Uncertainties in the production ofpnuclei in massive stars obtained from Monte Carlo variations

Abstract

Nuclear data uncertainties in the production of p nuclei in massive stars have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi. Their simultaneous impact was studied in postprocessing explosive trajectories for three different stellar models. It was found that the grid of mass zones in the model of a 25 M star, which is widely used for investigations of p nucleosynthesis, is too crude to properly resolve the detailed temperature changes required for describing the production of p nuclei. Using models with finer grids for 15 M and 25 M stars with initial solar metallicity, it was found that most of the production uncertainties introduced by nuclear reaction uncertainties are smaller than a factor of two. Since a large number of rates were varied at the same time in the Monte Carlo procedure, possible cancellation effects of several uncertainties could be taken into account. Key rates were identified for each p nucleus, which provide the dominant contribution to the production uncertainty. These key rates were found by examining correlations between rate variations and resulting abundance changes. This method is superior to studying flow patterns, especially when the flows are complex, and to individual, sequential variation of a few rates.

Uncertainties in s-process nucleosynthesis in massive stars determined by Monte Carlo variations

“…Iliadis et al 2014;Rauscher et al 2016). We use the PizBuin MC driver coupled with a nuclear reaction network.…”

“…We use the PizBuin MC driver coupled with a nuclear reaction network. This framework was developed for application to general nucleosynthesis processes and is described in more detail in Rauscher et al (2016), where its first application was to the γ-process in massive stars. In the following we only provide an outline of the most important concepts and especially of details particular to s-process nucleosynthesis.…”

“…Here, in the context of the s-process, the majority of reactions are based on experimental data. For more details and the derivation of Equation 2, see Rauscher et al (2016) and references therein.…”

“…We focus on (n, γ) reactions and β-decay on the path of s-process nucleosynthesis. We perform comprehensive rate variations using the PizBuin Monte-Carlo (MC) framework coupled with a reaction network code, described previously in Rauscher et al (2016). Analysing the results of the MC calculations, we determine the important reactions and decays that are the dominant sources of uncertainty for the production of "key" elements.…”

Uncertainty of the astrophysical O17,18(α,n)Ne20,21Mohr1 2017Phys. Rev. C9070View full textAdd to dashboardCite

“…The StM is well founded for heavy target nuclei, e.g. for (α,n) reactions under certain r-process conditions [4][5][6], and for inverse (γ,α) reactions in the γ-process [7,8]. Contrary to the situations in the r-process and γ-process, it is not clear whether the level density is sufficiently high for a reliable calculation of α-induced reactions for the light target nuclei in the s-process with masses A < ∼ 20.…”