SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE {sup 32}Si IN SUPERNOVAE
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)
- Laboratory for Space Sciences and the Physics Department, Washington University, St. Louis, MO 63130 (United States)
- Theoretical Division (T-2), LANL, Los Alamos, NM 87545 (United States)
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States)
- Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, D-55128 Mainz (Germany)
- Computational Physics and Methods (CCS-2), LANL, Los Alamos, NM 87545 (United States)
- Department of Physics and Astronomy, University of Victoria, Victoria, BC (Canada)
- Keele University, Keele, Staffordshire ST5 5BG (United Kingdom)
- Joint Institute for Nuclear Astrophysics, Notre Dame, IN 46556 (United States)
Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae (SNe) within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotopic signatures of explosive SN nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from SNe. They show peculiar abundance signatures for Si and S, isotopically heavy Si, and isotopically light S, which appear to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme {sup 32}S enrichments observed in C grains may be explained by the presence of short-lived {sup 32}Si ({tau}{sub 1/2} = 153 yr) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to molecular chemistry is needed to explain the {sup 32}S enrichments. The abundance of {sup 32}Si in the grains can provide constraints on the neutron density reached during the SN explosion in the C-rich He shell material. The impact of the large uncertainty of the neutron capture cross sections in the {sup 32}Si region is discussed.
- OSTI ID:
- 22118730
- Journal Information:
- Astrophysical Journal Letters, Vol. 771, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTRONOMY
ASTROPHYSICS
CAPTURE
CARBON
COSMOCHEMISTRY
CROSS SECTIONS
ELEMENT ABUNDANCE
FRACTIONATION
INTERSTELLAR GRAINS
LIMITING VALUES
METEORITES
NEUTRON DENSITY
NEUTRON REACTIONS
NUCLEOSYNTHESIS
SILICON 32
SILICON CARBIDES
STAR EVOLUTION
SULFUR 32
SUPERNOVAE