Power spectrum densities of the 1.3–12.1 keV RXTE/ASM light curve, including all the SSCs (top panel) and only SSC2 and SSC3 (bottom panel). We adopted a bin time of 50 ks for both light curves and a number of bins of 400 and 250, respectively. A periodic signal is evident in both light curves and corresponds to a period between 22.78 and 26.92 d, which are indicated with the vertical dashed red lines.