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Astron. Astrophys. 357, 169-176 (2000)


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The dynamical evolution of the fragmented, bipolar dust shell around the carbon star IRC +10 216 *

Rapid changes of a PPN-like structure?

R. Osterbart 1, Y.Y. Balega 2, T. Blöcker 1, A.B. Men'shchikov 1,3 and G. Weigelt 1

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany (osterbart@mpifr-bonn.mpg.de; bloecker@mpifr-bonn.mpg.de; weigelt@mpifr-bonn.mpg.de)
2 Special Astrophysical Observatory, Nizhnij Arkhyz, Karachaevo-Cherkesia, 357147, Russia (balega@sao.ru)
3 Stockholm Observatory, 133 36 Saltsjöbaden, Sweden (sasha@astro.su.se)

Received 16 June 1999 / Accepted 26 January 2000

Abstract

We present high-resolution J-, H-, and K-band observations and the first [FORMULA] color image of the carbon star IRC +10 216. The images were reconstructed from 6 m telescope speckle interferograms using the bispectrum speckle interferometry method. The H and K images with resolutions between 70 mas and 92 mas consist of several compact components within a [FORMULA] radius and a fainter asymmetric nebula. The brightest four components are denoted with A to D in the order of decreasing brightness in the 1996 image. A comparison of our images from 1995, 1996, 1997, and 1998 gives - almost like a movie of five frames - insight into the dynamical evolution of the inner nebula. For instance, the separation of the two brightest components A and B increased from 191 mas in 1995 to 265 mas in 1998. At the same time, component B is fading and the components C and D become brighter. The X -shaped bipolar structure of the nebula, most prominently present in the J-band image, implies an asymmetric mass-loss. Such asymmetries are often present in protoplanetary nebulae but are unexpected for AGB stars. IRC +10 216 is thus likely to be very advanced in its AGB evolution, shortly before turning into a protoplanetary nebula. The cometary shapes of A in the H and J images and in the 0.79 µm and 1.06 µm HST images suggest that the core of A is not the central star, but the southern lobe of a bipolar structure. The position of the central star is probably at or near the position of component B, where the [FORMULA] color has a value of 4.2. If the star is at or near B, then the components A, C, and D are likely to be located at the inner boundary of the dust shell.

Key words: techniques: image processing – stars: carbon – stars: circumstellar matter – stars: individual: IRC +10 216 – stars: mass-loss – stars: AGB and post-AGB

* based on observations performed with the 6 m telecope at the Special Astrophysical Observatory, Russia

Send offprint requests to: G. Weigelt

© European Southern Observatory (ESO) 2000

Online publication: May 3, 2000

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