Sazuna/UAT_keywords huggingface dataset:
Barrel Instability in Binary Asteroids. Most close-in planetary satellites are in synchronous rotation, which is usually the stable end-point of tidal despinning. Saturn's moon Hyperion is a notable exception by having a chaotic rotation. Hyperion's dynamical state is a consequence of its high eccentricity and its highly prolate shape. As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries, and a minority of asteroidal secondaries may be in that state. The question of secondary rotation is also important for the action of the binary Yarkovsky-O'Keefe-Radzievskii-Paddack (BYORP) effect, which can quickly evolve orbits of synchronous (but not nonsynchronous) secondaries. Here we report results of a large set of short numerical simulations which indicate that, apart from synchronous and classic chaotic rotation, close-in irregularly shaped asteroidal secondaries can occupy an additional, intermediate rotational state. In this "barrel instability" the secondary slowly rolls along its long axis, while the longest axis is staying largely aligned with the primary-secondary line. This behavior may be more difficult to detect through lightcurves than a fully chaotic rotation, but would likewise shut down BYORP. We show that the binary's eccentricity, separation measured in secondary's radii and the secondary's shape are all important for determining whether the system settles in synchronous rotation, chaotic tumbling, or barrel instability. We compare our results for synthetic asteroids with known binary pairs to determine which of these behaviors may be present in the near-Earth asteroid binary population.

Keywords: Asteroid satellites, Asteroid rotation, Asteroid dynamics
A Sublime Opportunity: The Dynamics of Transitioning Cometary Bodies and the Feasibility of In Situ Observations of the Evolution of Their Activity. The compositional and morphological evolution of minor bodies in the solar system is primarily driven by the evolution of their heliocentric distances, as the level of incident solar radiation regulates cometary activity. We investigate the dynamical transfer of Centaurs into the inner solar system, facilitated by mean motion resonances with Jupiter and Saturn. The recently discovered object P/2019 LD2 will transition from the Centaur region to the inner solar system in 2063. In order to contextualize LD2, we perform N-body simulations of a population of Centaurs and Jupiter-family comets. Objects between Jupiter and Saturn with Tisserand parameter T  J  ~ 3 are transferred onto orbits with perihelia q &lt; 4 au within the next 1000 yr with notably high efficiency. Our simulations show that there may be additional LD2-like objects transitioning into the inner solar system in the near future, all of which have low ΔV with respect to Jupiter. We calculate the distribution of orbital elements resulting from a single Jovian encounter and show that objects with initial perihelia close to Jupiter are efficiently scattered to q &lt; 4 au. Moreover, approximately 55% of the transitioning objects in our simulated population experience at least one Jovian encounter prior to reaching q &lt; 4 au. We demonstrate that a spacecraft stationed near Jupiter would be well positioned to rendezvous, orbit-match, and accompany LD2 into the inner solar system, providing an opportunity to observe the onset of intense activity in a pristine comet in situ. Finally, we discuss the prospect of identifying additional targets for similar measurements with forthcoming observational facilities.

Keywords: Comets, Centaur group, Trans-Neptunian objects
Near-UV Reddening Observed in the Reflectance Spectrum of High-inclination Centaur 2012 DR<SUB>30</SUB>. Centaurs with high orbital inclinations and perihelia (i &gt; 60°; q ≳ 5 au) are a small group of poorly understood minor planets that are predicted to enter the giant planet region of the solar system from the inner Oort Cloud. As such, they are one of the few samples of relatively unaltered Oort Cloud material that can currently be directly observed. Here we present two new reflectance spectra of one of the largest of these objects, 2012 DR30, in order to constrain its color and surface composition. Contrary to reports that 2012 DR30 has variable optical color, we find that consistent measurements of its spectral gradient from most new and published data sets at 0.55-0.8 μm agree with a spectral gradient of $S^{\prime} \simeq 10 \% \pm 1 \% /0.1\,\mu {\rm{m}}$ within their uncertainties. The spectral variability of 2012 DR30 at near-UV/blue and near-IR wavelengths, however, is still relatively unconstrained; self-consistent rotationally resolved follow-up observations are needed to characterize any spectral variation in those regions. We tentatively confirm previous detections of water ice on the surface of 2012 DR30, and we also consistently observe a steady steepening of the gradient of its spectrum from λ ~ 0.6 μm toward near-UV wavelengths. Plausible surface materials responsible for the observed reddening may include ferric oxides contained within phyllosilicates and aromatic refractory organics.

Keywords: Centaur group, Spectroscopy, Oort cloud objects
Libration-induced Orbit Period Variations Following the DART Impact. The Double Asteroid Redirection Test (DART) mission will be the first test of a kinetic impactor as a means of planetary defense. In late 2022, DART will collide with Dimorphos, the secondary in the Didymos binary asteroid system. The impact will cause a momentum transfer from the spacecraft to the binary asteroid, changing the orbit period of Dimorphos and forcing it to librate in its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit and libration state of Dimorphos are intertwined. Thus, as the secondary librates, it also experiences fluctuations in its orbit period. These variations in the orbit period are dependent on the magnitude of the impact perturbation, as well as the system's state at impact and the moments of inertia of the secondary. In general, any binary asteroid system whose secondary is librating will have a nonconstant orbit period on account of the secondary's fluctuating spin rate. The orbit period variations are typically driven by two modes: a long period and a short period, each with significant amplitudes on the order of tens of seconds to several minutes. The fluctuating orbit period offers both a challenge and an opportunity in the context of the DART mission. Orbit period oscillations will make determining the post-impact orbit period more difficult but can also provide information about the system's libration state and the DART impact.

Keywords: Celestial mechanics, Asteroid satellites, Asteroid dynamics, Orbital evolution
The Distance and Origin of the Cometary Globule CG 12. The cometary globule CG 12 and its associated young cluster NGC 5367 is located at a Galactic latitude of b = 21°, and the origin of this high-latitude star formation event has been unclear. Getman et al. identified a nearby group of B stars and suggested they could be the remnant of a group of massive stars of which one exploded as a supernova. We here use Gaia EDR3 data to measure the accurate distance of NGC 5367 and the B-stars. We find a mean distance of 670 pc for NGC 5367 and 675 pc for the B-stars, strongly supporting the suggestion of Getman et al.

Keywords: Star forming regions, Star formation, Supernovae, Molecular clouds
The Quasar SDSS J140821.67+025733.2 Does Not Contain a 196 Billion Solar Mass Black Hole. The black hole in the quasar SDSS J140821.67+025733.2 has been reported to have a mass of 1.96 × 1011 M⊙ based on measurements from the SDSS DR12 Quasar Catalog. As a result, references to this object as the most massive known black hole in the universe have recently appeared in scientific articles and in popular media including Wikipedia. We show that this extremely high mass estimate is incorrect, resulting from a faulty measurement of the C IV line width. From a new measurement of the Mg II line width, we derive an estimate of MBH ≈ 8 × 109 M⊙.

Keywords: Black hole physics, Supermassive black holes, Quasars
An Outburst by AM CVn Binary SDSS J113732.32+405458.3. We report the discovery of a one magnitude increase in the optical brightness of the 59.63 minutes orbital period AM CVn binary SDSS J113732.32+405458.3. Public g, r, and i band data from the Zwicky Transient Facility exhibit a subsequent decline over a 300 days period, while a few data points from commissioning show that the peak was likely seen. Such an outburst is likely due to a change in the state of the accretion disk, making this the longest period AM CVn binary to reveal an unstable accretion disk. The object is now back to its previously observed (by SDSS and PS-1) quiescent brightness that is likely set by the accreting white dwarf. Prior observations of this object also imply that the recurrence times for such outbursts are likely more than 12 yr.

Keywords: White dwarf stars, AM Canum Venaticorum stars
Radial Profile of the Polytropic Index of Solar Wind Plasma in the Heliosphere. We combine different measurements of the polytropic index of the proton plasma in the heliosphere: (i) near-adiabatic index in the inner heliosphere ∼1 au, (ii) subadiabatic indices in the outer heliosphere ∼20-40 au, and (iii) near-zero indices in the inner heliosheath. These observations are unified by a single theoretical model of the polytropic index throughout its radial extent in the heliosphere; the corresponding fitting reveals the decreasing trend of the polytropic index with increasing heliocentric distance R. We anticipate that with increasing R, (i) the Debye length and mean-free-path decreases; (ii) the Landau damping is less effective, transferring thus less wave energy to particles; and (iii) the collisionality degree increases, indicating that the proton plasma in the inner heliosheath might be collisionless.

Keywords: Slow solar wind, Space plasmas, Heliosphere, Solar wind, Plasma astrophysics, Astronomy data analysis
X-Ray Jet, Counter-jet, and Trail of the Fast-moving Pulsar PSR B2224+65. I report the detection of linear X-ray features associated with PSR B2224+65, based on a new Chandra observation, plus two obtained ∼6 and 12 yr earlier. This mid-aged pulsar is known for its extreme proper motion and its associated guitar-shaped optical nebula in the opposite direction. The main jet-like feature with the same proper motion is $\sim 2\buildrel{\,\prime}\over{.} 4$ long and directed 62° away from the nebula, which is associated with a faint X-ray tail detected for the first time. Also now clearly revealed are the sharp forward edge and epoch-dependent substructures of the feature and its curvature near the pulsar, as well as a much fainter/shorter counter-jet. Magnetic field appears to play a central role in the formation of the features, which represent the synchrotron radiation of energetic particles leaked out from the bow shock nebula through small holes, produced probably by localized magnetic reconnection, and streaming along interstellar magnetic field lines.

Keywords: X-ray astronomy, Plasma jets, Magnetic fields, Pulsars
Start-up of a Research Project on Activities of Solar-type Stars Based on the LAMOST Sky Survey. A research project on the activities of solar-type stars based on the LAMOST sky survey was initiated recently. We describe the data processing workflow of the project and perspective on scientific yields.

Keywords: Sky surveys, Solar analogs, Stellar chromospheres, Stellar activity, Spectroscopy
A Novel Analytic Atmospheric T(τ) Relation for Stellar Models. Stellar models often use relations between the temperature T and optical depth τ to evaluate the structure of their optically thin outer layers. We fit a novel analytic function to the Hopf function q(τ) of a radiation-coupled hydrodynamics simulation of near-surface convection with solar parameters by Trampedach et al. The fit is accurate to within 0.82% for the solar simulation and to within 13% for all the simulations that are not on either the low-temperature or low-gravity edges of the grid of simulations.

Keywords: Stellar physics, Stellar structures, Stellar surfaces, Stellar atmospheres
Evidence of Increased Macroturbulence for Betelgeuse during Great Dimming. We compared high-resolution spectra of Betelgeuse observed before and during the Great Dimming. Atomic lines are shallow and broad during the Great Dimming presumably because of molecular veiling and increased macroturbulence, νmacro ≳ 23 km s-1. The best fit for TiO bands was found for the MARCS model atmosphere with Teff = 3500 K.

Keywords: High resolution spectroscopy, M supergiant stars, Stellar properties, Stellar atmospheres
Estimated Orbital Parameters of Planetary Disk Particles as a Function of the Mass of Passing Stars. In this work, I present the effects of single passing stars on planetary disks and explore the orbital modification of their components. I analyze the effects of passing stars and look for differences between flyby masses of 0.25 M⊙, 0.5 M⊙, 0.75 M⊙, and 1 M⊙. Resultant eccentricities and inclinations of disk particles are fit to mathematical equations to estimate values for them as a function of their semimajor axes and the flyby mass.

Keywords: Exoplanet dynamics, Orbits, Stellar dynamics, Protoplanetary disks, Debris disks
Spectroscopic Confirmation of the Active Dwarf Nature of 2MASS J07363415+6538548. The star 2MASS J07363415+6538548 (hereafter 2M0736) was previously classified as a possible symbiotic binary, a cataclysmic variable, an H II region, a massive star cluster, a supernova remnant, or a high-mass X-ray binary. In the previous research, while analyzing disputable symbiotic candidates in our New Online Database of Symbiotic Variables, we employed multi-frequency photometric observations, and reclassified the object as an active K-type dwarf. Here, we analyze the low-resolution spectroscopy of 2M0736 to confirm its photometric classification and validate that our methods are able to provide comparable results with the optical spectroscopy. The obtained spectrum confirmed that 2M0736 is a K6 dwarf. The presence and strength of the Hα emission line have verified that the object is very active.

Keywords: K dwarf stars, Late-type dwarf stars, Astronomical techniques, Spectroscopy
A Method for a Pseudo-local Measurement of the Galactic Magnetic Field. Much of the information about the magnetic field in the Milky Way and other galaxies comes from measurements which are path integrals, such as Faraday rotation and the polarization of synchrotron radiation of cosmic ray electrons. The measurement made at the radio telescope results from contributions of volume elements along a long line of sight (LOS). A magnetic field measurement at a given spatial location is of much more physical significance. In this paper, I point out that H II regions fortuitously offer such a "point" measurement, albeit of one component of the magnetic field, and averaged over the sightline through the H II region. However, the LOS through an H II region is much smaller (e.g., 30-50 pc) than one through the entire Galactic disk, and thus constitutes a "pseudo-local" measurement. I use published H II region Faraday rotation measurements to provide a new constraint on the magnitude of magnetohydrodynamic turbulence in the Galaxy.

Keywords: Interstellar magnetic fields, Interstellar medium, Interstellar plasma
Limb and Gravity-darkening Coefficients for the Space Mission CHEOPS. The goal of this Research Note is to provide the theoretical calculations of the limb-darkening coefficients and gravity-darkening coefficients (GDC) for the space mission CHEOPS. We use two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX with spherical symmetry covering a wide range of effective temperatures, local gravities, and hydrogen/metal. These grids cover 19 metallicities ranging from 10-5 up to 10+1 solar abundances, 0 ≤ log g ≤ 6.0 and 2300 K ≤ Teff ≤ 50,000 K. The specific intensity distribution was fitted using six approaches: linear, quadratic, square root, logarithmic, power-2, and a series with four terms. The calculations of the GDC were performed for both stellar atmosphere models adopting an improved formulation.

Keywords: Stellar atmospheres
Gaia EDR3 Confirms that Westerlund 1 is Closer and Older than Previously Thought. Using Gaia Early Data Release 3 (EDR3) parallaxes and Bayesian inference, we infer a parallax of the Westerlund 1 (Wd1) cluster. We find a parallax of 0.34 ± 0.05 mas corresponding to a distance of ${2.8}_{-0.6}^{+0.7}$ kpc. The new Gaia EDR3 distance is consistent with our previous result using Gaia Data Release 2 (DR2) parallaxes. This confirms that Wd1 is less massive and older than previously assumed. Compared to DR2, the EDR3 individual parallax uncertainties for each star decreased by 30%. However, the aggregate parallax uncertainty for the cluster remained the same. This suggests that the uncertainty is dominated by systematics, which is possibly due to crowding, motions within the cluster, or motions due to binary orbits.

Keywords: Bayesian statistics, Massive stars, Luminous blue variable stars, Stellar types, Open star clusters, Star clusters
A Tentative Emission Line at z = 5.8 from a 3 mm Selected Galaxy. I report a tentative (∼4σ) emission line at ν = 100.84 GHz from "COS-3mm-1," a 3 mm selected galaxy reported by Williams et al. that is undetected at optical and near-infrared wavelengths. The line was found in the ALMA Science Archive after re-processing ALMA band 3 observations targeting a different source. Assuming the line corresponds to the CO(6 → 5) transition, this tentative detection implies a spectroscopic redshift of z = 5.857, in agreement with the galaxy's redshift constraints from multi-wavelength photometry. This would make this object the highest redshift 3 mm selected galaxy and one of the highest redshift dusty star-forming galaxies known to-date. Here, I report the characteristics of this tentative detection and the physical properties that can be inferred assuming the line is real. Finally, I advocate for follow-up observations to corroborate this identification and to confirm the high-redshift nature of this optically-dark dusty star-forming galaxy.

Keywords: Molecular gas, High-redshift galaxy clusters, Redshift surveys, Ultraluminous infrared galaxies, High-redshift galaxies
The Ultraviolet Spectra of Alpha Draconis Recorded by IUE. The comparison of all unpublished archival IUE spectra of the bright spectroscopic binary α Draconis shows that the far-ultraviolet flux has remained constant over the 18 yr of the mission, except possibly for one spectrum which shows significantly less flux below 1800 Å. The Si II lines undergo large radial velocity variations which are due to the orbital motion of α Draconis around the center of mass of the system. The far-UV energy distribution of α Draconis has more flux than that of Sirius A (α CMa) which reflects the weaker abundances of the metals in α Draconis compared to Sirius A.

Keywords: A giant stars
Re-analysis of Breakthrough Listen Observations of FRB 121102: Polarization Properties of Eight New Spectrally Narrow Bursts. We report polarization properties for eight narrowband bursts from FRB 121102 that have been re-detected in a high-frequency (4-8 GHz) Breakthrough Listen observation with the Green Bank Telescope, originally taken on 2017 August 26. The bursts were found to exhibit nearly 100% linear polarization, Faraday rotation measures bordering 9.3 × 104 rad m-2, and stable polarization position angles, all of which agree with burst properties previously reported for FRB 121102 at the same epoch. We confirm that these detections are indeed physical bursts with limited spectral occupancies and further support the use of sub-banded search techniques in FRB detection.

Keywords: Radio bursts, Polarimetry, Radio transient sources
Backyard Worlds: Planet 9 Discovery of an Unusual Low-mass Companion to an M Dwarf at 80 pc. We present the discovery of CWISE J203546.35-493611.0, a peculiar M8 companion to the M4.5 star APMPM J2036-4936 discovered through the citizen science project Backyard Worlds: Planet 9. Given CWISE J203546.35-493611.0's proper motion (μα, μδ) = (-126 ± 22, -478 ± 23) and angular separation of 34"2 from APMPM 2036-4936, we calculate a chance alignment probability of 1.15 × 10-6. Both stars in this system appear to be underluminous, and the spectrum obtained for CWISE J203546.35-493611.0 shows a triangular H band. Further study of this system is warranted to understand these peculiarities.

Keywords: Binary stars, Low mass stars
The Observed Rate of Binary Black Hole Mergers can be Entirely Explained by Globular Clusters. Since the first signal in 2015, the gravitational-wave detections of merging binary black holes (BBHs) by the LIGO and Virgo collaborations (LVC) have completely transformed our understanding of the lives and deaths of compact object binaries, and have motivated an enormous amount of theoretical work on the astrophysical origin of these objects. We show that the phenomenological fit to the redshift-dependent merger rate of BBHs from Abbott et al. is consistent with a purely dynamical origin for these objects, and that the current merger rate of BBHs from the LVC could be explained entirely with globular clusters alone. While this does not prove that globular clusters are the dominant formation channel, we emphasize that many formation scenarios could contribute a significant fraction of the current LVC rate, and that any analysis that assumes a single (or dominant) mechanism for producing BBH mergers is implicitly using a specious astrophysical prior.

Keywords: Gravitational wave sources, Astrophysical black holes
Atomic Clocks in Space: A Search for Rubidium and Cesium Masers in M- and L-dwarfs. I searched for the ground state 6.8 and 9.2 GHz hyperfine transitions of rubidium and cesium toward M- and L-dwarfs that show Rb and Cs optical resonance lines. The optical lines can pump the hyperfine transitions, potentially forming masers. These spin-flip transitions of Rb and Cs are the principal transitions used in atomic clocks (the 133Cs hyperfine transition defines the second). If they are detected in stellar atmospheres, these transitions would provide exceptionally precise clocks that can be used as accelerometers, as exoplanet detectors, as probes of the predictions of general relativity, as probes of light propagation effects, and as a means to do fundamental physics with telescopes. Observations of 21 M- and L-dwarfs, however, show no evidence for Rb or Cs maser action, and a previous survey of giant stars made no Rb maser detections.

Keywords: M dwarf stars, Radio spectroscopy, Atomic physics, L dwarfs, Atomic spectroscopy, Circumstellar masers, Astrophysical masers, Exoplanet detection methods, Stellar atmospheres
Reprocessing of a Green Bank 43 m Telescope Survey of Unidentified Bright Radio Sources for Pulsars and Radio Bursts. We have reprocessed a set of observations of 75 bright, unidentified, steep-spectrum polarized radio sources taken with the Green Bank 43 m telescope to find previously undetected sub-millisecond pulsars and radio bursts. The (null) results of the first search of these data were reported by Schmidt et al.. Our reprocessing searched for single pulses out to a dispersion measure (DM) of 1000 pc cm-3 which were classified using the Deep Learning based classifier FETCH. We also searched for periodicities at a wider range of DMs and accelerations. Our search was sensitive to highly accelerated, rapidly rotating pulsars (including sub-millisecond pulsars) in compact binary systems as well as to highly dispersed impulsive signals, such as fast radio bursts. No pulsars or astrophysical burst signals were found in the reprocessing.

Keywords: Surveys, Radio pulsars