Observations of Beryllium in Stars

Extract

Since a considerably higher temperature is necessary to consume Be atoms by (p, α) reactions than Li atoms, it has been thought that many clues to the understanding of the synthesis and destruction of the light elements could be found by studying Be abundances and the Li/Be-abundance ratios. Calculations have been made by Bodenheimer (1966) to determine the amount of convective depletion of Be during pre-main-sequence evolution. He found that a star reaching the main sequence at K5 would have destroyed 15% of its original Be; a K2 dwarf would have depleted its Be by 2%. For early K stars main-sequence depletion subsequent to this would be very slight. If there are no complicating effects such as magnetic fields and unusual patterns of circulation of stellar material, the observed Be abundances in stars of type G and earlier should be the initial pre-stellar or proto-star abundances. The BeII resonance lines lie far in the ultraviolet at λ 3131. But despite the very difficult nature of the observations, there are now Be abundances determined in about 60 dwarfs and sub-giants of types A, F, and G and in 2 K giants.