Delay Times and Rates for Type Ia Supernovae and Thermonuclear Explosions from Double-detonation Sub-Chandrasekhar Mass Models

TL;DR

This paper models the delay times and rates of Type Ia supernovae from double-detonation sub-Chandrasekhar mass white dwarf explosions, suggesting they could explain a significant fraction of observed SNe Ia with distinct formation channels.

Contribution

It introduces a population synthesis model for double-detonation sub-Chandrasekhar SNe Ia, identifying two main delay time channels consistent with observations.

Findings

Two main delay time channels: prompt (<500 Myr) and delayed (>800 Myr).

Double-detonation models could account for a substantial fraction of observed SNe Ia.

Explosions are expected to be bright and detectable.

Abstract

We present theoretical delay times and rates of thermonuclear explosions that are thought to produce Type Ia supernovae, including the double-detonation sub-Chandrasekhar mass model, using the population synthesis binary evolution code StarTrack. If detonations of sub-Chandrasekhar mass carbon-oxygen white dwarfs following a detonation in an accumulated layer of helium on the white dwarf's surface ("double-detonation" models) are able to produce thermonuclear explosions which are characteristically similar to those of SNe Ia, then these sub-Chandrasekhar mass explosions may account for at least some substantial fraction of the observed SN Ia rate. Regardless of whether all double-detonations look like 'normal' SNe Ia, in any case the explosions are expected to be bright and thus potentially detectable. Additionally, we find that the delay time distribution of double-detonation sub-Chandrasekhar mass SNe Ia can be divided into two distinct formation channels: the 'prompt' helium-star channel with delay times <500 Myr (~10% of all sub-Chandras), and the 'delayed' double white dwarf channel, with delay times >800 Myr spanning up to a Hubble time (~90%). These findings coincide with recent observationally-derived delay time distributions which have revealed that a large number of SNe Ia are prompt with delay times <500 Myr, while a significant fraction also have delay times spanning ~1 Gyr to a Hubble time.