COMMISSION 27 OF THE I. A. U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                                Number 2492

                                                     Konkoly Observatory
                                                     Budapest
                                                     16 March 1984

                                                     HU ISSN 0374 - 0676



        A CLOSE ECLIPSING BINARY SYSTEM IN CYGNUS


  The variability of the star PG7 (alpha= 19h29.9m, delta=+38d56'; 
1950.0) was discovered by P. Guida (cf. Harns, 1977).
  The finding chart of the variable is given in Figure 1, and the magnitudes 
of the comparison stars derived photographically from the photoelectric
standard sequence in NGC 6819 (Anner, 1974) using two plates, are presented
in Table I.

                                     Table I
  
                                 star   B

                                   a  12.09m
                                   b  12.71
                                   c  12.94
                                   d  13.34



                              [FIGURE 1]


We estimated the object`s brightness on 270 photographic plates of the
Sternberg Institute  plate collection taken during the interval J.D. 2436072-
2444436.The reduction of these observations has shown that the star is a
W Ursae Majoris  type system with the following light elements:
                       J.D.Min_hel= 2439415.247 + 0.4050654d * E   .
The range is 12.5- 12.9 B, and minima are of equal depth.
    Since the duration of the eclipse is slightly longer than one hour and
the typical exposure time 45m, the real depth of minima must be greater




than that found in our observations.
   Figure 2 shows the mean light curve based on the determined period value.
No period change was found during this time interval.


                             [FIGURE 2]


The comparison of the "red" and "blue" Palomar  prints shows that the
color of the star does not  differ significantly from that of the surrounding 
stars.
It is desirable to carry out photoelectric and spectroscopic observations
of the object in order to determine the physical characteristics of the 
components of this close binary system.





                             S.YU. SHUGAROV
                          Moscow University Astronomical Institute
                          Sternberg State Astronomical Institute
                          13 Universitetskij Prospect
                          Moscow 119899
                          U.S.S.R.


References:

Anner, G.: 1974, Astronomy and Astrophysics Suppl.Ser., 13, 143. [BIBCODE 1974A&AS...13..143A ]
Harns, G.L.: 1977, Journal of the A.A.V.S.O., 6, No. 2, 62. [BIBCODE 1978JAVSO...6...62H ]