Nouvelles étoiles candidates membres d’associations jeunes locales
The search for young objects is crucial for several fields of astrophysics. Searching for and directly imaging exoplanets is simplified for young systems as the luminosity ratio between the young host star and its orbiting planets, that still emit thermal radiation when young, is inferior less than for older systems. Moreover, constraining and refining stellar evolutionary models require a large number of known young stars. Finally, a large population of young objects is critical for constraining the initial mass function, especially in the low-mass regime. This thesis presents a search for young stars from a subset sample of the Tycho-Gaia Astrometric Solution comprising nearly 2 million objects, included in the first data release of the GAIA mission (Global Astrometric Interferometer for Astrophysics). With the BANYAN-  (Bayesian Analysis for Nearby Young AssociatioNs) and a colour magnitude diagram, we searched for young stars from 250,000 targets with known radial velocity. The result is a list of 42 potentially young late stars, all with association probability greater than 90% for groups younger than 60 Myr and with a luminosity significantly higher than old stars of the same colour on the main sequence. Finally, from their new Bayesian association probabilities and their lithium absorption equivalent width, available for 25 candidates, their status within their respective associations was revised. This study presents 10 new stars, never before associated, belonging to the comoving groups forming the region known as Scorpius-Centaurus. We also find 13 new bona fides members.
BANYAN-SIGMA Young stars Local co-moving groups