Neutron capture elements in globular cluster M15

We used high-resolution, high signal-to-noise ratio spectra obtained with the Subaru Telescope to determine neutron-capture elemental abundances in metal-poor globular cluster M15. We confirmed that there are star-to-star abundance variations in the abundance of heavy neutron-capture elements and there is no significant s-process contribution. We have found that there are anticorrelations between the abundance ratios of light to heavy neutron-capture elements and the abundance of heavy neutron-capture elements. Our observaitonal results indicates that at least two different processes have enriched light neutron-capture elements in the M15 progenitor. It has been pointed out that light neutron-capture elements in field stars should have been enriched by more than one process although astrophysical sites for such processes are still uncertain. Abundance distributions of neutron-capture elements in M15 give clues to understand the origin of light and heavy r-process elements.