Early-type stars

Although most current radiative-hydrodynamical models of stellar wind driving assume spherical symmetry, homogeneity, and time-independence, it is clear that all of these assumptions are flawed. This is significant, because gross departures from symmetry (e.g. disks, plumes) and clumpiness increase the wind-clumping factor, producing more recombinations per unit mass of wind than that expect for a smooth, spherical wind. Hence when we measure mass-loss (generally via recombination lines or free-free in the radio) we are at risk of overestimating the mass-loss rate.

	The image to the right shows electron-scattering optical depth for an O-supergiant whose wind is distorted by three spiral structures. The image is linked to a movie showing how the spiral structures rotate with the photosphere.
	A similar image showing how a clumpy wind might look. The image is linked to an mpeg movie showing how the clumps accelerate out into the wind.