Population II ⁶Li as a probe of nucleosynthesis and stellar structure and evolution

We discuss the importance of Population II ⁶Li as a diagnostic for models of primordial nucleosynthesis, cosmic-ray nucleosyntheses in the early Galaxy, and the structure and evolution of metal-poor solar-type stars. The observation of ⁶Li in the subdwarf HD 84937 is shown to be consistent with the existing Population II LiBeB data within the context of a simple three-component model: (1) standard big bang nucleosynthesis, (2) Population II cosmic-ray nucleosynthesis, (3) standard (nonrotating) stellar LiBeB depletion. If this interpretation is correct, we predict a potentially detectable boron abundance for this star: B/H ∼2 × 10^-12. Subsequent Population II LiBeB observations, and in particular further observations of Population II ⁶Li, are shown to be crucial to our understanding of the primordial and early galactic creation and destruction mechanisms for light elements.