Cellular Dynamics of Herium-rich Detonation on sub-Chandrasekhar Mass White Dwarf

TL;DR

This study investigates cellular detonation structures in white dwarf envelopes relevant to Type Ia supernovae, emphasizing the importance of cell size in detonation dynamics and the implications for numerical modeling accuracy.

Contribution

It applies terrestrial cell-based theories to astrophysical white dwarf detonations, providing detailed 2D simulation data on cellular structures and their effects on supernova modeling.

Findings

Cell width decreases with C/O contamination and is affected by alpha-capture reactions.

Nickel production timing is delayed in C/O-rich compositions.

Small cell widths challenge the resolution of full-star supernova simulations.

Abstract

Most previous efforts for hydrodynamic studies on detonation in the context of Type Ia supernovae did not take into account the scale of the cellular structure for a criterion in initiation, propagation, quenching, and the resolution requirement of detonation, whereas it is quite common to consider cell sizes in the discussion on terrestrial detonation in chemically reactive systems. In our recent study, the terrestrial cell-based theories, which incorporates the cell-size data acquired in 2D simulations of helium detonation in the double-detonation model, were demonstrated to be a powerful diagnostics in reproducing the thresholds in the initiation and quenching provided by previous studies. In the present study, 2D simulation results of the cellular detonation in the base of white-dwarf (WD) envelope are described in detail, in terms of the dynamic wave morphology and chemical abundance structure. The cellular structure is observed at a range of upstream density and envelope composition explored in the present work. C/O contamination by the WD core material reduces the cell width rapidly, as accelerated by the {\alpha}-capture reaction. It is also indicated that nickel production could be significantly delayed for the C/O-rich composition. The small cell width makes it extremely demanding to resolve the detonation structure in full-star simulations of SNe Ia; this could raise a concern on the robustness of the outcomes of some numerical simulations in terms of the success and failure of detonation. This issue may be overcome by sub-grid modeling that incorporates the cellular dynamics acquired in resolved simulations.