NGC 6778: a disrupted planetary nebula around a binary central star
  The planetary nebula (PN) NGC 6778 harbors a binary central star with a short
orbital period and displays two systems of fast collimated outflows. In order
to assess the influence of the evolution through a common-envelope phase of the
binary system of NGC 6778 on its formation and shaping, we have used
narrow-band images and high-dispersion long-slit spectra of the nebula to
investigate its detailed morphology and kinematics. We find that the overall
structure of NGC 6778 can be described as a bipolar PN. The equatorial ring is
highly disrupted and many radial features (filamentary wisps and cometary
knots) also evidence strong dynamical effects. There are clear connections
between the bipolar lobes and the fast collimated outflows: the collimated
outflows seem to arise from bright knots at the tips of the bipolar lobes,
whereas the kinematics of the bipolar lobes is distorted. We suggest that the
interaction of the fast collimated outflows of NGC 6778 with its nebular
envelope has resulted in the disruption of the nebular shell and equatorial
ring.
