Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: WR 7a: a V Sagittae or a qWR star?   The star WR 7a, also known as SPH 2, has a spectrum that resembles that of V
Sagittae stars although no O VI emission has been reported. The Temporal
Variance Spectrum - TVS - analysis of our data shows weak but strongly variable
emission of O VI lines which is below the noise level in the intensity
spectrum. Contrary to what is seen in V Sagittae stars, optical photometric
monitoring shows very little, if any, flickering. We found evidence of periodic
variability. The most likely photometric period is P(phot) = 0.227(14) d, while
radial velocities suggest a period of P(spec) = 0.204(13) d. One-day aliases of
these periods can not be ruled out. We call attention to similarities with HD
45166 and DI Cru (= WR 46), where multiple periods are present. They may be
associated to the binary motion or to non-radial oscillations. In contrast to a
previous conclusion by Pereira et al. (1998), we show that WR 7a contains
hydrogen. The spectrum of the primary star seems to be detectable as the N V
4604A absorption line is visible. If so, it means that the wind is optically
thin in the continuum and that it is likely to be a helium main sequence star.
Given the similarity to HD 45166, we suggests that WR 7a may be a qWR - quasi
Wolf-Rayet - star. Its classification is WN4h/CE in the Smith et al. (1996)
three dimensional classification system.

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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg