Sazuna/UAT_keywords huggingface dataset:
Ground-based Optical Transmission Spectroscopy of the Nearby Terrestrial Exoplanet LTT 1445Ab. Nearby M-dwarf systems currently offer the most favorable opportunities for spectroscopic investigations of terrestrial exoplanet atmospheres. The LTT 1445 system is a hierarchical triple of M dwarfs with two known planets orbiting the primary star, LTT 1445A. We observe four transits of the terrestrial world LTT 1445Ab (R = 1.3 R ⊕, M = 2.9 M ⊕) at low resolution with Magellan II/LDSS3C. We use the combined flux of the LTT 1445BC pair as a comparison star, marking the first time that an M dwarf is used to remove telluric variability from time-series observations of another M dwarf. We find Hα in emission from both LTT 1445B and C, as well as a flare in one of the data sets from LTT 1445C. These contaminated data are removed from the analysis. We construct a broadband transit light curve of LTT 1445Ab from 620 to 1020 nm. Binned to 3 minute time bins, we achieve an rms of 49 ppm for the combined broadband light curve. We construct a transmission spectrum with 20 spectrophotometric bins each spanning 20 nm and compare it to models of clear, 1× solar composition atmospheres. We rule out this atmospheric case with a surface pressure of 10 bars to 3.2σ confidence, and with a surface pressure of 1 bar to 3.1σ confidence. Upcoming secondary eclipse observations of LTT 1445Ab with the James Webb Space Telescope will further probe the cases of a high-mean-molecular-weight atmosphere, a hazy or cloudy atmosphere, or no atmosphere at all on this terrestrial world.

Keywords: Extrasolar rocky planets, M dwarf stars, Exoplanets, Optical astronomy, Transmission spectroscopy, Exoplanet astronomy, Spectroscopy, Exoplanet atmospheres
High-resolution Transmission Spectroscopy of the Terrestrial Exoplanet GJ 486b. Terrestrial exoplanets orbiting M-dwarf stars are promising targets for transmission spectroscopy with existing or near-future instrumentation. The atmospheric composition of such rocky planets remains an open question, especially given the high X-ray and ultraviolet flux from their host M dwarfs that can drive atmospheric escape. The 1.3 R ⊕ exoplanet GJ 486b (T eq ~ 700 K), orbiting an M3.5 star, is expected to have one of the strongest transmission spectroscopy signals among known terrestrial exoplanets. We observed three transits of GJ 486b using three different high-resolution spectrographs: IRD on Subaru, IGRINS on Gemini-South, and SPIRou on the Canada-France-Hawai'i Telescope. We searched for atmospheric absorption from a wide variety of molecular species via the cross-correlation method, but did not detect any robust atmospheric signals. Nevertheless, our observations are sufficiently sensitive to rule out several clear atmospheric scenarios via injection and recovery tests, and extend comparative exoplanetology into the terrestrial regime. Our results suggest that GJ 486b does not possess a clear H2/He-dominated atmosphere, nor a clear 100% water-vapor atmosphere. Other secondary atmospheres with high mean molecular weights or H2/He-dominated atmospheres with clouds remain possible. Our findings provide further evidence suggesting that terrestrial planets orbiting M-dwarf stars may experience significant atmospheric loss.

Keywords: Exoplanets, Exoplanet atmospheric composition , Planetary atmospheres, Exoplanet atmospheres
Evidence for Hidden Nearby Companions to Hot Jupiters. The first discovered extrasolar worlds-giant, "hot Jupiter" planets on short-period orbits-came as a surprise to solar system-centric models of planet formation, prompting the development of new theories for planetary system evolution. The near absence of observed nearby planetary companions to hot Jupiters has been widely quoted as evidence in support of high-eccentricity tidal migration, a framework in which hot Jupiters form further out in their natal protoplanetary disks before being thrown inward with extremely high eccentricities, stripping systems of any close-in planetary companions. In this work, we present new results from a search for transit timing variations across the full 4 yr Kepler data set, demonstrating that at least 12% ± 6% of hot Jupiters have a nearby planetary companion. This subset of hot Jupiters is expected to have a quiescent dynamical history such that the systems could retain their nearby companions. We also demonstrate a ubiquity of nearby planetary companions to warm Jupiters (≥70% ± 16%), indicating that warm Jupiters typically form quiescently. We conclude by combining our results with existing observational constraints to propose an "eccentric migration" framework for the formation of short-period giant planets through postdisk dynamical sculpting in compact multiplanet systems. Our framework suggests that hot Jupiters constitute the natural end stage for giant planets spanning a wide range of eccentricities, with orbits that reach small enough periapses-either from their final orbital configurations in the disk phase or from eccentricity excitation in the postdisk phase-to trigger efficient tidal circularization.

Keywords: Exoplanets, Hot Jupiters
Astrometric Calibration of the Beijing-Arizona Sky Survey. We present the astrometric calibration of the Beijing-Arizona Sky Survey (BASS). The BASS astrometry was tied to the International Celestial Reference Frame via the Gaia Data Release 2 reference catalog. For effects that were stable throughout the BASS observations, including differential chromatic refraction and the low charge transfer efficiency of the CCD, we corrected for these effects at the raw image coordinates. Fourth-order polynomial intermediate longitudinal and latitudinal corrections were used to remove optical distortions. The comparison with the Gaia catalog shows that the systematic errors, depending on color or magnitude, are less than 2 milliarcseconds (mas). The position systematic error is estimated to be about -0.01 ± 0.7 mas in the region between 30° and 60° of decl. and up to -0.07 ± 0.9 mas in the region north of decl. 60°.

Keywords: Photographic astrometry
Tidal Heating of Exomoons in Resonance and Implications for Detection. The habitability of exoplanets can be strongly influenced by the presence of an exomoon, and in some cases the exomoon itself could be a possible place for life to develop. For moons outside of the habitable zone, significant tidal heating may raise their surface temperatures enough for them to be considered habitable. Tidal heating of a moon depends on numerous factors such as eccentricity, semimajor axis, size of parent planet, and the presence of additional moons. In this work, we explore the degree of tidal heating possible for multimoon systems in resonance using a combination of semianalytic and numerical models. This demonstrates that even for a moon with zero initial eccentricity, when it moves into resonance with an outer moon, it can generate significant eccentricity and associated tidal heating. Depending on the mass ratio of the two moons, this resonance can either be short-lived (≤200 Myr) or continue to be driven by the tidal migration of the moons. This tidal heating can also assist in making the exomoons easier to discover, and we explore two scenarios: secondary eclipses and outgassing of volcanic species. We then consider hypothetical moons orbiting known planetary systems to identify which will be best suited for finding exomoons with these methods. We conclude with a discussion of current and future instrumentation and missions.

Keywords: Tides, Natural satellites (Extrasolar), Habitable planets, Exoplanets
Dynamical Evolution of Closely Packed Multiple Planetary Systems Subject to Atmospheric Mass Loss. A gap in exoplanets' radius distribution has been widely attributed to the photoevaporation threshold of their progenitors' gaseous envelope. Giant impacts can also lead to substantial mass loss. The outflowing gas endures tidal torque from the planets and their host stars. Alongside the planet-star tidal and magnetic interaction, this effect leads to planets' orbital evolution. In multiple super-Earth systems, especially in those that are closely spaced and/or contain planets locked in mean motion resonances, modest mass loss can lead to dynamical instabilities. In order to place some constraints on the extent of planets' mass loss, we study the evolution of a series of idealized systems of multiple planets with equal masses and a general scaled separation. We consider mass loss from one or more planets either in the conservative limit or with angular momentum loss from the system. We show that the stable preservation of idealized multiple planetary systems requires either a wide initial separation or a modest upper limit in the amount of mass loss. This constraint is stringent for the multiple planetary systems in compact and resonant chains. Perturbation due to either impulsive giant impacts between super-Earths or greater than a few percent mass loss can lead to dynamical instabilities.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation
MOA-2020-BLG-208Lb: Cool Sub-Saturn-mass Planet within Predicted Desert. We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio $q={3.17}_{-0.26}^{+0.28}\times {10}^{-4}$ , the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass ${m}_{\mathrm{planet}}={46}_{-24}^{+42}\,{M}_{\oplus }$ and a host star of mass ${M}_{\mathrm{host}}={0.43}_{-0.23}^{+0.39}\,{M}_{\odot }$ , located at a distance ${D}_{L}={7.49}_{-1.13}^{+0.99}\,\mathrm{kpc}$ . For the second scenario, we estimate ${m}_{\mathrm{planet}}={69}_{-34}^{+37}\,{M}_{\oplus }$ , ${M}_{\mathrm{host}}={0.66}_{-0.32}^{+0.35}\,{M}_{\odot }$ , and ${D}_{L}={7.81}_{-0.93}^{+0.93}\,\mathrm{kpc}$ . The planet has a projected separation as a fraction of the Einstein ring radius $s={1.3807}_{-0.0018}^{+0.0018}$ . As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models.

Keywords: Gravitational microlensing, Gravitational microlensing exoplanet detection, Binary lens microlensing
Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions. Directly imaging temperate rocky planets orbiting nearby, Sun-like stars with a 6 m class IR/O/UV space telescope, recently dubbed the Habitable Worlds Observatory, is a high-priority goal of the Astro2020 Decadal Survey. To prepare for future direct imaging (DI) surveys, the list of potential targets should be thoroughly vetted to maximize efficiency and scientific yield. We present an analysis of archival radial velocity data for southern stars from the NASA/NSF Extreme Precision Radial Velocity (EPRV) Working Group's list of high-priority target stars for future DI missions (drawn from the HabEx, LUVOIR, and Starshade Rendezvous studies). For each star, we constrain the region of companion mass and period parameter space we are already sensitive to based on the observational baseline, sampling, and precision of the archival radial velocity (RV) data. Additionally, for some of the targets, we report new estimates of magnetic activity cycle periods, rotation periods, improved orbital parameters for previously known exoplanets, and new candidate planet signals that require further vetting or observations to confirm. Our results show that for many of these stars we are not yet sensitive to even Saturn-mass planets in the habitable zone, let alone smaller planets, highlighting the need for future EPRV vetting efforts before the launch of a DI mission. We present evidence that the candidate temperate super-Earth exoplanet HD 85512b is most likely due to the star's rotation, and report an RV acceleration for δ Pav that supports the existence of a distant giant planet previously inferred from astrometry. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Exoplanet astronomy, Radial velocity, Exoplanet systems
Revising Properties of Planet-Host Binary Systems. III. There Is No Observed Radius Gap for Kepler Planets in Binary Star Systems. Binary stars are ubiquitous; the majority of solar-type stars exist in binaries. Exoplanet occurrence rate is suppressed in binaries, but some multiples do still host planets. Binaries cause observational biases in planet parameters, with undetected multiplicity causing transiting planets to appear smaller than they truly are. We have analyzed the properties of a sample of 119 planet-host binary stars from the Kepler mission to study the underlying population of planets in binaries that fall in and around the radius valley, which is a demographic feature in period-radius space that marks the transition from predominantly rocky to predominantly gaseous planets. We found no statistically significant evidence for a radius gap for our sample of 122 planets in binaries when assuming that the primary stars are the planet hosts, with a low probability (p &lt; 0.05) of the binary planet sample radius distribution being consistent with the single-star population of small planets via an Anderson-Darling test. These results reveal demographic differences in the planet size distribution between planets in binary and single stars for the first time, showing that stellar multiplicity may fundamentally alter the planet formation process. A larger sample and further assessment of circumprimary versus circumsecondary transits is needed to either validate this nondetection or explore other scenarios, such as a radius gap with a location that is dependent on binary separation. * Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Keywords: Extrasolar rocky planets, Binary stars, Exoplanets
Elemental Abundances of Kepler Objects of Interest in APOGEE DR17. The elemental abundances of planet host stars can shed light on the conditions of planet forming environments. We test if individual abundances of 130 known/candidate planet hosts in APOGEE are statistically different from those of a reference doppelgänger sample. The reference set comprises objects selected with the same T eff, $\mathrm{log}g$ , [Fe/H], and [Mg/H] as each Kepler Object of Interest (KOI). We predict twelve individual abundances (X = C, N, O, Na, Al, Si, Ca, Ti, V, Cr, Mn, Ni) for the KOIs and their doppelgängers using a local linear model of these four parameters, training on ASPCAP abundance measurements for a sample of field stars with high-fidelity (signal-to-noise ratio &gt; 200) APOGEE observations. We compare element prediction residuals (model-measurement) for the two samples and find them to be indistinguishable, given a high-quality sample selection. We report median intrinsic dispersions of ~0.038 dex and ~0.041 dex, for the KOI and doppelgänger samples, respectively, for these elements. We conclude that the individual abundances at fixed T eff, $\mathrm{log}g$ , [Fe/H], and [Mg/H] are unremarkable for known planet hosts. Our results establish an upper limit on the abundance precision required to uncover any chemical signatures of planet formation in planet host stars.

Keywords: Exoplanet astronomy, Stellar abundances, Exoplanet formation, High resolution spectroscopy
TOI-2525 b and c: A Pair of Massive Warm Giant Planets with Strong Transit Timing Variations Revealed by TESS. The K-type star TOI-2525 has an estimated mass of M = ${0.849}_{-0.033}^{+0.024}$ M ⊙ and radius of R = ${0.785}_{-0.007}^{+0.007}$ R ⊙ observed by the TESS mission in 22 sectors (within sectors 1 and 39). The TESS light curves yield significant transit events of two companions, which show strong transit timing variations (TTVs) with a semiamplitude of ~6 hr. We performed TTV dynamical and photodynamical light-curve analysis of the TESS data combined with radial velocity measurements from FEROS and PFS, and we confirmed the planetary nature of these companions. The TOI-2525 system consists of a transiting pair of planets comparable to Neptune and Jupiter with estimated dynamical masses of m b = ${0.088}_{-0.004}^{+0.005}$ and m c = ${0.709}_{-0.033}^{+0.034}$ M Jup, radii of r  b  = ${0.88}_{-0.02}^{+0.02}$ and r  c  = ${0.98}_{-0.02}^{+0.02}$ R Jup, and orbital periods of P b = ${23.288}_{-0.002}^{+0.001}$ and P c = ${49.260}_{-0.001}^{+0.001}$ days for the inner and outer planet, respectively. The period ratio is close to the 2:1 period commensurability, but the dynamical simulations of the system suggest that it is outside the mean-motion resonance (MMR) dynamical configuration. Object TOI-2525 b is among the lowest-density Neptune-mass planets known to date, with an estimated median density of ρ b = ${0.174}_{-0.015}^{+0.016}$ g cm-3. The TOI-2525 system is very similar to the other K dwarf systems discovered by TESS, TOI-2202 and TOI-216, which are composed of almost identical K dwarf primaries and two warm giant planets near the 2:1 MMR. ∗ Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under MPG program 0104.A-9007. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Keywords: Exoplanet astronomy, Exoplanet systems, Exoplanets
Exploring Thousands of Nearby Hierarchical Systems with Gaia and Speckle Interferometry. There should be about 10,000 stellar hierarchical systems within 100 pc with primary stars more massive than 0.5 M ⊙, and a similar amount of less-massive hierarchies. A list of 8000 candidate multiples is derived from wide binaries found in the Gaia Catalog of Nearby Stars where one or both components have excessive astrometric noise or other indicators of inner subsystems. A subset of 1243 southern candidates were observed with high angular resolution at the 4.1 m Southern Astrophysical Research Telescope, and 503 new pairs with separations from 0.″03 to 1″ were resolved. These data allow estimation of the inner mass ratios and periods, and help to quantify the ability of Gaia to detect close pairs. Another 621 hierarchies with known inner periods come from the Gaia catalog of astrometric and spectroscopic orbits. These two nonoverlapping groups, combined with existing ground-based data, bring the total number of known nearby hierarchies to 2754, reaching a completeness of ~22% for stars above 0.5 M ⊙. Distributions of their periods and mass ratios are briefly discussed, and the prospects of further observations are outlined.

Keywords: Multiple stars, Binary stars, Solar neighborhood, Speckle interferometry
Time-resolved Optical Polarization Monitoring of the Most Variable Brown Dwarf. Recent atmospheric models for brown dwarfs suggest that the existence of clouds in substellar objects is not needed to reproduce their spectra, nor their rotationally induced photometric variability, believed to be due to the heterogeneous cloud coverage of brown dwarf atmospheres. Cloud-free atmospheric models also predict that their flux should not be polarized, as polarization is produced by the light scattering of particles in the inhomogeneous cloud layers of brown dwarf atmospheres. To shed light on this dichotomy, we monitored the linear polarization and photometric variability of the most variable brown dwarf, 2MASS J21392676+0220226. We used FORS2 at the UT1 telescope to monitor the object in the z band for six hours, split on two consecutive nights, covering one-third of its rotation period. We obtained the Stokes parameters, and we derived its time-resolved linear polarization, for which we did not find significant linear polarization (P = 0.14% ± 0.07%). We modeled the linear polarimetric signal expected assuming a map with one or two spot-like features and two bands using a polarization-enabled radiative transfer code. We obtained values compatible with the time-resolved polarimetry obtained for 2MASS J21392676+0220226. The lack of significant polarization might be due to photometric variability produced mostly by banded structures or small-scale vortices, which cancel out the polarimetric signal from different regions of the dwarf's disk. Alternatively, the lack of clouds in 2MASS J21392676+0220226 would also explain the lack of polarization. Further linear polarimetric monitoring of 2MASS J21392676+0220226, during at least one full rotational period, would help to confirm or discard the existence of clouds in its atmosphere.

Keywords: Starlight polarization, Brown dwarfs, Atmospheric variability, T dwarfs
Measurement of the Angular Momenta of Pre-main-sequence Stars: Early Evolution of Slow and Fast Rotators and Empirical Constraints on Spin-down Torque Mechanisms. We use TESS full-frame imaging data to investigate the angular momentum evolution of young stars in the Orion Complex. We confirm recent findings that stars with rotation periods faster than 2 days are overwhelmingly binaries, with typical separations of tens of au; such binaries quickly clear their disks, leading to a tendency for rapid rotators to be diskless. Among (nominally single) stars with rotation periods slower than 2 days, we observe the familiar gyrochronological horseshoe-shaped relationship of rotation period versus T eff, indicating that the processes that govern the universal evolution of stellar rotation on gigayear timescales are already in place within the first few megayears. Using spectroscopic $v\sin i$ , we determine the distribution of $\sin i$ , revealing that the youngest stars are biased toward more pole-on orientations, which may be responsible for the systematics between stellar mass and age observed in star-forming regions. We are also able for the first time to make empirical, quantitative measurements of angular momenta and their time derivatives as functions of stellar mass and age, finding these relationships to be much simpler and monotonic as compared to the complex relationships involving rotation period alone; evidently, the relationship between rotation period and T eff is largely a reflection of mass-dependent stellar structure and not of angular momentum per se. Our measurements show that the stars experience spin-down torques in the range of ~1037 erg at ~1 Myr to ~1035 erg at ~10 Myr, which provide a crucial empirical touchstone for theoretical mechanisms of angular momentum loss in young stars.

Keywords: Inclination, Early stellar evolution, Binary stars, Young stellar objects, Stellar rotation