Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Chandra X-ray Observatory Study of PSR J1740--5340 and Candidate
  Millisecond Pulsars in the Globular Cluster NGC 6397   We present a deep Chandra X-ray Observatory study of the peculiar binary
radio millisecond pulsar PSR J1740--5340 and candidate millisecond pulsars
(MSPs) in the globular cluster NGC 6397. The X-rays from PSR J1740--5340 appear
to be non-thermal and exhibit variability at the binary period. These
properties suggest the presence of a relativistic intrabinary shock formed due
to interaction of a relativistic rotation-powered pulsar wind and outflow from
the unusual "red-straggler/sub-subgiant" companion. We find the X-ray source
U18 to show similar X-ray and optical properties to those of PSR J1740--5340,
making it a strong MSP candidate. It exhibits variability on timescales from
hours to years, also consistent with an intrabinary shock origin of its X-ray
emission. The unprecedented depth of the X-ray data allows us to conduct a
complete census of MSPs in NGC 6397. Based on the properties of the present
sample of X-ray--detected MSPs in the Galaxy we find that NGC 6397 probably
hosts no more than 6 MSPs.

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The categories of this paper are: cond-mat
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
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The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
37
The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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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: hep-lat
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int