TY - JOUR
T1 - The neutron capture process in the He shell in core-collapse supernovae
T2 - Presolar silicon carbide grains as a diagnostic tool for nuclear astrophysics
AU - Pignatari, Marco
AU - Hoppe, Peter
AU - Trappitsch, Reto
AU - Fryer, Chris
AU - Timmes, Francis
AU - Herwig, Falk
AU - Hirschi, Raphael
N1 - Funding Information:
We thank Yangting Lin, two anonymous referees, and guest editor Larry Nittler for constructive and helpful reviews. NuGrid acknowledges significant support from NSF grants PHY 02-16783 and PHY 08-22648 (Joint Institute for Nuclear Astrophysics, JINA), NSF grant PHY-1430152 (JINA Center for the Evolution of the Elements) and EU MIRG-CT-2006-046520. The continued work on codes and in disseminating data is made possible through funding from STFC and EU-FP7-ERC-2012-St Grant 306901 (RH, UK), and NSERC Discovery grant (FH, Canada). MP acknowledges support from the “Lendulet-2014” Programme of the Hungarian Academy of Sciences, from SNF (Switzerland) and thanks the resource allocations on the University of Hull High Performance Computing Facility viper. NuGrid data is served by Canfar/CADC. RT is supported by NASA Headquarters under the NASA Earth and Planetary Science Fellowship Program through grant NNX12AL85H and was partially supported by the NASA Cosmochemistry Program through grant NNX09AG39G (to A. M. Davis).
Publisher Copyright:
© 2017 Elsevier Ltd
PY - 2018/1/15
Y1 - 2018/1/15
N2 - 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.
AB - 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.
KW - Abundances
KW - Nuclear reactions
KW - Nucleosynthesis
KW - Stars
KW - Supernovae
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U2 - 10.1016/j.gca.2017.06.005
DO - 10.1016/j.gca.2017.06.005
M3 - Article
AN - SCOPUS:85028313856
SN - 0016-7037
VL - 221
SP - 37
EP - 46
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -