Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The various accretion modes of AM Herculis: Clues from multi-wavelength
  observations in high accretion states   We report on XMM-Newton and NuSTAR X-ray observations of the prototypical
polar, AM Herculis, supported by ground-based photometry and spectroscopy, all
obtained in high accretion states. In 2005, AM Herculis was in its regular mode
of accretion, showing a self-eclipse of the main accreting pole. X-ray emission
during the self-eclipse was assigned to a second pole through its soft X-ray
emission and not to scattering. In 2015, AM Herculis was in its reversed mode
with strong soft blobby accretion at the far accretion region. The blobby
acretion region was more luminous than the other, persistently accreting,
therefore called main region. Hard X-rays from the main region did not show a
self-eclipse indicating a pronounced migration of the accretion footpoint.
Extended phases of soft X-ray extinction through absorption in interbinary
matter were observed for the first time in AM Herculis. The spectral parameters
of a large number of individual soft flares could be derived. Simultaneous
NuSTAR observations in the reversed mode of accretion revealed clear evidence
for Compton reflection of radiation from the main pole at the white dwarf
surface. This picture is supported by the trace of the Fe resonance line at 6.4
keV through the whole orbit. Highly ionized oxygen lines observed with the
Reflection Grating Spectrometer (RGS) were tentatively located at the bottom of
the accretion column, although the implied densities are quite different from
expectations. In the regular mode of accretion, the phase-dependent modulations
in the ultraviolet (UV) are explained with projection effects of an
accretion-heated spot at the prime pole. In the reversed mode projection
effects cannot be recognized. The light curves reveal an extra source of UV
radiation and extended UV absorbing dips. An Ha Doppler map obtained
contemporaneously (abstract abridged)

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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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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: eess
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: stat