Studies of the Prompt Emission from the Short Hard Burst GRB 051221A
Abstract
We present the results of a detailed study of the prompt emission from the short burst GRB 051221A as measured by the Swift/BAT and Konus/Wind instruments. An analysis of the light curve and time-resolved spectroscopy of GRB 051221A reveals strong spectral evolution occurring during the burst that is similar to that described for GRB 060121 (Donaghy, et al., 2006). Simultaneous spectral fits of the Swift/BAT and Konus-Wind data have allowed us to study the detailed spectral properties of the prompt emission over a wide (15 keV - 2 MeV) energy range. An examination of the change in the fitted spectral parameters over different time intervals in the prompt emission light curve indicates a steady decline in both Epeak and the power law exponent alpha, more consistent with the usual hard to soft spectral evolution usually seen in long bursts. Results from the well-studied afterglow emission of GRB 051221A indicate that this burst has many characteristics that are intermediate between those usually ascribed to the short hard bursts (likely due to compact object mergers) and the long bursts (usually associated with core collapse.) The addition of the GRB 051221A prompt emission properties described here provides important information about the energetics and detailed spectral evolution over the (T90 = 1.4 ± 0.2 sec) duration of the initial burst. This combination of these detailed prompt emission results with the extensive afterglow results available for GRB 051221A offers an important opportunity to test theories about the progenitors and central engine mechanisms for both long and short burst classes.
- Publication:
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AAS/High Energy Astrophysics Division #9
- Pub Date:
- September 2006
- Bibcode:
- 2006HEAD....9.1352P