COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3609

                                               Konkoly Observatory
                                               Budapest
                                               21 May 1991

                                               HU ISSN 0374 - 0676


          1990 BV PHOTOELECTRIC OBSERVATIONS OF CG Cyg


The eclipsing binary CG Cyg was observed from 24 July through 1 Aug with the
1.2m Kryonerion telescope and a single channel photon counting photometer
described by Dapergolas and Korakitis (1987).  The photometer employs a high
gain 9789QB phototube and conventional BV filters.  Its output is fed directly
to a microcomputer enabling rapid data access.

Photometric observations for this star have been reported previously by
Dapergolas et al., (1988), Dapergolas et al., (1989a), Dapergolas et al.  
(1989b) and other investigators listed by Dapergolas et al.  (1989a).

The data reduction method is the standard one and as a comparison star was used
the BD +34d 4216. The constancy of the comparison star was verified by Milone
et al.  (1979).  The data presented here were obtained with an accuracy of
+-0.015mag.

Table I lists the dates of observations and phases covered whereas Figures 1
and 2 summarize the results for B and V colours.

  TABLE I

Date        Phase
16-7-1990   .96   .17
18-7-1990   .08   .41
19-7-1990   .60   .97
20-7-1990   .35   .58
23-7-1990   .94   .23
24-7-1990   .48   .85
25-7-1990   .07   .52
26-7-1990   .03   .09
20-8-1990   .33   .60

In Table II the times of minima and the O-C values are listed for the V and B
bands respectively.  Times of minima are calculated using the method described
by Kwee and van Woerden (1956) whereas the O-C values were determined from the
linear ephemeris T=2439425d.1221 + 0.631141d given by Milone et al.  (1974).


                                [FIGURE 1]
                                [FIGURE 2]


          TABLE II
                   V COLOUR
Date   Type of     Heliocentric
       minima      Jul. Day
16/7   Primary     2448089.4531
                  +-0.0002
20/7   Secondary   2448093.5543
                  +-0.0004
23/7   Primary     2448096.3960
                  +-0.0002
24/7   Secondary   2948097.3491
                  +-0.0003
20/8   Secondary   2448124.4820
                  +-0.0002

        B COLOUR
(O-C)   Heliocentric    (O-C)
phase   Jul. Day        phase
0.049   2448089.9532    0.044
       +-0.0002
0.541   2448093.5577    0.547
       +-0.0003
0.044   2448096.3961    0.044
       +-0.0002
0.549   2448097.3426    0.544
       +-0.0002
0.544   2448124.4821    0.544
       +-0.0002

From Fig.  1 and 2 it can be seen that there are irregularities outside the
eclipse already reported by Milone et al.  (1979); Dapergolas et al.  (1989b)
and Beckert et al.  (1989).

The observed difference between the primary and secondary minima is 0.48mag
for the B and 0.37mag for V whereas these values are 0.45mag and 0.39mag for
1989.  0.34mag and 0.30mag for 1988 and 0.41mag and 0.30mag for 1987
(Dapergolas et al.,  1988:  Dapergolas et al., 1989a:  Dapergolas et al.,
1989b).

From these values it can be seen that there is a variation in the difference
of the two minima depths for both colours for the years 1987-1988.  1988-1989
and 1989-1990 with values -0.07mag, +0.11mag, -0.03mag for B and 0.00mag,
+0.09mag and 0.02mag for V.  probably due to the photospheric activity of the
system.

From the times of minima found here and published by Dapergolas et al.,(1989a),
Dapergolas et al.,(1989b) and Milone et al.  (1979) the residuals (O-C) show
large variations which might be due to the continuous period variations of the
system.


A. DAPERGOLAS     and E. KONTIZAS
National Observatory of Athens
Astronomical Institute
P.O. Box 20048
GR Athens 118-10
GREECE

M. KONTIZAS
University of Athens
Laboratory of Astrophysics
Panepistimiopolis
GR-Athens 151-71
GREECE

REFERENCES

Beckert, D., Cox, D., Gordon, S., Ledlow, M. and Zeilik, M.:
   1989. Inf. Bull. Var. Stars, no 3398.
Dapergolas, A., Kontizas, E. and Kontizas, M.: 1988. 
   Inf. Bull. Var. Stars. no 3249.
Dapergolas, A., Kontizas, E. and Kontizas, M.: 1989a. 
   Inf. Bull. Var. Stars, no 3322.
Dapergolas, A., Kontizas, E. and Kontizas, M.: 1989b. 
   Inf. Bull. Var. Stars, no 3380.
Dapergolas. A. and Korakitis, R.: 1987. Publ. Nat. Obs. of
   Athens. Ser II. no 28.
Kwee, K.K. and van Woerden, H.: 1956, Bull. Astr. Inst.
   Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ]
Milone, E.F. and Ziebarth, K.E.: 1974. Publ. Astron. Soc.
   Pacific. 86. 684. [BIBCODE 1974PASP...86..684M ]
Milone, E.F., Castle, K.G., Swadrom, D., Burke, E.W., Hall,
   D.S., Michlovic, J.E. and Zissell, R.E.: 1979. Astron.
   J., 84. 417. [BIBCODE 1979AJ.....84..417M ]