COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                   Number 2228

                                Konkoly Observatory
                                Budapest
                                1982 November 17

                                HU ISSN 0374-0676





      PHOTOELECTRIC OBSERVATIONS OF THE PECULIAR SYSTEM VW Cep





  
VW Cep (= BD +75deg752 (7.2) = HD 197433 (G5) = GC 28804) is a W UMa-type
system. Since its discovery (Schilt, 1926) it has been frequently observed
because of its peculiar light variations. The orbital light-time effect proves
the existence of a third star in the system (Hershey, 1975).
  Mauder (1972), Rucinski (1973, 1974) and Giannone and Giannuzzi (1974)
made several studies explaining the physical properties of the VW Cep system.
  Schmidt and Schrick (1955) gave the following ephemeris:

       Min I = J.D. 2424658.759 + 0.27831993d. E.

  Brown and Pinnington (1969) studied VW Cep as a typical system of the
W UMa-type variables. Szczepanowska (1959) made photoelectric observations
of this star. She found that the variations of the O-C values were identical
for the primary and secondary minima, and the course of the O-C diagram
suggested a periodicity in the period variation.
  Szafraniec (1960) constructed a number of light curves for 3 eclipsing
binaries, among them was the VW Cep system. Todoran and Pop (1972) investigated
several minima of this star and found the following periodic elements:
Min I = HJD 2433483.4257 + 0.27831758d.E + 0.050d cos(0.0048deg(E-4700))
  Rovithis and Rovithis-Livaniou(1980) show that the period decrease which
started in 1960 is still present. Hershey (1975) discussed the period changes,
determined the absolute parallax and the astrometric orbit of VW Cep and
proved the presence of a third body in the system.
   Kreiner and Winiarski (1981) presented photoelectric observations of this
star in three successive nights and reported short time-scale variations in
the light curve. Mahdy and Soliman (1982) observed new light curves of
VW Cep using the ephemeris of Cristescu (1978):

         Min I = J.D. 2443448.2663 + 0.2783176d. E.
             


These elements are also used in the present work. Mahdy and Soliman concluded
that outside the eclipse, the VW Cep system is somewhat brighter, when the
larger and hotter component is advancing while the smaller and cooler component
is receding, than in the case of converse position.


                             [FIGURE 1]



 The observations of the present work were carried out at Kottamia Observatory 
using the 74" reflector on two successive clear nights, 7/8 and 8/9 of
July, 1982. The instruments were described in Mahdy and Soliman's (1982)
paper. BD +75deg877 was used as comparison star.
 The light curves in three colours are seen in Figure 1.
Four primary and four secondary eclipses were observed. The observations
will be published in Helwan Observatory Bulletin.
  The observed light curves are somewhat scattered and this is similar to
that observed by Mahdy and Soliman (1982). In order to describe the
variability of the VW Cep system more observations are needed. Further
photometric observations of this system are planned.





              A.S. ASAAD, S.M. NAWAR,

              M.A. SOLIMAN and N.S. AWADALLA

                Helwan Observatory
                    Egypt





References:

Brown, B.M.K. and Pinnington, E.H., 1969, A.J. 74, 541 [BIBCODE 1969AJ.....74..538B ]
Cristescu, C., 1978, I.B.V.S. No. 1383
Giannone, P. and Giannuzzi, M.A., 1974, Ap. and Sp. Sci. 26, 289 [BIBCODE 1974Ap&SS..26..289G ]
Hershey, J.L., 1975, A.J. 80, 662 [BIBCODE 1975AJ.....80..662H ]
Kreiner, J.M. and Winiarski, M.,1981, Acta Astr. 31, 351 [BIBCODE 1981AcA....31..351K ]
Mahdy, H.A. and Soliman, M.A., 1982, I.B.V.S. No. 2153
Mauder, H., 1972, Astron. Astrophys. 17, 1 [BIBCODE 1972A&A....17....1M ]
Rovithis, P. and Rovithis-Livaniou, H., 1980, Ap. and Sp. Sci. 73, 27 [BIBCODE 1980Ap&SS..73...27R ]
Rucinski, S., 1973, Acta Astr. 23, 79 [BIBCODE 1973AcA....23...79R ]
Rucinski, S., 1974, ibid 24, 119 [BIBCODE 1974AcA....24..119R ]
Schilt, J., 1926, Ap. J. 64, 221 [BIBCODE 1926ApJ....64..215S ]
Schmidt, H. and Schrick, K.W., 1955, Z. fur Astroph.,  37, 73 [BIBCODE 1955ZA.....37...73S ]
Szafraniec, R., 1960, Acta Astr. 10, 99 [BIBCODE 1960AcA....10...99S ]
Szczepanowska, A., 1959, Acta Astr. 9, 38 [BIBCODE 1959AcA.....9...38S ]
Todoran, I. and Pop, V., 1972 Acta Astr. 22, 267 [BIBCODE 1972AcA....22..267T ]