Visual Wide Binaries and the Structure of Planetary Nebulae

In a recent work Ciardullo et al. (1999) list 19 planetary nebulae surveyed by the Hubble Space Telescope for the presence of resolved visual binary companions of their central stars. For ten 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 non-axisymmetrical signatures. 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 Ciardullo et al.'s arguments for an association, or not, of the resolved stars with the planetary nebulae central stars. This shows that the departure, or not, of a planetary nebula from having pure axisymmetrical structure can be used to strengthen an argument for an association, or a non-association, of a putative wide companion with the stellar progenitor of the nebula.