THE BORON-TO-BERYLLIUM RATIO IN HALO STARS - A SIGNATURE OF COSMIC-RAY NUCLEOSYNTHESIS IN THE EARLY GALAXY

We discuss Galactic cosmic-ray (G-CR) spallation production of Li, Be, and B in the early Galaxy with particular attention to the uncertaint ies in the predictions of this model. The observed correlation between the Be abundance and the metallicity in metal-poor Population II star s requires that Be was synthesized in the early Galaxy. We show that t he observations and such Population II GCR synthesis of Be are quantit atively consistent with the big bang nucleosynthesis production of Li- 7. We find that there is a nearly model independent lower bound to B/B e of approximately 7 for GCR synthesis. Recent measurements of B/Be ap proximately 10 in HD 140283 are in excellent agreement with the predic tions of Population II GCR nucleosynthesis. Measurements of the boron abundance in additional metal-poor halo stars is a key diagnostic of t he GCR spallation mechanism. We also show that Population II CGR synth esis can produce amounts of Li-6 which may be observed in the hottest halo stars.