Implications of a high population 2 B/Be ratio

The observed boron/beryllium ratio in extreme Population II stars has been interpreted as evidence of Be and B synthesis by early Galactic cosmic rays. However, a recent reanalysis of the boron abundance in the Population II halo star HD 140823 suggests that B/H may be larger than previously reported, by as much as a factor of 4. This would yield a B/Be ratio lying in the range 14 less than or approximately equal to B/Be less than or approximately equal to 50. The possibilty of a high Population II B/Be ratio stresses the importance of the upper limit to the B/Be ratio arising from cosmic-ray production. It is found that the limit to cosmic-ray-produced B/Be depends upon the assumed cosmic-ray spectrum. For any Population II cosmic-ray spectrum that is a single power law in either total energy per nucleon or in momentum, the B/Be ratio constrained to lie in the range 7.6 less than or approximately equal to B/Be less than or approximately equal to 14. Thus, if the new B/Be ratio is correct, it requires either a bimodal cosmic-ray flux with a large low-energy component, or, for another B source, possibly the proposed nu-process in supernovae, either of which may be helpful in explaining the observed B-11/B-10 ratio. Finally, it is noted that the boron reanalysis highlights the uncertainty in our knowledge of the B/Be ratio, and the need for additional data on Be and B abundances.