Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Signatures of Energetic Protons in Hot Accretion Flows: Synchrotron
  Cooling of Protons in Strongly Magnetized Pulsars   The existence of hot, two-temperature accretion flows is essential to the
recent discussions of the low luminosity, hard X-ray emission from accreting
neutron stars and black holes in Galactic binaries and massive black holes in
low luminosity galactic nuclei. In these flows, protons are essentially
virialized and relativistic energies for non-thermal protons are likely.
Observational confirmation of the energetic protons' presence could further
support the two-temperature accretion flow models. We point out that
synchrotron emission from nonthermal relativistic protons could provide an
observational signature in strongly magnetized neutron star systems. The
self-absorbed synchrotron emission from an accreting neutron star with the
magnetic moment $\sim 10^{30} G cm^3$ is expected to exhibit a spectrum \nu
I_{\nu}~ \nu**2 with the luminosity ~ a few x 10^**33 (L_x/10**36 erg/s)**0.4
erg/s at \nu~10**15 Hz where L_x is the X-ray luminosity from the neutron star
surface. The detection of the expected synchrotron signature in optical and UV
bands during the low luminosity state of the pulsar systems such as 4U 1626-67
and GX 1+4 could prove the existence of the hot, two-temperature accretion
flows during their spin-down episodes. The detected optical emission in 4U
1626-67 has a spectral shape and luminosity level very close to our
predictions.

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The categories of this paper are: q-bio
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: math
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The categories of this paper are: chao-dyn