Wavelet analysis of the X-ray variability with the trend subtracted and the data interpolated on the regular grid. Left: Magnitude of the wavelet transform. The 95% confidence level is given in white contours. The cone of influence is given as the solid black line; the region out of the cone in the darker color shows less reliable periods that may be affected by edge effects (see text for details). Right: Wavelet transform profiles in gray and their median value in black indicate the variability periods of 14.9 and 4.5 days. The dashed lines correspond to the maxima of the Lomb-Scargle periodogram.