COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2245

                                    Konkoly Observatory
                                    Budapest
                                    1982 December 10

                                    HU ISSN 0374-0676



    THE FIRST PHOTOELECTRIC LIGHT CURVES AND THE PERIOD OF V 909 CYGNI



 The variability of V 909 Cygni (HBV 318=BD +27deg3441) was discovered 
photographically by Wachmann (1963) who obtained 14 minima from his 416 
photographic measurements. He classified the system as an Algol type eclipsing 
binary and gave the light elements as follows:

      J.D. Hel Min. = 24 35 317.465 + 1.4027080d.E .. ....(1)
                               +/-5       +/-83


He also presented the light curve of the system with 25 normal photographic
points. There is no secondary minimum in his light curve and the depth of the
primary minimum is about 0.42mag.
 In order to check the light variation and the period of V 909 Cygni, we
decided to observe it photoelectrically during the summer of 1982. Using the
single channel UBV photometer of Ege University Observatory, attached to the
98 cm Cassegrain telescope, the star was observed on 14 nights. An 
unrefrigerated EMI 9781 A photomultiplier tube and B,V filters very close to the
Johnson's standard system were used during the observations. BD +27deg3442 was
used as comparison throughout the observing period. The extinction coefficients 
in separate colours for each night were calculated from the observations 
of the comparison star using the conventional method; then, all differential 
observations (variable minus comparison) were corrected for the differential 
extinction. The corrections were small, because the comparison star is
very close to V 909 Cygni. Firstly we observed three minima; their E numbers
were even according to Wachmann's light elements. The depths of these
minima were equal. Then we observed another minimum. We saw that its E number 
was odd and it was considerably deeper than the previous ones. Therefore 
we decided that the period of the system should be twice that of given
by Wachmann (1963). During the observations four primary and three secondary



minima have been obtained and are given in the following table.



             The observed times of minimum

Hel.Min.J.D.   Min.   Filter   O-C

2445178.5261     II   B,V      -0.0009
    192.555      II   "        +0.001
    195.3592     II   "        -0.0003
    202.3736      I   "        +0.0005
    216.4002      I   "         0.0000
    230.4288      I   "        +0.0015
    261.2870      I   "         0.0000


  Using the above new photoelectric minimum times and the photographic ones
given by Wachmann (1963), the new light elements are calculated by the method
of weighted least squares as follows:

     Min.I = J.D. Hel 24 45 202.3731 + 2.8054230d E  .....(2)
                               +/-19       +/-10

The light and colour curves of the system are presented in Figure 1. The
phases in the Figure and the O-C values in the table were calculated with the
equation (2).

                                [FIGURE 1]



  The light curves show that V 909 Cygni is a typical well-detached Algol
type eclipsing binary. The colour of the system is slightly reddening at the
primary minimum and varies about 0.540mag and 0.500mag at the primary, 0.360mag and
0.360mag at the secondary minimum in blue and yellow light, respectively. The
solutions are in progress.
  This project is partly supported by the Turkish Scientific and Technical
Research Council.





               O. GULMEN, N. GUDUR, C. SEZER
               Ege University Observatory
               Bornova-Izmir-Turkey




Reference:
Wachmann, A.A.: 1963, Astronomische Abhandlungen der Hamburger Sternwarte,
  Bergedorf, Band VI, Nr. 7, 138