SUPERNOVA MIXING MODELS FOR ISOTOPIC RATIOS OF PRESOLAR GRAINS

Abstract

How many isotopic ratios of individual presolar grains from supernovae agree with those of the mixtures of Type I1 supernova ejecta with appropriate mixing ratios is investigated. Detailed nucleosynthesis during the evolution and supernova explosion of a 4 M D He star is calculated by postprocessing. Using the obtained supernova ejecta, two cases of mixtures are considered with artificial mixing ratios: one consists of the Si/S, O/Ne, He/C, and He/N layers and the other consists of the Ni, Si/S, He/C, and He/N layers. The isotopic ratios of 12C/13C, 14N/’5N, “Al/”Al, 2gSi/”Si, “‘Si/”Si, and 44Ti/48Ti are chosen from eleven S ic grains and four low density graphite ones which contain evidence for the original presence of the short-lived isotope 44Ti. For one S ic X grain and one low density graphite grain, four isotopic ratios are reproduced by the corresponding mixtures. For ten S ic X and low density graphite grains, three isotopic ratios of the grains agree with those of the mixtures. Most of the mixtures reproducing the isotopic ratios of the grains are rich in the composition of the He/N layer. The characteristics of the mixtures are found to be 0.1 < Si/C < 1 and Ti/C < 0.1.