Publications
of the
MPIfR
Optical & Infrared
Interferometry Group
T. Blöcker, K.-H. Hofmann, G. Weigelt
and Y. Balega:
Bispectrum speckle interferometry
observations and radiative transfer models
of the red supergiant NML Cyg
Abstract (poster) for:
Astronomische Gesellschaft Meeting Abstracts (AGM 15, P26)
New Astrophysical
Horizons
Annual Scientific Meeting of the Astronomische Gesellschaft, Sep 21-25,
1999, Göttingen, Germany
Abstract.
The star NML Cyg is one of the most prominent infrared objects of the
northern hemisphere. It was discovered by Neugebauer,
Martz & Leighton (1965) as an extremely red object. NML Cyg is a
highly
evolved OH/IR supergiant of very large luminosity
(spectral type M6 I) which suffers from an enormeous mass-loss
(1.5x10^-4 Msol/yr) and is highly enshrouded by
dust. It is supposed to be among the most luminous supergiants
(5x 10^5 Lsol) in the Galaxy.
We present the first diffraction-limited 2.13µm observations of NML Cyg
with 73 mas resolution. The speckle interferograms
were obtained with the 6 m telescope at the Special Astrophysical
Observatory. The two-dimensional power spectra show an
extended nebula. There is only marginal evidence for deviations from
spherical symmetry. The visibility function declines towards
the diffraction limit to 0.6.
We performed radiative transfer calculations assuming sphercial
symmetry to model the spectral energy distribution and 2.13µm
visibility function. Additionally we consider mid-infrared visibility
functions recently published by Monnier et al. (1997). The
observed dust shell properties do not appear to be in accordance with
standard single-shell models (uniform outflow) but seem to
require multiple components.
You can get this publication ...