Nucleosynthesis in the Early Galaxy

Abstract

Recent observations of r-process-enriched metal-poor star abundances reveal a non-uniform abundance pattern for elements $Z\leq47$. 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 $n_{n}\leq10^{13}$ $cm^{-3}$ or in the range $n_{n}\geq10^{24}$ $cm^{-3}$ best explain the observations.Comment: 28 pages, 7 Postscript figures. To be published in The Astrophysical Journa

The Hamburg/ESO R-process enhanced star survey (HERES)

“…It is similarly under-abundant, relative to the solar residuals, as in other highly r-process enhanced stars (Montes et al 2007). The 3404.579 Å line was not covered by our spectra of CS 29491−069; a reliable Pd abundance could not be measured.…”

“…Their origin has recently been under active discussion: studies of disk and halo stars by e.g. Aoki et al (2005), Mashonkina et al (2007), François et al (2007) and Montes et al (2007) found that their formation cannot be explained by a simple split into contributions from the "classical" s-process and r-process. Farouqi et al (2008b) give an average observed ratio of Sr/Y = 6.17 ± 1.06, taken from various analyses of halo stars at different metallicities and r-process enhancements.…”

Neutrino-driven wind simulations and nucleosynthesis of heavy elements

“…In the following sections we discuss the nucleosynthesis processes leading to these different isotopic abundances. The observed abundances [113,114,110] are shown by dots and rescaled to fit the solid line abundances.…”

Studies of exotic nuclei with advanced radiation detectors

“…It was postulated that they are partly synthesised in the so called light-element primary process (LEPP). The nature of this process as well as the possible sites for it are debated (νp process, additional r-process or s-process component) (Montes et al, 2007). The study of nuclei in this region, from the proton drip-line up to extremely neutron-rich isotopes, might help to shed more light on this mysterious process.…”