χ²-contour plots of the folding energy E_fold and the photon index Γ for four INTEGRAL observations. The contours correspond to χ² + 1.0 (the projections of this contour to the parameter axes correspond to the 68% uncertainty for one parameter of interest), and χ² + 2.3 (68% uncertainty for two parameters of interest). The respective luminosity (3−80 keV) in units of 10³⁷erg s^-1 is indicated.