Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetized GRB outflow model: weak reverse shock emission and short
  energy transfer timescale   We show that the absence of the bright optical flashes in most {\it Swift}
Gamma-ray Burst (GRB) afterglows can be explained, if the reverse shock region
is magnetized with a $\sigma \sim 1$, or the emission spectrum of the electrons
accelerated in the mildly magnetized ($0.1<\sigma<1$) reverse shock front is
very soft, or the reverse shock of a non-magnetized outflow is
sub-relativistic, where $\sigma$ is the ratio of the magnetic energy flux to
the particle energy flux. We also find that for $\sigma\gg 1$, the energy
transfer between the magnetized ejecta and the forward shock may be too quick
to account for the shallow decline phase that is well detected in many {\it
Swift} GRB X-ray afterglows.

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The categories of this paper are: math
1
The categories of this paper are: cs
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th