Multi-peaked long gamma-ray bursts

At this point, each GRB was simply treated as a discrete point process, whose realisation coincides with the sequence of peak times. We searched for possible periodic recurrences based on the multinomial distribution, after accounting for the clustering of peaks due to the non-stationarity of the GRB signals. Accounting for the multiple trial periods, the best candidate has a p-value of 3e-4 that there is no periodic recurrence.

However, accounting for the multiple trials of 555 searched GRBs, its statistical significance is demoted to 17%. The overall distribution of the p-values obtained for all GRBs is compatible with a uniform distribution in [0,1]. Our technique is sensitive to the presence of >~8 periodic peaks and a fraction of periodic peaks of ~75% at least.

We found no robust evidence for multi-peaked GRBs with periodic recurrences in the peak times. We can exclude that a sizeable fraction (>~0.75) of peaks of each GRB with at least 10 peaks are periodic. While our result does not necessarily clash with claimed periodicities based on Fourier techniques, it constrains the putative recurrent behaviour, which would not manifest itself through the sequence of peaks, but, evidently, in a more elusive way.