Phase-lag spectrum (left panel) and intrinsic coherence function (right panel) of Swift J1727.8–1613 for Group #9. The models are not fit to the data but predicted on the basis of the parameters of the Lorentzians fitted to the LE 2–10 keV and HE 28–200 keV PDS and the real and imaginary parts of the CS of those same two energy bands assuming the Gaussian phase-lag model (Fig. 8). The vertical gray bands indicate the QPO, the QPO second harmonic, and the dip feature, respectively.