Generalized Lomb-Scargle periodogram and window function. The computed periodogram (upper plot) is a convolution of the astrophysical signal and the sampling function (window function, lower plot). The periodogram is obtained from the sigma-clipped, bin-averaged dataset. The horizontal dashed lines indicate FAP levels of 10–1, 10–2, and 10–3. There is one significant peak at a period of 12.34 years with an FAP of 6.8 × 10^-4. The window function shows a significant peak at 365 days that is caused by the seasonal visibility of the source. Significant alias peaks caused by the sampling period are absent in the GLS periodogram.