Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Optical Gravitational Lensing Experiment. Optical Monitoring of the
  Gravitationally Lensed Quasar HE1104-1805 in 1997-2002   We present results of the long term monitoring of the gravitationally lensed
quasar HE1104-1805. The photometric data were collected between August 1997 and
January 2002 as a subproject of the OGLE survey.
  We determine the time delay in the light curves of images A and B of
HE1104-1805 to be equal to 157+/-21 days with the variability in the image B
light curve leading variability of the image A. The result is in excellent
agreement with the earlier determination by Ofek and Maoz.
  OGLE photometry of HE1104-1805 is available to the astronomical community
from the OGLE Internet archive.

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The categories of this paper are: gr-qc
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: supr-con
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: physics