COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1385

                                  Konkoly Observatory
                                  Budapest
                                  1978 February 8




          118 DAY OPTICAL VARIATIONS IN VV Cep




     The long period eclipsing binary system, VV Cep, was 
observed on 40 nights, from August 1975 to December 1977, using
Halpha and Hbeta wide- and narrow-band filters. The observations were
made with the 38-cm telescope at Villanova University Observatory 
using an uncooled EMI 9558QB photomultiplier. In September
1977 this cell was replaced by an RCA C31034A cell cooled to -10dC.
At this time it was noticed that the Hbeta filters had suffered some
deterioration and were replaced by an Oxygen I (7774Angstrom) wide- and
narrow-band filter set.
     The output of the photometer amplifier is fed to an 
integrating system with a digital output as well as a chart recorder, 
The observing sequence was the usual pattern of sky-comparison-
variable-comparison-sky. The integration time was typically 50
seconds per reading. The comparison star was 20 Cep and
BD+62d1994 served as the check star. No significant variations
were detected between comparison and check stars. Differential
extinction corrections between comparison and variable were 
applied although the corrections were small and the time of each
observation was converted to heliocentric J.D. On a given night
5 to 10 observations of the variable star were obtained in each
filter. The points plotted in Figure 1 represent the nightly
means for the Halpha wide filter vs. JD Hel. The standard deviation
for each normal is generally less than 0.006m. Similar variations
are evident in the other wide-band filters.
     Preliminary analysis indicates the existence of a light
variation with a period of approximately 118.5 days. This period is
considerably shorter than the period of ~150 days reported by
Hayasaka et al. (1977) which is based on an observing interval
of 248 days. It should be noted that at the wavelength of the
Halpha filter (6563Angstrom), the contribution of the B star is less than 3% of
the total light and the variations noted in Figure 1 inside and
outside eclipse are mainly due to the supergiant M star. First
contact is predicted to be JD 2443087 and second contact is 
predicted on 2443114.
     The last eclipse of this system was in 1956-1957 and it
was observed by Frederick (1960) and Larsson-Leander (1957, 1959).
Their data in the longer wavelength show some light variations
other than that due to the eclipse. Assuming a period of 118.37
days and a minimum at JD 2443459.5 for the M star, we can predict 
minima in good agreement with those seen in both Frederick's
and Larsson-Leander's data. The maxima although less definitive,
are also in good agreement with the above period. This indicates
that the period of this light variation has been stable over the
last 20 years.
     If we assume our period of light variation (118.37d) to be
equal to the pulsation period of the M star, a value of rho/rho_sun=
=1.05 x E-7 is found using the relationship: P_0 = 0.0383 sqrt(rho_sun/rho)
given by Ledoux (1958). Combining this with the mass of 20 M_sun
(Wright, 1977) we find a radius of ~575 R_sun which is in agreement
with the value of ~580 R_sun given by Frederick (1960), but in 
conflict with the value of 1600 R_sun given by Wright (1977).
     Superimposed on the 118 day cycle, there appears to be
a cyclic variation in amplitude with a period of at least 825
days. The light variation of the M star in the VV Cep system
is similar in some ways to those of alpha Ori and mu Cep, both 
supergiants.
     Observations of VV Cep are continuing and a complete 
analysis of the light variations, including the eclipse, will be
published in detail elsewhere.
     We would like to thank M. Acierno, L. Casswell, R. Del Conte,
O. Lupie, D. Turnshek, K. Young, for helping with the 
observations.



                          GEORGE P. McCOOK
                          EDWARD F. GUINAN
                          Department of Astronomy
                          Villanova University
                          Villanova, Pennsylvania 19085
                          U.S.A.


References:

Frederick, W.F., 1960, A.J. 65, 628 [BIBCODE 1960AJ.....65..628F ]
Hayasaka, T., Sato, H., Saito, M., Saijo, K., Kitamura, M., 1977,
       Tokyo Astr. Bull. Second Series, 247, 2865 [BIBCODE 1977TokAB.247.2865H ]
Larsson-Leander, G., 1957, Arkiv Astron., 2, nr. 12, 135 [BIBCODE 1958ArA.....2..135L ]
Larsson-Leander. G., 1959, Arkiv Astron., 2, nr. 27, 301 [BIBCODE 1960ArA.....2..301L ]
Ledoux, P., 1958, Handbuch der Physik, Springer-Verlag, 51, 353 [BIBCODE 1958HDP....51..353L ]
Wright, K.O., 1977, J.Roy.Astron.Soc.Can. 71, No. 2, 152 [BIBCODE 1977JRASC..71..152W ]


                       [FIGURE 1]

  Figure 1  Halpha-wide normal points against Heliocentric
  Julian Date for VV Cephei.