Stellar abundances of lithium, beryllium, and boron

Abstract

The present review is concerned with the stellar abundances of Li, Be, and B that are relevant to the origin of these light elements and to details of stellar structure. It is proposed that the best values for the cosmic abundances of these elements can be derived from abundance determinations in stellar atmospheres. The observed abundances are taken to indicate origins in spallation reactions involving galactic cosmic rays, with additional Li-7 probably produced during the big bang. Evidence is presented showing that the Li abundance with which stars are born is depleted during pre-main-sequence evolution, that atoms of the light elements are transported to regions within a star where they are destroyed by (p, alpha) reactions, and that many normal stars have large deficiencies of Li and Be. Overabundances and dilutions of the three elements in Ap stars, supergiants, and giants are discussed along with mechanisms that could account for both super-Li-rich stars and the great range of Li abundances in C and S stars