Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The May 1989 outburst of the Soft X-ray Transient GS 2023+338 (V404 Cyg)   We re-analyze archival Ginga data of the soft X-ray transient source GS
2023+338 covering the beginning of its May 1989 outburst. The source showed a
number of rather unusual features: very high and apparently saturated
luminosity, dramatic flux and spectral variability (often on ~1 sec time
scale), generally very hard spectrum, with no obvious soft thermal component
characteristic for soft/high state.
  We describe the spectrum obtained at the maximum of flux and we demonstrate
that it is very different from spectra of other soft X-ray transients at
similar luminosity. We confirm previous suggestions that the dramatic
variability was due to heavy and strongly variable photo-electric absorption.
We also demonstrate that for a short time the source's spectrum did look like a
typical soft/high state spectrum but that this coincided with very heavy
absorption.

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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: q-alg