PI: Howard E. Bond, Space Telescope Science Institute, firstname.lastname@example.org
Address: 3700 San Martin Drive, Baltimore, MD 21218, USA
CoI: Orsola De Marco, American Museum of Natural History
CoI: Dianne Harmer, NOAO
Title: Are All Planetary Nebulae Ejected from Binary Stars?
Abstract: For the past 2 years, we have used the WIYN Hydra spectrograph to search for radial-velocity (RV) variations among planetary-nebula nuclei (PNNi). Our aim was to find spectroscopic binaries with periods of several days to weeks. This program has been very successful: 10 out of 11 PNNi were found to have variable RVs. Combined with the fact that ~10% of PNNi were already known to be very short-period binaries (as shown by photometric variations), it now seems possible that most or even all planetary nebulae (PNe) are ejected from binary systems. However, we have not been able to determine definitive orbital periods for any of our WIYN RV variables, because the RV amplitudes are low, and the WIYN scheduling was optimized to find long periods, whereas it appears that the periods of our candidates are actually fairly short. It thus remains conceivable that we are actually observing some other phenomenon, such as variability in stellar-wind profiles, that mimics RV variations. We now propose an alternative approach in which we intensively monitor our candidates for 5 consecutive nights, using the highest spectral resolution available at KPNO, in order to determine high-accuracy RVs and orbital periods, or possibly reveal changes in line profiles characteristic of wind variability. Our program bears on the questions of the origin of compact binaries, the shaping of PNe, and whether single stars produce visible PNe at all.
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