1998A&A...333..956N

Mass-loss rates of Galactic Wolf-Rayet stars have been determined from their radio emission power and spectral index (α= dln(f_ν)/dln(ν)), accounting for the clumped structure and (potential) variable ionization in their outer winds. The average spectral index between mm- and cm- wavelengths is ∼0.77 for WN stars and ∼0.75 for WC stars, in contrast with ∼0.58 expected for smooth winds. The observed wavelength dependence of α can be explained using clumped wind models in some cases, with shocks (at 30-100 stellar radii) producing a higher ionization zone in the outer wind. We obtain an empirical formula relating mass-loss with observed optical emission line equivalent widths, with application to stars without measured radio fluxes. Clumping-corrected mass-loss rates are generally lower than those obtained by current smooth wind models. Specifically we find log{dot}(M)(clumpy)-log{dot}(M)(smooth)=-0.19 (σ=0.28) for WN stars, and log{dot}(M)(clumpy)-log{dot}(M)(smooth)=-0.62 (σ=0.19) for WC stars. New mass-loss rate estimates agree very well with (clumping independent) determinations of WR components in binary systems.