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The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics

Pignatari, Marco; Hoppe, Peter; Trappitsch, Reto; Fryer, Chris; Timmes, F.X.; Herwig, Falk; Hirschi, Raphael

Authors

Peter Hoppe

Reto Trappitsch

Chris Fryer

F.X. Timmes

Falk Herwig

Raphael Hirschi

Abstract

Carbon-rich presolar grains are found in primitive meteorites, with isotopic measurements to date suggesting a core-collapse supernovae origin site for some of them. This holds for about 1-2 % of presolar silicon carbide (SiC) grains, so-called Type X and C grains, and about 30 % of presolar graphite grains. Presolar SiC grains of Type X show anomalous isotopic signatures for several elements heavier than iron compared to the solar abundances: most notably for strontium, zirconium, molybdenum, ruthenium and barium. We study the nucleosynthesis of zirconium and molybdenum isotopes in the He-shell of three core-collapse supernovae models of 15, 20 and 25 M☉ with solar metallicity, and compare the results to measurements of presolar grains. We find the stellar models show a large scatter of isotopic abundances for zirconium and molybdenum, but the mass averaged abundances are qualitatively similar to the measurements. We find all models show an excess of 96Zr relative to the measurements, but the model abundances are affected by the fractionation between Sr and Zr since a large contribution to 90Zr is due to the radiogenic decay of 90Sr. Some supernova models show excesses of 95,97Mo and depletion of 96Mo relative to solar. The mass averaged distribution from these models shows an excess of 100Mo, but this may be alleviated by very recent neutron-capture cross section measurements. We encourage future explorations to assess the impact of the uncertainties in key neutron-capture reaction rates that lie along the n-process path.

Journal Article Type Article
Publication Date 2018-01
Journal Geochimica et cosmochimica acta
Print ISSN 0016-7037
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 221
Pages 37-46
Institution Citation Pignatari, M., Hoppe, P., Trappitsch, R., Fryer, C., Timmes, F., Herwig, F., & Hirschi, R. (2018). The neutron capture process in the He shell in core-collapse supernovae: Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics. Geochimica et cosmochimica acta, 221, 37-46. https://doi.org/10.1016/j.gca.2017.06.005
DOI https://doi.org/10.1016/j.gca.2017.06.005
Keywords Carbon-rich presolar grains
Publisher URL http://www.sciencedirect.com/science/article/pii/S0016703717303538
Copyright Statement ©2018, Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Additional Information This is the accepted manuscript of an article published in Geochimica et Cosmochimica Acta, 2018. The version of record is available at the DOI link in this record.

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Copyright Statement
©2018, Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/





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