Variation of χ² of the fit to the Stokes I profiles as a function of the projected rotational velocity. The curve, indicated with squares (black), shows the normalized deviation for the Fe and Cr lines; their minimum is indicated with the × symbol. The curve indicated with bullets (red) shows the same for the rare earth element lines; the minimum is shown with the ʏ symbol. The solid curves are interpolating cubic splines used to find the optimal projected rotational velocity.