Sazuna/UAT_keywords huggingface dataset:
A Comprehensive Spectral Rotational Analysis of the Interstellar Methyl Isocyanate CH<SUB>3</SUB>NCO. Methyl isocyanate (CH3NCO) is a recently identified interstellar molecule giving rise to many detected lines. Interestingly, its delayed identification was due not to weak lines but to a very complex rotational spectrum. To date, the only published laboratory transitions for this molecule are those between rotational energy levels with K ≤ 3. In the present work, Stark-modulation spectroscopy was used to record the room-temperature rotational spectrum of CH3NCO in the spectral region from 32 to 90 GHz. Observation of characteristic Stark effects, measured at specific low-voltage modulation conditions, and 14N nuclear quadrupole hyperfine structure allowed unambiguous assignment of rotational transitions up to K = 10. These newly assigned transitions were subsequently followed up to 364 GHz with the aid of Loomis-Wood-type displays. Since there are no reports on astrophysical detection of 13C isotopic species, first laboratory measurements between 50 and 300 GHz have also been performed for CH3N13CO and 13CH3NCO isotopologues. A comprehensive spectral analysis undertaken in this work made it possible to extend the knowledge of the rotational spectrum of CH3NCO to more than 2500 new transitions. Furthermore, more than 1200 lines were identified and analyzed for each of the isotopologues. The extensive line lists and sets of molecular parameters reported in this work provide the basis for further astrophysical searches of CH3NCO.

Keywords: Interstellar molecules, High resolution spectroscopy, Spectral line lists, Laboratory astrophysics, Experimental techniques, Molecular spectroscopy, Interstellar medium
Lithium-rich Giants in LAMOST Survey. I. The Catalog. Standard stellar evolution model predicts a severe depletion of lithium (Li) abundance during the first dredge up process (FDU). Yet a small fraction of giant stars are still found to preserve a considerable amount of Li in their atmospheres after the FDU. Those giants are usually identified as Li-rich by a widely used criterion, A(Li) &gt; 1.5 dex. A large number of works dedicated to searching for and investigating this minority of the giant family, and the amount of Li-rich giants, has been largely expanded on, especially in the era of big data. In this paper, we present a catalog of Li-rich giants found from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey with Li abundances derived from a template-matching method developed for LAMOST low-resolution spectra. The catalog contains 10,535 Li-rich giants with Li abundances from ∼1.5 to ∼4.9 dex. We also confirm that the ratio of Li-rich phenomenon among giant stars is about 1%—or more specifically, 1.29%—from our statistically important sample. This is the largest Li-rich giant sample ever reported to date, which significantly exceeds amount of all reported Li-rich giants combined. The catalog will help the community to better understand the Li-rich phenomenon in giant stars.

Keywords: Stellar abundances, Chemically peculiar stars, Late stellar evolution, Late-type giant stars
Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra. We present the determination of stellar parameters and individual elemental abundances for 6 million stars from ∼8 million low-resolution (R ∼ 1800) spectra from LAMOST DR5. This is based on a modeling approach that we dub the data-driven Payne (DD-Payne), which inherits essential ingredients from both the Payne and the Cannon. It is a data-driven model that incorporates constraints from theoretical spectral models to ensure the derived abundance estimates are physically sensible. Stars in LAMOST DR5 that are in common with either GALAH DR2 or APOGEE DR14 are used to train a model that delivers stellar parameters (T eff, log g, V mic) and abundances for 16 elements (C, N, O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Ba) over a metallicity range of -4 dex &lt; [Fe/H] &lt; 0.6 dex when applied to the LAMOST spectra. Cross-validation and repeat observations suggest that, for S/Npixel ≥ 50, the typical internal abundance precision is 0.03-0.1 dex for the majority of these elements, with 0.2-0.3 dex for Cu and Ba, and the internal precision of T eff and log g is better than 30 K and 0.07 dex, respectively. Abundance systematics at the ∼0.1 dex level are present in these estimates but are inherited from the high-resolution surveys’ training labels. For some elements, GALAH provides more robust training labels, for others, APOGEE. We provide flags to guide the quality of the label determination and identify binary/multiple stars in LAMOST DR5. An electronic version of the abundance catalog is made publicly available.12

Keywords: Astronomy data modeling, Sky surveys, Astronomy databases, Stellar properties, Fundamental parameters of stars, Stellar abundances, Astronomy data analysis, Spectroscopic binary stars, Spectroscopy, Stellar spectral lines, Milky Way Galaxy, Stellar atmospheres
Ordinary Oort Cloud Comets: An Update on the Past and Future Orbital Evolution of C/2018 F4 (PANSTARRS). Objects that follow hyperbolic paths may have an interstellar origin or an indigenous one. Robust examples of extrasolar visitors are 1I/2017 U1 ('Oumuamua) and 2I/Borisov; present-day, locally produced hyperbolic objects exist, but their properties could be different from those that escaped from an exoplanetary system. Here, we revisit the past and future orbital evolution of comet C/2018 F4 (PANSTARRS) using an improved orbit determination to understand its origin better. Our calculations show that the probability of C/2018 F4 being hyperbolic 1 Myr ago is 0.39 and that of being hyperbolic 1 Myr from now is 0.49. However, for 3 Myr-long integrations, the respective probabilities are 0.77 and 0.74. These results suggest that C/2018 F4 is a relatively recent acquisition from the Oort cloud that was inserted in a very unstable orbit that may soon lead the comet to interstellar space although nearly 5% of simulations ended up in a collision with Jupiter or the Sun.

Keywords: Oort cloud, Comets, Solar system
K2-19b and c are in a 3:2 Commensurability but out of Resonance: A Challenge to Planet Assembly by Convergent Migration. K2-19b and c were among the first planets discovered by NASA’s K2 mission and together stand in stark contrast with the physical and orbital properties of the solar system planets. The planets are between the size of Uranus and Saturn at 7.0 ± 0.2 {R}\oplus  and 4.1 ± 0.2 {R}\oplus , respectively, and reside a mere 0.1% outside the nominal 3:2 mean-motion resonance. They represent a different outcome of the planet formation process than the solar system, as well as the vast majority of known exoplanets. We measured the physical and orbital properties of these planets using photometry from K2, Spitzer, and ground-based telescopes, along with radial velocities from Keck/HIRES. Through a joint photodynamical model, we found that the planets have moderate eccentricities of e ≈ 0.20 and well-aligned apsides Δϖ ≈ 0°. The planets occupy a strictly nonresonant configuration: the resonant angles circulate rather than librate. This defies the predictions of standard formation pathways that invoke convergent or divergent migration, both of which predict Δϖ ≈ 180° and eccentricities of a few percent or less. We measured masses of M  p,b  = 32.4 ± 1.7 {M}\oplus  and M  p,c  = 10.8 ± 0.6 {M}\oplus . Our measurements, with 5% fractional uncertainties, are among the most precise of any sub-Jovian exoplanet. Mass and size reflect a planet’s core/envelope structure. Despite having a relatively massive core of {M}core} ≈ 15 {M}\oplus , K2-19b is envelope-rich, with an envelope mass fraction of roughly 50%. This planet poses a challenge to standard models of core-nucleated accretion, which predict that cores ≳10 {M}\oplus  will quickly accrete gas and trigger runaway accretion when the envelope mass exceeds that of the core.

Keywords: Exoplanet dynamics, Exoplanet astronomy, Exoplanet evolution, Exoplanet structure, Radial velocity, Exoplanet formation, Extrasolar gaseous giant planets
Identifying Exo-Earth Candidates in Direct Imaging Data through Bayesian Classification. Future space telescopes may be able to directly image between approximately 10 and 100 planets with sizes and orbits consistent with habitable surface conditions (“exo-Earth candidates” or EECs), but observers will face difficulty in distinguishing these from the potentially hundreds of nonhabitable “false positives” which will also be detected. To maximize the efficiency of follow-up observations, a prioritization scheme must be developed to determine which planets are most likely to be EECs. In this paper, we present a Bayesian method for estimating the likelihood that any directly imaged extrasolar planet is a true EEC by interpreting the planet’s apparent magnitude and separation in the context of existing exoplanet statistics. As a specific application of this general framework, we use published estimates of the discovery yield of future space-based direct-imaging mission concepts to conduct “mock surveys” in which we compute the likelihood that each detected planet is an EEC. We find that it will be difficult to determine which planets are EECs with &gt;50% confidence using single-band photometry immediately upon their detection. The best way to reduce this ambiguity would be to constrain the orbit of a given planet by revisiting the system multiple times or through a radial velocity precursor survey. Astrometric or radial velocity constraints on the mass of the planet would offer a lesser benefit. Finally, we show that a Bayesian approach to prioritizing targets would improve the follow-up efficiency of a direct imaging survey versus a blind approach using the same data. For example, the prioritized approach could reduce the amount of integration time required for the spectral detection (or rejection) of water absorption in most EECs by a factor of two.

Keywords: Bayesian statistics, Astronomical techniques, Astrobiology, Direct imaging, Space telescopes, Habitable planets
The Pre-He White Dwarf in the Post-mass Transfer Binary EL CVn. EL CVn is the prototype of a class of eclipsing binaries that consist of an A- or F-type main-sequence star and a hot, low-mass, pre-He white dwarf (pre-He WD), the stripped down remains of the former mass donor. Here we present the first direct detection and characterization of the spectrum of the pre-He WD in EL CVn that was made possible through far-UV spectroscopy with the Hubble Space Telescope Cosmic Origins Spectrograph. These spectra straddle the wavelength range where flux dominance shifts from the pre-He WD to the A star. Radial velocities of both components were measured from the far-UV spectra and new optical spectra from the Apache Point Observatory Astrophysical Research Consortium Echelle Spectrograph. We also obtained fast cadence photometry of the eclipses with the pt5m telescope at the Roque de los Muchachos Observatory. A combined analysis of the velocities and light curve yields the component masses and radii. We applied a Doppler tomography algorithm to reconstruct the individual spectra, and we compared these to models to estimate the effective temperatures. The pre-He WD has low mass (0.176 ± 0.004 M ⊙), is small (0.284 ± 0.003 R ⊙), and is relatively hot (11,800 ± 400 K), and these parameters are approximately consistent with predictions for a star stripped through stable mass transfer. The spectral lines of the pre-He WD show that its atmosphere is H-rich, He-depleted, and metal-poor, probably as the result of elemental diffusion that has occurred since mass transfer ceased.

Keywords: Eclipsing binary stars, White dwarf stars, Stellar evolution
Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 μm. As part of the Panchromatic Exoplanet Treasury program, we have conducted a spectroscopic study of WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a period of 3.66 days. Building on the original WASP and TRAPPIST photometry of Smalley et al., we examine Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) (1.125-1.650 μm), Magellan/Low Dispersion Survey Spectrograph (LDSS)-3C (0.6-1 μm) data, and Spitzer data (3.6 and 4.5 μm). Using data from all three instruments, we constrain the water abundance to be -2.20 ≤ log(H2O) ≤ -1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and H- in the atmospheric model. We also provide an updated ephemeris based on the Smalley, HST/WFC3, LDSS-3C, Spitzer, and Transiting Exoplanet Survey Satellite (TESS) transit times. With the detectable water feature and its occupation of the clear/cloudy transition region of the temperature/gravity phase space, WASP-79b is a target of interest for the approved James Webb Space Telescope (JWST) Director’s Discretionary Early Release Science (ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets have been approved for 78.1 hr of data collection, and with the delay in the JWST launch, WASP-79b is now a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hr in four different instrument modes, providing substantially more data by which to investigate this hot Jupiter.

Keywords: Observational astronomy, Exoplanet atmospheres, Spectroscopy
Supervised Machine Learning for Intercomparison of Model Grids of Brown Dwarfs: Application to GJ 570D and the Epsilon Indi B Binary System. Self-consistent model grids of brown dwarfs involve complex physics and chemistry, and are often computed using proprietary computer codes, making it challenging to identify the reasons for discrepancies between model and data as well as between the models produced by different research groups. In the current study, we demonstrate a novel method for analyzing brown dwarf spectra, which combines the use of the Sonora, AMES-cond, and HELIOS model grids with the supervised machine-learning method of the random forest. Besides performing atmospheric retrieval, the random forest enables information content analysis of the three model grids as a natural outcome of the method, both individually on each grid and by comparing the grids against one another, by computing large suites of mock retrievals. Our analysis reveals that the different choices made in modeling the alkali line shapes hinder the use of the alkali lines as gravity indicators. Nevertheless, the spectrum longward of 1.2 μm encodes enough information on the surface gravity to allow its inference from retrieval. Temperature may be accurately and precisely inferred independent of the choice of model grid, but not the surface gravity. We apply random forest retrieval to three objects: the benchmark T7.5 brown dwarf GJ 570D, and ∊ Indi Ba (T1.5 brown dwarf) and Bb (T6 brown dwarf), which are part of a binary system and have measured dynamical masses. For GJ 570D, the inferred effective temperature and surface gravity are consistent with previous studies. For ∊ Indi Ba and Bb, the inferred surface gravities are broadly consistent with the values informed by the dynamical masses.

Keywords: Astrostatistics techniques, Brown dwarfs, T dwarfs
MOPSS. II. Extreme Optical Scattering Slope for the Inflated Super-Neptune HATS-8b. We present results for the inflated super-Neptune HATS-8b from the Michigan Optical Planetary Spectra Survey (MOPSS). This program is aimed at creating a database of optical planetary transmission spectra all observed, reduced, and analyzed with a uniform method for the benefit of enabling comparative exoplanet studies. HATS-8b orbits a G dwarf and is a low-density super-Neptune with a radius of 0.873 R Jup, a mass of 0.138 M Jup, and a density of 0.259 g cm-3. Two transits of HATS-8b were observed in 2017 July and August with the Inamori-Magellan Areal Camera and Spectrograph (IMACS) instrument on the Magellan Baade 6.5 m telescope. We find an enhanced scattering slope on each night that agree within 2.3σ. This slope is stronger than one due only to Rayleigh scattering and cannot be fully explained by unocculted starspots. We explore the impact of condensates on the scattering slope and determine that MnS particulates smaller than 10-2 μm can explain up to 80% of our measured slope if the planet is warmer than equilibrium, or 50% of the slope at the equilibrium temperature of the planet for a low mean molecular weight atmosphere. The scattering slope that we observe is thus beyond even the most extreme haze case we consider. We suggest further follow up on this target and host star to determine if the temporal variation of the slope is primarily due to stellar or planetary effects, and to better understand what these effects may be.

Keywords: Hot Jupiters, Exoplanets, Hot Neptunes, Extrasolar gaseous giant planets, Exoplanet atmospheres
The Vanishing and Appearing Sources during a Century of Observations Project. I. USNO Objects Missing in Modern Sky Surveys and Follow-up Observations of a “Missing Star”. In this paper we report the current status of a new research program. The primary goal of the “Vanishing and Appearing Sources during a Century of Observations” project is to search for vanishing and appearing sources using existing survey data to find examples of exceptional astrophysical transients. The implications of finding such objects extend from traditional astrophysics fields to the more exotic searches for evidence of technologically advanced civilizations. In this first paper we present new, deeper observations of the tentative candidate discovered by Villarroel et al. in 2016. We then perform the first searches for vanishing objects throughout the sky by comparing 600 million objects from the US Naval Observatory Catalogue (USNO) B1.0 down to a limiting magnitude of ∼20-21 with the recent Pan-STARRS Data Release-1 (DR1) with a limiting magnitude of ∼23.4. We find about 150,000 preliminary candidates that do not have any Pan-STARRS counterpart within a 30″ radius. We show that these objects are redder and have larger proper motions than typical USNO objects. We visually examine the images for a subset of about 24,000 candidates, superseding the 2016 study with a sample 10 times larger. We find about 100 point sources visible in only one epoch in the red band of the USNO, which may be of interest in searches for strong M-dwarf flares, high-redshift supernovae, or other categories of unidentified red transients.

Keywords: Surveys, Transient sources, Astrobiology, Photographic photometry, Gamma-ray transient sources
HD 150382: A Lithium-rich Star at the Early-AGB Stage?. We report the discovery of a lithium-rich giant, HD 150382, a post-red-giant-branch clump star. The atmospheric parameters, the chemical abundances for 17 elements, and the isotopic ratio 12C/13C were determined using the equivalent width and the spectral synthesis methods. The lithium abundance was determined via spectral synthesis of the Li I resonance doublet at λ 6708 yielding log ɛ(Li)NLTE = 2.55. The excited-state line at λ 6104 also was analyzed. In addition, we have used theoretical evolutionary tracks to determine the mass and luminosity of HD 150382 and compare it with other well-known lithium-rich giants in the literature. Our results show that HD 150382 is a slowly rotating K-giant star having near-solar metallicity. We also show that HD 150382 is not s-process enriched, which is in agreement with its evolutionary status. Finally, based on the abundance results, we study the possible scenarios of the lithium enrichment. Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under the agreement with Observatório Nacional and under agreement between Observatório Nacional and Max-Planck Institute für Astronomie.

Keywords: High resolution spectroscopy, A giant stars, Asymptotic giant branch stars, Lithium stars, Chemically peculiar stars
Quantifying the Influence of Jupiter on the Earth’s Orbital Cycles. A wealth of Earth-sized exoplanets will be discovered in the coming years, providing a large pool of candidates from which the targets for the search for life beyond the solar system will be chosen. The target selection process will require the leveraging of all available information in order to maximize the robustness of the target list and make the most productive use of follow-up resources. Here, we present the results of a suite of n-body simulations that demonstrate the degree to which the orbital architecture of the solar system impacts the variability of Earth’s orbital elements. By varying the orbit of Jupiter and keeping the initial orbits of the other planets constant, we demonstrate how subtle changes in solar system architecture could alter the Earth’s orbital evolution—a key factor in the Milankovitch cycles that alter the amount and distribution of solar insolation, thereby driving periodic climate change on our planet. The amplitudes and frequencies of Earth’s modern orbital cycles fall in the middle of the range seen in our runs for all parameters considered—neither unusually fast nor slow, neither large nor small. This finding runs counter to the “Rare Earth” hypothesis, which suggests that conditions on Earth are so unusual that life elsewhere is essentially impossible. Our results highlight how dynamical simulations of newly discovered exoplanetary systems could be used as an additional means to assess the potential targets of biosignature searches, and thereby help focus the search for life to the most promising targets.

Keywords: Exoplanet systems, Gravitational interaction, Astrobiology, N-body simulations, Dynamical evolution
Bayesian Characterization of Main-sequence Binaries in the Old Open Cluster NGC 188. The binary fractions of open and globular clusters yield powerful constraints on their dynamical state and evolutionary history. We apply publicly available Bayesian analysis tools to a UBV RIJHK  S  photometric catalog of the open cluster NGC 188 to detect and characterize photometric binaries along the cluster main sequence. This technique has the advantage of self-consistently handling photometric errors, missing data in various bandpasses, and star-by-star prior constraints on cluster membership. Simulations are used to verify uncertainties and quantify selection biases in our analysis, illustrating that among binaries with mass ratios &gt;0.5, we recover the binary fraction to better than 7% in the mean, with no significant dependence on binary fraction and a mild dependence on assumed mass-ratio distribution. Using our photometric catalog, we recover the majority (65% ± 11%) of spectroscopically identified main-sequence binaries, including eight of the nine with spectroscopically measured mass ratios. Accounting for incompleteness and systematics, we derive a mass-ratio distribution that rises toward lower mass ratios (within our q &gt; 0.5 analysis domain). We observe a raw binary fraction for solar-type main-sequence stars with mass ratios q &gt; 0.5 of 42% ± 4%, independent of the assumed mass-ratio distribution to within its uncertainties, consistent with literature values for old open clusters but significantly higher than the field solar-type binary fraction. We confirm that the binaries identified by our method are more concentrated than single stars, in agreement with previous studies, and we demonstrate that the binary nature of those candidates that remain unidentified spectroscopically is strongly supported by photometry from Gaia DR2.

Keywords: Open star clusters, Bayesian statistics, Binary stars