GRB afterglow light curves from uniform and non-uniform jets

D. M. Wei; Z. P. Jin

doi:10.1051/0004-6361:20030007

paper

GRB afterglow light curves from uniform and non-uniform jets

arXiv:astro-ph/0212514 · doi:10.1051/0004-6361:20030007

Abstract

Here we calculate the GRB afterglow light curves from a relativistic jet as seen by observers at a wide range of viewing angles from the jet axis, and the jet is uniform or non-uniform. We find that, for uniform jet the afterglow light curves for different viewing angles are somewhat different: in general, there are two breaks in the light curve, corresponding to the time $γ \sim (θ_{j} - θ_{v})^{- 1}$ and $γ \sim (θ_{j} + θ_{v})^{- 1}$ respectively. However, for non-uniform jet, the things become more complicated. For the case $θ_{v} = 0$ , we can obtain the analytical results, for $k < 8/ (p + 4)$ there should be two breaks in the light curve correspond to $γ \sim θ_{c}^{- 1}$ and $γ \sim θ_{j}^{- 1}$ respectively, while for $k > 8/ (p + 4)$ there should be only one break corresponds to $γ \sim θ_{c}^{- 1}$ , and this provides a possible explanation for some rapidly fading afterglows whose light curves have no breaks since the time at which $γ \sim θ_{c}^{- 1}$ is much earlier than our first observation time. For the case $θ_{v} \neq = 0$ , our numerical results show that, the afterglow light curves are strongly affected by the values of $θ_{v}$ , $θ_{c}$ and $k$ . If the values of $θ_{v} / θ_{c}$ and $k$ are larger, there will be a prominent flattening in the afterglow light curve, which is quite different from the uniform jet, and after the flattening a very sharp break will be occurred at the time $γ\sim (θ_v + θ_c)^{-1}.

Latex, 5 pages, accepted for publication by A&A

GRB afterglow light curves from uniform and non-uniform jets

Abstract

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