Strong spectral evolution during the prompt emission of GRB 070616

TL;DR

This paper analyzes the complex spectral evolution during the prompt emission of the long-duration GRB 070616, using combined Swift and Suzaku data to track changes in spectral parameters over time.

Contribution

It provides detailed spectral evolution analysis of one of the longest GRB prompt emissions, highlighting the need for new mechanisms beyond curvature effect explanations.

Findings

Significant spectral evolution observed during the prompt phase.

Temporal changes in peak energy and spectral slope documented.

Extended duration of prompt emission offers new insights into GRB physics.

Abstract

Swift has revealed features in GRB early light curves, such as steep decays and X-ray flares, whose properties are consistent with an internal origin though they are far from understood. The steep X-ray decay is often explained using the curvature effect; however a significant number of GRBs display strong spectral evolution during this phase, and a new mechanism must be invoked to explain this. Of particular interest are the longest duration GRBs in which the early emission can be studied in most detail. Here we present data for GRB 070616, in which the prompt emission shows a complex multipeaked structure, leading to one of the longest prompt emission durations ever recorded. We take advantage of extensive coverage of such a long burst by all Swift instruments. Combining data from Swift and Suzaku we study the evolution of the prompt emission spectrum, following the temporal variability of the peak energy and spectral slope.