Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A long term spectroscopic and photometric study of the old nova HR Del   The Nova HR Del, discovered in 1967, was found to be exceptionally bright in
the optical and UV during the whole lifetime of the IUE satellite (ending in
1996) and appears to be still extremely luminous today. The reason for this
continuing activity is not clear; continuing weak thermonuclear burning might
be involved. HR Del was thus monitored over several years, both in broad band
photometry and spectroscopically in the H$\alpha$ spectral region. The profile
of the H$\alpha$ line shows two components: a narrow, central component; and
broader wings. The former is most easily understood as being due to an
accretion disk, whose geometry might lead to it partly occulting itself. That
component shows something like an S wave with an orbital phase dependance,
suggesting that it could be due to a spot bright in H$\alpha$. The wide
component must come from another region, with a probably non-negligible
contribution from the material ejected during the 1967 outburst. Non-orbital
variations of the H$\alpha$ equivalent width were found both on long and short
time scales. Similar variations were found in the photometry, showing a
component with a clear dependence on the orbital phase, but no obvious relation
with the H$\alpha$ variations. The orbital part of the photometric variations
can be explained by irradiation of the companion, while the properties of
H$\alpha$ are explicable by the presence of an accretion disk and a spot bright
in H$\alpha$.

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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
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The categories of this paper are: stat
8
The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: cs
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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: cond-mat
0
The categories of this paper are: hep-ph
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The categories of this paper are: comp-gas