Diagram of the X-ray luminosity L_X versus the optical depth parameter t_X. The dark red area indicates the region of parameters, where X-rays inhibit the stellar wind, the light red area indicates the region of parameters, where X-rays increase the mass-loss rate, and there is no strong effect of X-rays on the mass-loss rate in the white area. Overplotted is the position of the star HD 49798, corresponding to time period of X-ray eclipse and time period outside the X-ray eclipse (with L_X ≈ 10³² erg s^-1, Mereghetti et al. 2013).