A Three-Dimensional Picture of the Delayed-Detonation Model of Type Ia Supernovae

Deflagration models poorly explain the observed diversity of SNIa. Current multidimensional simulations of SNIa predict a significant amount of, so far unobserved, carbon and oxygen moving at low velocities. It has been proposed that these drawbacks can be resolved if there is a sudden jump to a detonation (delayed detonation), but this kind of models has been explored mainly in one dimension. Here we present new three-dimensional delayed detonation models in which the deflagraton-to-detonation transition (DDT) takes place in conditions like those favored by one-dimensional models. We have used a SPH code adapted to SNIa with algorithms devised to handle subsonic as well as supersonic combustion fronts. The starting point was a C-O white dwarf of 1.38 solar masses. When the average density on the flame surface reached 2-3x10^7 g/cm^3 a detonation was launched. The detonation wave processed more than 0.3 solar masses of carbon and oxygen, emptying the central regions of the ejecta of unburned fuel and raising its kinetic energy close to the fiducial 10^51 ergs expected from a healthy Type Ia supernova. The final amount of 56Ni synthesized also was in the correct range. However, the mass of carbon and oxygen ejected is still too high. The three-dimensional delayed detonation models explored here show an improvement over pure deflagration models, but they still fail to coincide with basic observational constraints. However, there are many aspects of the model that are still poorly known (geometry of flame ignition, mechanism of DDT, properties of detonation waves traversing a mixture of fuel and ashes). Therefore, it will be worth pursuing its exploration to see if a good SNIa model based on the three-dimensional delayed detonation scenario can be obtained.
Comment: To appear in A&A, 12 pages, 12 figures