Comparison between the NUFFT and the mtNUFFT periodograms of the Kepler-91 time series. The parameters of the multitaper periodograms are NW = 4 and K = 7. The mtNUFFT periodogram in blue has smaller variance compared to the untapered counterpart in gray. The inset shows the zoomed-in mtNUFFT periodogram along with its 95% jackknife confidence interval.