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Li6 in the early Galaxy: energetics, evolution and stellar depletion | | Nikos Prantzos
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5 Oct 2005 | | Affiliation: | Institut d’Astrophysique de Paris | | Abstract: | Motivated by the recent report of a high Li6 ``plateau’’ extending to low metallicities in Galactic halo stars, we study the energetics of an early production of Li6 through the interaction of energetic particles (EP) with the interstellar medium. We explore then the energetic potential of various candidate sources of pre-galactic EP and we show that, in general, they fail to satisfy the observational and theoretical requirements (especially, if the Li6 plateau is at a considerably higher level than observed). Succesfull candidates appear to be: supernova explosions of abnormally low metal yield; the massive black hole in the Galactic center (provided that it was formed early on and that it was then radiating much more efficiently than today); and, perhaps, supermassive black holes in galaxies. Assuming Li6 is indeed pre-galactic, we study in a self-consistent way the galactic evolution of the light isotopes Li7, Li6 and Be. We find that the existence of a Li6 plateau is hard to justify, unless a fine-tuned and metallicity-dependent depletion mechanism of Li6 in stellar envelopes is invoked. The depletion of Li6 should be different, both in magnitude and in its metallicity dependence, than the depletion required to explain current observations of Li (mostly Li6) in halo stars. If the recently reported Li6 ``plateau’’ is confirmed, our analysis suggests important implications for our understanding of the production, evolution and stellar depletion of the Li isotopes. | | Source: | arXiv, astro-ph/0510122 | | Services: | Forum | Review | PDF | Favorites | |
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