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

Marco Pignatari, Peter Hoppe, Reto Trappitsch, Chris Fryer, Francis Timmes, Falk Herwig, Raphael Hirschi

Research output: Contribution to journalArticle

4 Citations (Scopus)

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 25M[U+2609] 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.

Original languageEnglish (US)
JournalGeochimica et Cosmochimica Acta
DOIs
StateAccepted/In press - 2017

Fingerprint

Astrophysics
astrophysics
silicon
Neutrons
shell
Molybdenum
molybdenum
Nucleosynthesis
Meteorites
Strontium
ruthenium
Ruthenium
Graphite
barium
Barium
Fractionation
strontium
Isotopes
graphite
meteorite

Keywords

  • Abundances
  • Nuclear reactions
  • Nucleosynthesis
  • Stars
  • Supernovae

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

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, Francis; Herwig, Falk; Hirschi, Raphael.

In: Geochimica et Cosmochimica Acta, 2017.

Research output: Contribution to journalArticle

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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

PY - 2017

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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 25M[U+2609] 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 25M[U+2609] 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.

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