Results for GX And. Top left panel: index time series in black dots for I_{H α} and in red asterisks for scaled I_Ca,1. The corresponding solid lines represent the best second-degree polynomial fit. Top right panel: phase folded index time series of I_Hα (only present in case we found a period using Hα). Second row left panel: phase dispersion minimisation. The black line denotes Θ computed for I_Hα, while the redline denotes Θ for I_Ca,1. The dashed horizontal line marks the 1% FAP level. Second row right panel: string length method. Again, the black line denotes the string length L for I_{H α} and the red line is also the string length but computed for I_Ca,1. Third row left panel: GLS periodogram with FAP levels of 10, 5, and 1% in blue (dash-dotted, dashed, and solid), respectively. In the periodogram the black line denotes the normalised power calculated with I_{H α}, while the redline again is the power of I_Ca,1, and thecyan line the window function. Third row right panel: index time series of the Hα indices with the GP best-fit model in orange and its standard deviation shaded in light orange.