Predicted space of possible companions. Central values and uncertainties indicate the 10th, 50th, and 90th percentiles of the distribution of companion masses and separations (semi-major axes) for the transition discs with significant astrometric acceleration (30 sources, as no two-body solution was found for GG Tau). Sources with known companions are shown with a star symbol. Left panel: cavity size at millimetre wavelengths vs companion semi-major axis. One-to-one line is shown in black and ± 1 dex lines are shown in grey. All companions are consistent with being inside the dust cavity (MP Mus is the source appearing above the one-to-one line). Centre panel: cavity size vs companion mass. Right panel: companion semi-major axis vs companion mass.