COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3469

                                               Konkoly Observatory
                                               Budapest
                                               1 June 1990

                                               HU ISSN 0374 - 0676


             1989 BVR LIGHT CURVES OF RT And

   We have observed the short-period RS CVn system RT And (= BD +52d3383A =
#163 in the catalog of Strassmeier et al.,1988) at Capilla Peak Observatory since 1981. We
have analyzed these and other observations in the context of a starspot model (Zeilik et al.,
1989a). These data indicate that a single, large spotted region at a latitude near 45d and at
active longitudes of either 90d or 270d accounts for the maculation effects in the light
curves. The active region had a lower temperature than the photosphere by about 1200 K
in 1987. We have decided to monitor RT And from Capilla at least annually to track the
evolution of its magnetic activity.
   Our new BVR observations were made with the 61-cm telescope on clear and partially
clouded nights of 10,11, and 13 November 1989 and 12 December 1989 UT. the CCD
camera (Laubscher et al.,1988) is equipped with a new filter set that transforms easily to
the Johnson UBV Kron-Cousins RI systems (Beckert and Newberry,1989). The variable,
sky, and comparison star (BD + 52d 3384) were observed simultaneously in a multichannel
mode. Data were reduced with a software mask with an effective aperture of 30 arcsec.


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


   Figures 1-3 show the data (in normalized intensity units calculated from the
instrumental differential magnitudes). Here we display only the normal points (open
circles) made by binning the data in 2d intervals outside of the eclipses. Also shown in the
figures are optimized model fits (solid lines) for e = 88.4d, T1 = 6250 K, and T2 = 4900
K. RT And is peculiar in that it has an eccentric orbit. We use e=0.026 and M0 (mean
anomaly at phase zero) = 3.03 (Zeilik et al., 1989a) for the optimized fits. Figure 4 shows
the maculation effect at V-band (open circles) with an optimized one-spot fit (solid line).
The optimized starspot parameters are: longitude = 256.8d +/- 8.0d, latitude = 63.1d +/-
16.8d, and radius = 13.3d +/- 4.8d. We an also use the difference in the depths of the
maculation effects at B and R to calculate an average value of the temperature
difference between the spotted region and the photosphere. For these data, we find DeltaT_spot =
700 K +/- 370 K. Within the errors, these values somewhat lower than calculated
from V/R-band observations in January 1989 (Zeilik et al., 1989b). Hence, in a time span of a
little sell than a year, the only significant change has been a warming of the starspot region
on the primary star.

S. GORDON, S. HALL, M. LEDLOW,
E. MANN and M. ZEILIK
Capilla Peak Observatory
Institute for Astrophysics
The University of New Mexico
Albuquerque, NM 87131
U.S.A.

References

Beckert, D.C. and Newberry, M.V., 1989, Pub. Astron. Soc. Pac. 101, 849 [BIBCODE 1989PASP..101..849B ]
Budding, E. and Zeilik, M., 1987, Astrophys. J., 319, 827 [BIBCODE 1987ApJ...319..827B ]
Laubscher, B.E., Gregory, S., Bauer, T.J., Zeilik, M. and Burns, J.O., 1988,
   Pub. Astron. Soc. Pac. 100, 131 [BIBCODE 1988PASP..100..131L ]
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., Cox, D.A., DeBlasi, C., Rhodes, M., and Budding, E., 1989a,
   Astrophys. J., 345, 991 [BIBCODE 1989ApJ...345..991Z ]
Zeilik, M., Beckert, D., Cox, D., Dolby, J., Ledlow, M., Newberry, M., and
   Rhodes, M., 1989b, Inf. Bull. Var. Stars. No. 3301