Date of Award
Doctor of Philosophy
William R. Hix
William R. Hix, Otis Messer, Andrew W. Steiner, Mike Guidry, Tim Schulze
A core-collapse supernova (CCSN) is the result of a massive star’s core collapsing due to the inability of electron degeneracy pressure to provide sufficient support against gravity. Currently, there is a disconnect between when most three-dimensional CCSN simulations end (seconds) and when the explosion would reach the surface of the star and become visible (hours to days). We present three-dimensional simulations of CCSNe using the FLASH code that follow the progression of the explosion to the stellar surface, starting from neutrino-radiation hydrodynamic simulations of the first seconds performed with the Chimera code. We consider a 9.6-M⊙ zero-metallicity progenitor, starting from both 2D and 3D Chimera models, and a 10-M⊙ solar-metallicity progenitor starting from a 2D Chimera model, all simulated until shock breakout in 3D while tracking 160 nuclear species. The relative velocity difference between the supernova shock and the metal-rich Rayleigh-Taylor (R-T) “bullets” which launch from the inner precincts of the star determines how the ejecta evolves as it propagates through the progenitor and dictates the final morphology of the explosion. We find maximum 56Ni velocities of ~1950 km s−1 and ~1750 km s−1 at shock breakout from 2D and 3D 9.6-M⊙ Chimera models, respectively, due to the bullets’ ability to penetrate the He/H shell. When mapping from 2D, we find that the development of higher velocity structures is suppressed when the 2D Chimera model and 3D FLASH model meshes are aligned. The development of faster growing spherical-bubble structures, as opposed to the slower growing toroidal structure imposed by axisymmetry, allows for interaction of the bullets with the shock and seeds further R-T instabilities at the He/H interface. We see similar effects in the 10-M⊙ model, which achieves maximum 56Ni velocities of ~2500 km s−1 at shock breakout.
Sandoval, Michael A., "Extending Core-Collapse Supernova Simulations: from the Onset of Explosion to Shock Breakout. " PhD diss., University of Tennessee, 2021.