Dynamical power density spectrum (PDS) of the complete RXTE/ASM smoothed daily light curve (with negative flux values and the large burst of January 2009 removed). For the method to generate such a PDS see Wilms et al. (2001). Here we used an individual data set length of 2000d, a step size of 10d, calculating the power for 50 trial periods in the search range for the orbital period between 10d and 32d. A broad peak of enhanced power is found between 22d and 25d.