Bing Zhang and Peter Mészáros 2002 ApJ 571 876 doi:10.1086/339981
Bing Zhang1 and Peter Mészáros1
Show affiliationsWe consider a gamma-ray burst (GRB) model based on an anisotropic fireball with an axisymmetric energy distribution of the form
(θ)
θ-k and allow for the observer's viewing direction being at an arbitrary angle θv with respect to the jet axis. This model can reproduce the key features expected from the conventional on-axis uniform jet models, with the novelty being that the achromatic break time in the broadband afterglow light curves corresponds to the epoch during which the relativistic beaming angle is equal to the viewing angle, θv, rather than to the jet half-opening angle, θj. If all the GRB fireballs have such a similar energy distribution form with 1.5 < k
2, then GRBs may be modeled by a quasi-universal beaming configuration and an approximately standard energy reservoir. This conclusion also holds for some other forms of angular energy distributions, such as the Gaussian function.
Issue 2 (2002 June 1)
Received 2001 November 30, accepted for publication 2002 February 1
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