Diagram of the two-stage fitting process. Global parameters are iterated using nested sampling. For a fixed set of global parameters, the n_e envelopes (one per event) each have a set of local parameters comprising two envelope parameters, f₀, T₀ (see main text), and parameters for each of the n(k) sub-bursts (also denoted as n_b/e in the main text), with k the envelope index. Local parameters were fitted independently to the dynamic spectrum of each event using least-square minimisation. Initial guesses were obtained thanks to pre-processing.