STRUCTURED STELLAR WINDS

There are various, but indirect evidences that the radiation-driven winds from hot stars (O-type and WolfRayet) are not homogeneous. Clumping is discussed as an example that aects the integrated spectra, and thus the mass-loss diagnostics. To resolve structured winds, interferometers might be the currently best tools. 1. STELLAR WINDS - INTRODUCTION Observational indications for structured stellar winds are found from line prole variations such as discrete absorption components (Prinja & Howarth 1988, DACs) in O star spectra and discrete wind emission elements (DWEEs) in Wolf-Rayet (WR) star spectra (Moat et al. 1988; Lepine & Moffat 1999). They are thought to be connected with co-rotating interactive regions embedded within the stellar wind. In WR spectra, emission line wings from Thomson scattering by free electrons in the stellar wind show a weakness that can only be reproduced by stellar model atmospheres if small-scale wind inhomogeneity, i.e. \clumping", is taken into account.