The production of beryllium in the early Galaxy

The formation of beryllium in the early Galaxy is discussed. It is shown that if spallation occurs predominantly in regions rich in heavy elements, i.e., close to supernovae, the linear relation recently obtained by Gilmore et al. (1992) between beryllium and oxygen abundances for Population II stars may be reproduced. Estimates of relevant timescales for mixing show that the decisive factor, the ratio of the timescale of cosmic-ray diffusion out of the locally enriched regions to the decay time of cosmic rays in the Galaxy as a whole, admits this scenario. Although energetically possible, it requires, however, very high local cosmic-ray fluxes (greater than or equal to 105/sq cm/s), which predicts gamma-ray fluxes above those observed from supernova remnants and the Galaxy. We therefore consider other models, such as those given by Duncan et al. (1992) or Prantzos et al. (1993), more probable.