COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1607

                                 Konkoly Observatory
                                 Budapest
                                 1979 May 16


    PHOTOELECTRIC MINIMA AND NEW LIGHT ELEMENTS OF W UMa





    The variability of the short period eclipsing variable
W Ursae Majoris (BD +56d1400, HD 83950) was discovered by Muller
and Kempf (1903) at the beginning of this century. Previous 
observational data were well summarized up to now by several authors.
They have given different light elements for different intervals
of cycles. Kwee (1956) suggested that W UMa was a triple system.
    The observations in B and V were made at the Ege University
observatory. The light curve obtained from these observations has
been published by Evren et al. (1979). The photoelectric minima
obtained recently are given in the following table.

                Times of minima
JD Hel.        (O-C)_I (O-C)_II  Minimum type

2443563.3995    -.0016   .0006     primary
    564.4005    -.0015   .0006       "
    928.3998    -.0013  -.0001       "
    928.5658    -.0021  -.0009     secondary
    929.4009    -.0011   .0001     primary
    929.5668    -.0021  -.0008     secondary
    930.4019    -.0011   .0002     primary

    The photoelectric Min I observations from 1965 to 1979 March
were collected and the (O-C) values were calculated from the               
following light elements (Equ.1).
    Min I = JD Hel. 2437986.9742 + 0.33363808d*E        (1)
    The (O-C)_I variation is shown in the Figure. The new light
elements computed and the observations from 1965 to 1979 March
are represented with the following equation, on the assumption
that the (O-C)_I variation shows a sinusoidal curve;

     Min I = JD Hel. 2437986.97426 + 0.33363808d*E +
                              +/-5         +/-6

            0.00302d * sin(E*2pi/19200.9)               (2)
               +/-4                 +/-1


                          [FIGURE 1]

    The (O-C)_II values in the table are differences between 
observations and calculations with the new light elements (Equ.2),





                      Z. TUNCA, O. TUMER, S. EVREN
                        Ege University Observatory
                        Bornova - Izmir - Turkey



References:
Evren, S., Tunca, Z. and Tumer, O., 1979, I.B.V.S. No. 1577
Kwee, K.K., 1956, B.A.N. 12, 330 [BIBCODE 1956BAN....12..330K ]
Muller, G. and Kempf, P., 1903, Ap.J. 17, 201 [BIBCODE 1903ApJ....17..201M ]