First panel: radial velocity data and the joint astrometric and spectroscopic solution (black line) of the stellar binary system formed by GJ 338 A and GJ 338 B. The uncertainties are depicted with a gray color. ELODIE and HIRES absolute RVs are also shown. Second and third panels: zoom-in around the RVs of GJ 338 A and GJ 338 B, respectively. The straight line fit to the data is plotted as a green line. Given the high level of agreement between the adopted Keplerian solution and the straight line, the latter remains nearly hidden by the former in the two panels. Fourth panel: residuals of the RV observations minus the adopted Keplerian solution are shown with different symbols for the two stars. Bottom panel: ELODIE, HIRES, SOPHIE and CARMENES differential radial velocity curve (v_A − v_B) as a function of observing epoch. The values of the adopted Keplerian solution, which were fit using the ELODIE and HIRES data only, are shown with a black dashed line, errors in gray, and the straight line fit to the data is depicted with a green line. All four panels, from the second to the bottom one, have the same scale in the x-axis.