Evidence for a dispersion in the lithium abundances of extreme halo stars

Evidence is presented to the effect that there exists a small dispersion in the lithium abundances of extreme halo dwarfs. This dispersion cannot be accounted for by standard stellar models alone, particularly toward the turnoff, and would thus require early differential Galactic Li enrichment, perhaps independent of metallicity. The magnitude of the dispersion is also consistent with the predictions of evolutionary models of halo stars with rotation, which do not require, but do not rule out either, early Galactic enrichment. These rotational models also predict a significant depletion in the lithium abundance during the stars' lifetime. The rotational models predict that stars which formed with very low initial angular momentum will have lithium abundances measurably above the plateau.