Asteroseismic butterfly diagram of HD 173701, giving the latitude of the active region as a function of the median time of each quarter (labelled on the upper axis). The grey shades show the posterior densities obtained for each of the selected quarters and normalized to the global maximum; greyscale from 0 (white) to 1 (black). Red dots mark the maximum a posteriori estimates of the latitude. The vertical bars give the limits of the corresponding 68.3% credible intervals. The green squares show the maximum of the density of the 1024 estimates obtained from artificial time series. Lower panel: variation in amplitude of the signal, S_Q, normalized to its maximum.