COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2348

                                      Konkoly Observatory
                                      Budapest
                                      9 June 1983

                                      HU ISSN 0374-0676


         VARIABILITY OF THE HOTTER COMPONENT OF THE
             ECLIPSING BINARY MM CASSIOPEIAE


  The eclipsing binary MM Cas (alpha_1980 = 0h53.4m and delta_1980 = +54d20.5') was 
observed photoelectrically during 13 nights from December 1980 to September
1982 with the 104 cm telescope of the Uttar Pradesh State Observatory to obtain
the full UBV light curves. The telescope was equipped with a refrigerated
EMI 6094S photomultiplier and standard UBV filters. The light curve obtained
in V filter is given in Figure 1, the phases have been computed according to
the ephemeris:

             Min J.D. (Hel) = 2444581.227 + 1.1584704d E

                         [FIGURE 1]

          Figure 1  The V light curve of MM Cas

and the magnitude differences are referred to an anonymous star
(alpha_1980 = 0h53.6m, delta_1980  = +54d20.6').
Figure 1 shows the presence of brightness fluctuations of amplitude 0.08m

                         [FIGURE 2]

   Figure 2  A representation of the light curve of MM Cas between the phases
   0.15p and 0.35p in V filter. Note that the light curve is nearly
   sinusoidal.

                         [FIGURE 3]

   Figure 3  Same as Figure 2, but for between the phases 0.65p and 0.85p.

and period 3h40.0m +- 1m. These brightness fluctuations seem to be enhanced
during the secondary minima and disappear during the central phase of primary
minima. This behaviour is usually expected in the case of an intrinsic 
variability of the hotter component which is totally eclipsed during the primary
minima. The fragments of the observed light curve between the orbital phases
from 0.15P to 0.35P and from 0.65P to 0.85p of the MM Cas in V filter are given,
respectively, in Figure 2 and Figure 3. These observed photometric patterns
and the spectral type of the primary component given by Wood et al., (1980)
in light of the characteristics of Delta Scuti Stars (Breger, 1979 and Frolov,
1975) lead us to conjecture that the hotter component of MM Cas may be a
Delta Scuti variable.
  We would like to express our thanks to Drs. C.D. Kandpal, J.B. Srivastava,
T.D. Padalia and S.K. Gupta for their helpful discussions and valuable re-
marks.


                  U.S. CHAUBEY

             Uttar Pradesh State Observatory,
             Naini Tal, India - 263129


References:

Breger, M.: 1979, Publ. Astron. Soc. Pacific 91, 5 [BIBCODE 1979PASP...91....5B ]
Frolov, M.S.: 1975, in Pulsating Stars. ed. B.V. Kukarkin, Keter Publ. House
  Jerusalam Ltd., p. 201 [BIBCODE 1975pust.book..201F ]
Wood. F.B., Oliver, J.P., Florkowski, D.R. and Koch, R.H.: 1980, A Finding 
  List for Observers of Interacting Binary Stars, Pennsylvania Press, p. 20