Dust envelope modelling of the Red Rectangle nebula

Radiative transfer modelling of the dust shell of the post-AGE Red Rectangle nebula is proposed in non-spherical geometry. The present work follows a previous study by Yusef-Zadeh el al. (1984) in which the dust density law smoothly decreases with latitude above and below the midplane of the disc shaped envelope, Our aim is to take account of new observational constraints in addition to those already imposed by the image of the nebula at visible wavelengths. The broad band spectrum is fitted. The infrared map at 2.2 mu m is also taken into account for our model. As a result of our study, we find that the best compromise in the choice of the model parameters leads to a dust density law which differs from the one proposed previously The temperature of the hottest grains is about 1000 K. Large dust particles are present in the circumstellar environment, the largest of these being probably confined to the plane of the disc. We estimate the dust shell mass to be about 3.8 x 10(-4)M(.) assuming a distance of 330 pc for the Red Rectangle (Cohen et al. 1975).