Results of the expected observable velocity perturbations from a VSI unstable disk synthetic lines observations for different CO isotopologues. From left to right, the columns show predictions for ¹²CO, ¹³CO and C¹⁸O. From top to bottom, the rows show the results for disk inclinations of 5°, 20° and 35°. The mock data cubes have a velocity resolution of 0.05 km s⁻¹, and the images are convolved by a circular Gaussian beam of 50 mas, shown at the bottom left corner of each panel. The x- and y-axes indicate the RA and Dec angular offset from the position of the central star, in arcseconds.