Quiescent Times in Gamma‐Ray Bursts: Hints of a Dormant Inner Engine

We perform a statistical analysis of the temporal structure of longGamma-Ray-Bursts (GRBs). First we consider a sample of bursts in which a longquiescent time is present. Comparing the pre-quiescence with thepost-quiescence emission we show that they display similar temporal structures,hardness ratios and emitted powers, but, on the average, the post-quiescenceemission is roughly twice as long as the pre-quiescence emission. We thenconsider a sample of long and bright GRBs. We show that the duration of eachemission period is compatible with the duration of an active period computed invarious inner engine models. At the contrary, if the inner engine is assumed tobe always active, i.e. also during the quiescent times, in several cases thetotal duration of the burst largely exceeds the theoretical durations. Ouranalysis therefore does not support the interpretation of long quiescent timesin terms of stochastic modulation of a continuous wind. Instead the quiescenttimes can be interpreted as dormancy periods of the inner engine. Before andafter a dormancy period the inner engine produces similar emissions