COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2745

                                       Konkoly Observatory
                                       Budapest
                                       11 June 1985

                                       HU ISSN 0374 - 0676


    PHOTOELECTRIC Hbeta W AND Hbeta N OBSERVATIONS OF W UMa (BD+56deg1400)
     


  The photoelectric observations of W UMa were carried out on 7 nights of
April 3, 5, 6, 13, 15, 16 and 19, 1983. The observations were obtained using
the 51 cm, f/13.5 cassegrain reflector at Biruni Observatory of Shiraz 
University. The photoelectric photometer is equipped with an unrefrigerated RCA
4509 multiplier tube and a Leeds and Northrup Speedomax was used to record
the amplified signals from the photomultiplier. The observations were made
using Stromgren HbetaN and HbetaW filters, the characteristics of them are given
in Table I. The sequence of observations was the usual pattern of sky-
comparison-variable-comparison-sky, with each reading lasting about 50 seconds.

                  Table I: Filter characteristics

    Filter  Halfwidth (angstrom)        Max            lambda(max)(angstrom)
                                    transmission
    HbetaW       155                   86.5 %                 4859
    HbetaN        31                   47.5 %                 4858
  The comparison star was SAO 27274 and SAO 27268 served as a check star. No
significant variations were detected in the magnitude differences between the
comparison and check stars. The moments of minima were obtained using Russell
method according to the ephemeris (Hamzaoglu et al., 1982).

                JD Hel MinI=2444986.3624 + 0.33363808d E

  The observed minimum times and (O-C) values are given in Table II.


                             Table II
      JD Hel
    2440000+ Type of Min  Filter       E          (O-C) days
    5444.4468 Min I       HbetaN   1373           -0.0007
    5444.4456 Min I       HbetaW   1373           -0.0019
    5444.2802 Min II      HbetaN   1372.5         -0.0005
    5444.2789 Min II      HbetaW   1372.5         -0.0018

  One can see that the (O-C) values of the primary minimum are slightly
greater than those for the secondary. The light curves are presented in
Figure 1. Both light curves are asymmetrical where the maximum near 0.25
phase is brighter than the corresponding maximum at 0.75 phase. The differences
in the mean heights of the maximum at 0.25 phase relative to the maximum at


                            [FIGURE 1]

         Figure 1: The HbetaN and HbetaW light curves of W UMa.


0.75 phase are 0.013 mag and 0.010 for HbetaW and HbetaN observations 
respectively.
The loss of light at primary eclipse relative to the brighter maximum at 
0.25 phase is 0.670 mag and 0.712 mag in HbetaW and HbetaN respectively.
Consequently the primary minimum depth is deeper than the secondary minimum.
  I would like to express my gratitude to Mr. Y. Sobuti, Mr. D. Dorren,
Mr. H. Hadipour and Mr. N. Riazi for their help.


                           B.M. DAVAN
                           Biruni Observatory
                           Shiraz University
                           Shiraz, I.R. Iran


References :
Guinan, E., Najafi, S.I. 1979, I.B.V.S. No. 1662.
Hamzaoglu, M., Ecmekci, F. and Hamzaoglu, E. 1983, I.B.V.S. No. 2282.
Kaluzny, J., 1983, I.B.V.S., No. 2347.