COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 1480

                                                         Konkoly Observatory
                                                         Budapest
                                                         29 September 1978


W UMa PHOTOELECTRIC MINIMA: A NEW PERIOD INCREASE

Some new W UMa minima have been photoelectrically
observed with the 400 mm, f=200 mm newtonian reflector
of our observatory (1P21 photomultiplier unrefrigerated).
   The list below contains heliocentric times of minima
of this eclipsing binary, calculated by means of the Kwee
and Van Woerden method. Observations have been carried out
in 1977 and 1978 with a standard Johnson UBV filters system.
Column "(O-C)_1" has been determined with the elements given
in the "Rocznik Astronomiczny Observatorium Krakowskiego
1974", while "(O-C)_2" is referred to the elements:

  Min = 2435918.4154 + 0.33363808*E  (Cester 1973)          (1)
                   1            3  m.e.

Column N denotes the number of observations, while "m.e"
the mean error obtained by the above mentioned method.


filter   J.D.(hel.)     m.e     (O-C)1     (O-C)2    N
         2443.....

 V       161.3634    +-0.0001   -0.0083    -0.0011   65
 V       163.3712       .0003     .0070    +0.0003   47
 V       248.4454       .0003     .0060    +0.0014   54
 V       250.4452       .0003     .0080    -0.0007   46
 B       250.4448       .0004     .0083    -0.0010   46
 U       251.4474       .0002     .0062    +0.0011   40
 U       254.4497       .0003     .0072    +0.0002   30
 V       515.3547       .0002     .0074    +0.0002   20
 V       533.4168       .0001   -0.0075    +0.0002   36

   From 1973 to 1976 the period has been decreasing
(Baldinelli, Ghedini 1977) with:

              dp/p=~-0.1*10E-5

                  [Figure 1.]

 The O-C diagram, reported in the figure, contains the values
 indicated in the list and those of Mallama (1977) and Bones,
 Mirabo (1977). All the O-C are referred to the elements (1).
 The diagram shows that the period has begun to increase again.


             L. BALDINELLI, S. GHEDINI

  "Guido Horn D'Arturo Observatory", Bologna, Italy
            C.P. 1630, 40100 Bologna AD



References:

Baldinelli, L., Ghedini, S. 1977, Mem. S.A.It., 48, 83.
Bones, J., Myrabo, H.K. 1977, I.B.V.S., 1316.
Cester, B. Pucillo, M. 1973, Mem. S.A.It., 64, 201.
Mallama, A.D. et al. 1977, I.B.V.S., 1249.