Sn 1987A revisited as a major production site for r-process elements

The origin of nucleosynthesis products of rapid neutron capture reactions ( the r-process) is a long-standing astrophysical problem. Recent analyses of elemental abundances for extremely metal-poor stars shed light on the elem ental abundances of individual supernovae. Comparison of the abundance dist ributions of some extremely metal-poor stars with those of the best-observe d supernova SN 1987A clearly indicates that the overabundances of barium an d strontium found in SN 1987A that have been ascribed to the slow neutron c apture process must be results of r-process nucleosynthesis. The mass of fr eshly synthesized barium in SN 1987A is estimated to be 6 x 10(-6) M. based on the observed surface abundance and detailed hydrodynamical models for t his supernova. These new findings lead to the conclusion that 20 M. stars, one of which is the progenitor star of SN 1987A, are the predominant produc tion sites for r-process elements in the Galaxy and the r-process element d onors for notable neutron capture-rich giant stars, CS 22892-052 and CS 310 82-001.