Left: correlation of the power spectrum as obtained by Fossat et al. (2017) as a function of frequency lag for two different time series sampled at 80 s (top) and 60 s (bottom); this is comparable to Fig. 10 of Fossat et al. (2017). The green vertical lines correspond to frequencies at 210 nHz, 630 nHz, and 1260 nHz. Right: sum of the correlation for l = 1 and l = 2 modes as obtained by Fossat et al. (2017) as a function of rotation frequency for two different time series sampled at 80 s (top) and 60 s (bottom); this is comparable to Fig. 16 of Fossat et al. (2017).