Cyclotron line profiles of Fig. 3 for the four 35 d intervals (black crosses): Interval 1 (top left), Interval 2 (top right), Interval 3 (bottom left) and Interval 4 (bottom right), normalized to a common amplitude. The big red filled dots represent the weighted mean values of all four intervals. The solid blue line represents a best fit function (a combination of two cosine components). We conclude that, within the given statistics, there is no evidence for any change in shape of the profiles with 35 d phase.