COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3021

                                          Konkoly Observatory
                                          Budapest
                                          7 May 1987

                                          HU ISSN 0374-0676


          H-ALPHA OBSERVATIONS OF W UMa (BD+56d 1400).

 Photoelectric observations of the short period (0.3336d) eclipsing binary
system W UMa were carried out during eight clear nights of March 16,17,21,
23,24,25,27 and 29, 1983. H-alpha narrow (lambda max=6569 A; HWFH= 38 A) and
H-alpha wide (A max= 6583 A; HWFH= 238 A) filters with an unrefrigerated
RCA 4509 photomultiplier attached to the 51 cm f/13.5 Cassegrain reflector of
Biruni Observatory of Shiraz University were used for these observations.
The star (BD+55d 1339) served as a comparison star which is frequently used
by other investigators of the W UMa system.
 The present observations are a continuation of the observations which were
carried out through narrow and wide H-beta filters in 1983 (Davan, 1985). From
H-alpha observations 14 minimum times are obtained using the tracing paper
method (Szafraniec, 1948), The minima and the ( O-C ) values are calculated
according to the light elements:

     JD(Hel) Min I = 2444986.3624 + 0.33363808d * E

given by Hamzaoglu et al. (1982). The minimum times are as follows;

 Date        JD(Hel)   E    (O-C)    Filter
 March         2440000. +   d
 
 16,17   5410.4157   1271   -0.0007    H-alpha N
 21      5415.4178   1286   -0.0032    "
 23      5417.4260   1282   +0.0032    "
 24      5418.4237   1295    0.0000    "
 25      5419.4246   1298   -0.0001    "
 27      5421.4242   1304   -0.0023    "
 29      5423.2613   1309.5 -0.0002    "
16,17    5410.4151   1271   -0.0013    H-alpha W
 21      5415.4187   1286   -0.0023    "
 23      5417.4228   1292    0.0000    "
 24      5418.4212   1295   -0.0025    "
 25      5419.4232   1298   -0.0014    "
 27      5421.4245   1304   -0.0020    "
 29      5423.2611   1309.5 -0.0004    "

From the above minima the following two periods are determined:

  Period = 0.33363774 +/- 0.00000113 ; H alpha N
  Period = 0.33363700 +/- 0.00000053 ; H alpha W

The periods are accurately determined to within 0.10sec and 0.05 sec for H alpha N
and H alpha W observations, respectively.

  The variations of the ( O-C ) values versus number of cycles E are presented 
in Figure 1. The filled and open dots denote H alpha N and H alpha W 
observations, respectively. The last two dots refer to the secondary minimum 
observations.


                              [FIGURE 1]
                              [FIGURE 2]


  Some investigators found evidences for oscillatory variations in the (O-C)
values (Hamzaoglu et al., 1982; Tumer et al., 1980). One can see this oscillatory
behaviour among the present (O-C) values. There is a rapid change between
the E values of 1285-1300. This is an indication for the intensive activity
in the system through March 21 to 25, 1983. This statement will be confirmed
if one looks at the light curves of the observations which were obtained on
March 21 and 23. There is an increase of light amplitude up to about 0.15 
magnitude in H alpha N but a decrease of about 0.05 magnitude in H alpha W observations
in the phase interval 0.12 - 0.25. While it seemed that any possible light
curve wave of W UMa has an amplitude no more than 0.05 mag (Breinhorst, 1971;
Rigterink, 1972; Eaton et al., 1980). There are also two other blueing near
phases 0.72 and 0.87 in the observation of March 21. The light curves are
shown in Figure 2. The filled dots refer to the observation of March 21 and
the plus sign indicates the observations of March 23, 1983.


                            [FIGURE 3]
                            [FIGURE 4]


  According to the present observations on H-alpha narrow and wide colours
one can conclude that the changes both in the (O-C) values and the light 
amplitudes may be due to mass ejections and/or spot activities in the system.
Infrared observations of Shenavrin and Zhukov, (1984) which were carried out
in the observational season of 1982 are in good agreement with the present
observations. The similarity of the light amplitude changes in both infrared
and H-alpha observations also indicates that the sources of activities may
have periodic appearances.
  A compilation of the light curves, and colour index changes are shown
In Figures 3 and 4, respectively.
  I would like to offer my sincere gratitudes to Prof. W. Seitter and Dr.H.W.
Duerbeck for their hospitality during my stay at the Astronomisches Institut
der Universitat Munster and to Dr. A. Bruch for his assistance in using
computer facilities of the institute.
   I would also like to thank Mr. R. Dummler and Mr.R. Budell for their help.
This work is dedicated to V. Karimipour for his competences and talents.


                        B.M. DAVAN

                        Astronomisches Institut der Universitat
                        Munster, F.R.Germany On leave from
                        Biruni Observatory of Shiraz University,
                        Iran





 References:

 Breinhorst R. A. 1971, Ap. Space Sci., 10, 411. [BIBCODE 1971Ap&SS..10..411B ]
 Davan B.M., 1985, I.B.V.S. No. 2745
 Eaton J.A., Wu C, - C., Rucinski S.M., 1980, Astrophys. J., 239, 919 [BIBCODE 1980ApJ...239..919E ]
 Hamzaoglu E., Keskin V., Eker T., 1982. I.B.V.S., No. 2083
 Rigterink P.V., 1972, Astron. J. 77, 230 [BIBCODE 1972AJ.....77..230R ]
 Shenavrin V. I., Zhukov G.V., 1984, I.B.V.S. No. 2541
 Szafraniec R., 1948, Acta Astron., 4, 81
 Tumer O., Evren S. and Tunca Z., 1980, I.B.V.S. No. 1783