COMMISSIONS 27 AND 42 OF THE IAU
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 4062

                                                    Konkoly Observatory
                                                    Budapest
                                                    11 August 1994

                                                    HU ISSN 0374 - 0676


                  1993 BVRI PHOTOMETRY OF BH VIRGINIS

   BH Virginis (# 117 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. (1990) modeled the spot structure for available data from 1953 to 1986.
However, BH Vir has been observed too infrequently during this time period to provide
information on the spot evolution. We therefore started a program to systematically observe
BH Vir.
   We observed BH Vir on the nights of 22, 24, 25, 26, 27, 28, 29 and 30 July 1993 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 C.
The BVRI filters are chosen to closely match the Johnson Cousins system. Our comparison
star was star 0476 in region 4968 of the Hubble Guide Star Catalog. July is rather late in the
observing season for BH Vir, so we were only able to observe it for a short time each night.
Therefore our light curves have only 60 points and contain significant gaps. We do however
have enough data to model the spots. Our data, plotted in Figures 1 and 2 are differential
magnitudes (star-comparison) in the standard Johnson Cousins system.
   To model the data we used the Information Limit Optimization Technique (ILOT)
described in detail by Budding and Zeilik (1987). From the initial binary star fits we extract a
distortion wave. We then fit the distortion wave for the longitude, latitude and radius of
circular spots at OK. The fits for each wavelength are performed independently. We get:


               B band      V band         R band        I band
Longitude   282.5+/-4.9   271.4+/-5.3    281.9+/-6.7   278.7+/-6.4
Latitude     81.7+/-0.8    80.5+/-0.9     83.1+/-0.9    83.0+/-0.8
Radius       38.2+/-0.5    34.1+/-0.5     35.1+/-0.5    35.6+/-0.5
chi-square        84.36          56.1          50.1           51.8


   Figures 3 and 4 show our initial binary star fit and our spot fit for the V band. Note that
the models in the different bands agree well. Zeilik et al. (1990) find that the spots for BH Vir
tend to cluster in Active Longitude Belts at 90d and 270d. Our models show the same
phenomenon with the spot being in the 270d ALB. It is difficult to be certain because many
latitudes were adopted values, but the spot models of Zeilik et al. 1990) tend to be at mid
latitudes (~450d) and about 10d in radius. Our 1993 models show a much larger high latitude
spot, indicating that the spots on this star can vary considerably in latitude. Consistent
observations over a longer time period are needed to unravel the behavior patterns of the spots
on this system.

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


We thank Ron Angione for scheduling generous amounts of observing time at Mt.
Laguna. PAH received support from the Research Corporation for this work.


P.A. Heckert                  D.L. Summers
Dept. of Chem. & Physics      Kitt Peak National Observatory
Western Carolina University   National Optical Astronomy Observatories
Cullowhee, NC 28723 USA       Tucson. AZ 85727 USA


References:
Budding, E. and Zeilik, M., 1987, Astrophys. J., 319, 827. [BIBCODE 1987ApJ...319..827B ]
Strassmeier, K., et al., 1993, Astron. & Astrophys. Suppl., 100, 173. [BIBCODE 1993A&AS..100..173S ]
Zeilik. M., Ledlow, M.. Rhodes, M.. Arevalo, M.J. and Budding. E., 1990, Astrophys. J., 354,
  352. [BIBCODE 1990ApJ...354..352Z ]