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R. Osterbart, T. Blöcker, G. Weigelt,
Y. Balega and A.B. Men'shchikov:
The dynamical evolution of the fragmented,
bipolar dust shell around the carbon star IRC+10216
Abstract (poster) for:
Astronomische Gesellschaft Meeting Abstracts (AGM 15, P27)
New Astrophysical
Horizons
Annual Scientific Meeting of the Astronomische Gesellschaft, Sep 21-25,
1999, Göttingen, Germany
Abstract.
We present high-resolution J-, H-, and K-band observations and the
first H-K
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
image has the unprecedented resolution of 70 mas. The H and K images
consist
of several compact components within a 0.2'' radius
and a fainter asymmetric nebula. A comparison of our images from 1995,
1996,
1997, and 1998 gives - almost like a movie of five
frames - spectacular insight to 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 0.79µm and
1.06µm
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. 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.
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