Best-fit orbital solution from the UltraNest run. Top panel: Companion position over time, showing the ALMA June 2019 detection (observation: red cross, prediction: blue diamond), and the periastron position (green cross). The black dashed circle shows the apparent size of the primary (Paladini et al. 2018). Middle panel: Tangential velocity of the primary at the companion's orbital position, compared to the Gaia PMa of 6.07±0.33 km s⁻¹. The PMa direction (measured for A) is plotted at the position of C for January 2016, and reversed to correspond to the motion of C. Black squares indicate the orbital arc derived by Mayer et al. (2014). Bottom panel: Line-of-sight velocity of the C companion. The dashed line marks the null SiO and HCN moment 1 direction identified in Homan et al. (2020).