Sazuna/UAT_keywords huggingface dataset:
Re-examining the Radial Distributions of M13 Multiple Populations. We seek to resolve the tension in the literature regarding the presence of radially segregated multiple populations in the Galactic globular cluster M13. Previous studies of this nearby cluster have presented discordant results about the degree of dynamical mixing in M13's inner region. Using ground-based (UBVI) photometry, we show that cumulative radial distributions of stars on the blue and red sides of the red giant branch are statistically identical. Interestingly, these results are obtained using data from large-aperture, ground-based telescopes as well as a more modestly sized instrument, and both are in agreement with previous work done using Hubble Space Telescope and Strömgren photometry. Results are derived using the CU,B,I index, shown to be sensitive to compositional differences. We discuss our conclusions that the chemically distinct populations within M13 may be dynamically mixed in the context of published results from simulations.

Keywords: Globular star clusters, Broad band photometry, Red giant branch, Hertzsprung Russell diagram, Dynamical evolution
The K2 and TESS Synergy. I. Updated Ephemerides and Parameters for K2-114, K2-167, K2-237, and K2-261. Although the Transiting Exoplanet Survey Satellite (TESS) primary mission observed the northern and southern ecliptic hemispheres, generally avoiding the ecliptic, and the Kepler space telescope during the K2 mission could only observe near the ecliptic, many of the K2 fields extend far enough from the ecliptic plane that sections overlap with TESS fields. Using photometric observations from both K2 and TESS, combined with archival spectroscopic observations, we globally modeled four known planetary systems discovered by K2 that were observed in the first year of the primary TESS mission. Specifically, we provide updated ephemerides and system parameters for K2-114 b, K2-167 b, K2-237 b, and K2-261 b. These were some of the first K2 planets to be observed by TESS in the first year and include three Jovian sized planets and a sub-Neptune with orbital periods less than 12 days. In each case, the updated ephemeris significantly reduces the uncertainty in prediction of future times of transit, which is valuable for planning observations with the James Webb Space Telescope and other future facilities. The TESS extended mission is expected to observe about half of the K2 fields, providing the opportunity to perform this type of analysis on a larger number of systems.

Keywords: Radial velocity, Transit photometry, Transits, Exoplanets
Exoplanet Sciences with Nulling Interferometers and a Single-mode Fiber-fed Spectrograph. Understanding the atmospheres of exoplanets is a milestone to decipher their formation history and potential habitability. High-contrast imaging and spectroscopy of exoplanets is the major pathway toward the goal. Direct imaging of an exoplanet requires high spatial resolution. Interferometry has proven to be an effective way of improving spatial resolution. However, means of combining interferometry, high-contrast imaging, and high-resolution spectroscopy have been rarely explored. To fill in the gap, we present the dual-aperture fiber nuller (FN) for current-generation 8-10 m telescopes, which provides the necessary spatial and spectral resolution to (1) conduct follow-up spectroscopy of known exoplanets and (2) detect planets in debris-disk systems. The concept of feeding an FN to a high-resolution spectrograph can also be used for future space and ground-based missions. We present a case study of using the dual-aperture FN to search for biosignatures in rocky planets around M stars for a future space interferometry mission. Moreover, we discuss how an FN can be equipped on future extremely large telescopes by using the Giant Magellan Telescope as an example.

Keywords: Exoplanet astronomy, Interferometers, Habitable planets
The TESS Phase Curve of KELT-1b Suggests a High Dayside Albedo. We measured the optical phase curve of the transiting brown dwarf KELT-1b (TOI 1476) using data from the TESS spacecraft. We found that KELT-1b shows significant phase variation in the TESS bandpass, with a relatively large phase amplitude of ${234}_{-44}^{+43}$ ppm and a secondary eclipse depth of ${371}_{-49}^{+47}$ ppm. We also measured a marginal eastward offset in the dayside hot spot of 18°3 ± 7°4 relative to the substellar point. We detected a strong phase-curve signal attributed to ellipsoidal distortion of the host star with an amplitude of 399 ± 19 ppm. Our results are roughly consistent with the Spitzer phase curves of KELT-1b, but the TESS eclipse depth is deeper than expected. Our cloud-free 1D models of KELT-1b's dayside emission are unable to fit the full combined eclipse spectrum. Instead, the large TESS eclipse depth suggests that KELT-1b may have a significant dayside geometric albedo of Ag ∼ 0.5 in the TESS bandpass, which would agree with the tentative trend between equilibrium temperature and geometric albedo recently suggested by Wong et al. We posit that if KELT-1b has a high dayside albedo, it is likely due to silicate clouds that form on KELT-1b's nightside and are subsequently transported onto the western side of KELT-1b's dayside hemisphere before breaking up.

Keywords: Exoplanet atmospheric composition , Brown dwarfs, Hot Jupiters, Exoplanet atmospheres
Lyapunov and Clearing Timescales in Planetary Chaotic Zones. Debris disks in planetary systems are known to possess gaps "opened" by planets in their close-to-coorbital neighborhoods; the gaps are free from low-mass material such as planetesimals. We consider the escape process of the initially zero-eccentric particles from the gap zone in a scenario consisting of two basic consequent stages: (1) the particle orbit's eccentricity is inflated, while its specific energy is relatively constant, and (2) the particle orbit's semimajor axis is inflated, while its specific angular momentum is relatively constant. During the first stage, the chaotic transport (diffusion) proceeds along the "staircase" of (p + 1):p (with integer p ≫ 1) overlapping particle-planet resonances, and during the second stage, it proceeds along the p:1 particle-planet resonance staircase. A specialized two-dimensional area-preserving map (a "tokamap" version) is derived to describe the first stage, while a multiharmonic Kepler map theory is used to describe the second stage. We derive the μ (mass parameter) scaling for the clearing timescale in the planetary chaotic zone. At small μ, it turns out to be inverse-quadratic in μ. The μ scaling for the Lyapunov timescale inside the gap is also derived. The derived scalings are in qualitative agreement with available numerical-experimental data.

Keywords: Exoplanet dynamics, Orbital motion, Exoplanets, Orbital resonances, Exoplanet systems, Celestial mechanics, Three-body problem, Dynamical evolution
The Physical Parameters of Clumps Associated with Class I Methanol Masers. We present a study of the association between class I methanol masers and cold dust clumps from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. It was found that almost 100% of class I methanol masers are associated with objects listed in the ATLASGAL compact source catalog. We find a statistically significant difference in the flux density, luminosity, number and column density, and temperature distributions of ATLASGAL sources associated with 95/44 GHz methanol masers compared with those ATLASGAL sources devoid of 95 GHz methanol masers. The masers tend to arise in clumps with higher densities, luminosities, and temperatures compared with both the full sample of ATLASGAL clumps, as well as the sample of ATLASGAL sources that were cross-matched with positions previously searched for methanol masers but with no detections. Comparison between the peak position of ATLASGAL clumps and the interferometric positions of the associated class I and II methanol masers reveals that class I masers are generally located at larger physical distances from the peak submillimeter emission than class II masers. We conclude that the tight association between ATLASGAL sources and class I methanol masers may be used as a link toward understanding the conditions of the pumping of these masers and evolutionary stages at which they appear.

Keywords: Astronomy databases, Dust continuum emission, Astrophysical masers, Interstellar medium
Nature Versus Nurture: A Bayesian Framework for Assessing Apparent Correlations between Planetary Orbital Properties and Stellar Ages. Many exoplanets have orbital characteristics quite different from those seen in our own solar system, including planets locked in orbital resonances and planets on orbits that are elliptical or highly inclined from their host star's spin axis. It is debated whether the wide variety in system architecture is primarily due to differences in formation conditions (nature) or due to evolution over time (nurture). Identifying trends between planetary and stellar properties, including stellar age, can help distinguish between these competing theories and offer insights as to how planets form and evolve. However, it can be challenging to determine whether observed trends between planetary properties and stellar age are driven by the age of the system—pointing to evolution over time being an important factor—or other parameters to which the age may be related, such as stellar mass or stellar temperature. The situation is complicated further by the possibilities of selection biases, small number statistics, uncertainties in stellar age, and orbital evolution timescales that are typically much shorter than the range of observed ages. Here, we develop a Bayesian statistical framework to assess the robustness of such observed correlations and to determine whether they are indeed due to evolutionary processes, are more likely to reflect different formation scenarios, or are merely coincidental. We apply this framework to reported trends between stellar age and 2:1 orbital resonances, spin-orbit misalignments, and hot Jupiters' orbital eccentricities. We find strong support for the nurture hypothesis only in the final case.

Keywords: Exoplanet dynamics, Bayesian statistics, Stellar ages, Exoplanet systems, Exoplanet evolution
The Solar Neighborhood. XLVI. Revealing New M Dwarf Binaries and Their Orbital Architectures. We use 20 yr of astrometric data from the REsearch Consortium On Nearby Stars (RECONS) program on the Cerro Tololo Inter-American Observatory/SMARTS 0.9 m telescope to provide new insight into multiple star systems in the solar neighborhood. We provide new and updated parallaxes for 210 systems and derive nine high-quality astrometric orbits with periods of 2.49-16.63 yr. Using a total of 542 systems' parallaxes from RECONS, we compare systems within 25 pc to Gaia DR2 to define criteria for selecting unresolved astrometric multiples from the DR2 results. We find that three out of four unresolved multistar red dwarf systems within 25 pc in DR2 have parallax_error ≥ 0.32 mas, astrometric_gof_al ≥ 56, astrometric_excess_noise_sig ≥ 108.0, ruwe ≥ 2.0, and parallaxes more than ∼10% different from the long-term RECONS results. These criteria have broad applications to any work targeting nearby stars, from studies seeking binary systems to efforts targeting single stars for planet searches.

Keywords: Trigonometric parallax, Binary stars, M stars, Astrometric binary stars, Low mass stars, Astrometry
A Planar Five-body Problem in a Framework of Heterogeneous and Mass Variation Effects. The aim of the present paper is to study the effects of heterogeneous oblate spheroid and variable mass on the motion of the fifth infinitesimal body in the frame of the circular restricted five-body problem, with the imposition that the three primaries are placed at the vertices of an equilateral triangle and the fourth primary is placed at the center of the equilateral triangle. By using Jeans law and Meshcherskii space transformation, we evaluate the equations of motion and find a quasiJacobian integral. We determine the locations of equilibrium points, the regions of motion, and the attracting domain of in-plane motion. Furthermore, the effects of heterogeneous oblate spheroid and variable mass have been examined with the help of Poincaré surfaces of section. We studied the linear stability of equilibrium points and found that all of them are unstable.

Keywords: Celestial mechanics
Estimating the Ages of FGK Dwarf Stars through the Use of GALEX FUV Magnitudes. Stellar age cannot be directly measured, yet age determinations are fundamental to understanding the evolution of stars, planets, and galaxies. The work presented here builds upon the idea of a stellar-activity age. We utilized far-ultraviolet (FUV) photometry acquired by the Galaxy Evolution Explorer (GALEX) space telescope as an indicator of chromospheric activity to infer ages of late-F, G, and K type dwarf stars. We derived a purely empirical correlation between FUV magnitudes and stellar age in conjunction with (B - V) color. Our attention is restricted to Sun-like stars with color range $0.55\leqslant (B-V)\leqslant 0.71$ and absolute magnitude range 4.3 ≤ MV ≤ 5.3. The correlation is defined in terms of a FUV-excess parameter $Q(\mathrm{FUV}-B,B-V)$ . We related stellar age, τ, to Q through the relation ${\mathrm{log}}_{e}(\tau )={\mathrm{log}}_{e}(a)+{bQ}$ , where a and b are fit parameters and functions of (B - V). This correlation is functional up to 6 Gyr for FGK dwarfs. With such a correlation, one only needs Johnson (B - V) and FUV measurements to estimate the stellar age for Population I dwarf stars of solar-like temperature and metallicity. Such a calibration has utility in population studies of FGK dwarfs for further understanding of the chemical evolution of the Milky Way. As an illustration of one such application, we have constructed activity and FUV-age distributions for a sample of thin and thick disk stars, as distinguished by their chemical abundances. Considerable overlap is found between the activity distribution and age range of the two populations. We discuss the possibility that some high-[α/Fe] thick disk stars were formed as a result of the accretion of dwarf galaxies as recently as 4 Gyr ago.

Keywords: Stellar activity, Milky Way disk, Ultraviolet photometry, Milky Way evolution, Stellar evolution
Fast Transit Computation Using Tabulated Stellar Intensities. Limb-darkening laws are convenient parameterizations of the stellar intensity center-to-limb variation, and their use is ubiquitous in eclipse and transit modeling. But they are not "laws" in any sense—they are simple approximations of the real intensity variations, and their limitations are becoming more and more apparent as stellar atmosphere models improve and higher precision data become available. When fitting eclipses and transit light curves, one would ideally like to use model intensities that are based on fundamental stellar parameters such as the mass, radius, and effective temperature of the star, rather than a limb-darkening law representation and its coefficients. This is especially true when attempting to detect higher-order effects such as planetary oblateness, rings, satellites, or atmospheres. However, using model intensities requires numerically integrating many small-area "tiles" on the model stellar surface(s), and this has traditionally been too computationally expensive for general use. Here we present a fast technique to compute light curves and the Rossiter-McLaughlin effect that uses tabulated stellar models intensities. This is a step in the development of tools that obviate the need for limb-darkening laws.

Keywords: Transits, Exoplanets, Computational methods, Limb darkening, Eclipsing binary stars
Flare Statistics for Young Stars from a Convolutional Neural Network Analysis of TESS Data. All-sky photometric time-series missions have allowed for the monitoring of thousands of young (tage &lt; 800 Myr) stars in order to understand the evolution of stellar activity. Here, we developed a convolutional neural network (CNN), stella, specifically trained to find flares in Transiting Exoplanet Survey Satellite (TESS) short-cadence data. We applied the network to 3200 young stars in order to evaluate flare rates as a function of age and spectral type. The CNN takes a few seconds to identify flares on a single light curve. We also measured rotation periods for 1500 of our targets and find that flares of all amplitudes are present across all spot phases, suggesting high spot coverage across the entire surface. Additionally, flare rates and amplitudes decrease for stars tage &gt; 50 Myr across all temperatures Teff ≥ 4000 K, while stars from 2300 ≤ Teff &lt; 4000 K show no evolution across 800 Myr. Stars of Teff ≤ 4000 K also show higher flare rates and amplitudes across all ages. We investigate the effects of high flare rates on photoevaporative atmospheric mass loss for young planets. In the presence of flares, planets lose 4%-7% more atmosphere over the first 1 Gyr. stella is an open-source Python toolkit hosted on GitHub and PyPI.

Keywords: Convolutional neural networks, Stellar activity, Pre-main sequence stars, Stellar rotation, Time series analysis
Near-infrared Census of RR Lyrae Variables in the Messier 3 Globular Cluster and the Period-Luminosity Relations. We present new near-infrared (NIR), JHKs, time-series observations of RR Lyrae variables in the Messier 3 (NGC 5272) globular cluster using the WIRCam instrument at the 3.6 m Canada-France-Hawaii Telescope. Our observations cover a sky area of ∼21' × 21' around the cluster center and provide an average of 20 epochs of homogeneous JHKs-band photometry. New homogeneous photometry is used to estimate robust mean magnitudes for 175 fundamental-mode (RRab), 47 overtone-mode (RRc), and 11 mixed-mode (RRd) variables. Our sample of 233 RR Lyrae variables is the largest thus far obtained in a single cluster with time-resolved, multiband NIR photometry. NIR-to-optical amplitude ratios for RR Lyrae in Messier 3 exhibit a systematic increase moving from RRc to short-period (P &lt; 0.6 day) and long-period (P ≳ 0.6 day) RRab variables. We derive JHKs-band period-luminosity relations for RRab, RRc, and the combined sample of variables. Absolute calibrations based on the theoretically predicted period-luminosity-metallicity relations for RR Lyrae stars yield a distance modulus, $\mu =15.041\pm 0.017\,(\mathrm{statistical})\pm 0.036\,(\mathrm{systematic})$ mag, to Messier 3. When anchored to trigonometric parallaxes for nearby RR Lyrae stars from the Hubble Space Telescope and the Gaia mission, our distance estimates are consistent with those resulting from the theoretical calibrations, albeit with relatively larger systematic uncertainties.

Keywords: Globular star clusters, Stellar pulsations, Distance measure, Distance indicators, RR Lyrae variable stars
The Separation and Hα Contrasts of Massive Accreting Planets in the Gaps of Transitional Disks: Predicted Hα Protoplanet Yields for Adaptive Optics Surveys. We present a massive accreting gap planet model that ensures large gaps in transitional disks are kept dust free by the scattering action of three coplanar quasi-circular planets in a 1:2:4 mean motion resonance (MMR). This model uses the constraint of the observed gap size, and the dust-free nature of the gap, to determine within ∼10% the possible orbits for three massive planets in an MMR. Calculated orbits are consistent with the observed orbits and Hα emission (the brightest line to observe these planets) for LkCa 15 b, PDS 70 b, and PDS 70 c within observational errors. Moreover, the model suggests that the scarcity of detected Hα planets is likely a selection effect of the current limitations of non-coronagraphic, low (&lt;10%) Strehl, Hα imaging with adaptive optics (AO) systems used in past Hα surveys. We predict that as higher Strehl AO systems (with high-performance custom coronagraphs; like the 6.5 m Magellan Telescope MagAO-X system) are utilized at Hα, the number of detected gap planets will substantially increase by more than tenfold. For example, we show that &gt;25 ± 5 new Hα "gap planets" are potentially discoverable by a survey of the best 19 transitional disks with MagAO-X. Detections of these accreting protoplanets will significantly improve our understanding of planet formation, planet growth and accretion, solar system architectures, and planet-disk interactions.

Keywords: Accretion, Laser guide stars, Planetary system formation, Coronagraphic imaging, Direct imaging, Protoplanetary disks, Stellar accretion, Circumstellar disks, Stellar accretion disks, Exoplanet detection methods, Adaptive interferometry, Planet formation
HATS-37Ab and HATS-38b: Two Transiting Hot Neptunes in the Desert. We report the discovery of two transiting Neptunes by the HATSouth survey. The planet HATS-37Ab has a mass of $0.099\pm 0.042$ ${M}_{{\rm{J}}}$ (31.5 ± 13.4 M⊕) and a radius of $0.606\pm 0.016$ ${R}_{{\rm{J}}}$ , and is on a $P=4.3315$ day orbit around a $V=12.266\pm 0.030$ mag, ${0.843}_{-0.012}^{+0.017}$ ${M}_{\odot }$ star with a radius of ${0.877}_{-0.012}^{+0.019}$ ${R}_{\odot }$ . We also present evidence that the star HATS-37A has an unresolved stellar companion HATS-37B, with a photometrically estimated mass of $0.654\pm 0.033$ ${M}_{\odot }$ . The planet HATS-38b has a mass of $0.074\pm 0.011$ ${M}_{{\rm{J}}}$ (23.5 ± 3.5 M⊕) and a radius of $0.614\pm 0.017$ ${R}_{{\rm{J}}}$ , and is on a $P=4.3750$ day orbit around a $V=12.411\pm 0.030$ mag, ${0.890}_{-0.012}^{+0.016}$ ${M}_{\odot }$ star with a radius of $1.105\pm 0.016$ ${R}_{\odot }$ . Both systems appear to be old, with isochrone-based ages of ${11.46}_{-1.45}^{+0.79}$ Gyr, and $11.89\pm 0.60$ Gyr, respectively. Both HATS-37Ab and HATS-38b lie in the Neptune desert and are thus examples of a population with a low occurrence rate. They are also among the lowest-mass planets found from ground-based wide-field surveys to date. * The HATSouth network is operated by a collaboration consisting of Princeton University (PU), the Max Planck Institute für Astronomie (MPIA), the Australian National University (ANU), and Universidad Adolfo Ibáñez (UAI). The station at Las Campanas Observatory of the Carnegie Institution for Science is operated by PU in conjunction with UAI, the station at the High Energy Spectroscopic Survey site is operated in conjunction with MPIA, and the station at Siding Spring Observatory (SSO) is operated jointly with ANU. This work is based in part on observations made with the MPG 2.2 m Telescope at the ESO Observatory in La Silla and based on observations collected at the European Southern Observatory under ESO programmes 094.C-0428(A), 095.C-0367(A), 097.C-0571(A), 098.C-0292(A), 099.C-0374(A), 0100.C-0406(A), 0100.C-0406(B). This paper includes data gathered with the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile, and is based in part on observations made with the Anglo-Australian Telescope operated by the Australian Astronomical Observatory.

Keywords: Hot Neptunes, Exoplanets