The Laminar Flame Speedup by 22 Ne Enrichment in White Dwarf Supernovae

Abstract

Carbon-oxygen white dwarfs contain 22 Ne formed from {Œ}\pm-captures onto 14 N during core He burning in the progenitor star. In a white dwarf (Type Ia) supernova, the 22 Ne abundance determines, in part, the neutron-to-proton ratio and hence the abundance of radioactive 56 Ni that powers the light curve. The 22 Ne abundance also changes the burning rate and hence the laminar flame speed. We tabulate the flame speedup for different initial 12 C and 22 Ne abundances and for a range of densities. This increase in the laminar flame speed-about 30% for a 22 Ne 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, ~10 7 g cm -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.