Nuclear Aspects of the s- and n-Processes in Massive Stars

TL;DR

This paper models nucleosynthesis in massive stars from hydrogen burning to supernova, using theoretical and experimental reaction rates to understand the creation of heavy elements.

Contribution

It provides comprehensive simulations of nucleosynthesis in 15 and 25 solar mass stars, including all nuclides up to Bi, with reaction rates calculated via the NON-SMOKER code.

Findings

Complete stellar nucleosynthesis simulations from main sequence to supernova.

Assessment of uncertainties in key neutron capture and alpha-reaction rates.

Development of a comprehensive library of nuclear reaction rates for astrophysical use.

Abstract

In order to study the processes creating intermediate and heavy nuclei in massive stars it is necessary to provide neutron capture cross sections and reaction rates close to stability and for moderately unstable neutron-rich nuclei. Furthermore, one has to know the efficiency of neutron-releasing reactions in the main evolutionary phases of a massive star. We present simulations of the nucleosynthesis in a 15 and 25 solar mass star, for the first time followed completely from main sequence hydrogen burning until the type II supernova explosion including all nuclides up to Bi. Theoretical reaction rates were calculated with the NON-SMOKER code, providing a complete library of Hauser-Feshbach cross sections and rates for nuclear and astrophysical applications. Experimental rates at stability were taken from different sources. The impact of uncertainties in the rates on nucleosynthesis are illustrated by two examples, the reactions 62Ni(n,gamma)63Ni and 22Ne(alpha,n)25Mg.