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O. De Marco (Amrican Museum of Natural History), H.E. Bond (Space Telescope Science Institute), D. Harmer (National Optical Astronomy Observatories), A.J. Fleming (Michigan Technological University)
About 10% of planetary-nebula nuclei (PNNi) are very close binaries with periods of a few hours to a few days, which have been found through photometric monitoring. In order to search for longer-period binary PNNi, with periods of a few weeks to a few months, which are expected from population-synthesis studies, we have begun a radial-velocity (RV) monitoring survey with the 3.5-m WIYN telescope at Kitt Peak. The Hydra spectrograph yields a precision of ~5kms. Of the 15 PNNi for which we have sufficient observations, 6 show definite RV changes and 2 more are probably variable. Although we cannot as yet obtain the variability periods due to the sub-optimal sampling of the observations, we are reasonably confident that these variations are due to binary motion and not to wind variability. Our results, along with the prevalence of axisymmetric morphologies among PNe, suggest that binary-star processes play a major role in the ejection and shaping of PNe.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.