Sazuna/UAT_keywords huggingface dataset:
TESS Hunt for Young and Maturing Exoplanets (THYME). IV. Three Small Planets Orbiting a 120 Myr Old Star in the Pisces-Eridanus Stream. Young exoplanets can offer insight into the evolution of planetary atmospheres, compositions, and architectures. We present the discovery of the young planetary system TOI 451 (TIC 257605131, Gaia DR2 4844691297067063424). TOI 451 is a member of the 120 Myr old Pisces-Eridanus stream (Psc-Eri). We confirm membership in the stream with its kinematics, its lithium abundance, and the rotation and UV excesses of both TOI 451 and its wide-binary companion, TOI 451 B (itself likely an M-dwarf binary). We identified three candidate planets transiting in the Transiting Exoplanet Survey Satellite data and followed up the signals with photometry from Spitzer and ground-based telescopes. The system comprises three validated planets at periods of 1.9, 9.2, and 16 days, with radii of 1.9, 3.1, and 4.1 R⨂, respectively. The host star is near-solar mass with V = 11.0 and H = 9.3 and displays an infrared excess indicative of a debris disk. The planets offer excellent prospects for transmission spectroscopy with the Hubble Space Telescope and the James Webb Space Telescope, providing the opportunity to study planetary atmospheres that may still be in the process of evolving. * Sometimes called Meingast-1.

Keywords: Young star clusters, Exoplanet systems, Stellar activity, Exoplanet astronomy, Exoplanet evolution
Refined Telluric Absorption Correction for Low-resolution Ground-based Spectroscopy: Resolution and Radial Velocity Effects in the O<SUB>2</SUB> A-band for Exoplanets and K I Emission Lines. Telluric correction of spectroscopic observations is either performed via standard stars that are observed close in time and airmass along with the science target, or recently growing in importance, by theoretical telluric absorption modeling. Both approaches work fine when the telluric lines are resolved, i.e., at a spectral resolving power larger than about 10,000, and it is sufficient to facilitate the detection of spectral features at lower resolution. However, a meaningful quantitative analysis also requires the reliable recovery of line strengths. Here, we show for the Fraunhofer A-band of molecular O2 that the standard telluric correction approach fails in this at lower spectral resolutions, as an example for the general problem. Doppler-shift-dependent errors of the restored flux may arise, which can amount to more than 50% in extreme cases, depending on the line shapes of the target spectral features. Two applications are discussed: the recovery of the O2 band in the reflected light of an Earth analog atmosphere, as facilitated potentially in the future using an orbiting starshade and a ground-based extremely large telescope; and the recovery of the intrinsic ratio of the K I lines in the post-nova V4332 Sgr tracing the optical depth of the emitting region, to exemplify the relevance using present-day instrumentation. We show how one should derive correction functions for the compensation of the error in dependence of radial velocity shift, spectral resolution, and target line-profile function by use of high-resolution atmospheric transmission modeling, which has to be solved for the individual case.

Keywords: Earth atmosphere, Atmospheric extinction, Astronomy data analysis, Spectroscopy, Atmospheric effects, Exoplanet atmospheres
HD 63021: Chromospheric Activity and Mass Transfer in a Close Binary. Prompted by X-ray detections from multiple surveys, we investigated the A-type star HD 63021 and found that it is a double-lined spectroscopic binary with highly variable emission associated with the primary star. Analysis of our multiepoch spectroscopic observations, the majority of which were carried out on small-aperture telescopes, indicates a very short orbital period of just 2.9 days and a mass ratio M2/M1 of 0.23. The A1 V star is a slow rotator, with a rotational speed of ∼34 km s-1. Assuming that its mass is 2.3 M☉, the present-day secondary is an evolved star of ∼0.5 M☉ that nearly fills its Roche lobe. This secondary star rotates comparatively rapidly at ∼44 km s-1, and we see evidence that it is chromospherically active. Analysis of a photometric light curve from TESS reveals two strong periods, one at the orbital period for the system and another at half the orbital period. These findings suggest that HD 63021 is a close binary system undergoing mass transfer from the secondary star onto the primary star—in all ways like an Algol eclipsing binary system, except without the eclipse. We discuss the system's mass transfer, which is not steady but seems to run in fits and bursts, and infer the system's basic physical properties from an orbital parameter study, the Roche lobe geometry, and its extant X-ray emission.

Keywords: X-ray binary stars, Close binary stars, Ae stars, Algol variable stars, Stellar classification, Spectral energy distribution, Spectroscopy, Time domain astronomy, Variable stars, Stellar rotation, Orbit determination
Hot Stars with Kepler Planets Have High Obliquities. It has been known for a decade that hot stars with hot Jupiters tend to have high obliquities. Less is known about the degree of spin-orbit alignment for hot stars with other kinds of planets. Here, we reassess the obliquities of hot Kepler stars with transiting planets smaller than Neptune, based on spectroscopic measurements of their projected rotation velocities ( $v\sin i$ ). The basis of the method is that a lower obliquity—all other things being equal—causes $\sin i$ to be closer to unity and increases the value of $v\sin i$ . We sought evidence for this effect using a sample of 150 Kepler stars with effective temperatures between 5950 and 6550 K and a control sample of 101 stars with matching spectroscopic properties and random orientations. The planet hosts have systematically higher values of $v\sin i$ than the control stars, but not by enough to be compatible with perfect spin-orbit alignment. The mean value of $\sin i$ is 0.856 ± 0.036, which is 4σ away from unity (perfect alignment), and 2σ away from $\pi /4$ (random orientations). There is also evidence that the hottest stars have a broader obliquity distribution: when modeled separately, the stars cooler than 6250 K have $ \langle \sin i \rangle =0.928\pm 0.042$ while the hotter stars are consistent with random orientations. This is similar to the pattern previously noted for stars with hot Jupiters. Based on these results, obliquity excitation for early-G and late-F stars appears to be a general outcome of star and planet formation, rather than being exclusively linked to hot Jupiter formation. * 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: Stellar rotation, Exoplanets
Combining Transit and Radial Velocity: A Synthesized Population Model. We present a framework for estimating exoplanet occurrence rates by synthesizing constraints from radial velocity and transit surveys simultaneously. We employ approximate Bayesian computation and various mass-radius (M-R) relations to explore the population models describing these surveys, both separately and in a joint fit. Using this approach, we fit a planet distribution function of the form ${d}^{2}N/d\mathrm{log}{Pd}\mathrm{log}M\propto {P}^{\beta }{M}^{\alpha }$ , with a break in the power law in mass at Mb, to planets orbiting FGK stars with periods $P=[25,200]$ days and masses $M=[2,50]{M}_{\oplus }$ . We find that the M-R relation from Otegi et al. (2020), which lets rocky and volatile-rich populations overlap in mass, allows us to find a model that is consistent with both types of surveys. Our joint fit gives ${M}_{b}={21.6}_{-3.2}^{+2.5}{M}_{\oplus }$ (errors reflect 68.3% credible interval). This is nearly a factor of three higher than the break from transit-only considerations and an M-R relation without such an overlap. The corresponding planet-star mass ratio break ${q}_{b}\sim 7\times {10}^{-5}$ may be consistent with microlensing studies ( ${q}_{b}\sim 6\times {10}^{-5}-2\times {10}^{-4}$ ). The joint fit also requires that a fraction of ${F}_{\mathrm{rocky}}={0.63}_{-0.04}^{+0.04}$ planets in the overlap region belong to the rocky population. Our results strongly suggest that future M-R relations should account for a mixture of distinct types of planets in order to describe the observed planet population.

Keywords: Exoplanet catalogs, Bayesian statistics, Exoplanets, Radial velocity, Exoplanet astronomy, Exoplanet detection methods, Transit photometry
WASP-107b's Density Is Even Lower: A Case Study for the Physics of Planetary Gas Envelope Accretion and Orbital Migration. With a mass in the Neptune regime and a radius of Jupiter, WASP-107b presents a challenge to planet formation theories. Meanwhile, the planet's low surface gravity and the star's brightness also make it one of the most favorable targets for atmospheric characterization. Here, we present the results of an extensive 4 yr Keck/HIRES radial-velocity (RV) follow-up program of the WASP-107 system and provide a detailed study of the physics governing the accretion of the gas envelope of WASP-107b. We reveal that WASP-107b's mass is only 1.8 Neptune masses (Mb = 30.5 ± 1.7 M⊕). The resulting extraordinarily low density suggests that WASP-107b has a H/He envelope mass fraction of &gt;85% unless it is substantially inflated. The corresponding core mass of &lt;4.6 M⊕ at 3σ is significantly lower than what is traditionally assumed to be necessary to trigger massive gas envelope accretion. We demonstrate that this large gas-to-core mass ratio most plausibly results from the onset of accretion at ≳1 au onto a low-opacity, dust-free atmosphere and subsequent migration to the present-day ab = 0.0566 ± 0.0017 au. Beyond WASP-107b, we also detect a second, more massive planet ( ${M}_{c}\sin i=0.36\pm 0.04{M}_{J}$ ) on a wide eccentric orbit (ec = 0.28 ± 0.07) that may have influenced the orbital migration and spin-orbit misalignment of WASP-107b. Overall, our new RV observations and envelope accretion modeling provide crucial insights into the intriguing nature of WASP-107b and the system's formation history. Looking ahead, WASP-107b will be a keystone planet to understand the physics of gas envelope accretion.

Keywords: Exoplanet formation, Planetary structure, Exoplanet atmospheres
Relationships between the Stellar, Gaseous, and Star Formation Disks in LITTLE THINGS Dwarf Irregular Galaxies: Indirect Evidence for Substantial Fractions of Dark Molecular Gas. The stellar, gaseous and young stellar disks in the LITTLE THINGS sample of nearby dwarf irregular galaxies are fitted with functions to search for correlations between the parameters. We find that the H I radial profiles are generally flatter in the center and fall faster in the outer regions than the V-band profiles, while young stars are more centrally concentrated, especially if the H I is more centrally flat. This pattern suggests that the H I is turning into molecules in the center, and the molecular clouds are forming stars and FUV. A model that assumes the molecular surface density is proportional to the total gas surface density to a power of 1.5 or 2, in analogy with the Kennicutt-Schmidt relation, reproduces the relationship between the ratio of the visible to the H I scale length and the H I Sérsic index. The molecular fraction is estimated as a function of radius for each galaxy by converting the FUV to a molecular surface density using conventional calibrations. The average molecular fraction inside 3RD is 23% ± 17%. However, the break in the stellar surface brightness profile has no unified tracer related to star formation.

Keywords: Dwarf irregular galaxies, Star formation, Interstellar medium
Decaying Orbit of the Hot Jupiter WASP-12b: Confirmation with TESS Observations. Theory suggests that the orbits of some close-in giant planets should decay due to tidal interactions with their host stars. To date, WASP-12b is the only hot Jupiter reported to have a decaying orbit, at a rate of 29 ± 2 ms yr-1. We analyzed data from NASA's Transiting Exoplanet Survey Satellite (TESS) to verify that WASP-12b's orbit is indeed changing. We find that the TESS transit and occultation data are consistent with a decaying orbit with an updated period of 1.091420090 ± 0.000000041 days and a decay rate of 32.53 ± 1.62 ms yr-1. We find an orbital decay timescale of $\tau =P/| \dot{P}| =2.90\pm 0.14\,\mathrm{Myr}$ . If the observed decay results from tidal dissipation, the modified tidal quality factor is ${Q}_{\star }^{{\prime} }=1.39\pm 0.15\times {10}^{5}$ , which falls at the lower end of values derived for binary star systems and hot Jupiters. Our result highlights the power of space-based photometry for investigating the orbital evolution of short-period exoplanets.

Keywords: Exoplanet dynamics, Exoplanet astronomy, Exoplanet tides, Exoplanets
Dust Production from Mini Outbursts of Comet 29P/Schwassmann-Wachmann 1. Here we report on the results of observations of comet 29P/Schwassmann-Wachmann 1 obtained using four telescopes, in three different countries, from 2019 September 25 to 2020 January 19. During the last four months of 2019, comet 29P/Schwassmann-Wachmann 1 exhibited new outburst behavior indicative of small or mini outbursts in which the brightening of the comet lasted from only a few days to more than a week. We used Johnson-Cousins RC-band multi-aperture photometry measurements to calculate the dust production, via Afρ, the dust production rate, and the dust brightness profile of the comet for each night of observations. During these observations, the brightness of the comet fluctuated significantly multiple times, with notable changes in brightness ranging from 0.41 to 0.71 mag over time periods of only a couple of days to nearly two weeks.

Keywords: Comets, Centaur group, Small Solar System bodies, Coma dust
The Second Data Release of the Survey of the MAgellanic Stellar History (SMASH). The Large and Small Magellanic Clouds (LMC and SMC) are the largest satellite galaxies of the Milky Way and close enough to allow for a detailed exploration of their structure and formation history. The Survey of the MAgellanic Stellar History (SMASH) is a community Dark Energy Camera (DECam) survey of the Magellanic Clouds using ∼50 nights to sample over ∼2400 deg2 centered on the Clouds at ∼20% filling factor (but with contiguous coverage in the central regions) and to depths of ∼24th mag in ugriz. The primary goals of SMASH are to map out the extended stellar peripheries of the Clouds and uncover their complicated interaction and accretion history as well as to derive spatially resolved star formation histories of the central regions and create a "movie" of their past star formation. Here we announce the second SMASH public data release (DR2), which contains all 197 fully calibrated DECam fields including the main body fields in the central regions. The DR2 data are available through the Astro Data Lab hosted by the NSF's National Optical-Infrared Astronomy Research Laboratory. We highlight three science cases that make use of the SMASH DR2 data and will be published in the future: (1) preliminary star formation histories of the LMC, (2) the search for Magellanic star clusters using citizen scientists, and, (3) photometric metallicities of Magellanic Cloud stars using the DECam u-band.

Keywords: Local Group, Dwarf irregular galaxies, CCD photometry, Surveys, Dwarf galaxies, Small Magellanic Cloud, Large Magellanic Cloud, Photometry, Magellanic Clouds, Milky Way Galaxy
The Relationship between Photometric Measurements and Visual Magnitude Estimates for Red Stars. The nature of the relationship between visual brightness estimates for red stars and the corresponding V magnitudes has been investigated by comparing visual estimates in the American Association of Variable Star Observers database to photoelectric photometry of 39 semiregular variable stars obtained at Grinnell College over a 30 yr period. A general mathematical description of this relationship has been developed, but it applies only approximately for many individual stars because the actual relationship can be quite different for different stars. The overall trends should apply to visual magnitude estimates for red stars generally. These results are based on far more data over a wider range of color than was the case in earlier work and should provide a more robust description of the relationship between photometric measurements and visual estimates. A number of other issues related to visual magnitude estimates are also addressed.

Keywords: Photoelectric photometry, Semi-regular variable stars, Color equation
Variability in NGC 3201 Giant Stars and Its Impact on Their Spectroscopic [Fe/H] Determination. We present the analysis of 34 light curves in V and I of 17 giant stars in the globular cluster NGC 3201 to check if such stars are variable and if their variability has some kind of impact on the iron abundance as obtained from spectroscopic measurements. First, we computed the generalized Lomb-Scargle and phase dispersion minimization periodograms of the sample to check if the stars were variables. In this way, seven stars of the sample were found to be nonvariable, two stars are considered as possible variables, and eight stars were found to be variable, with periods ranging from 0.0881 ± 0.0001 to 0.5418 ± 0.0027 days. According to the literature, the variables have distinct values of [Fe I/H]: the three most metal-rich stars are in the red giant branch (RGB) stage, one has [Fe I/H] = -1.37 dex, while the other two have [Fe I/H] = -1.31 dex. The two most metal-poor variables have [Fe I/H] = -1.61 dex and [Fe I/H] = -1.62 dex, and are AGB stars; the remaining variables have [Fe I/H] = -1.44, -1.48, and -1.50 dex, the first two being RGB stars while the last is an AGB star. On the other hand, stars that appear to be nonvariable have -1.56 ≤ [Fe I/H] ≤ -1.40. We conclude that variability somehow affects the spectroscopic determination of the iron content of giant stars in NGC 3201, increasing the iron spread of the cluster. If variability is not taken into account, this spread could be incorrectly interpreted as due to an intrinsic iron spread affecting the stars of the cluster.

Keywords: Globular star clusters, Stellar abundances
Departure from the Exact Location of Mean Motion Resonances Induced by the Gas Disk in Systems Observed by Kepler. The statistical results of transiting planets show that there are two peaks, around 1.5 and 2.0, in the distribution of orbital period ratios. A large number of planet pairs are found near the exact location of mean motion resonances (MMRs). In this work, we find that the depletion and structures of the gas disk play crucial roles in driving planet pairs out of the exact location of MMRs. Under such a scenario, planet pairs are trapped into exact MMRs during orbital migration first and keep migrating at the same pace. The eccentricities can be excited. Due to the existence of a gas disk, eccentricities can be damped, leading to a change in orbital period, which will make planet pairs depart from the exact location of MMRs. With depletion timescales larger than 1 Myr, near-MMR configurations are formed easily. Planet pairs have higher possibilities of escaping from MMRs with a higher disk aspect ratio. Additionally, with a weaker corotation torque, planet pairs can depart farther from the exact location of MMRs. The final location of the innermost planets in the systems are directly related to the transition radius from the optically thick region to the outer optically thin disk. While the transition radius is smaller than 0.2 au at the late stage of the star evolution process, the period of the inner planets can reach around 10 days. Our formation scenario is a possible mechanism for explaining the formation of near-MMR configurations with the innermost planet farther than 0.1 au.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation
Three New Late-type Stellar Companions to Very Dusty WISE Debris Disks Identified with SPHERE Imaging. Debris disk stars are good targets for high-contrast imaging searches for planetary systems, since debris disks have been shown to have a tentative correlation with giant planets. We selected 20 stars identified as debris disk hosts by the WISE mission, with particularly high levels of warm dust. We observed these with the VLT/SPHERE high-contrast imaging instrument with the goal of finding planets and imaging the disks in scattered light. Our survey reaches a median 5σ sensitivity of 10.4 MJ at 25 au and 5.9 MJ at 100 au. We identified three new stellar companions (HD 18378B, HD 19257B, and HD 133778B): two are mid-M-type stars and one is a late-K or early-M star. Three additional stars have very widely separated stellar companions (all at &gt;2000 au) identified in the Gaia catalog. The stars hosting the three SPHERE-identified companions are all older (≳700 Myr), with one having recently left the main sequence and one a giant star. We infer that the high volumes of dust observed around these stars has been caused by a recent collision between the planets and planetesimal belts in the system, although for the most evolved star, mass loss could also be responsible for the infrared excess. Future mid-infrared spectroscopy or polarimetric imaging may allow the positions and spatial extent of these dust belts to be constrained, thereby providing evidence as to the true cause of the elevated levels of dust around these old systems. None of the disks in this survey is resolved in scattered light.

Keywords: Exoplanets, Circumstellar disks, Coronagraphic imaging, Direct imaging, Planetesimals, Debris disks, Extrasolar gaseous giant planets
The Red Supergiant Content of M31 and M33. We identify red supergiants (RSGs) in our spiral neighbors M31 and M33 using near-IR (NIR) photometry complete to a luminosity limit of $\mathrm{log}L/{L}_{\odot }=4.0$ . Our archival survey data cover 5 deg2 of M31, and 3 deg2 for M33, and are likely spatially complete for these massive stars. Gaia is used to remove foreground stars, after which the RSGs can be separated from asymptotic giant branch (AGB) stars in the color-magnitude diagram. The photometry is used to derive effective temperatures and bolometric luminosities via MARCS stellar atmosphere models. The resulting H-R diagrams show superb agreement with the evolutionary tracks of the Geneva evolutionary group. Our census includes 6400 RSGs in M31 and 2850 RSGs in M33 within their Holmberg radii; by contrast, only a few hundred RSGs are known so far in the Milky Way. Our catalog serves as the basis for a study of the RSG binary frequency being published separately, as well as future studies relating to the evolution of massive stars. Here we use the matches between the NIR-selected RSGs and their optical counterparts to show that the apparent similarity in the reddening of OB stars in M31 and M33 is the result of Malmquist bias; the average extinction in M31 is likely higher than that of M33. As expected, the distribution of RSGs follows that of the spiral arms, while the much older AGB population is more uniformly spread across each galaxy's disk.

Keywords: Red supergiant stars, Massive stars, Triangulum Galaxy, Andromeda Galaxy, Stellar evolution