The Ignition of Carbon Detonations via Converging Shock Waves in White Dwarfs

TL;DR

This paper investigates how converging shock waves in white dwarfs can trigger carbon detonations, contributing to understanding Type Ia supernovae, through analytic and numerical methods focusing on shock strength and core composition.

Contribution

It combines analytic and numerical techniques to determine the conditions under which converging shocks can ignite carbon detonations in white dwarf cores, advancing the double detonation supernova model.

Findings

He detonations can produce shocks strong enough to ignite C detonations in high-mass cores.

Convergence-driven detonations are less likely in low-mass C/O and O/Ne cores.

Multi-dimensional calculations are needed for robust detonation initiation predictions.

Abstract

The progenitor channel responsible for the majority of Type Ia supernovae is still uncertain. One emergent scenario involves the detonation of a He-rich layer surrounding a C/O white dwarf, which sends a shock wave into the core. The quasi-spherical shock wave converges and strengthens at an off-center location, forming a second, C-burning, detonation that disrupts the whole star. In this paper, we examine this second detonation of the double detonation scenario using a combination of analytic and numeric techniques. We perform a spatially resolved study of the imploding shock wave and outgoing detonation and calculate the critical imploding shock strengths needed to achieve a core C detonation. We find that He detonations in recent two-dimensional simulations yield converging shock waves that are strong enough to ignite C detonations in high-mass C/O cores, with the caveat that a truly robust answer requires multi-dimensional detonation initiation calculations. We also find that convergence-driven detonations in low-mass C/O cores and in O/Ne cores are harder to achieve and are perhaps unrealized in standard binary evolution.