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

Abstract

The s-process in massive stars produces the weak component of the s-process (nuclei up to A ∼ 90), in amounts that match solar abundances. For heavier isotopes, such as barium, production through neutron capture is significantly enhanced in very metal-poor stars with fast rotation. However, detailed theoretical predictions for the resulting final s-process abundances have important uncertainties caused both by the underlying uncertainties in the nuclear physics (principally neutron capture reaction and β-decay rates) as well as by the stellar evolution modeling. In this work, we investigated the impact of nuclear-physics uncertainties relevant to the s-process in massive stars. Using a Monte-Carlo based approach, we performed extensive nuclear reaction network calculations that include newly evaluated upper and lower limits for the individual temperature dependent reaction rates. We found that most of the uncertainty in the final abundances is caused by uncertainties in the neutron capture rates, while β-decay rate uncertainties affect only a few nuclei near s-process branchings. The sprocess in rotating metal-poor stars shows quantitatively different uncertainties and key reactions, although the qualitative characteristics are similar. We confirmed that our results do not significantly change at different metallicities for fast rotating massive stars in the very low metallicity regime. We highlight which of the identified key reactions are realistic candidates for improved measurement by 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).…”

Impacts of Nuclear-Physics Uncertainty in Stellar Temperatures on the s-Process Nucleosynthesis

“…1 and 2), few β-decay may cause larger uncertainty in nucleosynthesis. As we quantitatively analyse MC results calculating the correlation between decay rates and final abundances (see, [3,4]), we find that 64 Cu(β + ) 64 Zn and 80 Br(β + ) 80 Kr have dominant impact on the production of 64 Zn and 80 Se for the weak s-process, respectively. Besides, 122 Sb(β + ) 122 Te, competing with the β − -decay counterpart, is a dominant rate for the uncertainty of 122 Sn in the main s-process.…”

“…In this study, we investigate the impact of uncertainty due to nuclear physics on the s-process using the MC-based nuclear reaction network [4]. Adopting simplified stellar models that reproduce typical s-process patterns, we apply realistic temperature-dependent uncertainty of nuclear reaction and decay rates to nucleosynthesis calculation.…”

Uncertainties in the production of p nuclides in thermonuclear supernovae determined by Monte Carlo variations

“…The larger the absolute value of the Pearson coefficient, the stronger the correlation. As in Rauscher et al (2016); Nishimura et al (2017), a key rate is identified by |r| ≥ 0.65.…”

“…The standard rate set and the assigned uncertainties were the same as previously used in Rauscher et al (2016) and Nishimura et al (2017): 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).…”