Variation of the LSD profiles of α¹ Her, μ Cep, ρCas and CE Tau. For each observation point of Table 2, except for μ Cep, contiguous observations were averaged. For each star, the top panels represent all Stokes V profiles. The bottom panels represent the Stokes I profiles. For each panel the dashed vertical lines mark the mean velocity of the star in the heliocentric rest frame, the horizontal solid lines the position of 0 and the black vertical segments the mean 1σ level. The null diagnosis is shown in each panel as black crosses.