[TSUP]41[/TSUP]Ca in Presolar Graphite of Supernova Origin

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Abstract
Five low-density graphite grains from the Murchison meteorite have large 41K excesses that can be attributed to the decay of 41Ca. The inferred 41Ca/40Ca ratios, which range up to 1.7 × 10-2, and other isotopic signatures,15N,18O, and 28Si excesses and high 26Al/27Al ratios, indicate a Type II supernova origin for these grains and are evidence for heterogeneous mixing of supernova ejecta.41Ca seems to mainly originate from neutron capture in the C-rich and O-rich supernova zones, with only minor contributions from the O-burning zone. Admixture of material from the O-rich zone to outer C-rich layers is required to explain the abundance patterns of the stable Ca isotopes. In contrast, the Ti isotopic compositions reflect that of the C-rich zone and do not require substantial amounts of material from the O-rich zone.