Le mercredi 5 juillet 2023, Lionel GARCIA présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en Sciences spatiales) sous la direction de Michaël GILLON.

Cette épreuve consistera en la défense publique d’une dissertation intitulée :

“Towards the detailed atmospheric characterization of terrestrial exoplanets around late M-dwarfs”.

Abstract

In the coming decade, the atmospheric characterization of exoplanets as small as Earth will only be possible for planets transiting stars much smaller than the Sun: late M-dwarfs. While progress in instrumentation slowly enables the study of these distant worlds, many challenges remain. First of all, the transit signals of these exoplanets are mixed with correlated noise that hinders their detection. During this thesis, I developed a novel algorithm that can cope with these characteristics, and detect transiting exoplanets at an unprecedented level. In order to characterize the atmospheres of these exoplanets, I studied the effect of stellar contamination, as active regions on the stellar photosphere can hide the signatures from planetary atmospheres. I highlighted the limitations of using 1D theoretical stellar spectra to account for this effect, and showed the impact of this approach on the interpretation of the transit transmission spectra of the rocky exoplanet TRAPPIST-1h. To conclude, I underscored the capabilities of the SPECULOOS survey, which will help lay a path towards the detailed atmospheric characterization of terrestrial exoplanets around late M-dwarfs, in the search for life.

Lien Orbi

Le Jury sera composé de :

M. D. GRODENT (Président), Mme et MM. L. DELREZ (Secrétaire), B.O. DEMORY (University of Bern), J. de WIT (Massachusetts Institute of Technology), M. GILLON (Promoteur), D. QUELOZ (ETH Zurich).