Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray pulsar XTE J1858+034: discovery of the cyclotron line and the
  revised optical identification   We present results of a detailed investigation of the poorly studied X-ray
pulsar XTE J1858+034 based on the data obtained with the NuSTAR observatory
during the outburst of the source in 2019. The spectral analysis resulted in
the discovery of a cyclotron absorption feature in the source spectrum at ~48
keV both in the pulse phase averaged and resolved spectra. Accurate X-ray
localization of the source using the NuSTAR and Chandra observatories allowed
us to accurately determine the position of the X-ray source and identify the
optical companion of the pulsar. The analysis of the counterpart properties
suggested that the system is likely a symbiotic binary hosting an X-ray pulsar
and a late type companion star of K-M classes rather than Be X-ray binary as
previously suggested.

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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
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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: solv-int
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The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
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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: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex