1 Astronomical Observatory, Volgina 7, 11160 Belgrade, Serbia

1
A study of close binary system EE Cet G.
Djuraevic 1,2, D.Dimitrov 3, B.Arbutina 1,
B.Albayrak 4, and S.O.Selam 4
1 Astronomical Observatory, Volgina 7, 11160
Belgrade, Serbia Montenegro 2 Isaac Newton
Institute of Chile, Yugoslav branch 3 Institute
of Astronomy, Bulgarian Academy of Sciences,
Tzarigradsko Chosse 72, 1784 Sofia, Bulgaria 4
Ankara University, Faculty of Science, Department
of Astronomy and Space Science, 06100
Tandogan, Ankara, Turkey e-mail
gdjurasevic_at_aob.bg.ac.yu
2
W UMa-like stars W UMa-like stars are the most
common systems among the contact binaries. They
range from late F stars to K stars and are
characterized by common convective envelope.
There are actually two subtypes of the W UMa-type
systems A-type and W-type. In the A-type systems
the deeper primary minimum represents a transit,
while in the W case it is an occultation. The
temperature of the secondary star is in both
cases typically higher that the value we would
expect if the secondary was to be a single star.
This is because the temperatures correspond to
the common envelope. W UMa-type systems show
evi-dence for mass and energy transfer (loss) -
e.g. enhanced temperature in the neck region, and
magnetic acti-vity - the presence of starspots.
min I
min I
3
Case study EE Cet EE Cet is a W-subtype of the
W UMa-type binary systems. It has been discovered
as a variable star in the Hipparcos mission. We
have com-bined our photometric with earlier
spectroscopic observations of Rucinski et al.
(2002) to derive the following physical
parameters of the system comp. 1 2 Teff
K 6095 6305 M M 1.37 0.43 R
R 1.35 0.82 The system has the inclination
i79o. All the parameters are obtained by using
the numerical codes of Djuraevic (1992a,b) and
Djuraevic et al. (1998). A slight assymetry of
the light curves can be explained with the
presence of the cool spot at the primary
compo-nent.
Spectroscopic obs. Rucinski et al. (2002)
min I
min II
Photometric obs. Djuraevic et al. (2005)
min I
4
ADS 2163 a quadruple system ! EE Cet is the
southern binary component in the
visual-spectro-scopic triple system ADS 2163. Due
to the proximity of the visual companion
separated by 5.6, our light curves were
contaminated by the third light. Moreover, it
was found that the northern component is also a
close binary showing radial velocity variations,
thus turning ADS 2163 into a quadruple system .
Future studies of EE Cet and its northern
companion would therefore be particulary
interesting and will be necessary in order to
provide us with more accurate information on this
quadruple system and its com-ponents. 5th SCSLSA
Vrsac 2005 barbutina_at_aob.bg.ac.yu
ADS 2163