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F. Peng, A. Konigl (University of Chicago), J. Granot (Stanford University)
Recent observational and theoretical studies have raised the possibility that the collimated outflows in gamma-ray burst (GRB) sources have two distinct components: a narrow, highly relativistic outflow, from which the gamma-ray emission originates, and a wider, moderately relativistic surrounding flow. Using a simple synchrotron emission model, we calculate the R-band afterglow lightcurves expected in this scenario and derive algebraic expressions for the flux ratios of the emission from the two jet components at the main transition times in the lightcurve. We apply this model to GRB sources, to explain the structure of afterglows and source energetics, as well as to X-ray flash sources. We find that, for a range of ratios of the component kinetic energies that can plausibly arise in models of magnetically driven jets from a neutron-rich source, the emergence of the wide component in the afterglow lightcurve may mask the jet break in the narrow component, which in turn may lead to an overestimate of the gamma-ray energy emitted by the source and hence of the required gamma-ray emission efficiency.
This work was supported by NASA Astrophysics Theory Program and U.S. Department of Energy.
The author(s) of this abstract have provided an email address for comments about the abstract: fpeng@oddjob.uchicago.edu
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.