Simulation of the relative radial velocity variations induced by a spot (of same size) located at latitude (figures left, top to bottom): +60°, +8°, 0° and −6° for Vega (inclination angle i = 7°; the star is seen almost pole-on). Figures right, top to bottom: respective Lomb Scargle periodograms. The spot position at latitude +60° is taken as the reference with respect to the radial velocity and Lomb Scargle power spectrum amplitude.