Fig. 6

Top: peak emission frequency as a function of time. The red line is a single power-law fit of the form f = a(t − t0)b, where t0 accounts for the onset time of emission and we have a ≃ 150, b ≃ −0.6. Bottom: frequency drift rate, found by fitting power-laws to segments of the peak emission curve and differentiating these, as described in the text.
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