Reflected-light Phase Curves with PICASO: A Kepler-7b Case Study

• Published in: The Astrophysical journal 2024-12, Vol.976 (2), p.181
• Main Authors: Hamill, Colin D., Johnson, Alexandria V., Batalha, Natasha, Nag, Rowan, Gao, Peter, Adams, Danica, Kataria, Tiffany
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Atmosphere; Atmospheric clouds; Atmospheric models; Atmospheric scattering; Clouds; Condensates; Exoplanet atmospheres; Extrasolar gaseous planets; Extrasolar planets; Gas giant planets; Hot Jupiters; Jupiter; Light; Luminous intensity; Magnesium; Magnesium silicates; Radiative transfer; Sedimentation; Sedimentation & deposition; Silicates; Source code; Telescopes; Titanium dioxide
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ad7de6

Examining reflected light from exoplanets aids in our understanding of the scattering properties of their atmospheres and will be a primary task of future flagship space- and ground-based telescopes. We introduce an enhanced capability of Planetary Intensity Code for Atmospheric Scattering Observations ( PICASO ), an open-source radiative transfer model used for exoplanet and brown dwarf atmospheres, to produce reflected light phase curves from three-dimensional atmospheric models. Since PICASO is coupled to the cloud code Virga , we produce phase curves for different cloud condensate species and varying sedimentation efficiencies ( f sed ) and apply this new functionality to Kepler-7b, a hot Jupiter with phase curve measurements dominated by reflected starlight. We model three different cloud scenarios for Kepler-7b: MgSiO 3 clouds only, Mg 2 SiO 4 clouds only, and Mg 2 SiO 4 , Al 2 O 3 , and TiO 2 clouds. All our Virga models reproduce the cloudy region west of the substellar point expected from previous studies, as well as clouds at high latitudes and near the eastern limb, which are primarily composed of magnesium silicates. Al 2 O 3 and TiO 2 clouds dominate near the substellar point. We then compare our modeled reflected light phase curves to Kepler observations and find that models with all three cloud condensate species and low sedimentation efficiencies (0.03–0.1) match best, though our reflected light phase curves show intensities approximately one-third of those observed by Kepler. We conclude that a better understanding of zonal transport, cloud radiative feedback, and particle scattering properties is needed to further explain the differences between the modeled and observed reflected light fluxes.