Effect induced by the presence of a stellar spot on the rotational profile. Upper panel: Spot centred at (-x₀,y₀) on the projected stellar disc. The rotation of the star brings the spot centre to the new position on the disc (x₀,y₀). Bottom panel: Rotation profile modified by the presence of a spot. The Doppler-shift distribution exhibits a notch or dip at the spot’s position. As rotation carries the spot across the stellar disc, the position of the notch moves across the Doppler-shift distribution and its strength changes with the projected area of the spot and for the effect of the limb darkening. Figure adapted from Gray (2018).