Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Afterglow lightcurves, viewing angle and the jet structure of gamma-ray
  bursts   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.

33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc