Condensation of SiC Stardust in CO Nova Outbursts

This study on presolar grains compares high-precision isotopic compositions of individual SiC grains with low 12C/13C ratios, low 14N/15N ratios, large 30Si excesses, and high 26Al/27Al ratios, all available in the presolar grain database, to new CO and ONe nova models with white dwarf (WD) masses from 0.6 to 1.35 Me. The models were designed to match the Large Binocular Telescope high-dispersion spectra acquired for nova V5668 Sgr. These CO nova models provide elemental abundances up to calcium and include mixing of WD material into the accreted material in a binary star system under several scenarios, including one where mixing occurs only after temperatures >7x107 K are achieved during a thermonuclear runaway (TNR). The 1.15–1.35 Me simulations where 25% of the WD core matter mixes with 75% of the accreted material (assumed solar) from its binary companion provide the best fits to the measured isotopic data in the M11-151-4 presolar grain. For these five presolar grains, less than 25% of solar system material is required to be mixed with the CO and ONe nova ejecta to account for the grains’ compositions.