COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3384

                                           Konkoly Observatory
                                           Budapest
                                           17 October 1989

                                           HU ISSN 0374 - 0676


             1989 V AND K-BAND PHOTOMETRY OF WY Cnc


We report on new V and K band light curves of the short-period RS CVn star WY
Cancri (= BD 27d1706; #68 in the catalog of Strassmeier et. al, 1988). Very
few complete light curves are available for this system. Chambliss (1965)
presents observations from 1964-65; Sarma (1976) from 1973-74; Awadalla and
Budding (1979) from 1978, and Naftilan (1987) from 1982. Oliver (1974) also
provides a fairly complete set of data from 1969-70. We decided to reobserve
this binary as part of our long-term project to ascertain the activity cycles
of RS CVn systems.

We made observations on the nights of 19, 21, 22 and 23 April 1989 UT and 20
February 1989 with the 1.3-m telescope at Kitt Peak National Observatory. The
infrared detector was OTTO; the visual one, the Mark III Ga:As photometer
mounted in the side port of the infrared photometer. All observations used SAO
80598 (= BD 27d1708) as the comparison star; 39 Cnc served as the infrared
standard star (K=+4.23 on the KPNO infrared system). For the infrared, the
aperture size was 32" in the infrared; 34" in the visual. Standard
beam-switching techniques were used, with the beam separation set at 60", for
both visual and infrared observations. We aimed at a S/N>=100 for each datum;
occasional K-band points have S/N~=50. Phases were derived from the ephemeris
in Strassmeier et. al, (1988).

Figure 1 gives the V-band magnitude differences (comparison-variable) in the
instrumental system, which is very close to Johnson V. Figure 2 shows the same
data in normalized intensity units (circles) compared to an optimized light
curve (solid line) generated by our fitting program with a 5500 K primary star
and a 3500 K secondary (Budding and Zeilik, 1987). A minimum in the distortion
wave appears near phase 90deg; the optimized spot parameters are longitude =
108deg +-3deg, latitude = 39.4deg +-17.9deg, and radius = 11.7deg +- 2.4deg. 
Figures 3 and 4 present the K-band data in the same way as for the previous two
figures. The trough of the distortion wave at this wavelength has the same
longitude but only about half the amplitude as it does at V. Because the
observations at V and K were simultaneous, we can directly infer a temperature
for the dark, active region: 3970+-1550 K.


                              [FIGURE 1]

             Fig. 1   WY Cnc Instr. V-Band KPNO 1989

                              [FIGURE 2]

             Fig. 2   WY Cnc Instr. V-Band KPNO 1989

                              [FIGURE 3]

             Fig. 3   WY Cnc Instr. K-Band KPNO 1989

                              [FIGURE 4]

             Fig. 4   WY Cnc Instr. K-Band KPNO 1989


The observations were funded in part by the Small Grants program of the
American Astronomical Society to MZ and by the Graduate Student Research
Allocations Committee of UNM to ML.


M. ZEILIK, D. COX, M. LEDLOW, M. RHODES
Institute for Astrophysics
The University of New Mexico
Albuquerque, New Mexico 87131 USA

References:

Awadalla, N., and Budding, E., 1979, Ap. and Space Sci., 63, 479-489. [BIBCODE 1979Ap&SS..63..479A ]
Budding, E. and Zeilik, M. 1987, Ap.J., 319, 827-835. [BIBCODE 1987ApJ...319..827B ]
Chambliss, C., 1965, A.J., 70, 741-746. [BIBCODE 1965AJ.....70..741C ]
Naftilan, S., 1987, A.J., 94, 1327-1329. [BIBCODE 1987AJ.....94.1327N ]
Oliver, J. P., 1974, Ph. D. Thesis, University of California, Los Angeles. [BIBCODE 1974PhDT.........1O ]
Sarma, M.B.K., 1976, Bull. Astron. Instit. of Czechoslovakia, 27, 335-341. [BIBCODE 1976BAICz..27..335S ]
Strassmeier, K., Hall, D. G., Zeilik, M., Nelson, E., Eker, Z., and Fekel, F.,
   1988, Astron. Astrophys. Suppl. Series, 72, 291-345. [BIBCODE 1988A&AS...72..291S ]