Boron in the extreme Population II star HD 140283 and the production of light elements in the Early Galaxy
Gilmore, G.; Gustafsson, B.; Lambert, D. L.; Edvardsson, B.; Nissen, P. E.; Johansson, S. G.; Kiselman, D.
Abstract
Using observations of the 2496.7A Bi line with the HST GHRS at a nominal resolving power of 90,000, we have found the abundance of boron of HD140283 to be logɛ_B_(=12+log(N_B_/N_H_))=0.34+/-0.20. This result is found when a significant non-LTE effect in the formation of the Bi line is taken into account. The resulting N_B_/N_Be_ ratio is about 17 (in the range 9-34), which is in very good agreement with what is expected from spallation by cosmic rays. We conclude that this origin of Be and B in the Early Galaxy is the most probable of recently suggested formation mechanisms.