May 20, 2022

The ExoExplorer Science Series presents talks by cohort members Kiersten Boley (Ohio State) & Alison Farrish (GSFC) on May 20, 2022, from 11 AM - 12 PM Pacific / 2 PM - 3 PM Eastern. Connection information is below.

Speaker: Kiersten Boley (Ohio State)

Title: Impacts on Planet Formation: Planet Occurrence Rates around Metal-Poor Stars

Abstract: Planet formation models predict that below a certain protoplanetary disk metallicity, the surface density of solid material is too low to form planets. Observationally, previous works have indicated that short-period planets preferentially form around stars with solar and super solar metallicities. Given these findings, it is challenging to form planets within metal-poor environments. Due to the target selection process of previous surveys, there is little constraint on planet occurrence rates below [Fe/H] ~ -0.5, which is still higher than the predicted metallicity at which planet formation cannot occur. Expanding upon previous works, we construct a large sample of ~100,000 metal-poor stars with spectroscopically-derived stellar parameters observed by TESS. With this sample, we constrain planet occurrence rates within the metal-poor regime (-1.0 ≤ [Fe/H] ≤ -0.4) placing the most stringent upper limits on planet occurrence rates around metal-poor stars.

Speaker: Alison Farrish (GSFC)

Title: Modeling Exoplanet Host Star Magnetic and Coronal Activity

Abstract: Exoplanet systems are of interest not only for their potential for habitability, but also in the opportunity they provide for the study of comparative heliophysics. In applying solar- and heliophysics-based modeling tools to exoplanet systems, we can expand our understanding of the influence of stellar behavior on planetary environments and processes such as atmospheric loss. I will discuss my work employing a surface flux transport (SFT) model to examine the dynamics of magnetic flux on the surfaces of cool stars like the Sun and exoplanet host stars of interest. This flux transport modeling approach has been used to examine stellar coronal X-ray emission and other asterospheric properties as a function of host star magnetic activity. I will provide an overview of current efforts to extend this modeling framework to investigate host star EUV emission and stellar wind parameters for a range of exoplanet host stars. Since stellar EUV emission is both a) a key driver of atmospheric loss processes and b) difficult to observe due to interstellar medium extinction, these simulations of energetic coronal emission could fill gaps in our understanding of exoplanet atmospheric evolution caused by this dearth of observational evidence.

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