Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Frequency dependent radio structure of the gravitational lens system
  B0218+357   We present multi-frequency radio continuum VLBI observations of the
gravitational lens system B0218+357 carried out using a global VLBI network and
the VLBA. The source has been observed with resolutions from 0.2 milliarcsec to
5 milliarcsec and displays interesting structure. The spectral properties of
various components show that the lensed object is a standard flat spectrum
radio source which has many self-absorbed components. Based on the flux ratio
of the lensed images as a function of frequency we propose a simple model for
the background radio source.

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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: math
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The categories of this paper are: quant-ph
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat