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Paper: Structure in the Winds of OB Stars: Radio and Millimeter Observations
Volume: 361, Active OB-Stars: Laboratories For Stellar and Circumstellar Physics
Page: 186
Authors: Blomme, R.
Abstract: The thermal millimeter and radio continua of OB stars are formed in the stellar wind, at large distances from the surface (from ∼ 10 to ∼ 100 R*). Observations at these wavelengths therefore cover geometrical regions that cannot be studied in any other way. The continuum fluxes at long wavelengths are determined by both the mass-loss rate and by the structure that may be present. By using a range of wavelengths one can detect changes of structure with distance. We found evidence that the amount of structure decreases with distance in the stellar wind. The B0 supergiant ε Ori is an especially good example of a star showing this effect. Non-thermal radio fluxes were previously thought to be another indicator of structure in the stellar wind. The work of Van Loo et al. (2005) has shown, however, that these non-thermal radio emitters are most probably all colliding-wind systems. A preliminary reduction of recent millimeter observations of ζ Pup shows variability on the 19.6-hr period. If confirmed, this indicates that Corotating Interaction Regions are an important component of structure at distances beyond 10 R*.
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