2013MNRAS.428.1623B

We present the results of our systematic search for extended emission components following initial short gamma-ray burst (GRB) spikes, using Burst and Transient Source Experiment (BATSE) observations. We performed the extended emission search for both short- and long-duration GRBs to unveil the BATSE population of a new hybrid class of GRBs similar to GRB 060614. For the identified bursts, we investigate temporal and spectral characteristics of their initial spikes as well as their extended emission. Our results reveal that the fraction of GRBs with extended emission is ∼ 7 per cent of the total number of our BATSE sample. We find that the spectrum of the extended emission is, in general, softer than that of the initial spike, which is in accord with what has been observed in the prototypical bursts, GRB 060614. We also find that the energy fluence of the extended emission varies on a broad range from 0.1 to 40 times of the fluence of the initial spike. We discuss our results in the context of existing physical models, in particular within the two-component jet model.