Nucleosynthesis in the Early Galaxy

Abstract

Recent observations of r-process-enriched metal-poor star abundances reveal a non-uniform abundance pattern for elements $Z\le 47$. Based on non-correlation trends between elemental abundances as a function of Eu-richness in a large sample of metal-poor stars, it is shown that the mixing of a consistent and robust light element primary process (LEPP) and the r-process pattern found in r-II metal-poor stars explains such apparent non-uniformity. Furthermore, we derive the abundance pattern of the LEPP from observation and show that it is consistent with a missing component in the solar abundances when using a recent s-process model. As the astrophysical site of the LEPP is not known, we explore the possibility of a neutron capture process within a site-independent approach. It is suggested that scenarios with neutron densities $n_n\le 10^{13}$ $c{m}^{-3}$ or in the range $n_n\ge 10^{24}$ $c{m}^{-3}$ best explain the observations.

28 pages, 7 Postscript figures. To be published in The Astrophysical Journal

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