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

TL;DR

This study uses 3D hydrodynamics simulations to explore turbulent mixing and nucleosynthesis in the precollapse shells of massive stars, revealing complex turbulence behavior and its potential impact on supernova explosions.

Contribution

It provides the first detailed 3D analysis of shell burning in massive star progenitors, highlighting turbulence growth and nucleosynthetic distribution differences from 1D models.

Findings

Turbulent Mach number exceeds 0.1 in both models.

Episodic burning enhances turbulence and mixing.

Nucleosynthetic yields are more homogeneous in 3D.

Abstract

We present 3D hydrodynamics simulations of shell burning in two progenitors with zero-age main-sequence masses of 22 and 27 $M_{\odot}$ for $\sim$65 and 200 s up to the onset of gravitational collapse, respectively. The 22 and 27 $M_{\odot}$ 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 $\sim$10$^9$ cm and $\sim$5$\times 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 $\sim$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 $M_\odot$ 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.