Late formation of silicon carbide in type II supernovae

We have found that individual presolar silicon carbide (SiC) dust grains from supernovae show a positive correlation between ⁴⁹Ti and ²⁸Si excesses, which is attributed to the radioactive decay of the short-lived (t_½ = 330 days) ⁴⁹V to ⁴⁹Ti in the inner highly ²⁸Si-rich Si/S zone. The ⁴⁹V-⁴⁹Ti chronometer shows that these supernova SiC dust grains formed at least 2 years after their parent stars exploded. This result supports recent dust condensation calculations that predict a delayed formation of carbonaceous and SiC grains in supernovae. The astronomical observation of continuous buildup of dust in supernovae over several years can, therefore, be interpreted as a growing addition of C-rich dust to the dust reservoir in supernovae.