(Left panel) Semi-regularly spaced sinusoidal wave with period T_sine = 12.90 h (light blue), normal distribution with a standard deviation of σ = K × σ_sin with K = 15 (light grey), and combined signal with higher signal-to-noise ratio (red points). The samples are gathered into 125 intervals of eight hours spaced by N × 23.93 hours. (Right panel) Corresponding LS periodogram. The 95% confidence level is also shown in the LS periodogram.