Using Kepler to measure the binary fraction of planetary nebula central stars

The Kepler Observatory offers unprecedented photometric precision (<1 mmag) and cadence for monitoring the central stars of planetary nebulae (CSPN), allowing the detection of tiny light curve variations, a possible signature of binarity. With these precisions free from the observational gaps dictated by weather and lunar cycles, we are able to detect CSPN companions at much larger separations, with much smaller masses, and much longer periods than ever before. We have been awarded targeted observing time to obtain light-curves of the four known CSPN, plus one possible PN, plus one newly discovered PN in the Kepler field at cadences of both 30 min and one min for each of these CSPN. Five of the six objects have preliminary data. They are all periodic variables, although for two of them with the smallest amplitudes, the uncertainties are large. Preliminary analysis indicates that the periods span a range of 0.2 to 3.0 days, while the amplitudes lie between 0.002 and 0.050 mags. Only one of these objects would have been identified as variable in a typical ground-based program.