A proper description of clumping in hot star winds: the key to obtaining reliable mass-loss rates?

Jon O. Sundqvist (1), Joachim Puls (1), Achim Feldmeier (2), and Stanley P. Owocki (3)

1 - University Observatory Munich, Germany; 2 - Institute for physics and astronomy, Potsdam-Golm, Germany; 3 - University of Delaware, Bartol Research Institute, Newark, USA

Small-scale inhomogeneities, or `clumping', in the winds of hot, massive stars are conventionally included in spectral analyses by assuming optically thin clumps. To reconcile investigations of different diagnostics using this microclumping technique, very low mass-loss rates must be invoked for O stars.
Recently it has been suggested that by using the microclumping approximation one may actually drastically underestimate the mass-loss rates. Here we demonstrate this, present a new, improved description of clumpy winds, and show how corresponding models, in a combined UV and optical analysis, can alleviate discrepancies between previously derived rates and those predicted by the line-driven wind theory.
Furthermore, we show that the structures obtained in time-dependent, radiation-hydrodynamic simulations of the intrinsic line-driven instability of such winds, which are the basis to our current understanding of clumping, in their present-day form seem unable to provide a fully self-consistent, simultaneous fit to both UV and optical lines. The reasons for this are discussed.

Reference: 5 pages, 2 figures, to appear in the proceedings of 39th Liege International Astrophysical Colloquium on 'The multi-wavelength view of hot, massive stars', Liege, 12-16 July 2010
Status: Manuscript has been accepted

Weblink: http://arxiv.org/abs/1010.3987


Email: jon@usm.uni-muenchen.de