COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3363    

                                             Konkoly Observatory
                                             Budapest
                                             7 August 1989

                                             HU ISSN 0374 - 0676


          NEW PHOTOELECTRIC OBSERVATIONS OF VW CEPHEI


VW Cep is a short period variable star (HD 197433 = BD +75d752). It is the
brightest member of contact binaries of W-type (Binnendijk, 1970). This system
was discovered as a variable star by Schilt in 1926. It was the subject of
intensive study by various investigators. The irregularities in its light
curves and the changes in its period have led to different assumptions and
explanations to understand this system. Small humps seem to appear close to
the primary minimum. It is believed that these humps are produced by emissions
from a hot spot formed by a gas stream impacting on a circumstellar shell
around the hotter component (Pustylnik and Sorgsepp, 1976). Yamasaki (1982)
attempted to explain the irregularities and peculiarities in the light curve of
VW Cep in terms of star-spot model. According to his result the star-spot
moves on the stellar surface toward decreasing longitude with a period of about
2 years. Also this system suffers from both erratic and periodic changes in
the orbital period. These changes could be due to the distortion in the light
curve or due to the light-time effect. Some other investigators attributed
these changes to mass transfer between the two components (Karimie, 1983 and
Niarchos, 1984).

The present observation of VW Cep were made on the nights of 23 and 26 of
September, 1985. The 50 cm cassegrain telescope at Byurakan observatory in
Armenia (U.S.S.R.) equipped with a single-channel photoelectric photometer
furnished with an unrefrigerated RCAC 31034 A photomultiplier tube was used.

The stars chosen for comparison and check purposes are HD 195191 and 197665
respectively. The estimated uncertainties for the single observations are of
order 0.006m in B filter and 0.005m in V filter. The points which define 
the B and V light curves and B-V colour curve are potted in Figure 1.


                             [FIGURE 1]

             Fig. 1   Light curve of VW Cep in B and V


New times of minima have been obtained with Kwee and Van Woerden's method
(1956). The following ephemeris formulae (Kukarkin et. al. 1974) have been
used:

Min I (Hel.)=2439348.415+0.278314d E

The new moments of minima are as follows:

HJD               Min          O-C

2446333.4139      II           0.01328
2446336.3354      I            0.01249


N.L. JABIR   S.R. JABBAR
S.J. LAFTA   H.A. FLEYEH
Scientific Research Council
Astronomy Research Unit
Jadiriah - Baghdad - Iraq

References:

Binnendijk, L., 1970, Vistas in Astronomy, 12, 217. [BIBCODE 1970VA.....12..217B ]
Karimie, M. T., 1983, Astrophys. Space Sci., 92, 53. [BIBCODE 1983Ap&SS..92...53K ]
Kukarkin, B. V., et al., 1974, Second Suppl. to the Third Edition of the
   General Catalogue of Variable Stars, Moscow. [BIBCODE 1974sstt.book.....K ]
Kwee, K. K. and Van Woerden, H., 1956, Bull. Astron. Inst. Neth., 12, 327. [BIBCODE 1956BAN....12..327K ]
Niarchos, P. G., 1984, Astron. Astrophys. Suppl. Ser., 58, 261. [BIBCODE 1984A&AS...58..261N ]
Pustylnik, I. and Sorgsepp, L., 1976, Acta Astron., 26, 319. [BIBCODE 1976AcA....26..319P ]
Yamasaki, A., 1982, Astrophys. Space Sci., 85, 43. [BIBCODE 1982Ap&SS..85...43Y ]