Matter Mixing from Axisymmetric Supernova Explosion

The growth of Rayleigh-Taylor instabilities under axisymmetric explosion is investigated by two-dimensional hydrodynamical calculations. The degree of the axisymmetric explosion and amplitude of the initial perturbation are varied parametrically to find the most favorable parameter for reproducing the observed line profile of heavy elements. It is found that spherical explosion cannot produce ⁵⁶Ni travelling at high velocity (~3000 km s^-1), the presence of which is affirmed by observation, even if the amplitude of initial perturbation is as large as 30%. On the other hand, strong axisymmetric explosion models produce too much high-velocity ⁵⁶Ni. Weak axisymmetric explosion is favored for the reproduction of the observed line profile. We believe that this result shows the upper limit of the degree of axisymmetric explosion. This fact will be important for the simulation of collapse-driven supernovae, including rotation, magnetic field, and axisymmetric neutrino radiation, which can potentially cause axisymmetric supernova explosion. In addition, the origin of such a large perturbation does not seem to be the structure of the progenitor but the dynamics of the core collapse explosion itself, since small perturbation cannot produce the high-velocity element, even if axisymmetric explosion models are adopted.