COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1081

                                  Konkoly Observatory
                                  Budapest
                                  1976 January 13


       PHOTOELECTRIC MINIMA OF ECLIPSING BINARIES


    The list below contains minima of eclipsing binaries observed 
photoelectrically at the Fort Skala Observatory in Cracow.
The times of minima and limits of errors were obtained by the
tracing-paper method of Kordylewski (Szafraniec 1948). The 
consecutive columns of the list contain the name of the star, 
instrument used (Grubb, D = 20 cm; R tel, D = 50 cm), filter used,
heliocentric time of minimum, limit of error and O-C.


----------------------------------------------------
                          JD hel
Star     inst.  filter    2440000+   lim.er.   O-C
----------------------------------------------------
o And    Grubb    B       2319.4309  +0.0035d +0d0162
IM Aur   R tel    B       2749.4431   0.0015  -0.0105
                  V       2749.4436   0.0010  -0.0100
GK Cep   R tel    V       2685.5421   0.0025  -0.0015
---------------------------------------------------------


For o And the value of O-C is obtained according to the elements 
given by Schmidt (1959). Olsen (1972) suggests that the
changes of light may be explained also by intrinsic variations of
a single shell star with the following elements:

           Min I JD hel = 2439470.628 + 1.0185d E.
In this case O-C = +0.0584d.

For IM Aur and CK Cep the values of O-C are obtained according 
to elements given by Dworak (1974, 1975).
From the shape of the light curve IM Aur seems to be an
Algol-type star (Dworak 1974, Kondo 1966, Margoni et al. 1966),
but in the First Suppl. to the Third Ed. of the GCVS (Kukarkin et
al. 1971) it is classified as a beta Lyrae-type variable.
From the morphological point of view the star IM Aur may
be "an intermediate type between Algol-system and beta Lyrae-system",
similarly as the star GK Cep is "an intermediate type between a
B Lyrae and W Ursae Maioris-system" (Dworak 1975). The case of
IM Aur and GK Cep is a good example for the non-adequatness of
the classical division of eclipsing binaries.
Further observations of these three interesting variable
stars are very needed.


                           T.Z. DWORAK
                        Astronomical Observatory
                      of the Jagiellonian University
                           Krakow, Poland



References:

Dworak, T.Z.          1974, IBVS, No. 916.
                      1975, Acta Astr., 25, 103. [BIBCODE 1975AcA....25..103D ]
Kondo, Y.             1966, A.J., 71, 51.  [BIBCODE 1966AJ.....71...54K ]
Kukarkin, B.V.
et al.                1971, First Suppl. to the Third Ed. of the
                      GCVS, Moskva, Izd. AN SSSR. [BIBCODE 1971fstt.book.....K ]
Margoni, R. et al.    1966, IBVS, No. 131.
Olsen, E.H.           1972, As.Ap., 20, 167. [BIBCODE 1972A&A....20..167O ]
Schmidt, H.           1959, Zs. Ap., 48, 249. [BIBCODE 1959ZA.....48..249S ]
Szafraniec, R.        1948, Acta Astr ser. c, 4, 81.