Talk abstract details

AGB stars appear to lose mass spherically, but many PNe that result from the mass-loss have non-spherical morphologies, often with highly collimated sub-structures. Compact disks have been found in some bipolar PNe but their role in the axis-symmetrical shaping process remains unknown. At the cooler end of the AGB-PN transition, compact Keplerian disks are found to be common in post-AGB binaries. However, generally no resolved nebulae are found in these systems, so these objects may never develop into PNe. Another group of post-AGB stars, pre-PNe, actually have collimated nebulae shining by reflected light or shock ionisation. It is unknown why some, otherwise similar, post-AGB stars have resolved nebulae while others do not. The nebulae in pre-PNe are very similar to young PNe and are extremely likely to be their immediate predecessors. We are observing the inner circumstellar regions of pre-PNe at very high angular resolutions with the Very Large Telecsope Interferometer (VLTI). We seek to determine whether pre-PNe have disks similar to PNe. We wish to understand the potential link between disks observed in young PNe, the asymmetries observed in PNe, and the disks around binary post-AGB stars with no nebulae.