2010MNRAS.402..956Z

The chemical abundances of metal-poor stars are excellent sources of information for setting new constraints on models of Galactic chemical evolution at low metallicities. In this paper we present an attempt to fit the elemental abundances observed in the bright, metal-poor giant HD 175305, and derive isotopic fractions using a parametric model. The observed abundances can be well matched by the combined contributions from s- and r-process material. The component coefficients of the r- and s-processes are C₁= 3.220 and C₃= 1.134, respectively. The Sm isotopic fraction in this star where the observed neutron-capture elements are produced is predicted to be f_152+154= 0.582, which suggests that, even though the r-process is predominantly responsible for the synthesis of the neutron-capture elements in the early Galaxy, the onset of the s-process had already occurred at this metallicity of [Fe/H] = -1.6.