Afterglow light curves, viewing angle and the jet structure of γ-ray bursts |
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Authors: | Elena Rossi Davide Lazzati Martin J Rees |
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Institution: | Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA |
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Abstract: | Gamma-ray bursts are often modelled as jet-like outflows directed towards the observer; the cone angle of the jet is then commonly inferred from the time at which there is a steepening in the power-law decay of the afterglow. We consider an alternative model in which the jet has a beam pattern where the luminosity per unit solid angle (and perhaps also the initial Lorentz factor) decreases smoothly away from the axis, rather than having a well-defined cone angle within which the flow is uniform. We show that the break in the afterglow light curve then occurs at a time that depends on the viewing angle. Instead of implying a range of intrinsically different jets – some very narrow, and others with a similar power spread over a wider cone – the data on afterglow breaks could be consistent with a standardized jet, viewed from different angles. We discuss the implication of this model for the luminosity function. |
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Keywords: | gamma-rays: bursts X-rays: general X-rays: ISM |
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