Examples of spectral index determinations for W Aql (left) and U Her (right) computed from the combined Band 6 data. The spectral index (colours) is shown for the pixels where it is well-defined. The dashed green circle indicates the area, centred on the continuum peak, equal to the beam size convolved with the UD radius. Black contours indicate the combined continuum (see Figs. 4 and 8). Similar plots for the remaining ATOMIUM sources are given in Fig. B.5.