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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

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 ratesmore » 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. Lastly, our findings apply more generally to any i-process site with similar neutron exposure, such as rapidly accreting white dwarfs with near-solar metallicities.« less
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ;  [3] ;  [1] ; ORCiD logo [4] ; ORCiD logo [5] ;  [6] ;  [3]
  1. Univ. of Victoria, BC (Canada). Dept. of Physics & Astronomy; Michigan State Univ., East Lansing, MI (United States). Joint Inst. for Nuclear Astrophysics, Center for the Evolution of the Elements
  2. Michigan State Univ., East Lansing, MI (United States). Joint Inst. for Nuclear Astrophysics, Center for the Evolution of the Elements; Central Michigan Univ., Mount Pleasant, MI (United States). Dept. of Physics and Physical Sciences Program; Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.
  3. Michigan State Univ., East Lansing, MI (United States). Joint Inst. for Nuclear Astrophysics, Center for the Evolution of the Elements; Michigan State Univ., East Lansing, MI (United States). National Superconducting Cyclotron Lab.; Michigan State Univ., East Lansing, MI (United States). Dept. of Physics & Astronomy
  4. Univ. of Hull, Hull (United Kingdom). E.A. Milne Centre for Astrophysics, Dept. of Physics & Mathematics; Hungarian Academy of Sciences, Budapest (Hungary). Konkoly Observatory, Research Centre for Astronomy and Earth Sciences
  5. Heidelberg Inst. for Theoretical Studies, Heidelberg, (Germany); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. Michigan State Univ., East Lansing, MI (United States). Joint Inst. for Nuclear Astrophysics, Center for the Evolution of the Elements; Central Michigan Univ., Mount Pleasant, MI (United States). Dept. of Physics and Physical Sciences Program
Publication Date:
Report Number(s):
LA-UR-18-21509
Journal ID: ISSN 0954-3899
Grant/Contract Number:
89233218CNA000001
Type:
Accepted Manuscript
Journal Name:
Journal of Physics. G, Nuclear and Particle Physics
Additional Journal Information:
Journal Volume: 45; Journal Issue: 5; Journal ID: ISSN 0954-3899
Publisher:
IOP Publishing
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
National Science Foundation (NSF)
Contributing Orgs:
NuGrid Collaboration
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; nuclear reactions; nucleosynthesis; stars: abundances; stars: AGB and post-AGB
OSTI Identifier:
1492608

Denissenkov, Pavel, Perdikakis, Georgios, Herwig, Falk, Schatz, Hendrik, Ritter, Christian, Pignatari, Marco, Jones, Samuel, Nikas, Stylianos, and Spyrou, Artemis. 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. United States: N. p., Web. doi:10.1088/1361-6471/aabb6e.
Denissenkov, Pavel, Perdikakis, Georgios, Herwig, Falk, Schatz, Hendrik, Ritter, Christian, Pignatari, Marco, Jones, Samuel, Nikas, Stylianos, & Spyrou, Artemis. 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. United States. doi:10.1088/1361-6471/aabb6e.
Denissenkov, Pavel, Perdikakis, Georgios, Herwig, Falk, Schatz, Hendrik, Ritter, Christian, Pignatari, Marco, Jones, Samuel, Nikas, Stylianos, and Spyrou, Artemis. 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". United States. doi:10.1088/1361-6471/aabb6e. https://www.osti.gov/servlets/purl/1492608.
@article{osti_1492608,
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},
author = {Denissenkov, Pavel and Perdikakis, Georgios and Herwig, Falk and Schatz, Hendrik and Ritter, Christian and Pignatari, Marco and Jones, Samuel and Nikas, Stylianos and Spyrou, Artemis},
abstractNote = {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. Lastly, our findings apply more generally to any i-process site with similar neutron exposure, such as rapidly accreting white dwarfs with near-solar metallicities.},
doi = {10.1088/1361-6471/aabb6e},
journal = {Journal of Physics. G, Nuclear and Particle Physics},
number = 5,
volume = 45,
place = {United States},
year = {2018},
month = {4}
}