Modelling relativistic iron line profiles. The red, blue, and green curves represent the best-fit relativistic iron line profiles of Models A, B, and C, respectively. The dotted and dashed grey lines are non-spin BH solutions with different emissivity slopes. The former is derived from a grid search based on Table A.2, and the latter is one of solutions shown in Fig. 9. Both profiles correspond to the minimum C-statistic value for a non-spinning BH case. The grey data points represent the residuals of Model A (data − model) excluding the relativistic iron line, binned to 60 eV.