Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The broad-band spectrum of OAO1657-415 with BeppoSAX: In search of
  cyclotron lines   We report on a 30 ks observation of the high-mass X-ray binary pulsar
OAO1657-415 performed by BeppoSAX on September 1998. The wide band spectrum is
well fit by both a cutoff power law, or a power law modified by a high energy
cutoff, plus a fluorescence Iron line at 6.5 keV. The two models are
statistically equivalent. The inclusion of a cyclotron resonance feature at ~36
keV -- corresponding to a magnetic field strength 3.2 (1+z) x 10^12 G, where z
is the gravitational redshift -- improves significantly the X^2 for the cutoff
model but only marginally for the power law plus high energy cutoff model. The
statistical significance of our data is not adequate to discriminate between
the two models, and even the "Normalized Crab Ratio" technique, successfully
used to pinpoint cyclotron features in the spectra of other X-ray pulsars, is
not conclusive in answering the question whether the feature is real or it is
an artifact due to an improper modeling of the continuum used to fit the data.

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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc