The impact of (n,γ ) reaction rate uncertainties on the predicted abundances of i-process elements with 32 ≤ Z ≤ 48 in the metal-poor star HD94028

John E. McKay, Pavel A. Denissenkov, Falk Herwig, Georgios Perdikakis, Hendrik Schatz

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Several anomalous elemental abundance ratios have been observed in the metal-poor star HD94028.Weassumethatitshigh[As/Ge]ratioisaproductofaweakintermediate(i)neutroncapture process. Given that observational errors are usually smaller than predicted nuclear physics uncertainties, we have first set-up a benchmark one-zone i-process nucleosynthesis simulation results of which provide the best fit to the observed abundances. We have then performed Monte Carlo simulations in which 113 relevant (n,γ) reaction rates of unstable species were randomly varied within Hauser–Feshbach model uncertainty ranges for each reaction to estimate the impact on the predicted stellar abundances. One of the interesting results of these simulations is a double-peaked distribution of the As abundance, which is caused by the variation of the 75Ga (n,γ) cross-section. This variation strongly anticorrelates with the predicted As abundance, confirming the necessity for improved theoretical or experimental bounds on this cross-section. The 66Ni (n,γ) reaction is found to behave as a major bottleneck for the i-process nucleosynthesis. Our analysis finds the Pearson product–moment correlation coefficient rP > 0.2 for all of the i-process elements with 32 ≤ Z ≤ 42, with significant changes in their predicted abundances showing up when the rate of this reaction is reduced to its theoretically constrained lower bound. Our results are applicable to any other stellar nucleosynthesis site with the similar i-process conditions, such as Sakurai’s object (V4334 Sagittarii) or rapidly accreting white dwarfs.

Original languageEnglish
Pages (from-to)5179-5187
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume491
Issue number4
DOIs
StatePublished - Feb 1 2020

Keywords

  • Abundances
  • Nuclear reactions
  • Nucleosynthesis
  • Post-AGB
  • Stars: AGB
  • Stars: Abundances

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