Presolar SiC Grains of Type AB with Isotopically Light Nitrogen: Contributions from Supernovae?

Abstract

Primitive solar system materials contain presolar grains that formed in the winds of evolved stars and in the ejecta of stellar explosions. Here, we report on NanoSIMS measurements of C-, N-, Al–Mg-, Si-, and S-isotopic compositions of 10 submicrometer-sized presolar SiC grains of Type AB from the Murchison meteorite. Except for one grain with the highest12C/13C ratio we find good correlations between12C/13C,14N/15N, and26Al/27Al. The correlations are well explained by a 25�M⊙ supernova (SN) model that considers H ingestion into the He shell. The comparison of our data with the SN model suggests that SNe might have contributed not only AB grains with heavy N, as suggested previously, but also some with light N.