We report the abundances of neutron-capture elements in eight carbon-rich , metal-poor ( -2.7 \leq [ Fe/H ] \leq - 1.9 ) stars observed with the Subaru Telescope High Dispersion Spectrograph .
The derived abundance patterns indicate that the neutron-capture elements in these objects primarily originated from s -process nucleosynthesis , although the [ Ba/Eu ] abundance ratios in some objects are lower than that of the solar-system s -process component .
The present analysis has yielded the Pb abundances for seven objects , as well as an upper limit for one object , from use of the Pb i 4057 Å and 3683 Å lines .
The values of [ Pb/Ba ] in these objects cover a wide range , between -0.3 and +1.2 .
Theoretical studies of s -process nucleosynthesis at low metallicity are required to explain this large dispersion of the [ Pb/Ba ] values .
Variations in radial velocity have been found for two of the eight objects , suggesting that , at least in these instances , the observed excess of s -process elements is due to the transfer of material across a binary system including an AGB star .
Comparisons with predictions of AGB nucleosynthesis models are discussed .