifier based on 28 colors derived from optical and infrared photometry from SDSS, UKIDSS, and WISE. Our model achieves 99.7% accuracy in segregating L- and T-type UCDs from background sources, and 97% accuracy in separating spectral subgroups. A separate random forest regressor model achieved a spectral classification precision of 1.3 subtypes. We applied these models to a 12.6 deg2 region with overlapping SDSS, UKIDSS, and WISE coverage and identified 35 UCD candidates, five of which are previously reported, of which four are photometrically or spectroscopically classified UCDs. Our random forest model can be applied to multiple surveys to greatly expand the known census of UCDs.

Keywords: Brown dwarfs, Classification, Surveys, L dwarfs, Stellar classification, Low mass stars, Random Forests, T dwarfs
Applying Random Forest Classification to Ultracool Dwarf Discovery in Deep Surveys. II. Color Classification with PanSTARRS, 2MASS, UKIDSS, and WISE Photometry. We evaluate color-based classifiers in a synthesis of Pan-STARRS, 2MASS, UKIDSS, and AllWISE catalogs to identify ultracool dwarfs (UCDs). Using the Best et al. compilation of UCDs and a sample of background sources as our training set, we constructed a two-tier random forest model to segregate UCDs from non-UCDs and sort them into spectral subgroups. We also developed a regressor model to infer numerical classifications. Our classifier models achieved accuracies of 97%-99%, while our regressor model achieved a classification accuracy of 0.64 subtypes for classifications M5-T8. We applied these models to a 7 deg2 region with overlapping survey data and identified 336 UCD candidates, of which 26 are previously identified UCDs and 17 are extragalactic sources.

Keywords: M dwarf stars, Brown dwarfs, Surveys, L dwarfs, Random Forests, T dwarfs
The Refined Transit Ephemeris of TOI-2180 b. The Transiting Exoplanet Survey Satellite (TESS) observed a single transit of the giant exoplanet TOI-2180 b in Sector 19 of its primary mission. A subsequent effort to characterize this system found that the orbital period of TOI-2180 b is 260.8 ± 0.6 days. This level of precision precludes most efforts to detect future transits and to further understand this exoplanet. We present a new transit of TOI-2180 b observed by TESS in Sector 48 and update the planet's transit ephemeris with its precisely measured orbital period. The refined ephemeris enables future transit observations to explore this planet's atmosphere or to search for rings or moons.

Keywords: Exoplanet astronomy, Transits, Extrasolar gaseous giant planets
Solar Calibration of the Convective Mixing Length for Use with the ÆSOPUS Opacities in MESA. The simplistic but ubiquitous Mixing Length Theory (MLT) formalism is used to model convective energy transport within 1D stellar evolution calculations. The formalism relies on the free parameter α MLT, which must be independently calibrated within each stellar evolution program and for any given set of physical assumptions. We present a solar calibration of α MLT appropriate for use with the ÆSOPUS opacities, which have recently been made available for use with the MESA stellar evolution software. We report a calibrated value of α MLT = 1.931 and demonstrate the impact of using an appropriately calibrated value in simulations of a 3M ⊙ asymptotic giant branch star.

Keywords: Stellar convective zones, Stellar atmospheric opacity, Stellar evolutionary models
On the Stellar Metallicity Distribution Resulting from a Disrupted Milky Way Globular Cluster System. Consideration is given to the stellar metallicity distribution that would result from a hypothetical dissociation of all Milky Way globular clusters into field stars, and several characteristics are compared to an exponential distribution.

Keywords: Globular star clusters
Long-term Stability of Six Neptunian Trojans. This paper explores the long-term stability of six Neptunian Trojans. In contrast with other Neptunian Trojans, these objects have previously unknown lifetimes and larger orbital uncertainties due to their shorter observational arcs. We obtained new astrometry of the six Trojans using the Magellan telescope, refit their orbits, and performed Gyr-long numerical integrations to estimate their lifetimes. The results show that five of these six objects are stable over Gyr timescales. The remaining object, 2015 VV165, has a calculated lifetime of 0.691 ± 0.001 Gyr, which is similar to the previous estimate of 0.65 Gyr. As a result, the shorter lifetime of this latter object is most likely physical (rather than due to uncertainties in its orbital determination).

Keywords: Small Solar System bodies, Solar system, Trojan asteroids, Neptune trojans, Trans-Neptunian objects
Using Maximum Circular Velocity in Halo Occupation Distribution Models to Predict Galaxy Clustering. Standard halo occupation distribution (HOD) models predict how galaxies occupy halos based on a single property, the virial mass, M vir. To incorporate galaxy assembly bias, we consider alternative halo mass proxies to use in the HOD. A promising replacement is maximum circular velocity, ${V}_{\max }$ , which measures the halo's potential well, and successfully predicts galaxy clustering in subhalo abundance matching models. We fit galaxy clustering measurements from SDSS DR7 with two modified HODs besides the standard M vir-based model: one where ${V}_{\max }$ is used as the halo property that determines galaxy occupation, and the other adopting an adjustable combination of M vir and ${V}_{\max }$ . Except for the reduced volume M  r  &lt; - 20 threshold sample fit with ${V}_{\max }$ alone, neither change improves the model performance in predicting the projected two-point correlation function, w p. We conclude that switching the primary variable to ${V}_{\max }$ does not significantly improve the HOD model's ability to fit galaxy clustering.

Keywords: Galaxy dark matter halos, Galaxy formation, Astronomical models, Galaxy evolution
New Constraints on the Composition and Initial Speed of CNEOS 2014-01-08. We study the newly released light curve from the fireball of the first interstellar meteor CNEOS 2014-01-08. The measured velocity and three observed flares down to an altitude of 18.7 km imply ambient ram pressure in the range of 113-194 MPa when the meteor disintegrated. The required yield strength is ≳20 times higher than stony meteorites and ≳2 times larger than iron meteorites. The implied slowdown in the atmosphere suggests an initial speed of about 66.5 km s-1, strengthening the case for an interstellar origin of this meteor and making it an outlier relative to the velocity dispersion of local stars.

Keywords: Meteorite composition, Bolides, Meteors, Interstellar objects, Meteorites
Novel Correlations between Diffuse Interstellar Bands and Optical Reddening. The relatively new and expansive Apache Point Observatory Catalog of Optical Diffuse Interstellar Bands was analyzed to identify novel correlations between diffuse interstellar bands (DIBs) and optical reddening E(B - V), with a principal aim being to facilitate future identifications of the host molecular carriers. The following lines exhibit the highest Pearson r correlations in descending order (0.930 ≥ r ≥ 0.885), and are tied to DIBs featuring n ≥ 10 sightlines and possessing equivalent width uncertainties: λ (Å) ≃ 5236.27, 5793.24, 5797.18, 6449.27, 6795.26, 5948.87, 6113.22, 6860.02, 6059.34, 6520.74. Independent observations to confirm the preliminary trends are desirable, and extinction estimates could be subsequently inferred for targets by relying on longer-wavelength (NIR) photometric calibrations linked to a weighted subset of numerous DIBs. Lastly, several DIBs appear unassociated with E(B - V), thereby reaffirming that diverse carriers exist.

Keywords: Diffuse interstellar bands, Interstellar reddening, Interstellar medium, Astrochemistry
Rotationally Constrained Convection in the Sun: Applicable to Planetary Atmospheres?. Rotational suppression of convection can occur on length scales which are larger than a critical length. Featherstone &amp; Hindman suggest that this can account for a second preferred length-scale in solar convection on supergranule scales. Here, I explore if rotational suppression of convection also occurs in the atmospheres of Earth and Venus.

Keywords: Solar convective zone
A SuperWASP Light Curve Displaying a Single Long-duration Transit: A Jupiter Size Exoplanet in a Very Distant Orbit?. We present the SuperWASP light curve of a 10th magnitude A7V star containing a single, well-defined U-shaped transit-like event lasting around 11 days with a depth of 1.1%. The star is otherwise non-variable throughout the 8 yr duration of the observations. If the event is modeled as an exoplanet transit, it is compatible with a 1.8 R J exoplanet in a ~205 au orbit with a period of ~2200 yr.

Keywords: Transit photometry, Exoplanets
Gangotri Wave-A High Density Gas Ripple in the Inner Galaxy. Recently, we reported the discovery of a kpc-scale CO structure in the inner Galaxy which we named the Gangotri wave. The structure is at least 2 kpc in extent and its vertical distribution is wave-like in morphology. The analysis of the velocity data suggests Gangotri wave being a spur of the Milky Way or a sub-branch of the Norma arm. Following the discovery, there is a rebuttal published, expressing concerns on identifying the inner Galaxy CO emission features as a single coherent structure. In this article, we aim to address the concerns of the rebuttal article, hoping to clarify some of the criticisms.

Keywords: Spiral arms, Galaxy structure, Interstellar filaments
The Behavior of HgMn Stars in the Far UV -1: χ Lupi. The analysis of nine high resolution SWP spectra of the HgMn star χ Lupi obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far-ultraviolet flux of χ Lupi remained probably constant over a timescale of about 24 hr, i.e., about 25% of the recently determined rotational period. Whereas eight spectra have levels consistent with the average spectrum, one spectrum shows a lower flux by about 15%. This probably reflects an instrumental effect, possibly a loss of the flux (the star may have slipped outside the aperture for a fraction of the exposure). The available IUE data do not rule out variations in the FUV flux.

Keywords: Chemically peculiar stars
Regional Investigations of Polygonal Impact Craters on the Moon and Vesta. Studies suggest that fracture systems are the driving mechanism for the formation of polygonal impact craters (PICs) on planetary bodies including the Moon and Vesta. We used the Java Mission-planning and Analysis for Remote Sensing crater application to investigate PICs on regional scales for both the Moon and Vesta to further understand how surface and subsurface fracture systems play a role in PIC formation. We measured the number of straight rim segments (sides) for each PIC, measured the angle between each of the straight rim segments and calculated the mean angle for each crater and the mean angle for the body to conduct a further analysis with other planetary bodies. The comparison with other planetary bodies helps to identify how PIC formation may vary based on a body's surface composition. From this study, it appears that surface fractures are not the main driving mechanism for PIC formation within our study regions and instead subsurface fractures may be the more dominant factor.

Keywords: Asteroid satellites, Lunar craters, Vesta, Lunar impacts
The Behavior of HgMn Stars in the Far UV -2: μ Leporis. The analysis of 8 high resolution SWP spectra of the HgMn star μ Leporis obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far ultraviolet flux of μ Leporis remained probably constant over a timescale of about 29 hr, ie. about 40% of the recently determined rotational period. One spectrum taken 10 yr before also has the same level than the average spectrum of the run. Whereas seven spectra of the 29 hr run have levels consistent with the average spectrum, one spectrum shows a lower flux by about 7% probably caused by a loss of the flux. The spectra taken with the LWP camera consistently show that the mid-UV flux remained stable over the 29 hr run. Hence the available IUE data do not show evidence of real flux variations in the ultraviolet range for μ Leporis.

Keywords: Chemically peculiar stars
An Intuition for Physicists: Information Gain From Experiments. How much one has learned from an experiment is quantifiable by the information gain, also known as the Kullback-Leibler divergence. The narrowing of the posterior parameter distribution P(θ∣D) compared with the prior parameter distribution π(θ), is quantified in units of bits, as: ${D}_{\mathrm{KL}}(P| \pi )=\int {\mathrm{log}}_{2}\left(\displaystyle \frac{P(\theta | D)}{\pi (\theta )}\right)\,P(\theta | D)d\theta \mathrm{bits}$ This research note gives an intuition what one bit of information gain means. It corresponds to a Gaussian shrinking its standard deviation by a factor of three.

Keywords: Kullback-Leibler distance, Astronomy data analysis
The Study of Quasar Clustering at Low Redshifts. We use a nearest neighbor algorithm combined with the machine learning clustering function Density-Based Spatial Clustering of Applications with Noise to analyze a subset of quasars from the Sloan Digital Sky Survey. Our analysis shows evidence of clustering up to z ~ 2, with evidence of an increase in clustering at lower redshifts (z &lt; 0.5). Our findings may suggest that, over time, the gravitational interaction between quasars has led to more clustering at low redshifts.

Keywords: Clustering, Quasars
Characteristics of the Permanent Superhumps in V533 Herculis. We analyze two sectors of Transiting Exoplanet Sky Survey (TESS) photometry of the nova-like cataclysmic variable star V533 Her. We detect a periodicity consistent with the binary orbital period and estimate a revised value of 3.53709(2) hr. We also detect a strong signal near a period of 3.8 hr that we associate with positive superhumps. The superhump frequency varies over the TESS observations with the fractional difference between the superhump and orbital periods, ϵ, ranging between 0.055 ≤ ϵ ≤ 0.080. The superhump amplitude is correlated with its frequency such that the amplitude increases as ϵ decreases. Positive superhumps result from an instability that generates an eccentric accretion disk and ϵ is a measure of the disk precession rate in the binary rest frame. The observed correlation implies that as the disk precession rate slows, the disk eccentricity increases.

Keywords: Nova-like variable stars, Cataclysmic variable stars, White dwarf stars, SU Ursae Majoris stars
Spectroscopic Signature of a Re-established Accretion Disk in Symbiotic-like Recurrent Nova RS Ophiuchi. A novel method is presented which can pin down the time the accretion disk re-established itself in the RS Oph system after it experienced a nova disruption. The method is based on the re-ionization of the ejecta by photoionization from the radiation released in the boundary layer from accretion.

Keywords: Shocks, Recurrent novae, Classical novae
The Behavior of HgMn Stars in the Far UV-3: 53 Tau and HD 35548. The analysis of high resolution SWP spectra of the HgMn stars HD 27295 (53 Tau) and HD 33548 obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far ultraviolet flux of these two stars remained constant over the various observations with IUE. The TESS lightcurves of 53 Tau show a periodic sine structure with a period estimated to be around 4.43 days whereas that of HD 35548 do not show evidence for periodic variability. The absence of far and mid-UV variability of these two stars precludes the presence of large chemical gradients over their surfaces at the time of the IUE observations.

Keywords: Chemically peculiar stars
X-Ray and Ultraviolet Observations of the Eclipsing Binary V471 Tauri with XMM-Newton: X-Ray-Cycles, Eclipse Timings and Further Evidence of a Substellar Tertiary Companion. Few stars offer as much toward understanding fundamental aspects of stellar astrophysics and binary star evolution than the eclipsing binary V471 Tauri (DAZ+K2V; P = 12.52 hr). V471 Tauri (Tau) is the product of common-envelope binary evolution and a pre-cataclysmic variable. X-ray and UV (291 nm) observations were secured with XMM-Newton over ~ 62 ks during 2019 September. X-ray and UV photometry show variations over the binary's orbit as well as flares. A precise eclipse timing was obtained from the UV photometry with the Optical Monitor. The timing was added to prior measures and fit with a 35.6 yr Light-Travel-Time-Effect (LTTE) Keplerian orbit of a substellar, tentative brown dwarf companion. However, this companion was not detected by VLT/SPHERE. The LTTE third-body solution appears reliable, now covering ~50 yr of timings. The non-detection of the companion may be due to changes in its physical properties during the high-mass loss common envelope stage.

Keywords: Eclipsing binary stars, X-ray bursts, Stellar activity
An Implementation of Stochastic Forces for the N-body Code REBOUND. We describe the implementation of a new module which can be used to simulate physical systems in which the motion of particles is affected by stochastic forces. Such forces are expected to be present in turbulent circumstellar disks or remnant planetesimal disks. Our implementation offers a convenient way to generate correlated noise with a user-specified amplitude and auto-correlation time for each particle. The module has minimal memory requirements and is freely available within the REBOUNDx additional effects library.

Keywords: Planetary migration, Open source software, N-body simulations
370 New Eclipsing Binary Candidates from TESS Sectors 1-26. We present 370 candidate eclipsing binaries (EBs), identified from ~510,000 short cadence TESS light curves. Our statistical criteria identify 5105 light curves with features consistent with eclipses (~1% of the initial sample). After visual confirmation of the light curves, we have a final sample of 2288 EB candidates. Among these, we find 370 sources that were not included in the catalog recently published by Prša et al. We publish our full sample of 370 new EB candidates, and statistical features used for their identification, reported per observation sector.

Keywords: Eclipsing binary stars
Anisotropy of Halo Main Sequence Turnoff Stars Measured with New MMT Radial Velocities and Gaia Proper Motions. We measure the anisotropy of the Milky Way stellar halo traced by a dense sample of 18 &lt; r &lt; 21 mag F-type main sequence turnoff stars using Gaia eDR3 proper motions and new radial velocity measurements published here.

Keywords: Milky Way stellar halo, Milky Way dynamics, Halo stars, F stars
Detecting the Memory Effect from a Massive Black Hole Merger at the Galactic Center through Lunar Ranging. A gravitational wave pulse from a major merger of massive black holes at the Galactic center induces a permanent increase in the Earth-Moon separation. For black holes of mass ~106 M ⊙, the shift in the local gravitational potential is comparable to the Earth-Moon potential, leading to the Moon being perturbed relative to the Earth during the passage of the pulse. The permanent increase in the Earth-Moon separation is a fraction of a millimeter, measurable by lunar ranging for future merger events.

Keywords: Gravitational waves
A newly discovered southern HgMn star: HD 4065A. Evidence is presented that HD 4065A is a newly discovered HgMn star. The Hg II line at 3983.93 Å is present in two spectra acquired with the High Resolution Spectrograph mounted behind the South African Large Telescope and separated by about 2 months and 25 days. The lines on the second spectrum are redshifted reflecting the orbital motion of HD 4065A around the center of mass of a binary system. The far-ultraviolet spectrum, SWP 20399 collected with IUE, shows a strong resonance line of Ga II usually conspicuous in the far-ultraviolet spectra of HgMn star. A first spectrum synthesis of the spectral range from 3900 up to 4000 Å yields estimates of the abundances of calcium (0.10 solar), zirconium (25 solar) and mercury (50,000 solar).

Keywords: Chemically peculiar stars
Yet Another Odd Radio Circle?. The Odd Radio Circles are newly identified diffuse radio sources at ~1 GHz frequency, with edge-brightened nearly circular morphology, which is remarkably similar to supernova remnants although a physical association with previous population of Galactic supernova remnants is challenging due to detections of the Odd Radio Circles at high Galactic latitudes. Here, a serendipitous identification of a new source in a LOFAR 144 MHz image with similar morphology as that of Odd Radio Circles is reported. This is the first reported identification of an Odd Radio Circle at a very low frequency and with the LOFAR.

Keywords: Radio continuum emission, Extragalactic radio sources, Supernova remnants, Sky surveys
Intergalactic Travel with MOND Rockets. An attractive interpretation of MOdified Newtonian Dynamics as an alternative to dark matter, changes the inertia of matter at accelerations a ≲ a 0 ≈ 1.2 × 10-8 cm s-2. I show that if inertia is modified at low accelerations, this suppresses the exponential factor for the required fuel mass in low acceleration journeys. Rockets operating at a ≪ a 0 might allow intergalactic travel with a modest fuel-to-payload mass ratio.

Keywords: Baryonic dark matter, Dark matter
The Entry of Supergiants into the Astronomical Lexicon. The early use of the term supergiant within the published literature has been traced from text searches carried out with the SAO/NASA Astrophysics Data System.

Keywords: History of astronomy, Supergiant stars