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GAPS2: Transit-Radial Velocity Synergy to Unveil the Young Exoplanet Population History

Presentation #107.05 in the session Radial Velocity 1.

Published onJun 20, 2022
GAPS2: Transit-Radial Velocity Synergy to Unveil the Young Exoplanet Population History

The “GAPS” (Global Architecture of Planetary Systems) project gathers a large part of the Italian community working on exoplanets. One of our aims, with the Young Objects sub-program of GAPS2 (GAPS-YO), is the search for young exoplanets, since they are the key targets to study the early evolution of planetary systems and to understand the origin of their observed diversity.

Transit space missions are significantly contributing in our view of young planetary systems at close separations, providing robust candidates to be followed-up with the radial velocity (RV) technique and to investigate their orbital and physical evolution. Indeed, these targets are also useful to validate models of planetary evolution as the result of the atmospheric photo-evaporation due to the high-energy irradiation of the young stellar host. GAPS-YO searches for young planets by surveying members in young and intermediate age associations, and performs a HARPS-N RV follow-up of young transiting candidates, mainly provided by the NASA-TESS satellite.

We present some of the highlights of our GAPS-YO program. HARPS-N RV data of TOI-942 (30-80 Myr) and the TESS light curve allowed us to validate the candidate and detect an additional transiting planet. TOI-942 b and c are both hot-Neptunes, with a period of 4 and 10 days, respectively. This is one of the youngest multi-planet systems identified by TESS so far.

We also measured a mass upper limit for the 40 Myr old planet DS Tuc A b (TOI-200) indicating a very low density for this Neptune-size planet. We modelled the Rossiter-McLaughlin effect with ESPRESSO data showing that the orbit is not completely aligned and simulated the effects of photoevaporation on the planet’s atmosphere.

Furthermore, we characterized the youngest (~300 Myr) ultra-short period planet discovered so far: we measured its mass and radius, obtaining a density typical of rocky planets with no H/He thick envelope. It means that, during its “short” life, this strongly irradiated planet has already lost the large part of its atmosphere via, e.g., photo-evaporation processes.

These results, together with more young TOIs (ongoing analyses), will allow us preliminary assessment on the impact of stellar age, as well as photo-evaporation, on the mass/radius relationship.

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