Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variability in Optical Spectra of epsilon Orionis   We present the results of a time-series analysis of 130 echelle spectra of
epsilon Ori (B0 Ia), acquired over seven observing seasons between 1998 and
2006 at Ritter Observatory. The equivalent widths of Halpha (net) and He I 5876
were measured and radial velocities were obtained from the central absorption
of He I 5876. Temporal variance spectra (TVS) revealed significant wind
variability in both Halpha and He I 5876. The He I TVS have a double-peaked
profile consistent with radial velocity oscillations. A periodicity search was
carried out on the equivalent width and radial velocity data, as well as on
wavelength-binned spectra. This analysis has revealed several periods in the
variability with time scales of 2-7 d. Many of these periods exhibit sinusoidal
modulation in the associated phase diagrams. Several of these periods were
present in both Halpha and He I, indicating a possible connection between the
wind and the photosphere. Due to the harmonic nature of these periods, stellar
pulsations may be the origin of some of the observed variability. Periods on
the order of the rotational period were also detected in the He I line in the
98-99 season and in both lines during the 04-05 season. These periods may
indicate rotational modulation due to structure in the wind.

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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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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: cs
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The categories of this paper are: adap-org