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The APO-K2 Catalog. II. Accurate Stellar Ages for Red Giant Branch Stars across the Milky Way
García, Rafael A.; Stello, Dennis; Beaton, Rachael L. +11 more
We present stellar age determinations for 4661 red giant branch stars in the APO-K2 catalog, derived using mass estimates from K2 asteroseismology from the K2 Galactic Archaeology Program and elemental abundances from the Apache Point Galactic Evolution Experiment survey. Our sample includes 17 of the 19 fields observed by K2, making it one of the…
SOLES XII. The Aligned Orbit of TOI-2533 b, a Transiting Brown Dwarf Orbiting an F8-type Star
Rice, Malena; Wang, Songhu; Wang, Xian-Yu +1 more
Brown dwarfs occupy a middle ground in mass space between gaseous giant planets and ultracool dwarf stars, and the characterisation of their orbital orientations may shed light on how these neighbouring objects form. We present an analysis of the Rossiter–McLaughlin effect across the transit of TOI-2533 b, a brown dwarf on a moderately eccentric (…
The Importance of Optical Wavelength Data on Atmospheric Retrievals of Exoplanet Transmission Spectra
MacDonald, Ryan J.; Wakeford, Hannah R.; Fairman, Charlotte
Exoplanet transmission spectra provide rich information about the chemical composition, clouds, and temperature structure of exoplanet atmospheres. Most exoplanet transmission spectra only span infrared wavelengths (≳1 µm), which can preclude crucial atmospheric information from shorter wavelengths. Here, we explore how retrieved atmospheric…
Unveiling MOA-2007-BLG-192: An M Dwarf Hosting a Likely Super-Earth
Lu, Jessica R.; Anderson, Jay; Cole, Andrew A. +15 more
We present an analysis of high-angular-resolution images of the microlensing target MOA-2007-BLG-192 using Keck adaptive optics and the Hubble Space Telescope. The planetary host star is robustly detected as it separates from the background source star in nearly all of the Keck and Hubble data. The amplitude and direction of the lens–source separa…
Insight into the Formation of β Pic b through the Composition of Its Parent Protoplanetary Disk as Revealed by the β Pic Moving Group Member HD 181327
Sing, David K.; Lothringer, Joshua D.; Pueyo, Laurent +5 more
It has been suggested that β Pic b has a supersolar metallicity and subsolar C/O ratio. Assuming solar carbon and oxygen abundances for the star β Pic and therefore the planet's parent protoplanetary disk, β Pic b's C/O ratio suggests that it formed via core accretion between its parent protoplanetary disk's H2O and CO2 ice l…
Resonant and Ultra-short-period Planet Systems Are at Opposite Ends of the Exoplanet Age Distribution
Schlaufman, Kevin C.; Hamer, Jacob H.; Schmidt, Stephen P.
Exoplanet systems are thought to evolve on secular timescales over billions of years. This evolution is impossible to directly observe on human timescales in most individual systems. While the availability of accurate and precise age inferences for individual exoplanet host stars with ages τ in the interval 1 Gyr ≲ τ ≲ 10 Gyr would constrain this …
Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star HIP 39017
Salama, Maïssa; Currie, Thayne; Lewis, Briley L. +23 more
We present the direct-imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, γ Doradus (γ Dor)-type variable star HIP 39017 (HD 65526). The companion's SCExAO/CHARIS JHK (1.1–2.4 µm) spectrum and Keck/NIRC2 $L^{\prime} $ photometry indicate that it is an L/T transition object. A comparison of the…
Evolved Massive Stars at Low Metallicity. VI. Mass-loss Rate of Red Supergiant Stars in the Large Magellanic Cloud
Yang, Ming; Gao, Jian; Ren, Yi +4 more
Mass loss is a crucial process that affects the observational properties, evolution path, and fate of highly evolved stars. However, the mechanism of mass loss is still unclear, and the mass-loss rate (MLR) of red supergiant stars (RSGs) requires further research and precise evaluation. To address this, we utilized an updated and complete sample o…
A Survey of Protoplanetary Disks Using the Keck/NIRC2 Vortex Coronagraph
Ren, Bin B.; Knutson, Heather A.; Uyama, Taichi +34 more
Recent Atacama Large Millimeter/submillimeter Array (ALMA) observations of protoplanetary disks in the millimeter continuum have shown a variety of radial gaps, cavities, and spiral features. These substructures may be signposts for ongoing planet formation, and therefore these systems are promising targets for direct imaging planet searches in th…
TESS Giants Transiting Giants. IV. A Low-density Hot Neptune Orbiting a Red Giant Star
Rice, Malena; Angus, Ruth; Huber, Daniel +14 more
Hot Neptunes, gaseous planets smaller than Saturn (∼3–8 R ⊕) with orbital periods less than 10 days, are rare. Models predict this is due to high-energy stellar irradiation stripping planetary atmospheres over time, often leaving behind only rocky planetary cores. Using our TESS full-frame-image pipeline giants in conjunction with Keck/…