RV-residuals of the model fit. x-axis: the index of the RV points used for the fit, in order of increasing time. y-axis: the residual of the fit in m s⁻¹. The dashed black curve represents the residuals of the fit without any apsidal motion because we forced (including all relativistic and classical tidal terms), as well as V_tide = 0.0 m s⁻¹. The solid red curve represents the residuals of the model with apsidal motion (see Eq. (19)). A significant improvement in the residuals can be seen. Table A.1 helps to identify the observational point via its index.