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\IBVShead{4127}{20 December 1994}    % Use it with dummy or empty arguments

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\title{1994 BVRI PHOTOMETRY OF CG CYGNI}

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 CG Cygni (= BD+34\degr 4217 = \# 177 in the catalog of Strassmeier et al., 1993)
 is a member of the short period eclipsing RS CVn class of stars.  Budding 
 and Zeilik (1987) first modeled the spots on this star.  Zeilik et al. (1994)
 model the spot structure for available data from 1922 to 1993 and review the
 literature on this star.
   
        I observed CG Cyg on the nights of 13, 15, 16, 18, and 19 August 1994 
   using the San Diego State University 61-cm telescope on Mt. Laguna.  The telescope
   is equipped with a photometer using a Hamamatsu R943-02 tube operated at
   $-$1450V and cooled to $-$15\degr.  The BVRI filters are chosen to closely match the
   Johnson--Cousins system.  I used BD+34\degr 4216 (=SAO\,70728) as a comparison star.
   The data, plotted in Figures 1 and 2, are differential magnitudes (star$-$comparison)
   in the standard Johnson--Cousins system.  Zeilik et al. (1994) discuss
   small amplitude variations outside the eclipses that are seen by several different
   independent observers.  These variations are apparent in the 1994 
   data, but their nature is still uncertain.
   
        I modeled the data using the Information Limit Optimization Technique 
(ILOT) described in detail by Budding and Zeilik (1987).  I extracted a distortion
wave from the initial binary star fit, then fit the distortion wave for the
 longitude and radius of two 0K circular spots at a fixed 45\degr\ latitude. Figures
 3 and 4 show these fits for the B band.  The fits for each wavelength are
 performed independently.  I get:
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\begin{tabular}{lcccc}
       & B band&  V band&  R band&  I band\\
\\       
Longitude & 254.7$\pm$10.1& 258.5$\pm$8.1& 257.5$\pm$7.0& 259.9$\pm$7.5\\
Latitude  &      45   &   45     & 45       &  45\\
Radius    & 8.2$\pm$1.0   & 9.1$\pm$0.9  &10.1$\pm$0.8  & 9.6$\pm$0.9\\
Longitude & 106.5$\pm$10.7&113.9$\pm$16.0&125.3$\pm$13.6& 130.6$\pm$20.5\\
Latitude  &      45   &   45     & 45       & 45\\
Radius    &6.9$\pm$1.2    &5.3$\pm$1.6   & 6.1$\pm$1.4  &5.5$\pm$1.5\\
$\chi^{2}$   &132.2      & 103.3    & 92.9     &85.0\\
\end{tabular}
\end{center}
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        Note that the models in the different bands agree to within the errors.
    Zeilik et al. (1994) find that the spots for CG Cyg tend to cluster in Active
    Longitude Belts at 90\degr and 270\degr.  These models show the same phenomenon.
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\centerline{Figure 1}
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\centerline{Figure 2}
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\centerline{3}
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\centerline{\epsffile{4127-f3.ps}}
\centerline{Figure 3}
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\centerline{\epsffile{4127-f4.ps}}
\centerline{Figure 4}
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\centerline{4}
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        After performing the spot fits, the effects of the distortion wave were
   removed and clean fits were made to the corrected light curve.  I get:
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\small
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\begin{tabular}{cccccccr}
$\lambda$&  L$_1$  &  k=r$_2$/r$_1$  &  r$_1$& i   & L$_2$&q=M$_2$/M$_1$&$\chi^{2}$\\
B&0.700$\pm$0.076&0.948$\pm$0.181&0.237$\pm$0.024&82.8$\pm$1.3&0.264$\pm$0.079&0.623$\pm$0.293&107\\
V&   0.686$\pm$0.012&0.883$\pm$0.023&0.248$\pm$0.005&fixed   &0.280$\pm$0.012&0.485$\pm$0.077&73\\
R&   0.695$\pm$0.011&0.836$\pm$0.019&0.257$\pm$0.005&fixed   &0.277$\pm$0.012&0.469$\pm$0.097&162\\
I&   0.705$\pm$0.014&0.790$\pm$0.017&0.265$\pm$0.005&fixed   &0.272$\pm$0.015&0.544$\pm$0.373&50\\
\end{tabular}
\end{center}
\large
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        The values of L$_1$, k, r$_1$, i, and L$_2$ all agree with the values found by 
   Zeilik et al. (1994).  I was only able to simultaneously fit the inclination and
   mass ratio in the B band.  In the other bands I fixed the inclination to try
   to get some information on the mass ratio because the results of Zeilik et
   al. (1994) give a good value for the inclination.  Most previous values of the
   mass ratio are 1.0 (Naftilan and Milone 1985, Sowell et al. 1987).  Jassur
   (1980) gets 0.95 and Popper (1993) gets 0.84.  The values above are derived 
   from only photometric data at one epoch and are therefore less reliable than 
   values derived using spectroscopic data.  However these values lend credence 
   to the lower value of the mass ratio found by Popper (1993).

        Because I was unable to observe an entire primary or secondary eclipse on
   a single night I am not able to give a reliable observed time for either the
   primary or secondary eclipse.  However, the ILOT program makes a best fit 
   correction to the phase of primary minimum.  From that information averaged over
   the 4 observed wavelengths, I find that the eclipses are observed 
   0.02245+0.0001 days before they are computed to occur during this epoch.

        I thank Ron Angione for scheduling generous amounts of observing time at
    Mt. Laguna and the Research Corporation for providing generous financial support.
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% Call for macros \authors - \authorsrightcol - \endauthors
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P. A. HECKERT
Dept. of Chem. \& Physics
Western Carolina University
Cullowhee, NC 28723   USA
\endauthors

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\references

Budding, E. and Zeilik, M., 1987, {\it Astrophys. J.}, {\bf 319}, 827

Jassur, D. M. Z., 1980, {\it Ap. Space Sci.}, {\bf 67}, 19

Naftilan, S. A. and Milone, E. F., 1985, {\it Astron. J.}, {\bf 90}, 761

Popper, D. M., 1993, {\it Astrophys. J.}, {\bf 404}, L67

Sowell, J. R., Wilson, J. W., Hall, D. S., and Peyman, P. E., 1987, {\it Pub. 
Astron. Soc. Pac.}, {\bf 99}, 407

Strassmeier, K., et al., 1993, {\it Astron. \& Astrophys. Suppl.}, {\bf 100}, 173

Zeilik, M., Gordon, S., Jaderlund, E., Ledlow, M., Summers, D. L., Heckert, P. A.,
    Budding, E., and Banks, T. S., 1994, {\it Astrophys. J.}, {\bf 421}, 303

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