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The impact of (n, γ) reaction rate uncertainties of unstable isotopes near N = 50 on the i-process nucleosynthesis in He-shell flash white dwarfs

Denissenkov, Pavel; Perdikakis, Georgios; Herwig, Falk; Schatz, Hendrik; Ritter, Christian; Pignatari, Marco; Jones, Samuel; Nikas, Stylianos; Spyrou, Artemis

Authors

Pavel Denissenkov

Georgios Perdikakis

Falk Herwig

Hendrik Schatz

Christian Ritter

Samuel Jones

Stylianos Nikas

Artemis Spyrou



Abstract

The first-peak s-process elements Rb, Sr, Y and Zr in the post-AGB star Sakurai's object (V4334 Sagittarii) have been proposed to be the result of i-process nucleosynthesis in a post-AGB very-late thermal pulse event. We estimate the nuclear physics uncertainties in the i-process model predictions to determine whether the remaining discrepancies with observations are significant and point to potential issues with the underlying astrophysical model. We find that the dominant source in the nuclear physics uncertainties are predictions of neutron capture rates on unstable neutron rich nuclei, which can have uncertainties of more than a factor 20 in the band of the i-process. We use a Monte Carlo variation of 52 neutron capture rates and a 1D multi-zone post-processing model for the i-process in Sakurai's object to determine the cumulative effect of these uncertainties on the final elemental abundance predictions. We find that the nuclear physics uncertainties are large and comparable to observational errors. Within these uncertainties the model predictions are consistent with observations. A correlation analysis of the results of our MC simulations reveals that the strongest impact on the predicted abundances of Rb, Sr, Y and Zr is made by the uncertainties in the (n, γ) reaction rates of 85Br, 86Br, 87Kr, 88Kr, 89Kr, 89Rb, 89Sr, and 92Sr. This conclusion is supported by a series of multi-zone simulations in which we increased and decreased to their maximum and minimum limits one or two reaction rates per run. We also show that simple and fast one-zone simulations should not be used instead of more realistic multi-zone stellar simulations for nuclear sensitivity and uncertainty studies of convective–reactive processes. Our findings apply more generally to any i-process site with similar neutron exposure, such as rapidly accreting white dwarfs with near-solar metallicities.

Journal Article Type Article
Publication Date Apr 13, 2018
Journal Journal of Physics G: Nuclear and Particle Physics
Print ISSN 0954-3899
Electronic ISSN 1361-6471
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 45
Issue 5
Article Number 055203
Pages 055203
APA6 Citation Denissenkov, P., Perdikakis, G., Herwig, F., Schatz, H., Ritter, C., Pignatari, M., …Spyrou, A. (2018). The impact of (n, γ) reaction rate uncertainties of unstable isotopes near N = 50 on the i-process nucleosynthesis in He-shell flash white dwarfs. Journal of physics. an Institute of Physics journal. G, Nuclear and particle physics, 45(5), 055203. https://doi.org/10.1088/1361-6471/aabb6e
DOI https://doi.org/10.1088/1361-6471/aabb6e
Keywords Nuclear and High Energy Physics
Publisher URL http://iopscience.iop.org/article/10.1088/1361-6471/aabb6e/meta
Copyright Statement Copyright 2017 IOP Publishing - this is the accepted manuscript of an article published in Journal of Physics G: Nuclear and Particle Physics
Additional Information Journal title: Journal of Physics G: Nuclear and Particle Physics; Article type: paper; Article title: The impact of (n, γ) reaction rate uncertainties of unstable isotopes near N = 50 on the i-process nucleosynthesis in He-shell flash white dwarfs; Copyright information: © 2018 IOP Publishing Ltd; Date received: 2017-11-22; Date accepted: 2018-04-04; Online publication date: 2018-04-16

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Copyright Statement
Copyright 2017 IOP Publishing - this is the accepted manuscript of an article published in Journal of Physics G: Nuclear and Particle Physics





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