We propose to obtain high-resolution ultra-violet (UV) spectra with Subaru/HDS of two CEMP-r+s stars found in the LAMOST/Subaru sample of very metal-poor stars. A fraction of very metal-poor ([Fe/H]<−2) stars (about 20%) show large excess of carbon and are called Carbon-Enhanced Metal-Poor (CEMP) stars. A portion of CEMP stars exhibit excess of neutron-capture elements both by r- and s-processes (CEMP-r/s stars), among which only a few stars can be explained by a simple combination of the two processes (CEMP-r+s stars). Based on the optical spectra previously obtained, we determined abundances of carbon and a few neutron-capture elements, which indentified two promissing candidates of CEMP-r+s stars. Using the UV spectra obtained in this program, we plan to obtain abundances of more elements between Sr and Ba, as well as those heavier than Eu, which would provide a full abundance pattern of these peculiar objects. The new abundance measurements, together with theoretical modeling, enable us to examine the hypothesis that the heavy elements of these stars are originated from both r- and s-process, rather than other unknown processes, and shed lights on the origin of light neutron-capture elements.
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