Power density spectrum of KIC 8561221 short-cadence data at full resolution (grey curve) and after rebinning by a factor of 100 (black curve). The green line shows the spectrum smoothed by a box car with a width equal to the mean large separation Δν. The fitted background is the solid red line, and its three components (W, Bg, Ba) are plotted as red dotted lines. P-mode power excess, fitted as a Gaussian profile, is also represented with a red dashed line.