COMMISSION 27 OF THE I. A. U.
                  INFORMATION BULLETIN ON VARIABLE STARS
                               Number 2485

                                                     Konkoly Observatory
                                                     Budapest
                                                     5 March 1984

                                                     HU ISSN 0374 - 0676




               THE ECLIPSE OF THE SYMBIOTIC ECLIPSING BINARY

                         SYSTEM CI CYGNI IN 1982


   Regular UBV photometry of CI Cyg (P = 855.25d) has been carried out at
Crimean Astrophysical Observatory starting from 1973 (Belyakina, 1979 and
1983). The last eclipse of the hot component by the cold one in this binary
system occurred in 1982. Ten measurements of CI Cyg in UBVRI system were
realized at the 125 cm reflector in addition to the usual UBV photometry
carried out at the 64 cm meniscus telescope.
   The results of all these observations are plotted in Figures 1 and 2.
The brightness of CI Cyg had been rising before the eclipse in the U, B and
V bands (Figure 1). The eclipse began on about JD 244 5190. The brightness
in U, B, V and R bands decreased by 1.2m, 0.9m, 0.4m and 0.1m, respectively
till JD 244 5225. During that period the I-light remained constant. After
the phase 0.0 (~~JD 244 5250) the second light weakening occurred with the
amplitudes deltaB = 0.2m, deltaV = 0.4m, deltaR = 0.3m and deltaI= 0.2m. In this case the
U-light remained constant. According to Figure 2 the durations of the 1980
and 1982 eclipses are compatible. But both colour-indices in 1982 minimum
are redder than those in 1980.
  Apparently, the second light weakening in the minimum is caused by the
variations of the red component. From out total photometric data we inclined 
to conclude that the cold component of the CI Cyg binary system is an irregular
variable red giant changing its light within some dozens of days with
amplitudes deltaV<=0.4m. It is worth noting that, in this respect, it looks
like single red giant investigated by Stokes (1971). 
   The IR photometry also showed the variations of the cold component of
CI Cyg (Taranova and Yudin, 1981).         
   The observations of CI Cyg in the UBVRI system were carried out during
1- 3 hours with time resolution 25 sec in three nights indicated by the 
arrows in Figure 1. The obtained light variations did not exceed +-0.01 .


                              [FIGURE 1]
                              [FIGURE 2]



Apparently, in the 1982 eclipse of CI Cyg there were no light fluctuations
observed by Burchi et al. (1983) in 1980.





                           T.S. BELYAKINA

                     Crimean Astrophysical. Observatory
                      334413 Nauchny, Crimea, U.S.S.R.




References:

Belyakina, T.S. 1979, Izv. Krimsk. Astrophys. Obs., 59, 133.
Belyakina, T.S. 1983, Izv. Krimsk. Astrophys. Obs., 68, 108.
Burchi, R., Chochol, D., Dipaolantonio, A., Mancuso, S., Milano, L., and
    Vittone, R. 1983, Astrophys. Space Sci., 89, 387. [BIBCODE 1983Ap&SS..89..387B ]
Stokes, N.R. 1971, Monthly Notices R.A.S., 152, 165. [BIBCODE 1971MNRAS.152..165S ]
Taranova, O.G. and Yudin, B.F. 1981, Astron. J. (Soviet) 58, 1051. [BIBCODE 1981AZh....58.1051T ]