Nuclear uncertainty study of the s-process in massive stars based on Monte-Carlo simulations

The s-process in massive stars, the weak s-process, is origin of the solar s-process nuclei up to A = 90 as well as other heavier nuclei, e.g., Ba, in very metal-poor stars. The s-process still has a significant uncertainty of nuclear reactions, although we has used several theoretical abundance prediction for the comparisons with several observations. The present study is aimed at evaluating the reliability of the current theoretical s-process calculations. Based on different stellar evolution models, we performed Monte-Carlo simulations of the s-process with randomly varying neutron- captures rates. We found that the uncertainty propagates through the weak s-process nuclei up to Sr for a solar metallically star. On the other hand, a rotating metal-poor star shows different response to final abundances, which heavier s-process elements, i.e., Ba, have significant variation. In conclusion, the remaining uncertainty of neutron-capture reactions is still possible to change the results of s-process calculations. This uncertainty even can be caused in qualitative difference in the production of heavy s-process nuclei in a metal-poor stars.