Observing Transit morning-evening asymmetries with PLATO

The most recent JWST observations of WASP-39b and WASP-107b show that a comparison of the morning and evening atmosphere of cloudy hot Jupiters is possible by very precise monitoring of transit ingress and egress with next generation space telescopes. In addition, extensive modelling efforts have demonstrated that gas giants orbiting different host stars should exhibit different degrees of morning-evening asymmetries, where cloud formation is predicted to amplify existing hydrodynamically driven asymmetries in the local thermodynamics at each limb.

The PLATO space mission to be launched 2026 has the potential to yield detailed comparison between the morning and evening terminator of hot Jupiter in the optical wavelength range. In the optical, cloud scattering properties are expected to dominate as already outlined with Kepler data. As such these observations would be highly complementary to JWST IR observations that mainly probe differences in molecular chemistry across the limbs.

 

We explore in how far PLATO photometry may be used to study such terminator asymmetries driven by differences in cloud coverage as follow-up to Grenfell et al. 2020. We use a grid of 60 3D GCMs using ExoRad (Carone+2020, Schneider, Carone+2023) for gas giants orbiting M, G, F, K and A stars at various orbital distances such that their global temperature ranges from 600K - 2600K. For each of these models, cloud formation and gas-phase chemistry is calculated subsequently. This work is part of our science support efforts within the PLATO WPs 116700 and 116800.