The detailed abundance patterns of light neutron-capture elements in very metal-poor stars

We report the detailed abundance patterns of neutron-capture elements in four very metal-poor stars. The abundance patterns of heavy neutron-capture elements in the two objects HD 6268 and HD 115444 are quite similar to that of the r-process component in the Solar-System, while their abundances of light neutron-capture elements show deviation from that. The actinide element thorium is detected in these objects. These stars well represent the abundance pattern produced by the so-called main r-process. The other two stars, HD 88609 and HD 122563, have quite low abundances of heavy neutron-capture elements. However, the light neutron-capture elements in these stars show large excesses with respect to heavy ones, indicating a contribution of another process than the main r-process. These results provide useful for investigations of the neutroncapture nucleosynthesis in the early universe.