Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-Ray Beaming due to Resonance Scattering in the Accretion Column of
  Magnetic Cataclysmic Variables   Extremely strong ionized Fe emission lines, with the equivalent width
reaching about 4000 eV, were discovered with ASCA from a few Galactic compact
objects, including AX J2315-0592, RX J1802.1+1804 and AX J1842.8-0423. These
objects are thought to be binary systems containing magnetized white dwarfs
(WDs). A possible interpretation of the strong Fe-K line is the line-photon
collimation in the WD accretion column, due to resonance scattering of line
photons. The collimation occurs when the accretion column has a flat shape, and
the effect is augmented by the vertical velocity gradient there, which reduces
the resonant trapping of resonant photons along the magnetic field lines. This
effect was quantitatively confirmed with Monte-Carlo simulations. Furthermore,
with ASCA observations of the polar V834 Centauri, this collimation effect was
clearly detected as a rotational modulation of the equivalent width of the Fe-K
emission line. Extremely strong emission lines mentioned above can be explained
by our interpretation consistently. Combing this effect with other X-ray
information, the geometry and plasma parameters in the accretion column were
determined.

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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: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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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: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex