Continuum emission (coloured image) associated with the relativistic jet at the position of GX 13+1. The contours show the integrated intensity maps at the frequency of the lines detected around GX 13+1 (see Fig. 5 and Table 6 for details). The emission lines at each position are shown in Fig. 5. Magenta, red, and white contours correspond to the lines at 86.23, 96.73, and 99.29 GHz, respectively. The excess in the average continuum map of GX 13+1 at the NW position is due exclusively to the line emission at that position.