Same data as Fig. 3 with three different models of spirals matching S1 (green and blue lines) and S2 (purple line). The positions of the perturbers are indicated with a circle (panel a). Panel b: zoom in version of panel a, where only the best model reproducing the spiral twist in S1 is shown. Panel c: the contours of the CO map at the location of the candidate protoplanet are overlaid, together with the spiral model offset by 14.1° (dashed green line), corresponding to the 4 yr timelapse between ALMA and SPHERE observations.