AAS 195th Meeting, January 2000
Session 76. Geometrically Variable Stars
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[76.08] Polarization Variability of the Massive Binary System: V444~Cyg

R. Kurosawa, D. J. Hillier (U. Pittsburgh)

We present preliminary results of a 3D Monte Carlo polarization calculation for the binary system V444~Cyg which contains a WN5 Wolf-Rayet (W-R) star and an O6 star. V444~Cyg exhibits variability in polarization, line strength and X-ray flux as a function of its phase. This variability arises from occultation of the photospheres, from perturbations induced in the extended atmosphere of the W-R star by the O star and its wind, and from the wind-wind interaction region. In order to disentangle the complicated variability, we are using Monte Carlo simulations to model the line and continuum polarization as a function of phase. Later we also intend to model the line profile variability as a function of phase. This modeling will allow us to probe the structure of the wind of the W-R star, and the structure of the wind-wind interaction region.

Initially we are concentrating on interpreting the continuum polarization observations. This will provide an estimate of the mass-loss from the W-R star independent of the effects of clumping in its wind. With a complicated density distribution, a Monte Carlo simulation provides the only realistic method to predict variability in polarization, continuum flux and line strength. For the density structure we use either a semi-analytical density distribution, or the density distribution obtained from recent 3D hydrodynamical calculations of the V444 system by Pittard and Stevens (1999). Our modeling will thus provide important feedback on 3D hydrodynamical simulations. In addition, our modeling will allow us to identify variability signatures that can be used as probes of the colliding winds.

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