CLUMPING AND MASS-LOSS IN HOT STAR WINDS

We construct a simple model for the continuum free-free or subordinate line emission from Wolf-Rayet star winds, in which full-scale, compressible, supersonic turbulence is assumed to prevail. Based on observed properties of the turbulent eddies with extrapolation by analogy with Giant Molecular Clouds, such clumpy winds could lead to a decrease in the estimate of the mass-loss I ate by a factor greater than or similar to 3 compared to homogeneous winds of the same free-free or subordinate line flux. Clumping may be important in all hot stars with winds. In the particular case of the key eclipsing WR+O binary V444 Cygni, the observed difference between the higher values of M traditionally found from the radio free-free emission or the recombination flux of He I 1.08 mu m assuming homogeneity, and the lower hi values from dynamical arguments or polarimetry is found to be a factor greater than or similar to 3, in agreement with the above turbulence-based factor. The former methods depend on the square of the density and hence are sensitive to clumping effects, while the latter methods are impervious to density fluctuations and are considered more reliable.