The Absence of Ex-Companions in Type Ia Supernova Remnants

TL;DR

This paper investigates the absence of ex-companion stars in Type Ia supernova remnants, considering the effects of angular momentum gain and spin-down phases, which may explain why such stars are not observed.

Contribution

It introduces the impact of angular momentum gain and spin-down phases on the detectability of ex-companion stars in SNe Ia remnants, challenging previous assumptions.

Findings

Current absence of ex-companions does not rule out their existence.

Spin-down phases can make ex-companions too dim to detect.

Revises constraints on progenitor models of SNe Ia.

Abstract

Type Ia supernovae (SNe Ia) play important roles in our study of the expansion and acceleration of the Universe, but because we do not know the exact nature or natures of the progenitors, there is a systematic uncertainty that must be resolved if SNe Ia are to become more precise cosmic probes. No progenitor system has ever been identified either in the pre- or post-explosion images of a Ia event. There have been recent claims for and against the detection of ex-companion stars in several SNe Ia remnants. These studies, however, usually ignore the angular momentum gain of the progenitor WD, which leads to a spin-up phase and a subsequent spin-down phase before explosion. For spin-down timescales greater than 10^5 years, the donor star could be too dim to detect by the time of explosion. Here we revisit the current limits on ex-companion stars to SNR 0509-67.5, a 400 year old remnant in the Large Magellanic Cloud (LMC). If the effects of possible angular momentum gain on the WD are included, a wide range of single-degenerate progenitor models are allowed for this remnant. We demonstrate that the current absence of evidence for ex-companion stars in this remnant, as well as other SNe Ia remnants, does not necessarily provide the evidence of absence for ex-companions. We discuss potential ways to identify such ex-companion stars through deep imaging observations.