The role of stellar flares in planetary transits and exoatmospheres

Abstract

As the methods to characterize exoatmospheric components improve, the role played by stellar activity in the transmitted spectra is enhanced. Accurately detecting and modeling contributions like stellar flares is essential to remove their signals from the spectra. In this work, we analyze the light curves of TRAPPIST-1 b for the transits observed by the JWST NIRISS on 18 and 20 Jul 2022. A stellar flare during the transit has been found for 20 Jul using MCMC fitting and checking Hα emission. Our results indicate that, if not properly modeled and erased, flare contribution can mask and be misinterpreted as an atmospheric signal. The event found also has chemical implications, as the UV radiation emitted can induce certain chemical reactions. Furthermore, depending on its characteristics, it can be fatal for complex living organisms. This study highlights the importance of accounting for stellar activity in exoplanet studies to avoid misdetections and better understand the star-planet interaction.