Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the radiation beaming of bright X-ray pulsars and constraints on
  neutron star mass-radius relation   The luminosity of accreting magnetised neutron stars can largely exceed the
Eddington value due to appearance of accretion columns. The height of the
columns can be comparable to the neutron star radius. The columns produce the
X-rays detected by the observer directly and illuminate the stellar surface,
which reprocesses the X-rays and causes additional component of the observed
flux. The geometry of the column and the illuminated part of the surface
determines the radiation beaming. Curved space-time affects the angular flux
distribution. We construct a simple model of the beam patterns formed by direct
and reflected flux from the column. We take into account the possibility of
appearance of accretion columns, whose height is comparable to the neutron star
radius. We argue that depending on the compactness of the star the flux from
the column can be either strongly amplified due to gravitational lensing, or
significantly reduced due to column eclipse by the star. The eclipses of high
accretion columns result in specific features in pulse profiles. Their
detection can put constraints on the neutron star radius. We speculate that
column eclipses are observed in X-ray pulsar V 0332+53, leading us to the
conclusion of large neutron star radius in this system ($\sim15\,{\rm km}$ if
$M\sim 1.4M_\odot$). We point out that the beam pattern can be strongly
affected by scattering in the accretion channel at high luminosity, which has
to be taken into account in the models reproducing the pulse profiles.

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The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin