COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2102

                               Konkoly Observatory
                               Budapest
                               1982 March 8

                               HU ISSN 0374-0676




     PHOTOELECTRIC OBSERVATION OF W UMa (BD + 56d1400)




  This short period (0.33363808d) well known eclipsing variable
has been observed numerous times by many observers. A complete
set of photographic, visual and photoelectric data have been
available for the last 79 years.
  Since the system is well known for variations of period, the
available data as far as 1903 were compiled and O-C variation
were investigated.
     
                         [FIGURE 1]

Fig. 1. Compilation of O-C variation for various years. 
Triangles, open dots and filled dots refer to photographic, 
visual and photoelectric observations.
             
  In Figure 1, we present O-C variation from 1903 to 1982
(110 points). The last two dots correspond to latest observations
obtained at the Ege University Observatory with 48 cm Cassegrain
telescope.

  The star was photoelectrically observed and two accurate
minimum times were determined according to the chord bisection
method. These are,

     JD Hel Min I  = 244 4986.3624     January 16, 1982
     JD Hel Min II = 244 4986.5290            "
     JD Hel Min I  = 244 4987.3639     January 17, 1982


  We adopted JD Hel Min I = 244 4986.3624 (first minimum) as
T_0 and 0.33363808d (Cester, 1973) as the period and all available
110 (photographic, visual and photoelectric) JD Min I values
were recalculated and new O-C values obtained (see Figure 1).
                   
                      [FIGURE 2]

Fig. 2. The light curve of the star obtained on two nights
(16, 17 January, 1982) consecutively.
            
   In Figure 2 we present the average light curve obtained on
 16 and 17 January 1982. The first night, a complete light curve
 was obtained, the second night only the primary minima repeated.

 Acknowledgements:
   We would like to thank to Mr. Kucuktaka and to Mr. O. Tumer
 for their help.




                  E. HAMZAOGLU
                  V. KESKIN
                  T. EKER
             Ege University Observatory
             Department of Astronomy
             Izmir-Turkey





Reference:
Tunca, Z., Tumer, O., Evren, S., 1979 IBVS No. 1607.