COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 649

                                      Konkoly Observatory
                                      Budapest
                                      1972 March 29


UBV PHOTOMETRY OF TWO ECLIPSING VARIABLES IN THE VICINITY OF M67


The discovery of several short-period variable stars in the vicinity of M67 was
reported by Kurochkin (1960), who suggested that the new variables were
likely to be either RR Lyrae stars or dwarf cepheids. Efremov, et al. (1964)
argued that two of the stars, AH Cnc (SVS 1284) and AD Cnc (SVS 1277), were
more probably W Ursae Majoris stars because of their locations in the H-R
diagram; they are located on the main sequence at spectral types G0 and K0,
respectively. In the case of AH Cnc, the latter hypothesis has been
confirmed by Kurochkin (1965) and Eggen (1970).

Additional observations of AH Cnc and AD Cnc have been obtained with the
72-inch Perkins reflector of the Ohio State and Ohio Wesleyan Universities at
the Lowell Observatory. The resulting light and color curves on the UBV
system are shown in Figures 1 and 2. The light curves for both stars are
characteristic of W Ursae Majoris stars.

Comparison of the observations of AH Cnc in Figure 1 with those by Eggen
reveals a difference of about 0.15 mag. in the mean V brightness of the star
and approximately 0.04 mag. in the B-V color. The differences are in the sense
that the present observations show the star to be fainter and redder than in
1965 when observed by Eggen. It is certain that these differences do not
result from errors in transforming the present observations to the UBV system.
Very probably the differences are due to a real change in the brightness and
color of this eclipsing system. Additional photometric observations would
seem to be warranted.

Although nothing unusual is present in the light curve of AD Cnc, it is
interesting to note that the color variation is somewhat greater than usual for
W Ursae Majoris stars.

It is a pleasure to thank Dr. G.H. Herbig for providing a finder chart for
AD Cnc.


Lowell Observatory
Flagstaff, 7 March 1972
                                            ROBERT L. MILLIS

References:

Efremov, Y.N., Kholopov, F.N., Kukarkin, B.V., and Sharov, A.S. 1964. Comm. 27
   I.A.U., Inf. Bull. Var. Stars, No. 75.
Eggen, O.J. 1970, Mem. R.A.S. 70. 111. [BIBCODE 1967MmRAS..70..111E ]
Kurochkin, N.E. 1960, Astr. Circ. U.S.S.R., No. 212., 1965, Comm. 27 I.A.U.,
   Inf. Bull. Var. Stars, No. 79.

                         [FIGURE 1]

  Figure 1. Light and color curves of AH Cnc observed on December 15, 1969.

                         [FIGURE 2]

  Figure 2. Light and color curves of AD Cnc observed on February 16, 1972.