Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral and temporal properties of X-ray emission from the
  ultra-luminous source X-9 in M81   We have analysed the spectra and the variability of individual X-ray sources
in the M-81 field using data from the available ROSAT-PSPC and ROSAT-HRI
observations of this nearby spiral galaxy. Here we present the results on the
second brightest source in the field (X-9 - Fabbiano, 1988 ApJ 325 544), whose
identification and interpretation is still unclear. Our work includes the study
of the shape of X-9 from HRI data, the light curve and hardness ratio
evolution, and the spectral analysis.

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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph