Evolutions of the central density as functions of time for the three progenitors. The red, blue, and green curves correspond to the 15, 12, and ﹩9\ {M}_{\odot }﹩ models, respectively. The origin of the horizontal axis corresponds to the time when the dynamical simulations started. The initiation points of some major nuclear burnings as well as the evolutionary stages for the ONe-core progenitors are marked with labels.