Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Revisiting the Shape of Pulsar Beams   Characterizing the shape and evolution of pulsar radio emission beams is
important for understanding the observed emission. The various attempts by
earlier workers investigating beam shapes have resulted in widely different
conclusions. Using a carefully selected subset of the recently published
multifrequency polarimetry observations of 300 radio pulsars (Gould & Lyne,
1998), we attempt to model the shape of pulsar beams. Assuming that the beam
shape is elliptical, in general, and that it may depend on the angle between
the rotation and the magnetic axes, we seek a consistent model where we also
solve for the dependence of the beam size on frequency. From the six-frequency
data on conal triple and multiple component profiles, we show that a) the
pulsar emission beams follow a nested cone structure with at least three
distinct cones, although only one or more of the cones may be active in a given
pulsar; b) each emission cone is illuminated in the form of an annular ring of
width typically about 20% of the cone radius.
  Although some slight preference is evident for a model where the beam is
circular for an aligned rotator & latitudinally compressed for an orthogonal
rotator, the possibility that the beam shape is circular at all inclinations is
found to be equally consistent with the data. While the overall size scales as
$P^{-0.5}$ (where $P$ is the pulsar period) as expected from the notion of
dipolar open field lines, we see no evidence in support of the beam shape
evolution with pulsar period.

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The categories of this paper are: econ
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat