¹²CO (2–1) and ¹³CO (2–1) moment 0 maps for HD 9985, HD 145101, HD 155853, and HD 152989 (left and middle columns). At the bottom left of each panel the filled white ellipse shows the beam size. The length of the horizontal black bars corresponds to 100 au. The color bar units are mJy beam⁻¹ km s⁻¹. The contours plotted over the moment 0 maps of HD 9985 and HD 155853 show the continuum emission. The contour levels are in steps of [5,8,11,14,17]× rms noise of 15.9 μJy beam⁻¹ for HD 9985 and [4,6,8,10]× rms⁻¹ noise of 15.3 μJy beam⁻¹ for HD 155853. The right column displays the obtained CO spectra in all three isotopologs. For better visibility, the ¹³CO and C¹⁸O spectra have been shifted downward, and in the case of HD 9985 and HD 155853 the C¹⁸O spectrum has been multiplied by 4. The horizontal dashed lines show the zero flux levels of the spectra. The vertical dash-dotted and dotted lines mark the radial velocity of the star and its uncertainty in the LSR frame.