TC Hillwig,
DJ Frew, N Reindl, H Rotter… - The Astronomical …, 2016 - iopscience.iop.org
We find the central stars (CSs) of the planetary nebulae (PNe) HaTr 7 and ESO 330-9 to be
close-binary systems. Both have orbital periods of less than half a day and contain an …