Production of galactic Li-7 by slow mass loss

Abstract

The mass loss rate in super-lithium stars required to account for the galactic abundance of /sup 7/Li is calculated. In the first approach the required rate depends only on observational quantities, and the main uncertainties are the fraction of cool giants which are carbon stars and the Li abundances in the super-lithium stars. In the second approach these uncertain quantities are replaced by the integral of the Li abundance over time, taken from models of nucleosynthesis in hot-bottom convective envelopes, and the lifetime of the M giant phase of evolution, taken from considerations of the evolution of degenerate carbon-oxygen cores and mass loss rates. Both approaches require a mass loss rate of about 3 x 10/sup -6/ M/sub sun/yr/sup -1/ during the short-lived super-lithium phase with an estimated uncertainty of a factor of 5. Since the present model contains no adjustable parameters and the required mass loss rate is not inconsistent with observations, it is suggested that a significant source of galactic /sup 7/Li is slow mass loss from red giants. It is demonstrated that there is no obvious inconsistency between this mode of /sup 7/Li production and the galactic /sup 3/He abundance. (AIP)