ON THE INSTABILITY OF DEFLAGRATION FRONTS IN WHITE-DWARFS

We discuss the stability of a deflagration front in white dwarfs in th e context of burning mechanisms for Type Ia Supernovae. It is shown th at the basic characteristics of the instability of the deflagration fr ont are different from those of Rayleigh-Taylor instability, on which the deflagration models rely. In view of this, together with results f rom two-dimensional simulations, we argue that the deflagration model needs reconsideration, as Rayleigh-Taylor instability cannot explain t he required high flame speed required for producing an explosion simil ar to Type Ia Supernovae. On the other hand, the same arguments imply that delayed detonation is acceptable and that the transition to deton ation must occur in the very low density regime, where good agreement between observations and numerical results is obtained.