Dimensionless radiative line acceleration vs. radial distance (in units of R = 11.757   R_⊙) in the wind from an undistorted O5–V-star rotating with V_rot = 500 km s^-1 at the equator (see stellar parameters in Table 1 in Sect. 4). The dots represent the results from a numerical calculation of for discrete radial grid points . To determine the line acceleration parameters , γ, δ and in Eq. (39), these values were fit to this non-linear model equation resulting in the displayed fitting curve (solid line): see converged wind parameters in Table 1 (according to v_∞ = 2720 km s^-1) at the end of the iteration process described in Sect. 3.3 and (lower part of) Table A.1, respectively.