The ubiquity of the rapid neutron-capture process

Ian U Roederer, John J Cowan, Amanda Irene Karakas, Karl-Ludwig Kratz, Maria Anna Lugaro, Jennifer Simmerer, Khalil Farouqi, Chris Sneden

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154 Citations (Scopus)


To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn, Z= 30), yttrium (Y, Z= 39), lanthanum (La, Z= 57), europium (Eu, Z= 63), and lead (Pb, Z= 82). Our sample of 161 metal-poor stars includes new measurements from 88 high-resolution and high signal-to-noise spectra obtained with the Tull Spectrograph on the 2.7 m Smith Telescope at the McDonald Observatory, and other abundances are adopted from the literature. We use models of the s-process in asymptotic giant branch stars to characterize the high Pb/Eu ratios produced in the s-process at low metallicity, and our new observations then allow us to identify a sample of stars with no detectable s-process material. In these stars, we find no significant increase in the Pb/Eu ratios with increasing metallicity.
Original languageEnglish
Pages (from-to)975 - 993
Number of pages19
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 2010

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