Uncertainties in s-process nucleosynthesis in low mass stars determined from Monte Carlo variations

TL;DR

This study quantifies nuclear physics uncertainties affecting the s-process nucleosynthesis in low mass stars using Monte Carlo simulations, identifying key reactions that influence element abundance predictions.

Contribution

It introduces a comprehensive Monte Carlo approach to evaluate nuclear reaction uncertainties and identifies critical reactions impacting s-process element synthesis.

Findings

Neutron capture rate uncertainties dominate abundance uncertainties.

Total nuclear uncertainties are generally below 50%.

Key reactions include $^{56}$Fe(n,$ extgamma$), $^{64}$Ni(n,$ extgamma$), and $^{138}$Ba(n,$ extgamma$).

Abstract

The main s-process taking place in low mass stars produces about half of the elements heavier than iron. It is therefore very important to determine the importance and impact of nuclear physics uncertainties on this process. We have performed extensive nuclear reaction network calculations using individual and temperature-dependent uncertainties for reactions involving elements heavier than iron, within a Monte Carlo framework. Using this technique, we determined the uncertainty in the main s-process abundance predictions due to nuclear uncertainties link to weak interactions and neutron captures on elements heavier than iron. We also identified the key nuclear reactions dominating these uncertainties. We found that $\beta$-decay rate uncertainties affect only a few nuclides near s-process branchings, whereas most of the uncertainty in the final abundances is caused by uncertainties in neutron capture rates, either directly producing or destroying the nuclide of interest. Combined total nuclear uncertainties due to reactions on heavy elements are in general small (less than 50%). Three key reactions, nevertheless, stand out because they significantly affect the uncertainties of a large number of nuclides. These are $^{56}$Fe(n,$\gamma$), $^{64}$Ni(n,$\gamma$), and $^{138}$Ba(n,$\gamma$). We discuss the prospect of reducing uncertainties in the key reactions identified in this study with future experiments.