Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 4C 02.27: what is inside a double-double radio quasar?   Recently Jamrozy et al. (2009) identified 4C 02.27 (J0935+0204) as the first
possible example of a double-double radio source which is optically identified
with a quasar (i.e. not a galaxy), at the redshift of z=0.649. The overall
projected angular size of the radio source reaches about 1.5', with a prominent
"core" component in the centre. The two opposite pairs of radio lobes might
indicate two periods of episodic activity. We report on our short exploratory
1.6-GHz Very Long Baseline Interferometry (VLBI) observations of the innermost
radio structure of the quasar, conducted with the electronic European VLBI
Network (e-EVN) on 2009 September 30. These revealed a milliarcsecond-scale
compact source which is the base of the approaching one of the two symmetric
relativistic jets currently supplying the hot spots in the inner pair of the
arcsecond-scale radio lobes in 4C 02.27.

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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg
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The categories of this paper are: atom-ph