The Rise of the s-Process in the Galaxy
Abstract
From newly-obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is predominantly made by the s-process in the solar system, while Eu owes most of its solar system abundance to the r-process. The changing ratio of these elements in stars over a wide metallicity range traces the changing contributions of these two processes to the Galactic abundance mix. Large s-process abundances can be the result of mass transfer from very evolved stars, so to identify these cases, we also report carbon abundances in our metal-poor stars. Results indicate that the s-process may be active as early as [Fe/H]=-2.6, alalthough we also find that some stars as metal-rich as [Fe/H]=-1 show no strong indication of s-process enrichment. There is a significant spread in the level of s-process enrichment even at solar metallicity.
Keywords
Cite
@article{arxiv.astro-ph/0410396,
title = {The Rise of the s-Process in the Galaxy},
author = {J. Simmerer and C. Sneden and J. J. Cowan and J. Collier and V. M. Woolf and J. E. Lawler},
journal= {arXiv preprint arXiv:astro-ph/0410396},
year = {2009}
}
Comments
64 pages, 15 figures; ApJ 2004 in press