Three-Dimensional Simulations of the Deflagration Phase of the Gravitationally Confined Detonation Model of Type Ia Supernovae

We report the results of a series of three-dimensional (3-D) simulations of the deflagration phase of the gravitationally confined detonation mechanism for Type Ia supernovae. In this mechanism, ignition occurs at one or several off-center points, resulting in a burning bubble of hot ash that rises rapidly, breaks through the surface of the star, and collides at a point opposite breakout on the stellar surface. We find that detonation conditions are robustly reached in our 3-D simulations for a range of initial conditions and resolutions. Detonation conditions are achieved as the result of an inwardly-directed jet that is produced by the compression of unburnt surface material when the surface flow collides with itself. A high-velocity outwardly-directed jet is also produced. The initial conditions explored in this paper lead to conditions at detonation that can be expected to produce large amounts of $^{56}$Ni and small amounts of intermediate mass elements. These particular simulations are therefore relevant only to high luminosity Type Ia supernovae. Recent observations of Type Ia supernovae imply a compositional structure that is qualitatively consistent with that expected from these simulations.