PI: Howard E. Bond, Space Telescope Science Institute, email@example.com
Address: 3700 San Martin Dr., Baltimore, MD 21218, USA
CoI: Orsola De Marco, American Museum of Natural History
CoI: Diane Harmer, Kitt Peak National Observatory
Title: Searching for Spectroscopic Binaries in Planetary Nebulae
Abstract: There are increasing indications that binary-star processes are intimately related to the ejection of many, or possibly even most, planetary nebulae (PNe). The evidence includes: the fact that ~10% of PN nuclei are found to be very close binaries (periods of hours to a few days) through photometric monitoring; population- synthesis studies suggesting that these may be just the short-period tail of a much larger binary population extending up to orbital periods of several months; and the prevalence of highly non-spherical morphologies among PNe. The photometric search technique does not work for binaries in PNe with periods of more than a few days, since it relies on proximity effects. We therefore propose to carry out radial-velocity monitoring of a sample of relatively bright PN nuclei, in order to search for the anticipated population of binaries with periods up to a few months. If they do exist, there will be new implications for the evolution of binary populations, the origin of compact binaries (CVs, SN Ia progenitors), and even the question whether single stars can produce visible ionized PNe at all. This program was started in 2002B, but we have been plagued with very bad weather and some instrument problems. Nevertheless, about 50% of the small number of targets we were able to observe had clearly variable radial velocities, thus demonstrating the promise of our program and the potential impact on our understanding of the PN phenomenon. However, it will take additional observations for us to have robust statistics, and to determine orbital periods needed to show conclusively that the velocity variations are due to binary motion.
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