Parameter correlations for fits with a broken power-law emissivity (Model 3 in Table 2). High spin is required in all situations. First row: emissivity index ϵ and spin a. Second row: break radius r_break versus the spin a. Third row: inclination i with respect to the spin a. Fourth row: change in emissivity profile index ϵ with varying break radius r_break. 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, with respect to the best fit case.