Theoretical models of low-mass, pre-main sequence rotating stars I. The effects on lithium depletion

Rotating stellar models of 1.2 M down to 0.6 M have been computed to investigate the effects of rotation on the lithium depletion of low-mass, pre-main sequence stars. The models were generated under three different rotation laws (rigid body rotation, local conservation of angular momentum over the whole star, and local conservation of angular momentum in radiative zones and rigid body rotation in convective ones), no angular momentum loss and redistribution, and under two prescriptions for convection, namely the mixing length theory [MLT] and the turbulent convection introduced by Canuto & Mazzitelli (1991) [CM]. The general features of the rotating models are compatible with previous results by other authors. As for the lithium depletion, our results show that rotation decreases lithium depletion while the star is fully convective but increases it as soon as the star develops a radiative core, a result which is expected from the theory since rotating stars behave as non-rotating stars of lower mass and so must experience greater lithium depletion. The results hold for all three rotation laws assumed, but are specifically presented here for the case of rigid body rotation. This result shows that other physical mechanisms must play a role on the lithium depletion in the pre-main sequence, in order to explain the observational data on low-mass, pre-main sequence stars such as those from the Pleiades (Garcı́a López et al. 1994) and the α-Persei clusters (Balachandran et al. 1988, 1996).