Astron. Astrophys. 322, 868-877 (1997)

Dust envelope modelling of the Red Rectangle nebula

Bruno Lopez ¹, Eric Tessier ², Pierre Cruzalèbes ³, Jean Lefèvre ¹ and Thibaut Le Bertre <sup>4

1</sup> Observatoire de la Côte d'Azur, Département Fresnel UMR 6528, BP 4229, F-06034 Nice Cedex 4, France
² Groupe d'Astrophysique, Observatoire de Grenoble, Université Joseph-Fourier, BP 53X, F-38041 Grenoble Cedex, France
³ Observatoire de la Côte d'Azur, Département Fresnel UMR 6528, Av. Copernic, F-06130 Grasse, France
⁴ DEMIRM, Observatoire de Paris, 61 av. de l'Observatoire, F-75014 Paris, France

Received 9 July 1996 / Accepted 5 December 1996

Abstract

Radiative transfer modelling of the dust shell of the post-AGB Red Rectangle nebula is proposed in non-spherical geometry. The present work follows a previous study by Yusef-Zadeh et 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 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 assuming a distance of 330 pc for the Red Rectangle (Cohen et al. 1975).

Key words: radiative transfer stars: individual: HD 44179 circumstellar matter

Send offprint requests to: Bruno Lopez

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Contents

• 1. Introduction
  • 1.1. General aspects of the Red Rectangle
  • 1.2. Our goal
• 2. Appearance of the Red Rectangle in the infrared
• 3. Observational constraints used for the Red Rectangle modelling
• 4. The radiative transfer code
• 5. The models
  • 5.1. Results and validity for the unique grain size modelling
  • 5.2. Modelling with a grain size distribution
• 6. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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