Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: HE 1113-0641: The Smallest Separation Gravitational Lens Identified by a
  Ground-based Optical Telescope   The Hamburg/ESO quasar HE 1113-0641 is found to be a quadruple gravitational
lens, based on observations with the twin 6.5m Magellan telescopes at the Las
Campanas Observatory, and subsequently with the Hubble Space Telescope. The
z_S=1.235 quasar appears in a cross configuration, with i' band magnitudes
ranging from 18.0 to 18.8. With a maximum image separation of 0.67'', this is
the smallest-separation quadruple ever identified using a ground-based optical
telescope. PSF subtraction reveals a faint lensing galaxy. A simple lens model
succeeds in predicting the observed positions of the components, but fails to
match their observed flux ratios by up to a magnitude. We estimate the redshift
of the lensing galaxy to be z_L~0.7. Time delay estimates are on the order of a
day, suggesting that the flux ratio anomalies are not due to variability of the
quasar, but may result from substructure or microlensing in the lens galaxy.

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The categories of this paper are: funct-an
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: cs
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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: patt-sol
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn