COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2683

                                     Konkoly Observatory
                                     Budapest
                                     11 March 1985

                                     HU ISSN 0374 - 0676

               LIGHT VARIATION OF BW Dra


  The W UMa type binary BW Dra is the fainter member of the visual binary
system ADS 9537.
  Yamasaki (1979) carried out UBV observations of this star between March
20, 1976 - May 16, 1977, and as in the case of BV Dra he found some scatter
in the light curve, but gave no explanation for its origin.
  During the years 1976-1984 Geyer et al. (1982) observed this star in BV
and UBV systems. They found the light curve of BW Dra fairly symmetrical, with
slight changes. The measurements of the individual nights have shown about
0.05m deviations from the mean light curve at all phases. The depths of the
minima were also variable.
  In 1975 Rucinski and Kaluzny (1982) observed the star on 5 consecutive
nights and found no light curve variation.
  BW Dra was observed in UBV colours on 3 nights (May 31, June 5, 8) in 1984
at Kottamia Observatory of the Helwan Institute for Astronomy and Geophysics.
As comparison star BD +62d1385 was chosen (see Table I of Geyer et al., 
1981).
The light curve is displayed in Figure 1. Magnitudes have been given in the
instrumental system and the phases have been calculated using the elements
of Yamasaki (1979):

           phase = J.D. hel. 2442858.27767 + 0.29216579 E

                          [FIGURE 1]
                          [FIGURE 2]
                            
Unfortunately only primary minima were obtained:

           Min I.: 2445857.3706
                   2445860.2946 (in Delta b)
                          .2958 (in Delta v)

The two primary minima are drawn in details in Figure 2. The observations made
at 2445857 and 244 5860 running together until about 0.0 phase. After that the
two light curves deviate from each other by about 0.06m-0.08m and produce minima
of different depths. This behaviour of BW Dra was already noticed by Geyer
et al. (1981).


                         N.S. AWADALLA
                         M. HAMDY
                         A.B. MORCOS
                         Helwan Institute for Astronomy
                         and Geophysics, Helwan, Egypt


References:

Geyer, E.H., Hoffmann, M., Karimie, M.T., 1982, Astron.Astrophys., Suppl.
        48, 85. [BIBCODE 1982A&AS...48...85G ]
Rucinski, S.M., Kaluzny, J., 1982, Ap.Sp.Sci., 88, 433. [BIBCODE 1982Ap&SS..88..433R ]
Yamasaki, A., 1979, Ap.Sp.Sci., 60, 173. [BIBCODE 1979Ap&SS..60..173Y ]