Vol. 573
In section 8. Stellar atmospheres

V444 Cygni X-ray and polarimetric variability: Radiative and Coriolis forces shape the wind collision region

Colliding winds have almost become a vogue in studies of massive binaries and none are better documented than those for the WN+O star binary V444 Cyg. The authors present a comprehensive, multiwavelength picture of the system's behavior including phase-resolved X-ray and optical spectrophotometry. A particularly novel feature of the study is their use of optical spectropolarimetry to constrain the scattering geometry. Then using hydrodynamic modeling they determine the respective roles of radiative braking on the structure of the standing shock, and the phase distortions of the variations due to the dynamics. They also constrain the soft X-ray emission to be beyond the substellar collision point.