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 in vestigate the effects of rotation on the lithium depletion of low-mass, pre -main sequence stars. The models were generated under three different rotat ion laws (rigid body rotation, local conservation of angular momentum over the whole star, and local conservation of angular momentum in radiative zon es and rigid body rotation in convective ones), no angular momentum loss an d redistribution, and under two prescriptions for convection, namely the mi xing length theory [MLT] and the turbulent convection introduced by Canuto & Mazzitelli (1991) [CM]. The general features of the rotating models are c ompatible with previous results by other authors. As for the lithium deplet ion, our results show that rotation decreases lithium depletion while the s tar is fully convective but increases it as soon as the star develops a rad iative core, a result which is expected from the theory since rotating star s behave as non-rotating stars of lower mass and so must experience greater lithium depletion. The results hold for all three rotation laws assumed, b ut are specifically presented here for the case of rigid body rotation. Thi s result shows that other physical mechanisms must play a role on the lithi um depletion in the pre-main sequence, in order to explain the observationa l data on low-mass, pre-main sequence stars such as those from the Pleiades (Garcia Lopez et al. 1994) and the alpha-Persei clusters (Balachandran et al.1988,1996).