COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 3294

                                                         Konkoly Observatory
                                                         Budapest
                                                         23 February 1989

                                                         HU ISSN 0374 - 0676


                      1987 PHOTOMETRY OF CG Cyg

CG Cyg (= BD +34d4217 = No. 142 in the catalog of Strassmeier et al. 1988)
is a member of the short period RS CVn group. The system has been observed
at optical wavelengths since 1965. Sowell et al. (1987) solve the V band
light curves for 1979 and 1980 and also reference prior observations. Bedford
et al. (1987) and Davies et al. (1987) observed CG Cyg in the infrared during
1984 (BVJK) and 1986 (JHK). They found an infrared excess that they attribute
to circumsystem material. Budding and Zeilik (1987) modeled the 1981 light
curve of Zeilik et al. (1982) to infer two major spot groups centered at 121
deg and 219 deg longitude and 45 deg latitude.
   We observed CG Cyg on the nights of 18, 19, 21, 23, and 26 August and
7-10 September 1987 using the 61 cm telescope operated by San Diego State
University on Mt. Laguna California. The photoelectric photometer, which uses
an EMI 6256 phototube operated at -1300 V and cooled to -23 C, was equipped
with an OG-515 V band filter. Each observation consisted of 3 separate 60
second integrations through a 19" aperture. SAO 70728 (= BD +34d4216) was
the comparison star for all observations. To obtain the maximum time resolution 
needed for an analysis of starspot activity, we observed only in the
V band. Our reported data (Figure 1) are therefore in the instrumental V
band system. These instrumental differential magnitudes (comparison-variable)
are sufficient to model the geometrical starspot parameters; so, we made no
attempt to use an average (B-V) to convert to the Johnson UBV system (as done
by Sowell et al. 1987). Note that in Figure 1 the delta, magnitudes have been
normalized to unit intensity on the shoulders of the light curve. The open
circles are the observed points. Statistical errors in a single set of data
were rarely greater than 0.01 mag, with most between 0.005 and 0.008 mag.
The solid line is a binary model fit for unspotted stars, following the
techniques of Budding and Zeilik (1987).
   Using the technique of Budding and Zeilik (1987), we fit the starspot
parameters to the distortion wave. We find a single spot at longitude = 120 deg
+/- 3 deg, latitude = 38 +/- 17 deg, radius = 13 +/- 2 deg but no evidence 
for the spot


                             [FIGURE 1]

 
at longitude 219 deg observed in the 1981 data of Zeilik et al. (1982). In
Figure 2, the open circles are the observed maculation wave and the solid
line the single spot fit for a black (T = 0 K) spot area. We also observed
a possible flare on 26 July at 5:50 UT at longitude 72 deg, going into the
major distortion wave, as expected if the distortion wave is caused by a
large active region (starspots). No flare was visible in the 19 July observations, 
which covered the phase range from 0.09 to 0.90. Unfortunately,
weather conditions were less than perfect on the night of 26 July. Because
we experienced some variable extinction, we cannot completely rule out the
possibility that our apparent flare was caused by atmospheric variability.
However, we observed our comparison and check stars often enough that we
think the flare is real.
   We would like to thank Ronald Angione for scheduling generous amounts
of observing time at Mt. Laguna for this project.


                          [FIGURE 2]



      P.A. HECKERT                         M. ZEILIK

Dept. of Chemistry and Physics      Institute for Astrophysics
 Western Carolina University         University of New Mexico
   Cullowhee, NC 28723                 Albuquerque, NM 87131
          U.S.A.                              U.S.A.



References:

Bedford, D.K., Fuensalida, J.J., and Arevalo, M.J. 1987, Astron. Astrophys.,
    182, 264. [BIBCODE 1987A&A...182..264B ]
Budding, E., and Zeilik M. 1987, Astrophys. J., 319, 827. [BIBCODE 1987ApJ...319..827B ]
Davies, J.K., Bedford, D.K., Fuensalida, J.J., and Arevalo, M.J. 1987, 
    Inf. Bull. Var. Stars, No. 3012.
Sowell, J.R., Wilson, J.W., Hall, D.S., and Peyman, P. 1987, Pub. Astron.
    Soc. Pac., 99, 407. [BIBCODE 1987PASP...99..407S ]
Strassmeier, K.G., Hall, D.S., Zeilik, M., Nelson, E., Eker, Z., and Fekel,
    F.C. 1988, Astron. Astrophys. Suppl. Ser., 72, 291. [BIBCODE 1988A&AS...72..291S ]
Zeilik, M., Elston, R., Henson, G., Schmolke, P., and Smith, P. 1982, 
    Inf. Bull. Var. Stars, No. 2090.