The Two-Component Afterglow of Swift GRB 050802
Аннотация
This paper investigates GRB 050802, one of the best examples of a Swift gammaray burst afterglow that shows a break in the X-ray lightcurve, while the optical counterpart decays as a single power-law. This burst has an optically bright afterglow of 16.5 magnitude, detected throughout the 170- 650nm spectral range of the UVOT on-board Swift. Observations began with the XRT and UVOT telescopes 286 s after the initial trigger and continued for 1.2 × 10 6 s. The X-ray lightcurve consists of three power-law segments: a rise until 420s, followed by a slow decay with α2 = 0.63 ± 0.03 until 5000s, after which, the lightcurve decays faster with a slope of α3 = 1.59 ± 0.03. The optical lightcurve decays as a single power-law with αO =0.82 ± 0.03 throughout the observation. The X-ray data on their own are consistent with the break at 5000s being due to the end of energy injection. Modelling the optical to X-ray spectral energy distribution, we find that the optical afterglow can not be produced by the same component as the X-ray emission at late times, ruling out a single component afterglow. We therefore considered two-component jet models and find that the X-ray
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