Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Optical Spectroscopic Evolution of V1974 Cygni (Nova Cygni 1992)   Optical observations of nova V1974 Cygni (Cygni 1992), spanning a 4 year
period, have been used to study its spectroscopic evolution. The data cover a
wavelength range from $\sim 3200 - 8000$ \AA and follows the nebular
evolutionary phase of the ejecta. We have modeled the integrated fluxes by
means of the photoionization code CLOUDY. The models were run at a {\it fixed}
abundance value for the most prominent elements (i.e. H, He, C, O, N, Ne, Fe,
etc) over the entire time sequence. It is possible to constrain from this
simple model some of the physical conditions of the gaseous emitting region,
like temperature and density. Compared with previous studies of the gas
abundances of the heavy elements, we found that smaller enhancements of S, N
and Ar, and comparable values for O and Fe, are able to reproduce the
observations. The time evolution of the surface temperature of the ionizing
source and the high-ionization iron lines [Fe VII] 6087 \AA and [Fe X] 6374
\AA, is similar to what it is observed in the soft X-rays. The early line
profiles can be reproduced using a simple kinematical model consisting of an
equatorial ring and polar caps, expanding at a velocity of $\sim 1100$ km/s.
This simple model also approximates the structure of the resolved shell
observed by HST. Considering the complicated structure of the shell, the lack
of well defined values of its gas density and our limited knowledge of the time
evolution of the surface temperature of the photoionization source, the
comparison between models and observations agrees remarkably well.

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The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas