The relevance of the standing accretion shock instability (SASI) compared to neutrino-driven convection in three-dimensional (3D) supernova-core environments is still highly controversial. Studying a 27 Msun progenitor, we demonstrate, for the first
time, that violent SASI activity can develop in 3D simulations with detailed neutrino transport despite the presence of convection. This result was obtained with the Prometheus-Vertex code with the same sophisticated neutrino treatment so far used only in 1D and 2D models. While buoyant plumes initially determine the nonradial mass motions in the postshock layer, bipolar shock sloshing with growing amplitude sets in during a phase of shock retraction and turns into a violent spiral mode whose growth is only quenched when the infall of the Si/SiO interface leads to strong shock expansion in response to a dramatic decrease of the mass accretion rate. In the phase of large-amplitude SASI sloshing and spiral motions, the postshock layer exhibits nonradial deformation dominated by the lowest-order spherical harmonics (l=1, m=0,-1,+1) in distinct contrast to the higher multipole structures associated with neutrino-driven convection. We find that the SASI amplitudes, shock asymmetry, and nonradial kinetic energy in 3D can exceed those of the corresponding 2D case during extended periods of the evolution. We also perform parametrized 3D simulations of a 25 Msun progenitor, using a simplified, gray neutrino transport scheme, an axis-free Yin-Yang grid, and different amplitudes of random seed perturbations. They confirm the importance of the SASI for another progenitor, its independence of the choice of spherical grid, and its preferred growth for fast accretion flows connected to small shock radii and compact proto-neutron stars as previously found in 2D setups.
We present 3D simulations of supernova (SN) explosions of nonrotating stars, triggered by the neutrino-heating mechanism with a suitable choice of the core-neutrino luminosity. Our results show that asymmetric mass ejection caused by hydrodynamic ins
tabilities can accelerate the neutron star (NS) up to recoil velocities of more than 700 km/s by the gravitational tug-boat mechanism, which is enough to explain most observed pulsar velocities. The associated NS spin periods are about 100 ms to 8 s without any correlation between spin and kick magnitudes or directions. This suggests that faster spins and a possible spin-kick alignment might require angular momentum in the progenitor core prior to collapse. Our simulations for the first time demonstrate a clear correlation between the size of the NS kick and anisotropic ejection of heavy elements created by explosive burning behind the shock. In the case of large NS kicks the explosion is significantly stronger opposite to the kick vector. Therefore the bulk of the Fe-group elements, in particular nickel, is ejected mostly in large clumps against the kick direction. This contrasts with the case of low recoil velocity, where the Ni-rich lumps are more isotropically distributed. Intermediate-mass nuclei heavier than Si (like Ca and Ti) also exhibit a significant enhancement in the hemisphere opposite to the direction of fast NS motion, while the distribution of C, O, and Ne is not affected, and that of Mg only marginally. Mapping the spatial distribution of the heavy elements in SN remnants with identified pulsar motion may offer an important diagnostic test of the kick mechanism. Different from kick scenarios based on anisotropic neutrino emission, our hydrodynamical acceleration model predicts enhanced ejection of Fe-group elements and of their nuclear precursors in the direction opposite to the NS recoil. (abridged)
