Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical Flash of GRB 990123: constraints on the physical parameter of
  the reverse shock   The optical flash accompanying GRB 990123 is believed to be powered by the
reverse shock of a thin shell. With the best fitted physical parameters for GRB
990123 (Panaitescu & Kumar 2001) and the assumption that the parameters in the
optical flash are the same as those in the afterglow, we show that: 1) the
shell is thick but not thin, and we have provided the light curve for the thick
shell case which coincides with the observation; 2) the theoretical peak flux
of the optical flash accounts for only 3\times10^{-4} of the observed. In order
to compensate this divergency, the physical parameters the electron energy
ration and the magnetic ratio $\epsilon_e$, $\epsilon_B$ should be 0.61, 0.39
respectively, which are much different from those in the late afterglow.

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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: econ
0
The categories of this paper are: hep-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin