Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectrophotometric follow-up of GU Mus, the (X-ray) Nova Muscae 1991   The spectrophotometric follow-up of the X-ray nova GU Mus (=GS 1124-68) is
presented. We have analysed 128 B, V and R frames and 19 optical spectra,
collected at ESO-La Silla, from the epoch of the discovery to January 1992. The
optical lightcurve appears to be typical for a X-ray nova and exhibits
secondary maxima in coincidence with the X-ray ones. The spectra show that
Balmer and He II 4686 emission lines and the N III 4640 emission blend widen
during the decline. A possible explanation of this behaviour is proposed and
applied to the spectral evolution of other X-ray novae.

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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: nucl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: cs
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The categories of this paper are: econ