Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Swift XRT Observations of the Breaking X-ray Afterglow of GRB 050318   We report the results of Swift X-Ray Telescope (XRT) observations of GRB
050318. This event triggered the Burst Alert Telescope (BAT) aboard Swift and
was followed-up with XRT and UVOT for 11 consecutive orbits starting from 54
minutes after the trigger. A previously unknown fading X-ray source was
detected and accurately monitored. The source was found to decrease in
intensity with time and a clear temporal break occurring at ~18000 s after the
trigger was observed. The X-ray light curve was found to be consistent with a
broken power-law with decay indices -1.17 +/- 0.08 and -2.10 (+0.22) (-0.24)
before and after the break. The spectrum of the X-ray afterglow was well
described by a photoelectrically absorbed power-law with energy index of -1.09
+/-0.09. No evidence of spectral evolution was found. We compare these results
with those obtained with UVOT and separately reported and refine the data
analysis of BAT. We discuss our results in the framework of a collimated
fireball model and a synchrotron radiation emission mechanism. Assuming the GRB
redshift derived from the farthest optical absorption complex (z = 1.44), the
event is fully consistent with the E_p-E_iso correlation.

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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an