The ignition of thermonuclear flames in type Ia supernovae

In the framework of the Chandrasekhar-mass deflagration model for type Ia supernovae (SNe Ia), a persisting free parameter is the initial morphology of the flame front, which is linked to the ignition process in the progenitor white dwarf. Previous analytical models indicate that the thermal runaway is driven by temperature perturbations ("bubbles") that develop in the white dwarf's convective core. In order to probe the conditions at ignition (diameters, temperatures, and evolutionary timescales), we performed hydrodynamical 2D simulations of buoyant bubbles in white dwarf interiors. Our results show that fragmentation occurring during the bubble rise affects the outcome of the bubble evolution. Possible implications for the ignition process of SNe Ia are discussed.