Convection during the Late Stages of Simmering in Type Ia Supernovae

TL;DR

This paper investigates the convective processes during the simmering phase of Type Ia supernovae, highlighting how long conductive timescales and compositional differences influence the convective structure and potentially affect the explosion characteristics.

Contribution

It provides a detailed analysis of time-dependent convection in the simmering phase, emphasizing the impact of composition and thermal timescales on the convective boundary and supernova outcomes.

Findings

Convective luminosity decreases near the top boundary due to long conductive timescales.

Composition differences, especially 22Ne sedimentation, significantly alter the convective boundary.

Diversity in WD models may influence the properties of resulting supernovae.

Abstract

Following unstable ignition of carbon, but prior to explosion, a white dwarf (WD) in a Type Ia supernova (SN Ia) undergoes a simmering phase. During this time, a central convective region grows and encompasses ~1 Msun of the WD over a timescale of ~1000 yrs, which sets the thermal and turbulent profile for the subsequent explosion. We study this time-dependent convection and summarize some of the key features that differ from the traditional, steady-state case. We show that the long conductive timescale above the convective zone and the extraction of energy to heat the WD core leads to a decrease of the convective luminosity and characteristic velocities near the convective zone's top boundary. In addition, differences in the composition between the convective core and the conductive exterior will significantly alter the location of this boundary. In this respect, we find the biggest effect due to complete 22Ne sedimentation prior to carbon ignition. These effects add diversity to the possible WD models, which may alter the properties of the SN Ia explosion.