Pre-main Sequence models with convection described by 2D-RHD numerical simulations

The T_eff location of Pre-Main Sequence (PMS) evolutionary tracks depends on the treatment of over-adiabaticity. We present here the PMS evolutionary tracks computed by using the mixing length theory of convection (MLT) in which the α_MLT = l/H_p parameter calibration is based on 2D-hydrodynamical models (Ludwig et al. 1999). These MLT-α^2D stellar models and tracks are very similar to those computed with non-grey ATLAS9 atmospheric boundary conditions and Full Spectrum of Turbulence (FST) convection model both in the atmosphere and in the interior. As for the FST models, the comparison of the new tracks with the location on the HR diagram of pre-MS binaries is not completely satisfactory; and the pre-MS lithium depletion in the MLT-α^2D tracks is still much larger than that expected from the observations of lithium in young open clusters. Thus, in spite of the fact that 2D RHD models should provide a better convection description than any local model, their introduction is not sufficient to reconcile theory and observations. Lithium depletion in young clusters points towards a convection efficiency which, in pre-MS, should be smaller than in the MS.