COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2063

                                 Konkoly Observatory
                                 Budapest
                                 1982 January 4

                                 HU ISSN 0374-0676




MT CASSIOPEIAE, ANOTHER CONTACT BINARY WITH COMPLETE ECLIPSES




     MT Cas was discovered by Gotz and Wenzel (1956) as a
W UMa type eclipsing binary. They did not publish a light
curve, but the amplitudes were given as 0.4m and 0.3m for the
primary and secondary minimum, respectively.
This 13th magnitude star was observed at Hoher List Observatory 
with the double beam photometer at the 1.06m telescope
in B between October and December, 1981 (JD 2444901, 2444914,
2444941, 2444955). Comparison star was a 12th magnitude star
5' north of MT Cas. This star is 0.8m redder than the variable. 
Unfortunately it was not possible to fill the gaps in
the light curve at phases 0.05p and 0.40p, and only the 
observations between 0.43p and 0.93p could be obtained during very
good weather conditions. With exception of the first night,
also some additional V observations were made.

Minimum times were determined:

JD hel.  2444901.5705 Epoch 50249.5 O-C +0.0442d
         2444941.5925       50377.0     +0.0469
         2444955.2420       50420.5     +0.0428 

Epochs and O-C's were calculated according to the light 
elements given by Gotz and Wenzel (1956). Although the minima
are now displaced by 0.14p from their predicted instants,
this can still be explained by the uncertainty of the period
determination from the minimum observations by Gotz and 
Wenzel (1956).

                    [FIGURE 1]

         Figure 1: B observations of MT Cas

                    [FIGURE 2]

         Figure 2: V observations of MT Cas

The B light curve is shown in Fig. 1. It can be seen that
the amplitude of MT Cas is much larger than previously 
assumed. It amounts roughly 0.7m. The minima have flat 
intervals of 0.04p. It is concluded that this eclipsing binary has
complete eclipses. However, between the second and third
contacts of both eclipses the light curve is slightly ascending. 
This "intrinsic" variability affects also the symmetry
of the incomplete eclipse parts and complicates the determination 
of minimum times, therefore, as well as attempts for
a solution of the system parameters.
The maximum at phase 0.25p, though poorly covered with 
observations, seems to be a little brighter than the other one.
Considerable displacements of the maxima from the mid-points
between the minima towards the secondary minimum are visible.
The wider primary minimum suggests that MT Cas is of W type.
This is not unusual if the period and the amplitude (moderately 
great mass ratio) is taken into account.
Fig. 2 shows the V observations. The main features of this
light curve are the same as in B in principle, but the amplitude 
is smaller. Since V observations are lacking for the
first observing night, the B and V light curves may only be
comparable with restriction, however.





                    M. HOFFMANN

                Observatorium Hoher List
                5568 Daun / Eifel, BRD





Reference:
Gotz, W., Wenzel, W., 1956, Veroff. Sternw. Sonneberg 2, 279