A search for transiting planets around hot subdwarfs - Results from TESS Cycle I

In this talk I will present our project that is dedicated to the search for transiting planets around hot subdwarfs (sdOB). These peculiar bodies are evolved stars that lost most of their envelope at the tip of the Red-Giant-Branch (RGB). They are small, hot and short-lived stars which have the interesting particularity to have no confirmed planets around them. In this project we perform a wide analysis of all the sdOB observed by the missions Kepler, K2, TESS and CHEOPS in order to, firstly, find transiting planets and compute their occurrence rates and secondly, bring observational constraints for the survival of close-in planets while their host star goes through the RGB. With our current technological means it is often impossible to reach Earth-sized bodies around post-RGB stars, but thanks to the small size of sdOB stars, we are able to do it here. Moreover, the short lifetime of sdOB would most likely not allow for planetary migration or the formation of second-generation planets, which means that short-period planets around them would correspond to planets that were engulfed during the RGB phase. This make them pristine candidates to understand the fate of close-orbiting exoplanets after the RGB phase of their host. In this talk I will present the method we set to analyse the data, from the initial search run to the confirmation steps of interesting signals. I will put an emphasis on the analysis of the 792 sdOB observed during the cycle 1 of the mission TESS as this part is now finished and is the topic of a submitted paper (Thuillier et al. 2022).