2001A&A...379..229Y -
Astronomy and Astrophysics, volume 379, 229-234 (2001/11-3)
Speckle interferometry and radiative transfer modelling of the Wolf-Rayet star WR 118.
YUDIN B., BALEGA Y., BLOECKER T., HOFMANN K.-H., SCHERTL D. and WEIGELT G.
Abstract (from CDS):
object{WR 118} is a highly evolved Wolf-Rayet star of the WC10 subtype surrounded by a permanent dust shell absorbing and re-emitting in the infrared a considerable fraction of the stellar luminosity. We present the first diffraction-limited 2.13µm speckle interferometric observations of
WR 118 with 73mas resolution. The speckle interferograms were obtained with the 6m telescope at the Special Astrophysical Observatory. The two-dimensional visibility function of the object does not show any significant deviation from circular symmetry. The visibility curve declines towards the diffraction cut-off frequency to ∼0.66 and can be approximated by a linear function. Radiative transfer calculations have been carried out to model the spectral energy distribution, given in the range of 0.5-25µm, and our 2.13µm visibility function, assuming spherical symmetry of the dust shell. Both can be fitted with a model containing double-sized grains (``small'' and ``large'') with the radii of a=0.05µm and 0.38µm, and a mass fraction of the large grains greater than 65%. Alternatively, a good match can be obtained with the grain size distribution function n(a)∼a
–3, with a ranging between 0.005µm and 0.6µm. At the inner boundary of the modelled dust shell (angular diameter Θ
in=(17±1)mas), the temperature of the smallest grains and the dust shell density are 1750K±100K and (1±0.2)x10
–19g/cm
3, respectively. The dust formation rate is found to be (1.3 ±0.5)x10
–7M
☉/yr, assuming V
wind=1200km/s.
Abstract Copyright:
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Journal keyword(s):
techniques: image processing - circumstellar matter - stars: individual: WR 118 - stars: mass-loss - stars: Wolf-Rayet - infrared: stars
Simbad objects:
6
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