COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1741

                                     Konkoly Observatory
                                     Budapest
                                     1980 February 12


              B V LIGHT CURVES OF SZ Psc


The RS CVn type eclipsing binary SZ Psc was observed photoelectrically at the
Ege University Observatory from July 18 to December 1, 1979. The observations
were made in two colours, B and V, with the 48 cm Cassegrain telescope equipped
with an unrefrigerated EMI 9781 A photomultiplier.

As comparison star, HD 219150 was used as suggested by Jakate (1979) since the
former comparison HD 219018 was reported to be an intrinsic variable by some
authors. A total of 108 observations have been obtained in each colour in 14
nights. The phases of each observation were computed by the following light
elements

Min I = JD Hel. 2443894.885+3.96525d*E.

The differential observations, taken as comparison minus variable, have been
corrected for atmospheric extinction. They were plotted against phase and are
shown in Figure 1 and 2.

It is clearly seen that the mid-primary is displaced and falls at around the
phase 0.05. No observations falling within secondary minimum have been
obtained, thus making it difficult to estimate the mid-secondary. However,
from the shoulders of secondary minimum it seems that mid-secondary is around
the phase 0.52 and is not separated by the half period. This may be the
consequence of either an eccentric orbit or a migrating wave as proposed by
Hall (1976) for RS CVn-type binaries.

The most distinguished features of the light curves of the eclipsing binary SZ
Psc are the asymmetric and unequal maxima. Two possible alternatives may be
considered for the light variation of SZ Psc.

                          [FIGURE 1]

               Fig. 1.  B light curve of SZ Psc

                          [FIGURE 2]

               Fig. 2.  V light curve of SZ Psc


i) The comparable light variation outside eclipses and displaced secondary
minimum suggest that the system is a semidetached one with eccentric orbit.

ii) The light variation seen outside eclipses is caused by stellar-spots, and
the distortion wave possesses two minima separated by almost half a period.

However, the preliminary solution given by Weiler (1977) shows that neither
component fills its Roche lobe. Thus, it may seem that the possibility of a
semi-detached system is ruled out. The second alternative to explain the light
variations outside eclipses by stellar-spots leads to a conclusion that two
minima in the distortion wave are either caused by two groups of spots on one
component separated by nearly 180 degrees in longitude or two spots suitably
located on both components.

In order to clarify the problem, more observations in future are greatly
desired.

This study is a part of research project No. 375 supported by the Scientific
and Technical Research Council of Turkey.


O. TUMER, M. KURUTAC, Z. TUNCA,
S. EVREN, A.Y. ERTAN, C. IBANOGLU
Ege University Observatory
Bornova-Izmir, Turkey

References :

Hall, D.S. 1976, I.A.U. Comm. 42, Circ. 2
Jakate, S.M., 1977, I.B.V.S. No. 1578
Weiler, E.J., 1977, Mon. Not. R. astr. Soc. 182, 88 [BIBCODE 1978MNRAS.182...77W ]