Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
G. Weigelt, Y.Y. Balega, T. Blöcker,
K.-H. Hofmann, A.B. Men'shchikov, J.M. Winters:
Bispectrum speckle interferometry of
IRC+10216:
the dynamic evolution of the innermost circumstellar environment from
1995 to 2001
Astronomy and Astrophysics 392, 131 (2002)
Abstract.
We present new
near-infrared (JHK) bispectrum speckle-interferometry monitoring
of the carbon star IRC+10216 obtained between 1999 and 2001
with the SAO 6m telescope.
The J-, H-, and K-band resolutions are
50mas, 56mas, and 73mas, respectively.
The total sequence of K-band observations covers now 8 epochs
from 1995 to 2001
and shows the dynamic evolution of the inner dust shell.
The present observations show that the appearance of the dust shell
has considerably changed compared to the epochs of 1995 to 1998.
Four main components within a 0.2" radius can be identified
in the K-band images.
The apparent separation of the two
initially brightest components A and B increased
from ~191mas in 1995 to ~351mas in 2001.
Simultaneously, component B has been fading and almost disappeared in
2000
whereas the initially faint components C and D became brighter
(relative to
peak intensity).
The changes of the images can be related to changes of the optical
depth
caused, for instance, by mass-loss variations or new dust condensation
in the
wind. Our recent two-dimensional radiative transfer model of
IRC+10216 suggests that the observed relative motion of
components A and B is not consistent with the outflow of gas and dust
at the
well-known terminal wind velocity of 15 km/s. The apparent motion with
a deprojected velocity of 19 km/s on average and of recently
27 km/s appears to be
caused by a displacement of the dust density peak due to dust
evaporation in the optically thicker and hotter environment.
The present monitoring, covering more than 3 pulsation
periods, shows that the structural variations are not related to the
stellar pulsation cycle in a simple way.
This is consistent with the predictions of
hydrodynamical models that enhanced dust formation takes place on a
timescale
of several pulsation periods. The timescale of the fading of
component B can well be explained by the formation of new dust in the
circumstellar envelope.
You can get this publication ...