COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2138

                                  Konkoly Observatory
                                  Budapest
                                  1982 May 4

                                  HU ISSN 0374-0676





              1981 UBVR PHOTOMETRY OF CG Cyg


   UBVR photometric observations of the eclipsing binary CG Cyg (BD +34d4217)
were made during 1981 as part of our long-term photometry program of RS CVn 
systems. CG Cyg is a short period (0.63 day) system that has shown evidence of
period variability (Milone and Ziebarth, 1974) and a migrating distortion wave
in the light curve (Milone, et al., 1979). The observations were made with the
University of New Mexico's 61-cm telescope at Capilla Peak Observatory and a
single-channel, photon-counting system using an EMR 641A phototube cooled to
-20dC. The star +34d4216 (SAO 70728) was used as the comparision star 
for all
observations. The nights in which observations of CG Cyg were made are listed
in Table I. Phases were calculated using HJD=2439425.1221+0.631141E (Milone and
Ziebarth, 1974).




            Table I - Phase Log of CG Cyg

Date (UT)   Phase        Date (UT)   Phase
---------  ----------   ----------   ---------
6/10        0.03->0.20    8/20        0.25->0.52
6/22        0.89->0.09    8/24        0.76->0.96
7/5         0.49->0.78   10/10        0.16->0.28




   Figures 1-4 summarize our results which are given in the instrumental UBVR
system. The data has been folded in order to show the primary and secondary
eclipses more clearly. Statistical errors for the data points are typically
+-0.02 magnitude.

                         [FIGURE 1]
                         [FIGURE 2]
                         [FIGURE 3]
                         [FIGURE 4]
                      
   Milone et al. (1979) followed the behavior of CG Cyg from 1965 to 1977 and
found that the distortion wave sweeps through the light curve at a rapid rate
and that the mean V light level had risen 14% during this 12 year period. The
V light curve presented here is similar to the Milone et al. V curve of 1967 in
that the distortion wave reaches a maximum amplitude at about 0.8 phase. The
same comparison star was used for both the 1967 and 1981 observations although
differences between the photometric systems used (which should not be too 
significant) were not taken into account. We note these differences 
between our
curve and the 1967 curve: (1) the distortion wave is not as pronounced now as in
1967 and (2) the system is markedly brighter in the 1981 curve. The secondary
minimum is 0.2 magnitude brighter now then in 1967 with the portions of the curve
outside of eclipse being about 0.1 magnitude brighter.
   From our observations we find that the primary eclipse becomes shallower and
the secondary eclipse more prominent relative to the primary as wavelength 
increases. The discontinuity in the light curve at 0.25 phase (best seen in Figure
2) is evidence of short-term variations (~2 month) in the light curve of CG Cyg.





        M. ZEILIK, R.  ELSTON, G. HENSON, P. SCHMOLKE, P. SMITH
                       Capilla Peak Observatory
                 Department of Physics and Astronomy
                    The University of New Mexico
                        Albuquerque, NM 87131
                               U.S.A.





References:

Jassur, D. M. Z., 1978, IBVS # 1458.
Milone, E. F. and Ziebarth, K. E., 1974, Pub. Astron. Soc. Pacific 86, 684. [BIBCODE 1974PASP...86..684M ]
Milone, E.F., Castle, K.G., Robb, R. M., Swadron, D., Burke, E. W., Hall, D. S.,
  Michlovic, J. E., and Zissell, R. E., 1979, Astron J. 84, 417. [BIBCODE 1979AJ.....84..417M ]
Naftilan, S. A. and Milone, E. F., 1979, Astron J. 84, 1218. [BIBCODE 1979AJ.....84.1218N ]