National Research Council of Canada. National Science Infrastructure
The Physics of Evolved Stars: A Conference Dedicated to the Memory of Olivier Chesneau, June 8–12, 2015, Nice, France
We have investigated pulsations and searched for binarity in 7 bright proto-planetary nebulae. All are found to pulsate, with dominant periods of 39−132 days. However, no strong evidence of binarity is found in any of them. This implies that any binary companion must have either a very long period (>30 yr) or low mass (<0.2 Msun). This appears to rule out Roche lobe overflow as a contribution to the shaping of the surrounding nebula.
The Physics of Evolved Stars: A Conference Dedicated to the Memory of Olivier Chesneau: 127–128.