Ther‐Process in the Early Galaxy

We report Sr, Pd and Ag abundances for a sample of metal-poor field giantsand analyze a larger sample of Y, Zr, and Ba abundances. The [Y/Zr] and [Pd/Ag]abundance ratios are similar to those measured for the r-process-rich stars CS22892-052 and CS 31082-001. The [Pd/Ag] ratio is larger than predicted from thesolar-system r-process abundances. The constant[Y/Zr] and [Sr/Y] values in thefield stars places strong limits on the contributions of the weak s-process andthe main s-process to the light neutron-capture elements. Stars in the globularcluster M 15 possess lower [Y/Zr] values than the field stars. There is a largedispersion in [Y/Ba]. Because the r-process is responsible for the productionof the heavy elements in the early Galaxy, these dispersions require varyinglight-to-heavy ratios in r-process yields.Comment: 10 pages, 5 color figures, to be published in Ap