Magneto-Convection and Lithium Age Estimates of the β Pictoris Moving Group

Although the means of the ages of stars in young groups determined from Li depletion often agree with mean ages determined from Hertzsprung - Russell diagram isochrones, there are often statistically significant differences in the ages of individual stars determined by the two methods. We find that inclusion of the effects of inhibition of convection due to the presence of magnetic fields leads to consistent ages for the individual stars. We illustrate how age consistency arises by applying our results to the \beta Pictoris moving group. We find that, although magnetic inhibition of convection leads to increased ages from the Hertzsprung - Russell diagram isochrones for all stars, Li ages are decreased for fully convective M stars and increased for stars with radiative cores. Our consistent age determination for the \beta Pictoris moving group of 40 Myr is larger than previous determinations by a factor of about two.