Velocity Law in the Extended Photosphere of the WN5 Star in the Eclipsing Binary V444 Cygni

An algorithm for the solution of Fredholm's equations of the first kind describing light curves of WR + O binary systems on a set of nonnegative monotonically decreasing convex functions is developed. The algorithm is applied to the narrow-band continuum The λ4244 Ålight curve of the eclipsing binary V444 Cygni (WN5 + O6). Reliable information about the distribution of the linear absorption coefficientα (r) and the velocity law in the extended photosphere of the WN5 star is obtained from the analysis. Recent accurate spectrophotometric estimate of the luminosity ratio of the components in the binary was used to establish the relationship between the two geometrical parameters of the model: the radius of the O6 star and the orbital inclination. It is shown that the flow of matter in the WN5 photosphere is accelerating and that the value of the acceleration is relatively low. The expansion velocity at the distance r ? 3.8R _⊙ (at which_τ4244(r) ? 1) reaches a few hundreds km/s, i.e., the flow at this point is supersonic.