The Laminar Flame Speedup by 22Ne 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 neutron-to-proton ratio and hence the abundance of radioactive ⁵⁶Ni that powers the light curve. 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 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.