Spectral stacking of the pulsar signal from 28 FAST observations of NGC 6517, including five additional recent 2.5 hr observations (with an animation showing the sequence from stack number 1 to 28 and with a real-time duration of 6 s). (a) Power spectrum from a single 0.5 hr FAST observation. (b) Combined spectrum after stacking all 28 observations. The accompanying animation shows the stacking process for the 28 observations in the order of observation dates. Note that NGC 6517B is a binary with an orbital period of 57.89 days, so its powers will not all sum at the same frequency.

(An animation of this figure is available in the online article.)

(An animation of this figure is available.)

The video/animation of this figure is available in the online journal.