Diagrams of X-ray luminosity vs. the optical depth parameter Eq. (13) for models without clumping and for individual stars from Table 1. Each point describes models with different L_X and D. Individual symbols discriminate between different effects of X-ray ionization on the wind: black plus symbols (+) denote models with negligible influence of X-ray irradiation, while red crosses () denote models where X-ray irradiation leads to the decrease of the wind terminal velocity. The shaded area () marks the regions of the L_X − t_X parameters where the wind inhibition appears. Overplotted are the positions of non-degenerate components of HMXBs from Table 4 (filled circles, ().