The Impact of Stellar Uncertainties on Planetary Atmosphere Parameter Estimation

M-dwarfs—which make up about 75% of stars in our galaxy, are notorious for their photospheric heterogeneities. Fewer constraints are known to account for spectral differences between the entire photosphere of the star and the disk-integrated stellar spectrum due to star spots and faculae which ultimately affect the observed transmission spectrum of the planet. Overall star-planet interaction and therefore the impact of stellar uncertainties on planetary spectra has been a daunting problem in characterization of their atmospheres as it is often degenerate with solutions of opacity sources such as haze or clouds. This work takes advantage of the data-driven Bayesian Retrieval method coupled with self-consistent thermochemical equilibrium radiative transfer code CHIMERA to do a parameter sweep and identify constraints on spot and facelae covering fractions to mitigate the degeneracies exhibited in the transmission spectrum. With this, we will be able to acquire the percent precision needed to aid with future observations such as JWST to understand whether there are false signals or muted features occurring in the transmission spectrum due to presence of spots/faculae. In addition, constraints from this work would also help in acquiring better estimates of the bulk densities and volatile contents which are important questions when characterizing terrestrial planets orbiting M-dwarfs.

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