Position–velocity diagram of the continuum subtracted C¹⁸O line along the disc major axis. The Δv is relative to the systemic velocity of 4.5 km s^-1. The solid line shows the midplane Keplerian velocity for a stellar mass of 1 M_⊙ and an inclination of 48°. The dashed lines correspond to stellar masses of 0.9 and 1.1 M_⊙. The data have been spectrally smoothed to a resolution of 80 m s^-1. The spectro-spatial resolution is indicated in the lower left corner.