Wavelet analysis for OGLE-SMC-CEP-0020. The first panel shows the O − C diagram, while the second panel presents the O − C diagram with Gaussian Process Regression (GPR) applied (black), along with its uncertainty (gray). The third panel displays the wavelet transform of the smoothed GPR, with power represented by the colour bar. The fourth panel shows the maximum power (cyan) distribution, with global peaks highlighted in red. The highest peak determines the dominant variability timescale and amplitude.