COMMISSION 27 OF THE I. A. U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 2090

                                          Konkoly Observatory
                                          Budapest
                                          1982 February 17

                                          HU ISSN 0374-0676


                   1981 UBVR PHOTOMETRY OF RT And




As part of our long-term program of UBVR photometry of RS CVn binaries, we
have observed the short-period (0.63 day) system RT And (=BD +52d3383a), which
has a very peculiar light curve known since 1949 (Gordon, 1948). The 
observations spanned the time September to November 1981 and were made with the
University of New Mexico's 61-cm Capilla Peak Observatory telescope. A single-
channel, photon-counting system with a cooled (-20d C) EMR 641A phototube was
used; the filters were from Kitt Peak. The star BD +52d3383 (SAO 35204) was
the comparison for all observations, which are reported in the instrumental
UBVR system.
Figures 1-4 summarize the results. The data have been folded so that both
primary and secondary eclipses are clearly visible. The statistical error in
any point is +-0.01 magnitude or better. Phases were calculated using HJD=2441508.5550
+0.62892990E (Mancuso et al., 1978). Table I provides a log of the observation.
RT And has been well observed since 1949 (see the summary of light curves
in Milano et al., 1981). It exhibits complex, variable behavior, such as
sudden changes in period (Williamon, 1974), a pronounced asymmetry in secondary 
eclipses (Dean, 1974), and a variable level of intensity outside of eclipses.
Our data reinforce the long-term nature of this erratic behavior. Specifically,
we can compare our V-light curve (Figure 3) to those from 1949 to 1978 (Milano
et al., 1981). We note: (1) a large asymmetry in the secondary eclipse, (2)
statistically significant fluctuations during ingress to secondary minimum,
(3) continued symmetry in the primary eclipse, and (4) changes in outside-eclipse
intensities by as much as 0.1 magnitude over a period of only two months. These 
latter variations are so large that a combined light curve has noticeable jumps in
it (see Figure 3 near phase 0.3 and 0.6).


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


Table I - Phase Log of RT And
--------------------------------
Date (UT)       Phase
--------------------------------
 9/20        0.19 --> 0.36
 9/27        0.47 --> 0.62
10/17        0.85 --> 0.50
10/26        0.37 --> 0.50
11/16        0.58 --> 0.86
--------------------------------



   As noted by Milano et al. (1981), the distortion wave has a small amplitude 
and a period of about 22 years. The wave was most apparent in 1974, with
a peak at about phase 0.24. The phase of maximum amplitude of the wave has
been decreasing; a linear fit to the rate indicates a peak at about phase 0.0
in 1981, which unfortunately coincides with the primary eclipse. Hence, it is
not readily visible in our light curve.





      M. ZEILIK, R. ELSTON, G. HENSON, P. SCHMOLKE, P. SMITH

                Capilla Peak Observatory
            Department of Physics and Astronomy
              The University of New Mexico
                  Albuquerque, NM 87131
                        U.S.A.





References:

Dean, C. A., 1974, Pub. Astron. Soc. Pacific 86, 912. [BIBCODE 1974PASP...86..912D ]
Gordon, K., 1948, Astron. J. 53, 198. [BIBCODE 1948AJ.....53R.198G ]
Mancuso, S., Milano, L., Russo, G., and Sollazzo, C., 1978, IBVS # 1409.
Milano, L., Russo, G., and Mancuso, S., 1981, Astron. Astrophys. 103, 57.[BIBCODE 1981A&A...103...57M ]
Williamon, R., 1974, Pub. Astron. Soc. Pacific 86, 924.[BIBCODE 1974PASP...86..924W ]