Axisymmetric ab initio core-collapse supernova simulations of 12-25 M _· stars

We present an overview of four ab initio axisymmetric core-collapse supernova simulations employing detailed spectral neutrino transport computed with our CHIMERA code and initiated from Woosley & Heger progenitors of mass 12, 15, 20, and 25 M_·. All four models exhibit shock revival over ∼200 ms (leading to the possibility of explosion), driven by neutrino energy deposition. Hydrodynamic instabilities that impart substantial asymmetries to the shock aid these revivals, with convection appearing first in the 12 M_· model and the standing accretion shock instability appearing first in the 25 M_· model. Three of the models have developed pronounced prolate morphologies (the 20 M_· model has remained approximately spherical). By 500 ms after bounce the mean shock radii in all four models exceed 3000 km and the diagnostic explosion energies are 0.33, 0.66, 0.65, and 0.70 Bethe (B = 10⁵¹ erg) for the 12, 15, 20, and 25 M_· models, respectively, and are increasing. The three least massive of our models are already sufficiently energetic to completely unbind the envelopes of their progenitors (i.e., to explode), as evidenced by our best estimate of their explosion energies, which first become positive at 320, 380, and 440 ms after bounce. By 850 ms the 12 M_· diagnostic explosion energy has saturated at 0.38 B, and our estimate for the final kinetic energy of the ejecta is ∼0.3 B, which is comparable to observations for lower mass progenitors.