Silicon Nitride from Supernovae

Publisher Website
Google Scholar
Abstract
Seven presolar silicon nitride (Si3N4) dust grains have been identified (five unambiguously and two probably) in separates of the Tieschitz (H3.6) and Murchison (CM2) meteorites, confirming previous tentative identifications of this mineral as a presolar component. These rare (2 ppb in Murchison) grains have isotopic compositions similar to those of the uncommon class of meteoritic SiC known as grains X (~60 ppb in Murchison), namely 28Si and 15N excesses relative to solar, both 13C excesses and deficits, and extremely high inferred 26Al/27Al ratios. These isotopic compositions coupled with Ca and Ti isotopic anomalies seen in some SiC grains X point to an origin in Type II supernova ejecta for SiC grains X, and by analogy for the Si3N4 grains as well. However, substantial discrepancies exist between the isotopic characteristics of the grains and the compositions predicted by supernova models.