Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007apj...666.1048y&link_type=abstract
The Astrophysical Journal, Volume 666, Issue 2, pp. 1048-1068.
Astronomy and Astrophysics
Astronomy
4
Ism: Dust, Extinction, Nuclear Reactions, Nucleosynthesis, Abundances, Solar System: Formation, Stars: Supernovae: General
Scientific paper
Most of supernova-originating presolar grains, such as silicon carbide type X (SiC X) and low-density graphite, show excesses of 28Si. Some of them also indicate evidence for the original presence of short-lived nuclei 44Ti. In order to reproduce isotopic and elemental signatures of these grains, large-scale heterogeneous mixing in supernova ejecta is required. I investigate supernova mixtures that reproduce as many isotopic ratios as possible of 18 individual SiC X and 26 individual low-density graphite grains. The supernova ejecta are divided into seven layers, i.e., the Ni, Si/S, O/Si, O/Ne, C/O or O/C, He/C, and He/N layers. Then, mixtures indicating isotopic ratios with small differences from those of individual single grains are sought. Mixtures reproducing five isotopic ratios in 12C/13C, 14N/15N, 26Al/ 27Al, 29Si/28Si, 30Si/ 28Si, and 44Ti/48Ti are obtained for three SiC grains. For 10 SiC X grains for which five, four, or three isotopic ratios have been measured, the mixtures reproducing all measured isotopic ratios are also found. For 20 low-density graphite grains, the mixtures reproducing six isotopic ratios in 12C/13C, 14N/ 15N, 16O/17O, 16O/18O, 26Al/27Al, 29Si/28Si, 30Si/28Si, and 44Ti/48Ti are obtained. The mixing ratios of each mixture strongly depend on reproduced isotopic ratios. The main component of most mixtures is one of the Ni, He/C, and He/N layers. The carbon-to-oxygen ratio of the mixtures is larger than unity for most cases. The ratios of Fe/C and Fe/Si in the mixtures have large varieties. Most of the mixtures for low-density graphite indicate Fe/Si larger than unity. The elemental signatures of the mixtures will constrain grain formation in supernovae.
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