On lithium removal from G dwarfs

Lithium is observed to be progressively removed from the atmospheres of main-sequence G stars. In the presence of enough mass loss, this removal can be explained by the eventual dilution of the material in the surface convective zone by lithium-free matter which enters this zone from below and which previously occupied deeper, hotter layers of the star. An approximate theory of this dilution is developed and is applied to the sun. A cumulative mass loss of 0.041 solar suffices to account for the apparent removal of about 99 percent of the lithium which was initially present in the solar atmosphere. The surface Li/H abundances observed in G dwarfs in the Hyades, NGC 752, and M67 are then used to determine, under this dilution hypothesis, the required time-averaged rates of mass loss near the ZAMS, for stars with masses M/M(solar) = 0.8-1.1 and ages t = 0.7-5 Gyr. The resulting rates decrease rapidly with increasing stellar mass and age, from initial values much larger than in the present solar wind. 23 refs.