Visual Wide Binaries and the Structure of Planetary Nebulae

Abstract

In recent work Ciardullo et al. listed 19 planetary nebulae surveyed by the Hubble Space Telescope for the presence of resolved visual binary companions of their central stars. For 10 planetary nebulae they argue for probable physical association of the resolved stars with the central stars, while for nine the association is less likely. Such stellar companions, at orbital separations of hundreds to thousands of astronomical units, will cause the structures of these planetary nebulae to possess a nonaxisymmetric signature. By using images from the literature of these 19 planetary nebulae, I demonstrate that the structures of the planetary nebulae are compatible in most cases with the arguments of Ciardullo et al. for association or nonassociation of the resolved stars with the planetary nebulae central stars. This shows that whether a planetary nebula departs from having purely axisymmetric structure can be used to strengthen an argument for an association or a nonassociation of a putative wide companion with the stellar progenitor of the nebula.