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

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 β-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,γ), 64 Ni(n,γ), and 138 Ba(n,γ). We discuss the prospect of reducing uncertainties in the key reactions identified in this study with future experiments.

Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components

“…Within the multievent model it was possible to evaluate the major uncertainties (both nuclear and due to abundance measurements) affecting the prediction of the s-(r-)abundance distribution. Goriely (1999) concluded that the uncertainties in the ob-served meteoritic abundances and the relevant (n, γ) rates have a significant impact on the predicted s-component of the solar abundance and, consequently, on the derived rabundances, especially concerning the s-dominated nuclei (see also Nishimura et al 2017 andCescutti et al 2018).…”

Uncertainties in νp-process nucleosynthesis from Monte Carlo variation of reaction rates

“…3. The standard rate set and the assigned uncertainties were the same as previously used in our works (Rauscher et al 2016;Nishimura et al 2017Nishimura et al , 2018Cescutti et al 2018): rates for neutron-, proton-, and α-induced reactions were a combination of theoretical values by Rauscher & Thielemann (2000), supplemented by experimental rates taken from Dillmann et al (2006) and Cyburt et al (2010). Decays and electron captures were taken from a REACLIB file compiled by Freiburghaus & Rauscher (1999) and supplemented by rates from Takahashi & Yokoi (1987) and Goriely (1999) as provided by Aikawa et al (2005) and Xu et al (2013).…”

Impact of Uncertainties in Astrophysical Reaction Rates on Nucleosynthesis in the νp Process

“…The trajectories specify the temporal evolution of density and temperature and can be taken from any astrophysical simulation. PizBuin so far was already applied to a number of processes: the γ process in core-collapse supernovae (ccSN) [1], the production of p nuclei in white dwarfs exploding as thermonuclear (type Ia) supernovae (SNIa) [2], the weak s process in massive stars [3], and the main s process in AGB stars [4].…”