Imaging and spectroscopy of ejected common envelopes --

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Abstract
Imaging and spectroscopy are presented for four planetary nebulae known to contain close binary central stars resulting from a recent phase of common-envelope evolution. All the objects appear to exhibit axisymmetric nebulae which may be interpreted as inclined bipolar nebulae. In at least one object the bipolar caps can be seen, demonstrating the tightly collimated nature of the PN having an aspect ratio of ∼7. Determinations of the nebular abundances show that He is significantly enhanced in all of the objects. These results are in agreement with theoretical expectations. Uncertainties in the nebular electron temperature constrain other abundances less well. The line fluxes indicate that N is unexpectedly underabundant. This effect is probably not real and may be an artefact of electron temperature fluctuations within the nebulae.

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