000002738 001__ 2738
000002738 005__ 20160701171710.0
000002738 037__ $$aASTROimport-895
000002738 100__ $$aHrivnak, B.
000002738 245__ $$aExpanding the Search for Spectroscopic Binaries in Proto-Planetary Nebulae
000002738 260__ $$c2014
000002738 520__ $$aBinaries are often invoked as a shaping mechanism for the asymmetrical shapes of planetary nebulae and proto-planetary nebulae (PPNe) - particularly those that are elliptical, bipolar, or point symmetric. To test this hypothesis, we have been carrying out radial velocity monitoring of a sample of PPNe. The results of an initial study of seven bright PPNe have been published, based primarily on our observations from 1991-1995 and 2007-2010 at the Dominion Astrophysical Observatory (Victoria, Canada). Six of the seven showed no long-term variations between the two time intervals while one, IRAS 22272+5435, gave evidence of a variation consistent with a P > 22 yr (Hrivnak et al. 2011, ApJ, 734, 25). All seven of these objects do show shorter-term pulsational variations, on the order of 35-130 day over a range of about 14 km/s (peak-to-peak). We have expanded this search in two ways. Firstly, we have increased the temporal baseline by continuing to monitor the bright seven objects in radial velocity and increased the sampling with the addition of observations from the Hermes spectrograph on the Mercator telescope (Canary Islands). This has resulted in a second object with possible long-term variability that may indicate a binary companion. Secondly, we have started to monitor three edge-on PPNe with near-infrared spectroscopy; the stars are hidden in visible light but seen in the near infrared. These should show the full orbital velocity if it exists. Observations were begun in 2010, primarily from the ESO-VLT. While the spectra are more complicated than expected, we have found tantalizing evidence for systematic velocity variations in one of these three. Preliminary results for both of these expanded studies were presented. The research is supported in part by a grant from the NSF to BJH (AST-1009974). 
000002738 700__ $$a Bohlender, D.
000002738 700__ $$a Kerber, F.
000002738 700__ $$a Lu, W.
000002738 700__ $$a Seifahrt, A.
000002738 700__ $$a Van de Steene, G.
000002738 700__ $$a Van Winckel, H.
000002738 773__ $$c39$$pAsymmetrical Planetary Nebulae VI Conference$$y2014
000002738 85642 $$ahttp://esoads.eso.org/abs/2014apn6.confE..39H
000002738 905__ $$apublished in
000002738 980__ $$aNONREF