Enrichment of the r-process Element Europium in the Galactic Halo

Abstract

We investigate the enrichment of europium, as a representative of r-process elements, in the Galactic halo. In present chemical evolution models, stars are assumed to be formed through shock processes by supernovae (SNe). The enrichment of the interstellar medium is calculated by a one-zone approach. The observed large dispersions in [Eu/Fe] for halo stars, converging with increasing metallicity, can be explained with our models. In addition, the mass range of SNe for the {\it r}-process site is constrained to be either stars of $8-10 M_\odot$ or $\gtrsim 30 M_\odot$.