Relative ionisation population of iron (left panel) and ratio of He-like to H-like iron (right panel) as a function of the ionisation parameter. In the left panel, the different colours show the populations of Fe xxiv (green), Fe xxv (black) and Fe xxvi (red), respectively. In both panels the solid, dotted, dashed, dotted-dashed and dot-long dashed curves represent increasing disc temperatures of 1.40, 1.44, 1.46, 1.56 and 1.64 keV. The long-dashed lines show the same parameters for obs 6, for which the SED is composed of the disc and a non-thermal component.