Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multiband Photometry of the Blazar PKS 0537-441: A Major Active State in
  December 2004 - March 2005   Multiband VRIJHK photometry of the Blazar PKS 0537-441 obtained with the REM
telescope from December 2004 to March 2005 is presented. A major period of
activity is found with more than four magnitudes variability in the V filter in
50 days and of 2.5 in 10 days. In intensity and duration the activity is
similar to that of 1972 reported by Eggen (1973), but it is much better
documented. No clear evidence of variability on time-scale of minutes is found.
The spectral energy distribution is roughly described by a power-law, with the
weaker state being the softer.

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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: math