ar X iv : a st ro - p h / 94 05 07 3 v 1 3 1 M ay 1 99 4 The Primordial Abundance of 6 Li and 9 Be Brian Chaboyer

Light element (Li, Li and Be) depletion isochrones for halo stars have been calculated with standard stellar evolution models. These models include the latest available opacities and are computed through the sub-giant branch. If Li is not produced in appreciable amounts by stellar flares, then the detection of Li in HD 84937 by Smith, Lambert & Nissen (1993) is compatible with standard stellar evolution and standard big bang nucleosynthesis only if HD 84937 is a sub-giant. The present parallax is inconsistent with HD 84937 being a sub-giant star at the 2.5 σ level. The most metal poor star with a measured Be abundance is HD 140283, which is a relatively cool sub-giant. Standard stellar evolution predicts that Be will have been depleted in this star by ∼ 0.3 dex (for Teff = 5640 K). Revising the abundance upward changes the oxygen-beryllium relation, suggesting incompatibility with standard comic ray production models, and hence, standard big bang nucleosynthesis. However, an increase in the derived temperature of HD 140283 to 5740 K would result in little depletion of Be and agreement with standard big bang nucleosynthesis. Subject headings: early universe – nucleosynthesis – stars: interiors – stars: abundances submitted to Astrophysical Journal Letters