The Laminar Flame Speedup by Neon-22 Enrichment in White Dwarf Supernovae

Carbon-oxygen white dwarfs contain 22Ne formed from α-captures onto 14N during core He burning in the progenitor star. In a white dwarf (type Ia) supernova, the 22Ne abundance determines, in part, the neutronto-proton ratio and hence the abundance of radioactive 56Ni that powers the lightcurve. The 22Ne abundance also changes the burning rate and hence the laminar flame speed. We tabulate the flame speedup for different initial 12C and 22Ne abundances and for a range of densities. This increase in the laminar flame speed—about 30% for a 22Ne mass fraction of 6%—affects the deflagration just after ignition near the center of the white dwarf, where the laminar speed of the flame dominates over the buoyant rise, and in regions of lower density ∼ 107 gcm−3 where a transition to distributed burning is conjectured to occur. The increase in flame speed will decrease the density of any transition to distributed burning. Subject headings: nuclear reactions, nucleosynthesis, abundances — supernovae: general — white dwarfs — galaxies: evolution