Parameters A, B, C, D, E and F of Eq. (8) as a function of the black hole spin a. The fitting function (blue line) has the general form of Eq. (9). We note how the residuals are always on the order of 1% (or less), except for F (on the order of ~10%). These relatively large residuals for F could be reduced using more than six parameters for the fit, but we found it unnecessary for the aim of this work. Red bars are associated with the uncertainties on the parameter values from the fit of the bolometric luminosity at different viewing angles (Fig. B.2.)