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arXiv · astro-ph/0112083

Afterglow lightcurves, viewing angle and the jet structure of gamma-ray bursts

E. Rossi·D. Lazzati·M. J. Rees
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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 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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E. Rossi, D. Lazzati, M. J. Rees. 2002-05-09. Afterglow lightcurves, viewing angle and the jet structure of gamma-ray bursts. https://doi.org/10.1046/j.1365-8711.2002.05363.x

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