Portions of the light curve from the 2004 observations (left panels) and its power spectrum. The power spectrum is obtained from a larger data set spanning from JD 2 453 348 to 2 453 361. The highest peak of the power spectrum at f_LPP = 7.0079   day^-1 corresponds to the long photometric period (s. 2.2). The peak at f_OP = 16.78   day^-1 is, within errors, the orbital period determined from spectroscopy. The rest of the peaks in the power spectrum are either transient, or aliases, like the one at 2 × f_LPP = 14.1. The lines on the light curve are sinusoidal fits of OP (dot-dashed; magenta), LPP (dotted; cyan) and the sum of both (black).