Three-dimensional Hydrodynamics Simulations of Precollapse Shell Burning in the Si- and O-rich Layers

We present 3D hydrodynamics simulations of shell burning in two progenitors with zero-age main-sequence masses of 22 and 27 M for similar to 65 and 200 s up to the onset of gravitational collapse, respectively. The 22 and 27 M stars are selected from a suite of 1D progenitors. The former and the latter have an extended Si- and O-rich layer with a width of similar to 10(9) cm and similar to 5 x 10(9) cm, respectively. Our 3D results show that turbulent mixing occurs in both of the progenitors with the angle-averaged turbulent Mach number exceeding similar to 0.1 at the maximum. We observe that an episodic burning of O and Ne, which takes place underneath the convection bases, enhances the turbulent mixing in the 22 and 27 M models, respectively. The distribution of nucleosynthetic yields is significantly different from that in 1D simulations, namely, in 3D more homogeneous and inhomogeneous in the radial and angular direction, respectively. By performing a spectrum analysis, we investigate the growth of turbulence and its role of material mixing in the convective layers. We also present a scalar spherical harmonics mode analysis of the turbulent Mach number. This analytical formula would be helpful for supernova modelers to implement the precollapse perturbations in core-collapse supernova simulations. Based on the results, we discuss implications for the possible onset of the perturbation-aided neutrino-driven supernova explosion.

Automated summary

The study investigates turbulent mixing in the shell burning process of 22 and 27 solar mass stars in 3D simulations, revealing high turbulent Mach numbers. Turbulent mixing is influenced by episodic burning of O and Ne, leading to significant differences in the distribution of nucleosynthetic yields between 3D and 1D simulations.