Upper-left panel: PDS in the 4–10 keV energy band. Lower-left panel: Phase lag vs. Fourier frequency (phase-lag spectrum) together with the derived model obtained from the fits to the power and cross spectra. Upper-right and lower-right panels: Real and imaginary parts of the cross spectrum calculated for the 4–10 keV band with respect to the 2–4 keV band. For the fitting and the plot, we rotated the cross-vector by 45°. We modeled the PDS using seven Lorentzian functions. Additionally, we fit the real and imaginary parts of the cross spectrum by fixing the frequency and FWHM of each Lorentzian to the values derived from the best-fit model of the PDS. Type-C QPO corresponds to the Lorentzian function used to fit the type-C QPO, while L_l and L_h represent the Lorentzian functions fitting the two high-frequency humps.