Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The broadband afterglow of GRB 030328   We here report on the photometric, spectroscopic and polarimetric monitoring
of the optical afterglow of the Gamma-Ray Burst (GRB) 030328 detected by
HETE-2. We found that a smoothly broken power-law decay provides the best fit
of the optical light curves, with indices alpha_1 = 0.76 +/- 0.03, alpha_2 =
1.50 +/- 0.07, and a break at t_b = 0.48 +/- 0.03 d after the GRB. Polarization
is detected in the optical V-band, with P = (2.4 +/- 0.6)% and theta = (170 +/-
7) deg. Optical spectroscopy shows the presence of two absorption systems at z
= 1.5216 +/- 0.0006 and at z = 1.295 +/- 0.001, the former likely associated
with the GRB host galaxy. The X-ray-to-optical spectral flux distribution
obtained 0.78 days after the GRB was best fitted using a broken power-law, with
spectral slopes beta_opt = 0.47 +/- 0.15 and beta_X = 1.0 +/- 0.2. The
discussion of these results in the context of the "fireball model" shows that
the preferred scenario is a fixed opening angle collimated expansion in a
homogeneous medium.

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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat