Top panels: contour plots of the iron line centroid energy vs. normalization measured from the spectrum E (left), I (middle), and O (right). The contours correspond to the 68%, 90%, and 99% c.l. There is a marginal indication of a change in the centroid energy of the line between the time interval E and the other two. Bottom panels: the ratio of the data to the model of the spectra extracted during the time interval E (left), I (middle), and O (right). All these spectra were fit by using only an absorbed power-law model in order to highlight the presence of the iron line in the residuals from the fit.