Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observations of Binary and Single Wolf-Rayet Stars with XMM-Newton and
  Chandra   We present an overview of recent X-ray observations of Wolf-Rayet (WR) stars
with XMM-Newton and Chandra. A new XMM spectrum of the nearby WN8 + OB binary
WR 147 shows hard absorbed X-ray emission, including the Fe K-alpha line
complex, characteristic of colliding wind shock sources. In contrast, sensitive
observations of four of the closest known single WC (carbon-rich) WR stars have
yielded only non-detections. These results tentatively suggest that single WC
stars are X-ray quiet. The presence of a companion may thus be an essential
factor in elevating the X-ray emission of WC + OB stars to detectable levels.

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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: math-ph
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The categories of this paper are: gr-qc
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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: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph