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 kin d describing light curves of WR+O binary systems on a set of nonnegati ve monotonically decreasing convex functions is developed. The algorit hm is applied to the narrow-band continuum lambda 4244 Angstrom, light curve of the eclipsing binary V444 Cygni (WN5+O6). Reliable informati on about the distribution of the linear absorption coefficient alpha(r ) and the velocity law in the extended photosphere of the WN5 star is obtained from the analysis. Recent accurate spectrophotometric estimat e of the luminosity ratio of the components in the binary was used to establish the relationship between the two geometrical parameters of t he 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 expansio n velocity at the distance r similar or equal to 3.8R. (at which tau(4 244)(r) similar or equal to 1) reaches a few hundreds km/s, i.e., the flow at this point is supersonic.