Matter Mixing in Core-collapse Supernova Ejecta: Large Density Perturbations in the Progenitor Star?

TL;DR

This study uses 2D hydrodynamic simulations to demonstrate that large density perturbations in a supernova progenitor can generate Rayleigh-Taylor instabilities, leading to high-velocity nickel clumps consistent with observations of SN 1987A.

Contribution

First to propose large density perturbations in CCSN progenitors as a mechanism for effective matter mixing and high-velocity nickel clumps.

Findings

Large density perturbations induce Rayleigh-Taylor instabilities.

Both spherical and aspherical explosions can produce high-velocity $^{56}$Ni.

Optimal models include bipolar and asymmetric explosions with at least 25% perturbation.

Abstract

Matter mixing is one important topic in the study of core-collapse supernova (CCSN) explosions. In this paper, we perform two-dimensional hydrodynamic simulations to reproduce the high velocity $^{56}$Ni clumps observed in SN 1987A. This is the first time that large density perturbation is proposed in the CCSN progenitor to generate Rayleigh-Taylor (RT) instability and make the effective matter mixing. In the case of a spherical explosion, RT instability is efficient at both C+O/He and He/H interfaces of the SN progenitor. Radial coherent structures shown in perturbation patterns are important for obtaining high velocity $^{56}$Ni clumps. We can also obtain matter mixing features and high velocity $^{56}$Ni clumps in some cases of aspherical explosion. We find that one of the most favorable models in our work has a combination of bipolar and equatorially asymmetric explosions in which at least 25\% of density perturbation is introduced at different composition interfaces of the CCSN progenitor. These simulation results are comparable to the observational findings of SN 1987A.