Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Is Supernova Remnant Cassiopeia A a PeVatron?   Cassiopeia A, a well-observed young core-collapse supernova remnant (SNR), is
considered as one of the best candidates for studying very high-energy particle
acceleration up to PeV via the diffusive shock mechanism. Recently, MAGIC
observations revealed a $\gamma$-ray spectral cutoff at $\sim3.5$ TeV,
suggesting that if the TeV $\gamma$-rays have a hadronic origin, SNR Cas A can
only accelerate particles to tens of TeV. Here, we propose a two-zone emission
model for regions associated with the forward (zone 1) and inward/reverse
shocks (zone 2). Given the low density in zone 1, it dominates the
high-frequency radio emission, soft X-ray rim via the synchrotron process and
TeV $\gamma$-ray via the inverse Comptonization. With a relatively softer
particle distribution and a higher cut-off energy for electrons, emissions from
zone 2 dominate the low-frequency radio, hard X-ray via the synchrotron process
and GeV $\gamma$-ray via hadronic processes. There is no evidence for
high-energy cutoffs in the proton distributions implying that Cas A can still
be a PeVatron. Hadronic processes from zone 1 dominate very high-energy
gamma-ray emission. Future observations in hundreds of TeV range can test this
model.

18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
1
The categories of this paper are: cs