Are Presolar Silicon Carbide Grains from Novae Actually from Supernovae?

Abstract

We report Si, C, N, Mg-Al, Ca, and Ti isotopic data for three micron-sized presolar SiC grains from the Murchison meteorite. These grains have very low 12 C/ 13 C and 14 N/ 15 N ratios, similar to grains for which an origin in classical ONe novae has been previously ascribed. Isotopic signatures in one grain ( 28 Si, 49 Ti, and 44 Ca excesses and a very high inferred 26 Al/ 27 Al ratio) indicate that it in fact formed in a supernova, not a nova. Similarly, a large 47 Ti excess in another grain argues against a nova origin. The new data raise the question whether all grains previously attributed to novae might have in fact originated in Type II supernovae. The results also point to coupled synthesis of 13 C and 15 N in Type II supernovae. © The American Astronomical Society. All rights reserved.