Distribution of waiting times between gamma-ray flares of FSRQ detected with the iSRS method (100 MeV sample). Left columns: distribution (ρ(log(Δ_t)) of log(Δ_t). Right columns: same distribution divided by the bin size; this new distribution is proportional to ρ(log(Δ_t))e^−Δ_t. The top row reports the distribution for all the sources. The other rows report the distribution of waiting times for sources selected on account of detected flares (from top to bottom): N_flares ≤ 9, 10 ≤ N_flares ≤ 19, N_flares ≥ 20. Solid histograms represent the data, dashed curves the multi-loghat fitting function. The solid grey line in the top row is the composite model obtained adding a Poissonian process to the multi-loghat fitting function.