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Astron. Astrophys. 350, 120-128 (1999)

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The circumstellar envelope of AFGL 4106 *

J.Th. van Loon 1, F.J. Molster 1, H. van Winckel 2 and L.B.F.M. Waters 1,3

1 Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
2 Institute of Astronomy, Catholic University of Leuven, Celestijnenlaan 200B, B-3001 Heverlee, Belgium
3 Space Research Organization Netherlands, Landleven 12, 9700 AV Groningen, The Netherlands

Received 17 May 1999 / Accepted 30 June 1999


We present new imaging and spectroscopy of the post-red supergiant binary AFGL 4106. Coronographic imaging in H[FORMULA] reveals the shape and extent of the ionized region in the circumstellar envelope (CSE). Echelle spectroscopy with the slit covering almost the entire extent of the CSE is used to derive the physical conditions in the ionized region and the optical depth of the dust contained within the CSE.

The dust shell around AFGL 4106 is clumpy and mixed with ionized gas. H[FORMULA] and [N II ] emission is brightest from a thin bow-shaped layer just outside of the detached dust shell. On-going mass loss is traced by [Ca II ] emission and blue-shifted absorption in lines of low-ionization species. A simple model is used to interpret the spatial distribution of the circumstellar extinction and the dust emission in a consistent way.

Key words: stars: binaries: spectroscopic – stars: circumstellar matter – stars: individual: AFGL 4106 – stars: mass-loss – stars: AGB and post-AGB – stars: supergiants

* Based on observations obtained at the European Southern Observatory, La Silla, Chile

Send offprint requests to: Jacco Th. van Loon (jacco@ast.cam.ac.uk)

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© European Southern Observatory (ESO) 1999

Online publication: September 24, 1999