Publications
of the
MPIfR Optical & Infrared Interferometry Group
Ohnaka,
K., Beckmann, U., Berger. J.-P.,
Brewer,
M.K.,
Hofmann, K.-H., Lacasse, M.G., Malanushenko, V., Millan-Gabet, R.,
Monnier,
J.D., Pedretti, E., Schertl, D., Schloerb, F.P., Shenavrin, V., Traub,
W.
A., Weigelt, G., and Yudin, B.
IOTA observations of the circumstellar envelope of R CrB
in: W.A. Traub
(ed.),
Interferometry for Optical Astronomy II, SPIE Conf. Vol. 4838
(2003)
Abstract.
We report the first long-baseline interferometric observations of R
CrB. The
observations were carried out at the Infrared Optical Telescope Array
(IOTA),
using our new JHK beam combiner which enables us to record fringes
simultaneously
in the J-, H-, and K-bands. The circumstellar envelope of R CrB is
resolved
at a baseline of 21 m, and the K-band visibility is derived to be 0.61
+/-
0.03 along a position angle of about 170 degrees. The visibility
obtained
with IOTA, as well as speckle visibilities with baselines up to 6 m and
the
spectral energy distribution (SED), are fitted with 2-component models
consisting
of the central star and an optically thin dust shell. The K-band
visibilities predicted by the models are about 10% smaller than the
visibility obtained
with IOTA. However, given the simplifications adopted in our models and
the
complex nature of the object, this can be regarded as rough agreement.
As
a hypothesis to explain the small discrepancy, we propose that there
might
be a group of newly formed dust clouds, which might appear as a third
visibility
component.
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