A Search for a Surviving White Dwarf Companion in SN 1006

TL;DR

This study used deep imaging to search for a surviving white dwarf companion in SN 1006, finding no such object and suggesting the companion may have been destroyed or is too dim to detect.

Contribution

The paper provides the deepest search to date for a white dwarf companion in SN 1006, setting new constraints on its possible properties and existence.

Findings

No white dwarf companion detected within the remnant

Any surviving white dwarf must be older than 10^8 years and very dim

Results support scenarios where the companion was destroyed or is undetectably cool

Abstract

Multiple channels have been proposed to produce Type Ia supernovae, with many scenarios suggesting that the exploding white dwarf accretes from a binary companion pre-explosion. In almost all cases, theory suggests that this companion will survive. However, no such companion has been unambiguously identified in ancient supernova remnants -- possibly falsifying the accretion scenario. Existing surveys, however, have only looked for stars as faint as $\approx 0.1 L_\odot$ and thus would have missed a surviving white dwarf companion. In this work, we present very deep DECAM imaging $(u, g, r, z)$ of the Type Ia supernova remnant SN 1006 specifically to search for a potential surviving white dwarf companion. We find no object within the inner third of the SN 1006 remnant that is consistent with a relatively young cooling white dwarf. We find that if there is a companion white dwarf, it must have formed long ago and cooled undisturbed for $> 10^8$ yr to be consistent with the redder objects in our sample. We conclude that our findings are consistent with the complete destruction of the secondary (such as in a merger) or an unexpectedly cool and thus very dim surviving companion white dwarf.