Gamma Ray Bursts with Extended Emission Observed with BATSE
  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 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% 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.
