Exploring Broadband GRB Behavior During Gamma-Ray Emission
Yost, S. A., et al. (46 co-authors)
The robotic ROTSE-III telescope network detected prompt optical
emission contemporaneous with the gamma-ray emission of Swift
events GRB 051109A and GRB 051111.
Both data sets have continuous coverage at high signal-to-noise
levels from the prompt phase onward, and thus the early observations
are readily compared to the Swift XRT and BAT high-energy detections.
In both cases, the optical afterglow is established, declining steadily
during the prompt emission.
For GRB 051111, there is evidence of an excess optical component during
the prompt emission.
The component is consistent with the flux spectrally extrapolated from
the gamma-rays, using the gamma-ray spectral index.
A compilation of spectral information from previous prompt detections
shows that such a component is unusual.
The existence of two prompt optical components - one connected to the
high-energy emission, the other to separate afterglow flux, as indicated
in GRB 051111 - is not compatible with a simple ``external-external''
shock model for the GRB and its afterglow.
Status:
2007, ApJ, 657, 925.
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