  We have obtained X-ray observations of the bipolar planetary nebulae (PNe)
NGC 2346 and NGC 7026 with XMM-Newton. These observations detected diffuse
X-ray emission from NGC 7026 but not from NGC 2346. The X-ray emission from NGC
7026 appears to be confined within the bipolar lobes of the PN and has spectral
properties suggesting a thermal plasma emitting at a temperature of 1.1
+0.5/-0.2 times 10^6 K. The X-ray spectrum of NGC 7026 is modeled using nebular
and stellar abundances to assess whether a significant amount of nebular
material has been mixed into the shocked-wind, but the results of this
comparison are not conclusive owing to the small number of counts detected.
Observations of bipolar PNe indicate that diffuse X-ray emission is much less
likely detected in open-lobed nebulae than closed-lobed nebulae, possibly
because open-lobed nebulae do not have strong fast winds or are unable to
retain hot gas.
