Supernovae Ia in 2017: a long time delay from merger/accretion to explosion

TL;DR

This paper argues that a significant time delay between white dwarf merger or accretion and explosion is essential for type Ia supernovae, favoring the core degenerate scenario over others.

Contribution

It introduces the concept of a merger/accretion to explosion delay (MED) as a key factor in supernova models, highlighting its importance in scenario viability.

Findings

MED is necessary for spherical explosion and avoiding pre-explosion ionization.

Core degenerate scenario is more favorable given the MED requirement.

Single degenerate scenario is less likely for normal SN Ia.

Abstract

I use recent observational and theoretical studies of type Ia supernovae (SNe Ia) to further constrain the viable SN Ia scenarios and to argue that there must be a substantial time delay between the end of the merger of the white dwarf (WD) with a companion or the end of mass accretion on to the WD and its terminal explosion. This merger/accretion to explosion delay (MED) is required to allow the binary system to lead to a more or less spherical explosion and to prevent a pre-explosion ionizing radiation. Considering these recent results and the required MED, I conclude that the core degenerate scenario is somewhat more favorable over the other scenarios, followed by the double degenerate scenario. Although the single degenerate scenario is viable as well, it is less likely to account for common (normal) SN Ia. As all scenarios require substantial MED, the MED has turned from a disadvantage of the core degenerate scenario to a challenge that theory should overcome. I hope that the requirement for a MED will stimulate the discussion of the different SN Ia scenarios and the comparison of the scenarios to each other.