Impacts of nuclear-physics uncertainties in the s-process determined by Monte-Carlo variations

The s-process, a production mechanism based on slow-neutron capture during stellar evolution, is the origin of about half the elements heavier than iron. Abundance predictions for s-process nucleosynthesis depend strongly on the relevant neutron-capture and β-decay rates, as well as on the details of the stellar model being considered. Here, we have used a Monte-Carlo approach to evaluate the nuclear uncertainty in s-process nucleosynthesis. We considered the helium burning of massive stars for the weak s-process and low-mass asymptotic-giant-branch stars for the main s-process. Our calculations include a realistic and general prescription for the temperature dependent uncertainty for the reaction cross sections. We find that the adopted uncertainty for (n,γ) rates, tens of per cent on average, affects the production of s-process nuclei along the line of β-stability, and that the uncertainties in β-decay from excited state contributions, have the strongest impact on branching points. (author)