DIX Planetary Science Seminar

Tuesday, May 30, 2023
4:00pm to 5:00pm
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South Mudd 365
Characterizing Hot, Rocky Exoplanets in the Era of JWST/TOI-1259 A b: A Gas Giant's Origin Story Revealed in Metastable Helium
Kim Paragas, Graduate Student, Planetary Sciences, California Institute of Technology,
Morgan Saidel, Graduate Student, Planetary Sciences, California Institute of Technology,

Kim Paragas - JWST's Mid InfraRed Instrument (MIRI) provides a unique opportunity to search for signatures of exoplanet surfaces with low resolution spectroscopy. Close-in, rocky planets orbiting M dwarfs are ideal targets for these studies. Though these planets are likely to have completely lost their primordial H/He atmospheres, they may outgas secondary, high mean molecular weight atmospheres. Consequently, it is important to consider how the presence of such an atmosphere with unknown mass and composition would impact our ability to robustly characterize the surfaces of rocky exoplanets. We modified the open-source Python package PLATON (Zhang et al. 2020) to perform simultaneous atmosphere and surface retrievals on secondary eclipse measurements of rocky super-Earth planets. These new features, including the ability to constrain different surface types through spectral features in emission and an improved prior scheme for retrieving an arbitrary mixture of atmospheric gases, will be made publicly available in a future release of PLATON.

Morgan Saidel - The lack of close-in Neptune-mass exoplanets evident in transit surveys has largely been attributed either to photoevaporative mass-loss or high-eccentricity migration. In one of the best testbeds for photoevaporation versus high-eccentricity migration, we probe the extended upper atmosphere of TOI-1259 A b, a Saturn-mass exoplanet lying along the upper edge of the Neptune desert. TOI-1259 A b's orbit around a K dwarf with a white dwarf companion marks the system as a potential candidate for high eccentricity migration. However, the close proximity of TOI-1259 A b's orbit to its host star indicates that the planet may be sculpted by photoevaporative mass-loss. Using transit photometry with Palomar/WIRC and near-infrared spectroscopy with KECK/NIRSpec, we attempt to uncover the mass-loss history of the planet by searching for escaping metastable helium in the planet's atmosphere. We report a detection of escaping metastable helium on TOI-1259 A b, indicating the presence of an atmospheric outflow. We discuss the implications of this result and the feasibility of high-eccentricity migration for this system.

For more information, please contact Ryleigh Davis by email at [email protected].