Energy spectra of the persistent emission in 4U 1728–34. Panel a) shows the hard state spectrum with for the nthcomp + powerlaw model (magenta lines) and the reflect × nthcomp model (cyan lines). The dotted lines show the nthcomp component, the dot-dashed line shows the powerlaw component and the long-dashed line shows the reflection component. Panel b) shows the soft state spectra SS1 (red), SS2 (blue) and SS3 (green). The dotted line shows the bb component, the dashed line shows the diskbb component and the dot-dashed line shows the powerlaw component. The bottom panels show the residuals, [(data − model)/error].