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Astron. Astrophys. 361, 982-990 (2000)
Evidence for a hot spot in the contact binary VW Cephei
I.B. Pustylnik 1 and
P.G. Niarchos 2
1 Department of Astrophysics, Tartu observatory, Tartu region, Toravere 61602, Estonia (izold@aai.ee)
2 Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, University of Athens, Panepistimiopolis, 15784 Zografos, Athens, Greece (pniarcho@cc.uoa.gr)
Received 31 March 2000 / Accepted 3 July 2000
Abstract
We study the nature of asymmetry and the intrinsic variability in
the light curves of VW Cep. We analyze our own B,V light curves as
well as other data from published sources. In view of the presence of
significant intrinsic brightness variations at a level of
![[FORMULA]](img1.gif)
on time scales comparable to the
orbital period we deal only with individual light curves
sampled in one-two consecutive orbital cycles. The manifold evidence
for the presence of a small hot spot region close to the neck
connecting both components is summarized: a) displacements of the
brightness maxima from the predicted epochs of elongations suggestive
of an additional energy input presumably of hot chromospheric origin,
b) the overall pattern of asymmetry in brightness maxima and minima,
c) systematic colour changes with the orbital phase, d) the presence
of significant cosine odd harmonics in truncated series of the
observed light curves. We find that a hot spot with a characteristic
size of ![[FORMULA]](img2.gif)
and the temperature contrast
![[FORMULA]](img3.gif)
located on the surface of the more
massive star can explain the afore-mentioned peculiarities and model
light curves based on our model give a rather good fit to the observed
data studied so far. The possible physical nature of the hot spot in
the light of our results compared with the spectroscopic data
(specifically Mg II resonance doublet) and flare activity signatures
are briefly discussed.
Key words: stars: binaries:
close 
stars: binaries:
eclipsing
stars: individual: VW Cep
Send offprint requests to: I.B. Pustylnik
Contents
- 1. Introduction
- 2. Epochs of maxima, displacement in respect to elongation
- 3. Estimate of the parameters of the hot spot
- 4. The short-time intrinsic variability
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: October 10, 2000
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