Sazuna/UAT_keywords huggingface dataset:
Probing the Evolutionary History of Comets: An Investigation of the Hypervolatiles CO, CH<SUB>4</SUB>, and C<SUB>2</SUB>H<SUB>6</SUB> in the Jupiter-family Comet 21P/Giacobini-Zinner. Understanding the cosmogonic record encoded in the parent volatiles stored in cometary nuclei requires investigating whether evolution (thermal or otherwise) has modified the composition of short-period comets during successive perihelion passages. As the most volatile molecules systematically observed in comets, the abundances of CO, CH4, and C2H6 in short-period comets may serve to elucidate the interplay between natal conditions and post-formative evolution in setting present-day composition, yet secure measurements of CO and CH4 in Jupiter-family comets (JFCs) are especially sparse. The highly favorable 2018 apparition of JFC 21P/Giacobini-Zinner enabled a sensitive search for these “hypervolatiles” in a prototypical carbon-chain depleted comet. We observed 21P/Giacobini-Zinner with the iSHELL spectrograph at the NASA Infrared Telescope Facility on four pre-perihelion dates, two dates near-perihelion, and one post-perihelion date. We obtained detections of CO, CH4, and C2H6 simultaneously with H2O on multiple dates. We present rotational temperatures, production rates, and mixing ratios. Combined with previous work, our results may indicate that the hypervolatile coma composition of 21P/Giacobini-Zinner was variable across apparitions as well as within a particular perihelion passage, yet the spread in these measurements is a relatively small fraction of the variation in each molecule from comet to comet. We discuss the implications of our measured hypervolatile content of 21P/Giacobini-Zinner for the evolution of JFCs, and place our results in the context of findings from the Rosetta mission and ground-based studies of comets.

Keywords: High resolution spectroscopy, Molecular spectroscopy, Near infrared astronomy
Spectroscopically Identified Cataclysmic Variables from the LAMOST Survey. I. The Sample. A sample of cataclysmic variables (CVs) is presented including spectroscopically identified 380 spectra of 245 objects, of which 58 CV candidates are new discoveries. The BaggingTopPush and the Random Forest algorithms are applied to the Fifth Data Release (DR5) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to retrieve CVs with strong emission lines and with broad absorption lines respectively. Based on spectroscopic classification, 134 dwarf novae, 41 nova-like variables, and 19 magnetic CVs are identified from the sample. In addition, 89 high-inclination systems and 33 CVs showing companion stars are recognized and discussed for their distinct spectral characteristics. Comparisons between CVs from LAMOST and from published catalogs are made in spatial and magnitude distribution, and the difference of their locus in the Gaia color-absolute magnitude diagram (CaMD) are also investigated. More interestingly, for two dwarf novae observed through LAMOST and SDSS in different epochs, their spectra both in quiescence phase and during outburst are exhibited.

Keywords: Astronomy data analysis, Dwarf novae, Nova-like variable stars, Cataclysmic variable stars, Catalogs
XO-7 b: A Transiting Hot Jupiter with a Massive Companion on a Wide Orbit. Transiting planets orbiting bright stars are the most favorable targets for follow-up and characterization. We report the discovery of the transiting hot Jupiter XO-7 b and of a second, massive companion on a wide orbit around a circumpolar, bright, and metal-rich G0 dwarf (V = 10.52, {T}eff}=6250+/- 100 {{K}}, [{Fe}/{{H}}]=0.432+/- 0.057 {dex}). We conducted photometric and radial velocity follow-up with a team of amateur and professional astronomers. XO-7 b has a period of 2.8641424+/- 0.0000043 days, a mass of 0.709+/- 0.034 {M}{{J}}, a radius of 1.373+/- 0.026 {R}{{J}}, a density of 0.340+/- 0.027 {{g}} {cm}}-3, and an equilibrium temperature of 1743+/- 23 {{K}}. Its large atmospheric scale height and the brightness of the host star make it well suited to atmospheric characterization. The wide-orbit companion is detected as a linear trend in radial velocities with an amplitude of ∼ 100 {{m}} {{{s}}}-1 over two years, yielding a minimum mass of 4 {M}{{J}}; it could be a planet, a brown dwarf, or a low-mass star. The hot Jupiter orbital parameters and the presence of the wide-orbit companion point toward a high-eccentricity migration for the hot Jupiter. Overall, this system will be valuable to understand the atmospheric properties and migration mechanisms of hot Jupiters and will help constrain the formation and evolution models of gas giant exoplanets.

Keywords: High resolution spectroscopy, Transits, Hot Jupiters, Exoplanets, Transit instruments, Surveys, Optical astronomy, Exoplanet systems, Exoplanet astronomy, Radial velocity, Transit photometry, Extrasolar gaseous giant planets
Uranus in Northern Midspring: Persistent Atmospheric Temperatures and Circulations Inferred from Thermal Imaging. We present results from mid-infrared imaging of Uranus at wavelengths of 13.0 and 18.7 μm, sensing emission from the stratosphere and upper troposphere, acquired using the VISIR instrument at the Very Large Telescope, 2018 September 4-October 20. Using a combination of inverse and forward modeling, we analyze these northern midspring (L  s  ∼ 46°) images and compare them to archival data to assess seasonal changes since the 1986 southern solstice and subsequent equinox. We find the data are consistent with little change (&lt;0.3 K) in the upper tropospheric temperature structure, extending the previous conclusions of Orton et al. well past equinox, with only a subtle increase in temperature at the emerging north pole. Additionally, spatial-temporal variations in 13 μm stratospheric emission are investigated for the first time, revealing meridional variation and a hemispheric asymmetry not predicted by models. Finally, we investigate the nature of the stratospheric emission and demonstrate that the observed distribution appears related and potentially coupled to the underlying tropospheric emission six scale heights below. The observations are consistent with either midlatitude heating or an enhanced abundance of acetylene. Considering potential mechanisms and additional observations, we favor a model of acetylene enrichment at midlatitudes resulting from an extension of the upper tropospheric circulation, which appears capable of transporting methane from the troposphere, through the cold trap, and into the stratosphere for subsequent photolysis to acetylene.

Keywords: Atmospheric circulation, Planetary atmospheres, Solar system gas giant planets, Atmospheric science, Planetary science, Uranus
Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies. We present deep spectroscopy from Keck/DEIMOS of Andromeda I, III, V, VII, and X, all of which are dwarf spheroidal satellites of M31. The sample includes 256 spectroscopic members across all five dSphs. We confirm previous measurements of the velocity dispersions and dynamical masses, and we provide upper limits on bulk rotation. Our measurements confirm that M31 satellites obey the same relation between stellar mass and stellar metallicity as Milky Way (MW) satellites and other dwarf galaxies in the Local Group. The metallicity distributions show trends with stellar mass that are similar to those of MW satellites, including evidence in massive satellites for external influence, like pre-enrichment or gas accretion. We present the first measurements of individual element ratios, like [Si/Fe], in the M31 system, as well as measurements of the average [α/Fe] ratio. The trends of [α/Fe] with [Fe/H] also follow the same galaxy mass-dependent patterns as MW satellites. Less massive galaxies have more steeply declining slopes of [α/Fe] that begin at lower [Fe/H]. Finally, we compare the chemical evolution of M31 satellites to M31's Giant Stellar Stream and smooth halo. The properties of the M31 system support the theoretical prediction that the inner halo is composed primarily of massive galaxies that were accreted early. As a result, the inner halo exhibits higher [Fe/H] and [α/Fe] than surviving satellite galaxies. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: Local Group, Stellar abundances, Dwarf galaxies, Andromeda Galaxy
A Fireball and Potentially Hazardous Binary Near-Earth Asteroid (164121) 2003 YT<SUB>1</SUB>. We present a fireball detected in the night sky over Kyoto, Japan on UT 2017 April 28 at {15}{{h}} {58}{{m}} {19}{{s}} by the SonotaCo Network. The absolute visual magnitude is {M}{{v}} = -4.10 ± 0.42 mag. Luminous light curves obtain a meteoroid mass of m = 29 ± 1 g, corresponding to the size of a s = 2.7 ± 0.1 cm. Orbital similarity assessed by D-criterions (see D SH = 0.0079) has identified a likely parent, the binary near-Earth asteroid (164121) 2003 YT1. The suggested binary formation process is a Yarkovsky-O’Keefe-Radzievskii-Paddack-driven rotational disintegration. The asynchronous state indicates the age of &lt;104 yr, near or shorter than the upper limit to meteoroid stream lifetime. We examine potential dust production mechanisms for the asteroid, including rotational instability, resurfacing, impact, photoionization, radiation pressure sweeping, thermal fracture, and sublimation of ice. We find some of them capable of producing the meteoroid-scale particles. Rotational instability is presumed to cause mass shedding, in consideration of the recent precedents (e.g., asteroid (6478) Gault), possibly releasing millimeter-centimeter scale dust particles. Impacts by micrometeorites with a size ≃1 mm could be a trigger for ejecting the centimeter-sized particles. Radiation pressure can sweep out the millimeter-sized dust particles, while not sufficient for the centimeter-sized. The other mechanisms are unprovable or unidentified. The feasibility in the parental aspect of 2003 YT1 is somewhat reconciled with the fireball observation, yielding an insight into how we approach potentially hazardous objects.

Keywords: Near-Earth objects, Fireballs, Micrometeoroids, Asteroids, Surveys, Meteor radiants, Meteors, Catalogs, Solar system astronomy
OGLE-2018-BLG-1700L: Microlensing Planet in Binary Stellar System. We report a planet in a binary that was discovered from the analysis of the microlensing event OGLE-2018-BLG-1700. We identify the triple nature of the lens from the fact that the anomaly pattern can be decomposed into two parts produced by two binary-lens events, in which one binary pair has a mass ratio of ∼0.01 between the lens components and the other pair has a mass ratio of ∼0.3. We find two sets of degenerate solutions, in which one solution has a projected separation between the primary and its stellar companion less than the angular Einstein radius {θ }{{E}} (close solution), while the other solution has a separation greater than {θ }{{E}} (wide solution). From the Bayesian analysis with the constraints of the event timescale and angular Einstein radius, we find that the planet has a mass of {4.4}-2.0+3.0 {M}{{J}} and the stellar binary components have masses of {0.42}-0.19+0.29 {M}⊙  and {0.12}-0.05+0.08 {M}⊙ , respectively, and the distance to the lens is {D}{{L}}={7.6}-0.9+1.2 {kpc}. The planet is a circumstellar planet according to the wide solution, while it is a circumbinary planet according to the close solution.

Keywords: Binary stars, Exoplanet systems
Gravitational Lensing Signatures of Axion Dark Matter Minihalos in Highly Magnified Stars. Axions are a viable candidate for cold dark matter, which should generically form minihalos of subplanetary masses from white-noise isocurvature density fluctuations if the Peccei-Quinn phase transition occurs after inflation. Despite being denser than the larger halos formed out of adiabatic fluctuations from inflation, axion minihalos have surface densities much smaller than the critical value required for gravitational lensing to produce multiple images or high magnification, and hence are practically undetectable as lenses in isolation. However, their lensing effect can be enhanced when superposed near critical curves of other lenses. We propose a method to detect them through photometric monitoring of recently discovered caustic transiting stars behind cluster lenses, under extreme magnification factors μ ≳ 103-104 as the lensed stars cross microlensing caustics induced by intracluster stars. For masses of the first gravitationally collapsed minihalos in the range ∼10-15-10-8 h -1 M ⊙, we show that axion minihalos in galaxy clusters should collectively produce subtle surface density fluctuations of amplitude ∼10-4-10-3 on projected length scales of ∼10-104 au, which imprint irregularities on the microlensing lightcurves of caustic transiting stars. We estimate that, inside a cluster halo and over the age of the universe, most of these minihalos are likely to avoid dynamic disruption by encounters with stars or other minihalos.

Keywords: Cosmology, Galaxy clusters, Gravitational lensing, Gravitational microlensing, Dark matter
Identifying Multiple Populations in M71 Using CN. We have observed the CN features at ∼3800 and 4120 Å as well as the CH band at ∼4300 Å for 145 evolved stars in the Galactic globular cluster M71 using the multi-object spectrograph, Hydra, on the Wisconsin-Indiana-Yale-NOAO-3.5 m telescope. We use these measurements to create two δCN indices finding that both distributions are best fit by two populations: a CN-enhanced and CN-normal. We find that 42% ± 4% of the red giant branch stars in our sample are CN-enhanced. The percentage of CN-enhanced is 40% ± 13% for the asymptotic giant branch and 33% ± 9% for the horizontal-branch stars (HB stars), which suggests there are no missing second generation stars at these stages of stellar evolution. The two generations also separate in magnitude and color on the HB, which allows us to find the difference in He abundance between the two populations by fitting appropriate zero-age horizontal branches. The broad range of distances from the cluster’s center covered by our sample allows us to study the dependence of the ratio of the number of first to second population stars on the distance from the cluster’s center, and we find that this ratio does not vary radially and that the two populations are spatially mixed. Finally, we compare our identification of multiple populations with the classification based on the Na-O anti-correlation and the Hubble Space Telescope UV photometry, and we find good agreement with both methods.

Keywords: Globular star clusters, Stellar astronomy, Spectroscopy
Evaluating Climate Variability of the Canonical Hot-Jupiters HD 189733b and HD 209458b through Multi-epoch Eclipse Observations. Here we present the analysis of multi-epoch secondary eclipse observations of HD 189733b and HD 209458b as a probe of temporal variability in the planetary climate using both Spitzer channels 1 and 2 (3.6 and 4.5 μm). We expect hot-Jupiter atmospheres to be dynamic environments exhibiting time varying weather. However, it is uncertain to what extent temporal variability will be observable when considering disk integrated observations. We do not detect statistically significant variability and are able to place useful upper limits on the infrared variability amplitudes in these atmospheres. There are very few planets with multi-epoch observations at the required precision to probe variability in dayside emission. The observations considered in this study span several years, providing insight into temporal variability at multiple timescales. In the case of HD 189733b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 102 ppm about a median depth of 1827 ppm and in channel 1 exhibit a scatter of 88 ppm about a median depth of 1481 ppm. For HD 209458b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 22 ppm about a median depth of 1406 ppm, and in channel 1 exhibit a scatter of 131 ppm about a median depth of 1092 ppm. The precision and scatter in these observations allow us to constrain variability to less than (5.6% and 6.0%) and (12% and 1.6%) for channels (1, 2) of HD 189733b and HD 209458b, respectively.

Keywords: Exoplanet astronomy, Exoplanet atmospheric variability, Exoplanet structure, Exoplanet atmospheres
Magnetic Inflation and Stellar Mass. V. Intensification and Saturation of M-dwarf Absorption Lines with Rossby Number. In young Sun-like stars and field M-dwarf stars, chromospheric and coronal magnetic activity indicators such as Hα, X-ray, and radio emission are known to saturate with low Rossby number (Ro ≲ 0.1), defined as the ratio of rotation period to convective turnover time. The mechanism for the saturation is unclear. In this paper, we use photospheric Ti I and Ca I absorption lines in the Y band to investigate magnetic field strength in M dwarfs for Rossby numbers between 0.01 and 1.0. The equivalent widths of the lines are magnetically enhanced by photospheric spots, a global field, or a combination of the two. The equivalent widths behave qualitatively similar to the chromospheric and coronal indicators: we see increasing equivalent widths (increasing absorption) with decreasing Ro and saturation of the equivalent widths for Ro ≲ 0.1. The majority of M dwarfs in this study are fully convective. The results add to mounting evidence that the magnetic saturation mechanism occurs at or beneath the stellar photosphere.

Keywords: M dwarf stars, High resolution spectroscopy, Stellar properties, Stellar activity, Infrared astronomy, Spectroscopy, Stellar rotation, Magnetic fields, Near infrared astronomy
Imaging the 44 au Kuiper Belt Analog Debris Ring around HD 141569A with GPI Polarimetry. We present the first polarimetric detection of the inner disk component around the pre-main-sequence B9.5 star HD 141569A. Gemini Planet Imager H-band (1.65 μm) polarimetric differential imaging reveals the highest signal-to-noise ratio detection of this ring yet attained and traces structure inward to 0.″25 (28 au at a distance of 111 pc). The radial polarized intensity image shows the east side of the disk, peaking in intensity at 0.″40 (44 au) and extending out to 0.″9 (100 au). There is a spiral arm-like enhancement to the south, reminiscent of the known spiral structures on the outer rings of the disk. The location of the spiral arm is coincident with 12CO J = 3-2 emission detected by ALMA and hints at a dynamically active inner circumstellar region. Our observations also show a portion of the middle dusty ring at ∼220 au known from previous observations of this system. We fit the polarized H-band emission with a continuum radiative transfer Mie model. Our best-fit model favors an optically thin disk with a minimum dust grain size close to the blowout size for this system, evidence of ongoing dust production in the inner reaches of the disk. The thermal emission from this model accounts for virtually all of the far-infrared and millimeter flux from the entire HD 141569A disk, in agreement with the lack of ALMA continuum and CO emission beyond ∼100 au. A remaining 8-30 μm thermal excess a factor of ∼2 above our model argues for an as-yet-unresolved warm innermost 5-15 au component of the disk.

Keywords: Polarimetry, Astronomical techniques, Coronagraphic imaging, Direct imaging, Circumstellar disks, Debris disks
Atomic Oxygen Escape on Mars Driven by Electron Impact Excitation and Ionization. Neutral escape on Mars is well known to be dominated by atomic oxygen (O) escape via the dissociative recombination (DR) of ${{\rm{O}}}_{2}^{+}$ , the most abundant ion species in the Martian upper atmosphere. In this study, we suggest an alternative mechanism due to the impact excitation and ionization of CO2 by photoelectrons on the dayside or precipitating solar wind electrons on the nightside. These electron impact (EI) processes are capable of producing hot O atoms via the predissociation of CO2 and ${\mathrm{CO}}_{2}^{+}$ in electronically excited states. An evaluation with the aid of the combined data set accumulated by several instruments on board the Mars Atmosphere and Volatile Evolution spacecraft reveals that CO2 EI makes a non-negligible contribution to total atomic O escape on Mars, with a median EI-to-DR escape flux ratio of 10% on the dayside and 20% on the nightside. CO2 EI is found to be able to drive stronger O escape than atmospheric sputtering, an alternative escape mechanism well studied on Mars. Our results highlight the importance of a neutral escape mechanism largely ignored in previous studies.

Keywords: Electron impact ionization, Planetary atmospheres, Upper atmosphere
A Flexible Bayesian Framework for Assessing Habitability with Joint Observational and Model Constraints. The catalog of stellar evolution tracks discussed in our previous work is meant to help characterize exoplanet host stars of interest for follow-up observations with future missions like the James Webb Space Telescope. However, the utility of the catalog has been predicated on the assumption that we would precisely know the age of the particular host star in question; in reality, it is unlikely that we will be able to accurately estimate the age of a given system. Stellar age is relatively straightforward to calculate for stellar clusters, but it is difficult to accurately measure the age of an individual star to high precision. Unfortunately, this is the kind of information we should consider as we attempt to constrain the long-term habitability potential of a given planetary system of interest. This is ultimately why we must rely on predictions of accurate stellar evolution models, as well a consideration of what we can observably measure (stellar mass, composition, orbital radius of an exoplanet) in order to create a statistical framework wherein we can identify the best candidate systems for follow-up characterization. In this paper we discuss a statistical approach to constrain long-term planetary habitability by evaluating the likelihood that at a given time of observation, a star would have a planet in the 2 Gy continuously habitable zone (CHZ2). Additionally, we will discuss how we can use existing observational data (i.e., data assembled in the Hypatia catalog and the Kepler exoplanet host star database) for a robust comparison to the catalog of theoretical stellar models.

Keywords: Stellar properties, Exoplanets, Stellar evolutionary models, Astrobiology, Interdisciplinary astronomy, Habitable zone, Stellar evolutionary tracks, Habitable planets, Catalogs, Stellar evolution