Active carbon and oxygen shell burning hydrodynamics

We have simulated 2.5 × 10³ s of the late evolution of a 23 M_⊙ star with full hydrodynamic behavior. We present the first simulations of a multiple-shell burning epoch, including the concurrent evolution and interaction of an oxygen- and a carbon-burning shell. In addition, we have evolved a three-dimensional model of the oxygen-burning shell to sufficiently long times (300 s) to begin to assess the adequacy of the two-dimensional approximation. We summarize striking new results: (1) strong interactions occur between active carbon- and oxygen-burning shells; (2) hydrodynamic wave motions in nonconvective regions, generated at the convective-radiative boundaries, are energetically important in both two and three dimensions, with important consequences for compositional mixing; and (3) a spectrum of mixed p- and g-modes are unambiguously identified with corresponding adiabatic waves in these computational domains. We find that two-dimensional convective motions are exaggerated relative to three-dimensional ones because of vortex instability in three dimensions. We discuss the implications for supernova progenitor evolution and symmetry breaking in core collapse.