Magneto-convective Modeling of Low-mass Pre-main Sequence Stars: Postponing the Depletion of Lithium

Abstract

Standard evolutionary models of pre-main sequence (PMS) low-mass stars often predict radii R and Li abundances A(7Li) which are too small to agree with empirical data, while effective temperatures T eff are predicted to be too large. There are also discrepancies in replicating the stellar age. Discrepancies in R, T eff, and A(7Li) are reported by Stassun et al. for both components (A/B) of the eclipsing binary 2M1222-57 belonging to the young Lower Centaurus Crux association. Using the output of a magneto-convective stellar evolution model which we applied in an early study (in 2010) of PMS stars in a different young association, we show that the discrepancies reported by Stassun et al. in the 2M1222-57 system are alleviated. The models are instructive in showing why larger lithium abundances occur in magnetic PMS stars: it takes longer for the central gas in such a star to become hot enough to destroy lithium.