Companion stars of Type Ia supernovae and single low-mass white dwarfs

TL;DR

This study investigates the properties of companion stars surviving Type Ia supernovae in the WD + MS channel, suggesting they are low-mass and could explain the origin of single low-mass white dwarfs.

Contribution

It provides a detailed binary population synthesis analysis of surviving companions in the WD + MS channel, linking them to low-mass white dwarf formation.

Findings

Surviving companions are low-mass stars (<0.45Msun).

Properties of companions can be tested by future observations.

Explains the origin of single low-mass white dwarfs.

Abstract

Recent investigations of the WD + MS channel of Type Ia supernovae (SNe Ia) imply that this channel may be the main contribution to the old population (>1Gyr) of SNe Ia. In the WD + MS channel, the WD could accrete material from a main-sequence or a slightly evolved star until it reaches the Chandrasekhar mass limit. The companions in this channel would survive after SN explosion and show distinguishing properties. In this Letter, based on SN Ia production regions of the WD + MS channel and three formation channels of WD + MS systems, we performed a detailed binary population synthesis study to obtain the properties of the surviving companions. The properties can be verified by future observations. We find that the surviving companions of the old SNe Ia have a low mass, which provides a possible way to explain the formation of the population of single low-mass WDs (<0.45Msun).