New elements for three eclipsing X-ray binary systems: HZ Herculis, Centaurus X-3, and Vela X-1

A contribution to the theoretical analysis of eclipsing x-ray binary systems and the calculation of physical and geometrical elements, are represented. The principle of this work is to make fitting between the observational light curve and the synthetic light curve built up in accordance with the Roche model, and to consider the elements of the best fitting as new elements. This method were applied to three systems, there are: (i) HZ Herculis (Hercules X-1). (ii) Krzemenski's star (Centaurus X-3). (iii) HD 77851 (Vela X-1). Finally, the mass-luminosity relation and the H-R diagram for the optical components of the three systems, have been plotted and studied.