Dynamical PDS and light curves (white lines) around bursts 4 (left), 22 (middle), and 23 (right) of 4U 1636-536. The image corresponds to a series of 1 s PDS plotted as a function of time, convolved with a 6 Hz and 20 s averaging kernel for better visibility. Power is color-coded with a linear scale between 2 (black) and 3 (white). The blue zones and vertical dashed lines represent the time and frequency intervals used to probe the significance of the QPO nondetection in the simulations, namely 80−248 s and 840−865 Hz for burst 4, 20−100 s and 815−845 Hz for burst 22, and 20−100 s and 815−855 Hz for burst 23. We note that for burst 23 an observation interruption limits the analysis to ~150 s after the burst.