COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3012


                                       Konkoly Observatory
                                       Budapest
                                       17 April 1987

                                       HU ISSN 0374-0676



                  JHK LIGHT CURVES OF CG CYGNI

  Infrared photometry of CG Cygni (=BD+34d 4217), a short period (P=0.63d)
active late-type eclipsing binary, was obtained during four consecutive nights
1986. Aug. 30 - Sept. 3. The comparison star was SAO 70728 (=BD+34d 4217);
BS 8430 was used as the standard. The observations were made at the Observatorio
del Teide, Tenerife, with the 1.5 m Sanchez Magro Telescope (Infrared
Flux Collector). A single channel infrared photometer was used, with a focal
plane chopper and a cooled InSb detector. For each data point, the star was
exposed for 10s alternately in the two beams until a signal-to-noise ratio
>100 was achieved.


                            [FIGURE 1]

 Figure 1: The J, H and K light curves of CG Cygni during 1986 Aug/Sept.


 CG Cygni shows most of the characteristics of the RS CVn class of stars
(Hall 1975), although it appears that neither component has yet evolved far
off the main sequence. Both components are active. The spectral classification 
seems to have been reliably established to be G9 V + K3 V (or perhaps
K3 IV-V) by Naftilan and Milano (1979) who, with co-workers, have extensively
studied the system. Infrared excesses in J and K ~ 0.2 mag have been 
confirmed by Bedford, Fuensalida and Arevalo (1987).
  The JHK light curves presented here in Figures 1a, 1b, 1c form part of
our continuing programme of observations of CG Cygni. The data have been
folded according to the ephemeris of Milone and Ziebarth (1974):

           HJD = 2439425.1221 + 0.6311410dE.

and the differential magnitudes have been normalised to an approximate 
uneclipsed reference level (Delta m = 0).




                    J.K. DAVIES, D. K. BEDFORD
                    University of Birmingham
                    Dept. of Space Research
                    Birmingham B15 2TT
                    U.K.


                    J.J. FUENSALIDA, M.J. AREVALO
                    Instituto de Astrofisica de Canarias
                    38071 La Laguna
                    Tenerife
                    Spain




References:
Bedford, D.K., Fuensalida, J.J., Arevalo, M.J.: 1987, Astron
    Astrophys.(submitted) [BIBCODE 1987A&A...182..264B ]
Hall, D.S.: 1975, IAU Colloquium 29, ed. W.S. Fitch, Reidel,
    Dordrecht, p.287. [BIBCODE 1976ASSL...60..287H ]
Milone, E.F., Ziebarth, K.E. : 1974, Publ. Astron. Soc. Pacific 86,
    684. [BIBCODE 1974PASP...86..684M ]
Naftilan, S.A., Milone, E.F.: 1979, Astron. J. 84, 1218 [BIBCODE 1979AJ.....84.1218N ]