COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3416

                                          Konkoly Observatory
                                          Budapest
                                          8 January 1990

                                          HU ISSN 0374 - 0676



           1988 AND 1989 BV PHOTOMETRY OF WY Cnc

  Among the short-period group of RS CVn stars, WY Cnc (=BD 27d1706; #58 in the
catalog of Strassmeier et al., 1988) has been infrequently observed. In order to understand
the magnetic activity of binary systems of cool stars, a long time base of continuous,
high-quality observations is required. We report here on new BV observations that
complement those of Zeilik et al. ( 1989).
   We observed WY Cnc on the nights 10-15,19-21 May 1989, and 8,13,18,19 May 1988
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 -10deg C, was equipped with V and B filters matching the Johnson
system. Each observation consisted of two separate 40-second integrations in the sequence
VBBV through a 19" aperture or a 26" one on a few nights of poorer seeing. SAO 80583
was the comparison and SAO 80598 the check star for all observations. Our reported data
(Figures 1 and 2) are in the instrumental B and V band system. These instrumental
differential magnitudes (comparison-variable) are sufficient to model the geometrical
starspot parameters; so, we did not convert to the Johnson UBV system. The open circles
are the observed points in 1988; the filled squares, 1989. Statistical errors in a single set of
data were rarely greater than 0.01 mag, with most between 0.005 and 0.008 mag. Both years
are plotted on the same scale so that the distortion wave changes are readily apparent.
Clearly, the distortion wave has migrated to increasing longitude between 1988 and 1989.


                            [FIGURE 1]
                            [FIGURE 2]
                            [FIGURE 3]
                            [FIGURE 4]


   Using the technique of Budding and Zeilik (1987), we optimized fits to the observed
data to extract the distortion wave. Figures 3 and 4 show the binary model fits (solid lines)
at V-band for unspotted stars; the open circles are the data transformed to normalized
intensity units. Though the 1989 data are sparser than 1988, we still were able to extract a
distortion wave. We then calculated optimized solutions for a black (T= 0 K), circular
spotted region to account for the maculation effects. The results were:

           1988            1988        1989           1989
           V-band         B-band      V-band         B-band
Longitude  36.2 +-4.0     35.7 +-4.8  115.7 +-3.4    105 +-2
Latitude   0              0           0              0
Radius     8.0 +-0.3      6.9 +-0.4   12.5 +-0.4     13.3 +-0.7


We were not able to find determinate solutions for the latitude; however, the  Chi-square -minimized
values indicate a low latitude for the spotted regions. So we set the latitude
equal to 0deg for
each fit. We note that, despite the incomplete light curve in 1989, we were still able to
extract most of the distortion wave and generate a good fit. We can compare the spot
parameters derived here to those of Zeilik et al. (1989), who completed a light curve at
V-band. Their 1989 data results in a longitude of 107.7deg = 2.6deg and a radius of 11.7deg =
2.4deg ; within the formal errors, the parameters are the same. The active region has migrated
about 80deg and increased in area a little more than a factor of 2 from 
1988 to 1989. The B-band observations give essentially the same results.
 We thank Ronald Angione for scheduling the observing time at Mt. Laguna for the
project. PAH received travel support from Western Carolina University in the form of a
Faculty Development Grant and supplemental funds. This work was supported in part by
NSF grant AST-8903174 to MZ.


P.A. HECKERT                               M. ZEILIK

Dept. Chemistry and Physics                Institute for Astrophysics
Western Carolina University                The University of New Mexico
Cullowhee, NC 28723 USA                    Albuquerque, New Mexico 87131 USA


References:
Budding, E. and Zeilik, M. 1987, Ap.J., 319, 827. [BIBCODE 1987ApJ...319..827B ]
Strassmeier, K., Hall, D. G., Zeilik, M., Nelson, E., Eker, Z., and Fekel, F., 1988, Astron.
   Astrophys. Suppl. Series, 72, 291. [BIBCODE 1988A&AS...72..291S ]
Zeilik, M., Cox, D., Ledlow, M., Rhodes, M., 1989, IBVS, No. 3384.