Position-velocity (PV) diagrams for VLA 1623A (left), VLA 1623B (centre), and VLA 1623W (right). The background images show the observed data, and contours show the synthetic data from the best-fit model for each source. The PV diagrams were extracted with an aperture width of ~0.35″, i.e. about one beam-width, perpendicular to the extracted spatial direction for VLA 1623B and VLA 1623W as the emission for both sources is marginally resolved. As VLA 1623A is much better resolved, we instead used a width of ~0.7″ to extract its PV diagram. Velocities between 3.25 km s⁻¹ and 5.5 km s⁻¹ were masked for VLA 1623A to avoid channels with significant envelope emission, and velocities between −2.5 km s⁻¹ and 6.75 km s⁻¹ were masked for VLA 1623B to avoid confusion from emission associated with VLA 1623A. We note that these cuts lead to asymmetries in the number of channels available on either side of the line centre. We also show example Keplerian rotation curves for stars with a range of stellar masses as a simple visual comparison.