We investigate energetic type Ic supernovae as production sites for Li6 and
Be in the early stages of the Milky Way. Recent observations have revealed that
some very metal-poor stars with [Fe/H]<-2.5 possess unexpectedly high
abundances of Li6. Some also exbihit enhanced abundances of Be as well as N.
From a theoretical point of view, recent studies of the evolution of
metal-poor massive stars show that rotation-induced mixing can enrich the outer
H and He layers with C, N, and O (CNO) elements, particularly N, and at the
same time cause intense mass loss of these layers. Here we consider energetic
supernova explosions occurring after the progeniter star has lost all but a
small fraction of the He layer. The fastest portion of the supernova ejecta can
interact directly with the circumstellar matter (CSM), both composed of He and
CNO, and induce light element production through spallation and He-He fusion
reactions. The CSM should be sufficiently thick to energetic particles so that
the interactions terminate within its innermost regions. We calculate the
resulting Li6/O and Be9/O ratios in the ejecta+CSM material out of which the
very metal-poor stars may form. We find that they are consistent with the
observed values if the mass of the He layer remaining on the pre-explosion core
is 0.01-0.1 solar mass, and the mass fraction of N mixed in the He layer is
about 0.01. Further observations of Li6, Be and N at low metallicity should
provide critical tests of this production scenario.Comment: 12 pages, 2 figures, revised with referee suggestions, final version
accepted in ApJ Letter