Parameter correlations for the coronal model with a cutoff power-law and relativistic reflection with ϵ fixed at ϵ = 3 and as a free parameter (Models 1 and 2 in Table 2). First row: holding the inclination fixed at i = 27° results in one best fit solution for the emissivity index ϵ and spin a. Second row: for i let free, one more solution emerges. We chose the physical one as the best fit (see Sect. 3.3.2). Third row: ϵ = 3 is chosen to describe the correlation between i and a. Fourth row: interplay between ϵ and i. Shown are the χ² significance contours for two parameters of interest based on Δχ² = 2.30, 4.61 and 9.21, i.e., 68%, 90% and 99% confidence levels, with respect to the best fit case.