New detections of r-process elements in extremely metal-poor stars with subaru/HDS Original Research Article

We have obtained high-resolution, high quality spectra of 22 very metal-poor stars with Subaru/HDS, in order to carry out detailed abundance studies of their neutron-capture elements. We have detected Th in seven stars in our sample. The abundance pattern of the heavy neutron-capture elements (56 ≤ Z ≤ 69) of these stars is similar to the r-process component in the solar-system. However, the Th abundances relative to other neutron-capture elements show a non-negligible departure from the abundance pattern of the solar-system r-process component. The meaning of this result in the context of studies of the r-process and cosmocronology are discussed.