Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing Cosmic Rays with Fe K$\alpha$ Line Structures Generated by
  Multiple Ionization Process   Supernova remnants (SNRs) have been regarded as major acceleration sites of
Galactic cosmic rays. Recent X-ray studies revealed neutral Fe K$\alpha$ line
emission from dense gas in the vicinity of some SNRs, which can be best
interpreted as K-shell ionization of Fe atoms in the gas by sub-relativistic
particles accelerated in the SNRs. In this Letter, we propose a novel method of
constraining the composition of particles accelerated in SNRs, which is
currently unknown. When energetic heavy ions collide with target atoms, their
strong Coulomb field can easily cause simultaneous ejection of multiple
inner-shell electrons of the target. This results in shifts in characteristic
X-ray line energies, forming distinctive spectral structures. Detection of such
structures in the neutral Fe K$\alpha$ line strongly supports the particle
ionization scenario, and furthermore provides direct evidence of heavy ions in
the accelerated particles. We construct a model for the Fe K$\alpha$ line
structures by various projectile ions utilizing atomic-collision data.

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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: cs
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The categories of this paper are: patt-sol