The enigmatic central star of the planetary nebula PRTM 1
  The central star of the planetary nebula PRTM 1 (PN G243.8-37.1) was
previously found to be variable by M. Pena and colleagues. As part of a larger
programme aimed towards finding post common-envelope binary central stars we
have monitored the central star of PRTM 1 spectroscopically and photometrically
for signs of variability. Over a period of ~3 months we find minimal radial
velocity (<10 km/s) and photometric (< 0.2 mag) variability. The data suggest a
close binary nucleus can be ruled out at all but the lowest orbital
inclinations, especially considering the spherical morphology of the nebula
which we reveal for the first time. Although the current data strongly support
the single star hypothesis, the true nature of the central star of PRTM 1
remains enigmatic and will require further radial velocity monitoring at higher
resolution to rule out a close binary. If in the odd case that it is a close
binary, it would be the first such case in a spherical planetary nebula, in
contradiction to current thinking.
