Lithium Depletion in Pre–Main‐Sequence Solar‐like Stars

We examine the internal structure of solar-like stars in detail between 0.8and 1.4M Sun and during pre-main sequence phase. Recent opacity computations ofOPAL along with a new hydrodynamical mixing process have been considered. Wealso introduce up-to-date nuclear reaction rates and explore the impact ofaccretion, mixing-length parameter, non-solar distributions among metals andrealistic rotation history. We compare models predictions of lithium depletionto the $^7Li$ content observations of the Sun and to 4 young clusters ofdifferent metallicities and ages. We show that we can distinguish two phases inlithium depletion: 1- a rapid nuclear destruction in the T-Tauri phase before20 Myrs : this is independent of the mass used within our range but largelydependent on the extension and temperature of the convective zone, 2- a secondphase where the destruction is slow and moderate and which is largely dependenton the (magneto)hydrodynamic instability located at the base of the convectivezone. In terms of composition, we show the interest on considering helium andespecially the mixture of heavy elements : carbon, oxygen, silicium and iron.We outline the importance of O/Fe ratio. We note a reasonable agreement onlithium depletion for the two best known cases, the Sun and the Hyades clusterfor solar-like stars. Other clusters suggest that processes which may partlyinhibit the predicted premainsequence depletion cannot be excluded, inparticular for stars below ~ 0.9M Sun. Finally we suggest different researchareas such as initial stellar models and more realistic atmospheres which couldcontribute to a better understanding of this early phase of evolution and whichshould become the object of subsequent research.Comment: Astrophysical Journal, in pres