LSD I (bottom), V (top) and N (middle) profiles of the stars of our sample. For comparison, the profiles of a star with no detected field, HD 132058, are also plotted. The V and N profiles have been shifted and multiplied by a magnification factor for display purpose. The mean error bars in V and N are plotted on the side of each profile. HD 66765: the observations obtained at phases 0.06 (black), 0.43 (light grey) and 0.81 (dark grey) are plotted. HD 67621: the observations obtained at phases 0.11 (dark grey), 0.37 (light grey) and 0.73 (black) are plotted. HD 109026: the observations obtained at phases 0.42 (black), 0.71 (light grey) and 0.95 (dark grey) are plotted. For all other stars, the profiles have been plotted in order of decreasing darkness for decreasing V S/N. The three observations of HD 133518 are almost perfectly superimposed.