X-ray colour-colour diagram for Wd1-9. S, M, and H represent the net counts in the soft (0.5–2.0 keV), medium (2.0–4.0 keV), and hard (4.0–8.0 keV) bands, respectively. The 36 EWOCS observations are shown with red circles along with their 1σ error bars. The grey-dotted grid and the N_H and kT values correspond to the results of simulated absorbed thermal spectra (model used: tbabs×apec).