RICERCA DI ESOPIANETI IN ASSOCIAZIONI STELLARI DA DATI TESS

For the predominant part of exoplanet's hosts the age is not well constrained and consequently planet properties, demographics, and occurrence rates have been widely unmapped as a function of time. Discovering exoplanets in stellar associations can shed light on these topics as they provide the opportunity to investigate planet formation and evolution in environments with well-defined age. Moreover, for the members of stellar associations we can define with high accuracy their stellar properties and consequently characterize a potential exoplanet around them more efficiently in comparison with field stars. The Full-Frame Images (FFIs) of Transiting Exoplanet Survey Satellite (TESS) offer a huge data mining archive of millions of targets to investigate. We have analyzed the light curves of ~ 12000 stars belonging in 40 young associations and moving groups with ages spanning from 1 to 680 Myr. Our targets have been monitored during the primary mission of TESS (July 2018 -- July 2020) from Sector 1 to 26. We have extracted the light curves of young association's members from the FFIs, corrected the systematic errors that affected them, accounted for stellar variability, performed transit simulations to probe the detection efficiency of our technique to discover different types of transiting exoplanets, and estimate their frequency. We report the detection of 24 candidate exoplanets in our sample. Eighteen of our candidates are novel discoveries. Our candidate planets belong in 10 different young stellar associations with ages between 10 and 50 Myr and have been validated through a series of vetting tests (odd/even, secondary transit depth, etc). We also measured the frequencies of candidate planets in stellar associations for different orbital periods and planetary radii, taking into consideration the detection efficiency of our technique and the false positive probabilities of our candidates. Furthermore, we exploited the Stellar Age -- Planet radius distribution of known candidates and confirmed exoplanets with well measured ages and orbital periods less than 100 days. Giant (RP ≥ 11.2 R⊕) and small (RP < 3.9 R⊕) size planets do not show any peculiar trend on their distribution, whereas the distribution of planets in the radius regime of 4 R⊕ ≤ RP ≤ 10 R⊕ have attracted a lot of interest within the exoplanet community. These planets are concentrated at ages less than 100 Myr and it is still unclear why there are no detections of planets with this size orbiting older stars. Various scenarios (i.e atmospheric escape, core-powered mass loss, dynamical evolution etc) have been proposed to explain this behavior but until today no secure conclusions have been made. Consequently, increasing the candidate and eventually confirmed exoplanets around young stars we can take significant steps towards the understanding of the evolution and formation mechanisms that prevail in the early stages of an exoplanet's life which are still into debate among the exoplanet community.