0 v 1 1 5 M ar 2 00 4 Quiescent Burst Evidence for Two Distinct GRB Emission Components

We have identified two quiescent GRBs (bursts having two or more widelyseparated distinct emission episodes) in which the post-quiescent emission exhibits distinctly different characteristics than the pre-quiescent emission. In these two cases (BATSE GRBs 960530 and 980125), the second emission episode has a longer lag, a smoother morphology, and softer spectral evolution than the first episode. Although the pre-quiescent emission satisfies the standard internal shock paradigm, we demonstrate that the post-quiescent emission is more consistent with external shocks. We infer that some observed soft, faint, long-lag GRBs are external shocks in which the internal shock signature is not observed. We further note that the peak luminosity ratio between quiescent episodes is not in agreement with the ratio predicated by the lag vs. peak luminosity relationship. We briefly discuss these observations in terms of current collapsar jet models. Subject headings: gamma rays: bursts—methods: data analysis