July 11-15, 2011
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The nature of clumping in hot star winds and its consequences

Jon Sundqvist (University of Delaware)

Stan Owocki, Delaware, Joachim Puls, Munich

Winds from hot, massive stars are well described by line-driven wind theory. While initial models assumed a stationary, smooth, and spherically symmetric outflow, over the years there has amassed extensive theoretical as well as observational evidence that these winds are inherently inhomogeneous and time-dependent. This talk first reviews the origin and nature of the strong line de-shadowing instability, intrinsic to the driving of these winds. We next examine the consequences of the predicted structure in density and velocity, focusing on how to properly account for such wind clumping in the diagnostic tools needed to interpret observed stellar spectra, from the X-ray to the radio regime. By accounting, when necessary, for a non-monotonic velocity field and the effects of clumps of arbitrarily optical thickness (in contrast to the standard assumptions of a smooth velocity field and optically thin clumps), previous inconsistencies among empirical mass-loss rates derived from different wavelength bands may be resolved, and discrepancies between observed and theoretical rates can be alleviated. Finally, we discuss challenges that lie ahead in developing self-consistent, multi-dimensional radiation-hydrodynamic simulations to model the complex structure of hot, massive star winds.
(to be confirmed by the SOC)