COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3656

                                           Konkoly Observatory
                                           Budapest
                                           4 September 1991

                                           HU ISSN 0374 - 0676


       PHOTOMETRIC OBSERVATIONS OF THE CLOSE BINARY
                        DH CEPHEI


DH Cep (BD+57d 2607, HD 215835) is an early type (O5-6 V), massive,
double-lined spectroscopic binary with the orbital period equal to 2.11 days.
In 1949 Pearce determined spectrographically the orbital eccentricity of the
star as equal to 0.127. He also suggested a fast apsidal motion of the system.
These reasons made that the star was included into a programme of photometry of
the stars with apsidal motion conducted by the author in early sixties. The
lack of other photometric observations required as reference for check of the
apsidal motion and also some incompleteness of the obtained light curve
discouraged the author from publishing the observations in those old times. As
in the meantime some other photometric observations of the star were obtained
(Lines et al., 1986) it is perhaps worthwhile to publish also the old ones that
could serve for comparison in future investigation of the object.

The photoelectric observations of DH Cep were carried out in the period between
June 25 and October 23, 1963 in the Crimean Astrophysical Observatory with a
20-cm (MTM-200) telescope equipped with one channel photoelectric photometer
with the V (GG 11) filter. The photometry was differential. The star
BD+56d 2865 (HD 215923) was used as the comparison. 


                              [FIGURE 1]

       Figure 1. The light curve of DH Cep obtained in 1963.


Fig. 1 represents the
light curve of DH Cep. Delta V denotes the difference of the instrumental V
magnitudes between the variable and comparison stars. The phase was calculated
using the ephemeris:

         HJD Min = 2438272.358 + 2.11104 E.

The period in the ephemeris is the spectrographic period of Pearce (1949),
while the epoch was determined on the basis of the present observations.

The light curve resembles in outline the light curves of DH Cep obtained 22
years later by Lines et al. (1986). Like the observations of those authors
also the 1963 light curve does not show any evidence of the periastron motion.
The two minima also appear about one half period apart. It indicates (what was
already suggested by Lines et al.) that the spectrographic eccentricity of
Pearce must be spurious, unless the longitude of periastron is, both in 1963 as
in 1985, equal to 90deg or 270deg. In that case the apsidal motion period 
might be 22 or 44 years.

Fig. 1 shows also a slight difference in the shape of the two minima. Like in
the Lines et al. observations the minimum at 0.0P appears to be sharper and
narrower than the minimum at 0.5P. Assuming that the corresponding minima in
the two epochs (1963 and 1985) are due to the same geometric configuration in
relation to observer, we can try to determine a photometric period of DH Cep.
The values closest to the Pearce value are 2.11093 and 2.11149 days.
Additional photometric observations are needed to obtain a real value of
period.


                          IRENA SEMENIUK
                          Astronomical Observatory
                          of the Warsaw University
                          WARSZAWA, Poland

References:

Lines, H. C., Lines, R. D., Guinan, E. F., and Robinson, C. R.
   1986, Inf. Bull. Var. Stars, No. 2932.
Pearce, J. A., 1949, Astron. J., 54, 135. [BIBCODE 1949AJ.....54..135P ]