Time-frequency analysis of KIC 8561221. Top left panel: long-cadence light curve starting on June 20, 2009 where dotted lines indicate the transitions between the observing quarters. Top right panel: associated power density spectrum expressed in periods between 0.5 and 180 days. The blue shaded regions were removed in the analysis. Middle left panel: wavelet power spectrum computed using a Morlet wavelet between 0.5 and 180 days on a logarithmic scale. Middle right panel: GPS as a function of the period of the wavelet. The dotted line is the confidence level corresponding to a 95% probability. Bottom panel: the scale-averaged time series reconstructed from the periods in the range 15 to 150 days. The discontinuities at Q5 and Q13 are a consequence of the rejected regions (enlarged to avoid border effects).