COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1169

                                 Konkoly Observatory
                                 Budapest
                                 1976 August 17

     OBSERVATIONS OF THE SYMBIOTIC STAR CI Cyg IN 1975



   Activity of the symbiotic star CI Cyg in 1971-74 increased
considerably as compared with 1900-70 years. (Belyakina, 1974;
Tempesti, 1976). In 1975 this star also continued to be active.
It was demonstrated by photoelectric observations carried out
with 64-cm meniskus telescope of the Crimean Astrophysical 
Observatory, having an instrumental system close to the UBV system.
The star +35d3821 (V=10.49m, B-V=+0.31m, U-B=+0.13m) was used as
comparison star.
   Our observations in the instrumental system are plotted in
Fig. 1 (filled circles). Open circles and open triangles correspond 
to the visual observations of AAVSO (Mattei, 1975 and J. Bortle
(1975). One can see from Fig. 1 that the amplitude of CI Cyg in
yellow light exceeds 2.5m, but those of the blue and ultraviolet
lights exceed 3.0m.
   In Fig. 2 our observations of 1973-75 carried out in blue
light are compared with two photographic composite light curves
of CI Cyg having a 855d period. Open triangles, open circles and
the solid line correspond to our observations in 1966, 1973-74
and 1975 (Belyakina 1966, 1974). Filled circles and crosses show
two photographic composite light curves according to the estimates 
of N.K. Greenstein; 1937) and D. Hoffleit (1968) (Pucinskas,
1972).
   It follows from Fig. 2 that the deep minimum of 1975 coincides
with that of the composite light curves, being more narrow than
the last. It can be supposed this minimum is a display of an eclipse,
in the binary system.


                         T.S. BELYAKINA
                    Crimean Astrophysical Observatory

References:
Belyakina, T.S. 1966, Izv.Krimsk.Astrophys.Obs. 38, 171
Belyakina, T.S. 1974, IBVS No. 863
Bortle, J, 1975, IAU Circ. 2825 [BIBCODE 1975IAUC.2825....4B ]
Greenstein, N.K. 1937, Bul.Harv.Obs. No. 906
Hoffleit, D. 1968, Irish Astron.Journal 8, 149 [BIBCODE 1968IrAJ....8..149H ]
Mattei, J.A., 1975, IAU Circ. 2788
Pucinskas, A., 1972, Bul.Vilnius Astr.Obs. No. 33, 50 [BIBCODE 1972VilOB..33...50P ]
Tempesti, P. 1976, IBVS No. 1094


                     [FIGURE 1]
                     [FIGURE 2]