The following document lists the file abstract/RWATERS_REDRECT2.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
===================================================================== ==> In this proposal, more time is being requested for RWATERS.REDRECT ===================================================================== The Red Rectangle (RR) nebula is the proto-type of a class of carbon-rich proto-planetary nebulae. The central star HD 44179 is a cool post-asymptotic giant branch star, and is also member of a wide binary system (Porb = 318 days). This system is surrounded by a circum-binary disk, which is optically thick at optical and near-IR wavelengths and which we see edge-on. It is a very well studied object, because of its brightness and the prominent carbon-rich UIR dust features, usually attributed to Polycyclic Aromatic Hydrocarbons (PAHs). Surprisingly, ISO-SWS observations have revealed a prominent oxygen-rich component in the circumstellar environment of the RR. We have discovered strong emission from crystalline silicates longward of 20 microns, and absorption from gas-phase CO2 at 4.27 and 15.3 microns. Also, we have found emission from 12CO and 13CO at 4.66 microns. Ground-based narrow-band IR images reveal that the carbon rich dust is predominantly located in the bipolar outflow, which leaves the circum-binary disk for the location of the oxygen-rich material. This is in accordance with the gas phase CO2 absorption we found at 4.27 and at 15.3 micron. The observations are consistent with an evolutionary scenario in which the more massive star of the system evolved to the AGB, and by wind interaction or roche lobe overflow created an oxygen-rich stationary circum-binary disk. The AGB star subsequently evolved to the C-rich phase and created the C-rich bipolar nebula.