出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We investigate energetic Type Ic supernovae as production sites for 6Li 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 6Li. Some also exhibit 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 the intense mass
loss of these layers. Here we consider energetic supernova explosions occurring after the progenitor
star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta
and the circumstellar matter (CSM), both of which are composed of He and CNO, can interact
directly 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 6Li/O and 9Be/O ratios in the ejecta+CSMmaterial
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 M
and if the mass fraction of N mixed in the He layer is 0.01. Further observations of 6Li, Be, and
N at low metallicity should provide us with critical tests of this production scenario.
