Diagrams of the X-ray luminosity versus the optical depth parameter in Eq. (10) for wind models without clumping of individual B supergiants with parameters given in Table 1. Individual symbols correspond to models with different L_X and D. Different symbols distinguish between various effects of X-ray ionization on the wind: black plus symbols denote models with a negligible influence of X-ray irradiation and red crosses denote models where the X-ray irradiation reduces the terminal velocity. The antique pink area marks the parameter region where the wind is inhibited by X-rays. The positions of B supergiant components of HMXBs from Table 5 are overplotted (green filled circles).