Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
Figure 1:
Two consecutive interferograms of R CrB. The fringes are
spectrally dispersed in the horizontal direction and are recorded
simultaneously in the J, H, and
bands,
as shown in each panel.
These three bands are separated by telluric absorption, which can be
seen as vertical dark lanes between the J and H bands
as well as between the H and
bands.
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.I., Traub, W.A., Weigelt, G., Yudin, B.F.
JHK'-band IOTA interferometry of the
circumstellar environment of R CrB
Astronomy and Astrophysics, 408, 553(2003)
Abstract
We report the first long-baseline interferometry of the circumstellar
dust environment of R CrB. The observations were carried out with the
Infrared Optical Telescope Array (IOTA), using our new JHK' beam
combiner which enables us to record fringes in the J, H, and K' bands
simultaneously. The circumstellar dust envelope of R CrB is resolved at
a baseline of 21 m along a position angle of ~ 170 degrees, and the
visibilities in the J, H, and K' bands are 0.97 +- 0.06, 0.78 +- 0.06,
and 0.61 +- 0.03, respectively. These observed visibilities, together
with the K'-band visibility obtained by speckle interferometry with
baselines of up to 6 m, and the spectral energy distribution are
compared with predictions from spherical dust shell models which
consist of the central star and an optically thin dust shell. The
comparison reveals that the observed J- and H-band visibilities are in
agreement with those predicted by these models, and the inner radius
and inner boundary temperature of the dust shell were derived to be 60
-- 80~Rstar and 950 -- 1050 K, respectively. However, the predicted
K'-band visibilities are found to be ~ 10% smaller than the one
obtained with IOTA. Given the simplifications adopted in our models and
the complex nature of the object, this can nevertheless be regarded as
rough agreement. As a hypothesis to explain this small discrepancy, we
propose that there might be a group of newly formed dust clouds, which
may appear as a third visibility component.
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