The X-ray emission of the colliding wind binary V444 Cyg
Department of Astrophysics, Geophysics and Oceanography, University of Liège, Belgium
Department of Astrophysics, Geophysics and Oceanography, University of Liège, Belgium, and Observatoire de Haute-Provence, Saint-Michel l’Observatoire, France
Department of Astrophysics, Geophysics and Oceanography, University of Liège, Belgium
Abstract
This paper presents the analysis of six XMM-Newton observations of the colliding wind system V444 Cyg. Unlike what one might have expected at first, it appears that the O star wind most probably dominates the WN wind: the bow shock is wide open, with the hard X-ray emission arising close to the WN star. An important radiative braking could partly explain this situation but revising the wind parameters may also prove necessary. Furthermore, we have probably observed for the first time an occultation of the colliding wind zone by the binary components.