期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 221, 期 -, 页码 37-46出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2017.06.005
关键词
Stars; Nuclear reactions; Nucleosynthesis; Abundances; Supernovae
资金
- NSF [PHY 02-16783, PHY 08-22648, PHY-1430152]
- EU [MIRG-CT-2006-046520]
- STFC
- EU-FP7-ERC-St [306901]
- NSERC Discovery grant (FH, Canada)
- Lendulet Programme of the Hungarian Academy of Sciences
- SNF (Switzerland)
- NASA Headquarters under the NASA Earth and Planetary Science Fellowship Program [NNX12AL85H]
- NASA Cosmochemistry Program [NNX09AG39G]
- STFC [ST/R006547/1, ST/R000840/1] Funding Source: UKRI
- Direct For Mathematical & Physical Scien
- Division Of Physics [1430152] Funding Source: National Science Foundation
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-circle dot 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 Zr-96 relative to the measurements, but the model abundances are affected by the fractionation between Sr and Zr since a large contribution to Zr-90 is due to the radiogenic decay of Sr-90. Some supernova models show excesses of Mo-95,Mo-97 and depletion of Mo-96 relative to solar. The mass averaged distribution from these models shows an excess of Mo-100, 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. (C) 2017 Elsevier Ltd. All rights reserved.
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