Position-velocity diagram of the ²⁹SiO v = 0, J = 5 − 4 line at a rest frequency of 214.385741 GHz. The diagram is extracted along a slit through the star with a width of 0.1′′ at a position angle of 135°. Contours are drawn at − 16 to 16σ in steps of 4σ, where σ = 0.9 mJy beam⁻¹. We only show the blue-shifted channels to highlight the linear feature extending to ~ 0.4′′. The offset is with respect to the star. The stellar velocity is 6.7 km s⁻¹. The blue lines indicates solid-body rotation with an angular velocity of (3.5 ± 0.3) × 10⁻⁹ rad s⁻¹ (for a position angle of the rotation axis of 45°, the dotted lines correspond to the quoted uncertainties). The black line corresponds to an angular velocity of 6.7 × 10⁻⁹ rad s⁻¹ when assuming a position angle of the rotation axis of 7°. The absorption feature against the star is due to the dynamic stellar atmosphere.