First quadrant of the PV diagram of the extended SiO data (Fig. 11, right panel) in log-scale. The dotted lines represent Keplerian trends for the respectively colour-coded central masses. The vertical, white dashed line represents the position of the ring of compact SiO emission shown in Fig. 13, which is assumed to be the inner rim of the disc. The offset is measured with respect to the stellar position. The contours are drawn at 3, 6, and 24 times the noise rms. At offsets larger than the inner rim position, the 3 × σ_rms contour lies between the 2 and 4 M_⊙ Keplerian trends, following the 3 M_⊙ trend quite closely.