Post-common envelope PN, fundamental or irrelevant?
  One in 5 planetary nebulae are ejected from common envelope binary interactions but Kepler Space Telescope results are already showing this proportion to be larger. Their properties, such as abundances can be starkly different from those of the general population, so they should be considered separately when using PN as chemical or population probes. Unfortunately post-common envelope PN cannot be discerned using only their morphologies, but this will change once we couple our new common envelope simulations with PN formation models. 
Orsola De Marco, T. Reichardt, R. Iaconi, T. Hillwig, G. H. Jacoby, D.   Keller, R. G. Izzard, J. Nordhaus, E. G. Blackman
astro-ph.SR