Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long-term Photometric Behavior of the Eclipsing Binary GW Cephei   New CCD photometry during 4 successive years from 2005 is presented for the
eclipsing binary GW Cep, together with reasonable explanations for the light
and period variations. All historical light curves, obtained over a 30-year
interval, display striking light changes, and are best modeled by the
simultaneous existence of a cool spot and a hot spot on the more massive cool
component star. The facts that the system is magnetically active and that the
hot spot has consistently existed on the inner hemisphere of the star indicate
that the two spots are formed by (1) magnetic dynamo-related activity on the
cool star and (2) mass transfer from the primary to the secondary component.
Based on 38 light-curve timings from the Wilson-Devinney code and all other
minimum epochs, a period study of GW Cep reveals that the orbital period has
experienced a sinusoidal variation with a period and semi-amplitude of 32.6 yrs
and 0.009 d, respectively. In principle, these may be produced either by a
light-travel-time effect due to a third body or by an active magnetic cycle of
at least one component star. Because we failed to find any connection between
luminosity variability and the period change, that change most likely arises
from the existence of an unseen third companion star with a minimum mass of
0.22 $M_\odot$ gravitationally bound to the eclipsing pair.

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The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
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The categories of this paper are: adap-org