Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Relativistic Jet Orientation and Host Galaxy of the Peculiar Blazar
  PKS 1413+135   PKS 1413+135 is one of the most peculiar blazars known. Its strange
properties led to the hypothesis almost four decades ago that it is
gravitationally lensed by a mass concentration associated with an intervening
galaxy. It exhibits symmetric achromatic variability, a rare form of
variability that has been attributed to gravitational milli-lensing. It has
been classified as a BL Lac object, and is one of the rare objects in this
class with a visible counterjet. BL Lac objects have jet axes aligned close to
the line of sight. It has also been classified as a compact symmetric object,
which have jet axes not aligned close to the line of sight. Intensive efforts
to understand this blazar have hitherto failed to resolve even the questions of
the orientation of the relativistic jet, and the host galaxy. Answering these
two questions is important as they challenge our understanding of jets in
active galactic nuclei and the classification schemes we use to describe them.
We show that the jet axis is aligned close to the line of sight and PKS
1413+135 is almost certainly not located in the apparent host galaxy, but is a
background object in the redshift range $0.247 < z < 0.5$. The intervening
spiral galaxy at $z = 0.247$ provides a natural host for the putative lens
responsible for symmetric achromatic variability and is shown to be a Seyfert 2
galaxy. We also show that, as for the radio emission, a "multizone" model is
needed to account for the high-energy emission.

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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: adap-org