EFFECTS OF ROTATION ON STANDING ACCRETION SHOCK INSTABILITY IN NONLINEAR PHASE FOR CORE-COLLAPSE SUPERNOVAE

We study the effects of rotation on standing accretion shock instability (SASI) by performing three-dimensional hydrodynamics simulations. Taking into account a realistic equation of state and neutrino heating/cooling, we prepare a spherically symmetric and steady accretion flow through a standing shock wave onto a proto-neutron star (PNS). When the SASI enters the nonlinear phase, we impose uniform rotation on the flow advecting from the outer boundary of the iron core, whose specific angular momentum is assumed to agree with recent stellar evolution models. Using spherical harmonics in space and Fourier decompositions in time, we perform mode analysis of the nonspherical deformed shock wave to observe rotational effects on the SASI in the nonlinear phase. We find that rotation imposed on the axisymmetric flow does not make any spiral modes and hardly affects sloshing modes, except for steady l = 2, m = 0 modes. In contrast, rotation imposed on the nonaxisymmetric flow increases the amplitude of spiral modes so that some spiral flows accreting on the PNS are more clearly formed inside the shock wave than without rotation. The amplitudes of spiral modes increase significantly with rotation in the progressive direction.