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arXiv · astro-ph/0410396

The Rise of the s-Process in the Galaxy

J. Simmerer·C. Sneden·J. J. Cowan·J. Collier·V. M. Woolf·J. E. Lawler
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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.

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J. Simmerer, C. Sneden, J. J. Cowan, J. Collier, V. M. Woolf, J. E. Lawler. 2004-10-15. The Rise of the s-Process in the Galaxy. https://doi.org/10.1086/424504

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