Top left: Real and imaginary parts of the cross spectrum of Swift J1727.8–1613 for Group #9 in Fig. 4. Top right: Real and imaginary parts of the cross spectrum rotated counterclockwise by 45°. Bottom left: Modulus of the cross spectrum. Bottom right: Phase and time lags. For a clear presentation of the real and imaginary parts of the cross spectrum, data in the cross spectrum with absolute values greater than or equal to 5 × 10⁻⁴ are scaled logarithmically, while values with absolute values smaller than 5 × 10⁻⁴ are scaled linearly.