Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unveiling the nature of the gamma-ray emitting AGN PKS 0521-36   PKS 0521-36 is an Active Galactic Nucleus (AGN) with uncertain
classification. We investigate the properties of this source from radio to
gamma rays. The broad emission lines in the optical and UV bands and steep
radio spectrum indicate a possible classification as an intermediate object
between broad-line radio galaxies (BLRG) and steep spectrum radio quasars
(SSRQ). On pc-scales PKS 0521-36 shows a knotty structure similar to misaligned
AGN. The core dominance and the gamma-ray properties are similar to those
estimated for other SSRQ and BLRG detected in gamma rays, suggesting an
intermediate viewing angle with respect to the observer. In this context the
flaring activity detected from this source by Fermi-LAT between 2010 June and
2012 February is very intriguing. We discuss the gamma-ray emission of this
source in the framework of the structured jet scenario, comparing the spectral
energy distribution (SED) of the flaring state in 2010 June with that of a low
state. We present three alternative models corresponding to three different
choices of the viewing angles theta_v = 6, 15, and 20 deg. We obtain a good fit
for the the first two cases, but the SED obtained with theta_v = 15 deg if
observed at a small angle does not resemble that of a typical blazar since the
synchrotron emission should dominate by a large factor (about 100) the inverse
Compton component. This suggests that a viewing angle between 6 and 15 deg is
preferred, with the rapid variability observed during gamma-ray flares
favouring a smaller angle. However, we cannot rule out that PKS 0521-36 is the
misaligned counterpart of a synchrotron-dominated blazar.

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The categories of this paper are: stat
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The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph