HID of all Swift/XRT observations. Colours and shapes distinguish the different states of the outburst. Hardness is defined here as the ratio of fluxes in the two energy bands 6–10 keV, and 3–6 keV. Each data point represents one entire observation. Black squares are observations for which a state classification was not possible. The errors in the flux are shown but are almost always smaller than the symbols used for the data points.