The ratio between the radiative luminosity at the critical point and the mass-loss rate (given by Equation (19)) times the Bernoulli parameter, as a function of entropy (in units of k_B) and the Bernoulli parameter ε (in units of U/μ), for Bernoulli parameter values between 0.01 and 0.99. The red zone in the upper-left corner is where radiative diffusion becomes dominant.