Delayed detonation at a single point in exploding white dwarfs

Delayed detonation in an exploding white dwarf, which propagates from an off-center transition point rather than from a spherical transition shell, is described and simulated. The differences between the results of two-dimensional simulations and the one-dimensional case are presented and discussed. The two-dimensional effects become significant in transition density below 3 rho(7), where the energetics, the production of Fe group elements, and the symmetry of the explosion are all affected. In the two-dimensional case, the explosion is less energetic and less Ni is produced in the detonation phase of the explosion. For low transition density, the reduction in Ni mass can reach 20%-30%. The asymmetry in abundances between regions close to the transition point and regions far from that point is large and could be a source of polarization patterns in the emitted light. We conclude that the spatial and temporal distribution of transition locations is an important parameter that must be included in delayed detonation models for Type Ia supernovae.