Comparison of a simulated RM signal observed by different techniques and/or instruments. We used the line profiles of Fig. 8b. The open diamonds, circles and squares represent the RM signal obtained numerically with the iodine cell technique on the HIRES line profile, and with the Gaussian fit to the HARPS, or CORALIE, CCFs, respectively. In a) the gray curve corresponds to the numerical maximization of the cross-correlation of the HIRES profiles inside and outside transits. In b), c), and d), the numerical RM signal computed on the HIRES, HARPS, and CORALIE line profiles, respectively, are compared with the analytical formulas v_CCF (14) in solid red and v_iodine (27) in dash-dotted green.