COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1842

                                   Konkoly Observatory
                                   Budapest
                                   1980 September 13

                                   HU ISSN 0374-0676



        PHOTOELECTRIC MINIMA OBSERVATIONS OF THE
            ECLIPSING BINARY SV CENTAURI





   SV Cen is an early type contact binary (B1 III + B4) which
has shown the largest known period decreases of (dP/dT)/P =
-2x10^{-5} y^{-1} (cf. e.g. Drechsel et al. 1977 and literature quoted
therein). Photoelectric UBV observations of this close eclipsing
binary were carried out in 1978, 1979 and 1980 to determine further 
times of minima. For the observations we used the ESO 50 cm 
telescope and the double channel photometer, the Bochum 61 cm
telescope with its standard photometric equipment, and the ESO
50 cm telescope with the single channel photometer, respectively. 
For a description of the photometric facilities   cf. the
ESO Users Manual.
   We used CoD-59d3946 as a nearby comparison star. The times
of minima T_min were reduced to the Sun and are given in the
Table below.

                    Table
          Times of primary minima of SV Cen

                Tmin        S.D.
         JD_o 2443601.6566+-0.0018
              2444024.5668+-0.0003
              2444299.8849+-0.0020
              2444304.8624+-0.0002

   The first entry in the table denotes a graphically determined 
minimum derived from a complete lightcurve (Drechsel et al.,
1980b). The other minima were obtained using the method described 
by Kwee and van Woerden (1956). The standard deviation was
calculated from the individual minima determined from the UBV
measurements.
   The first two minima given in the table show the continuing

decrease of the orbital period as expected from previous observations. 
The last two minima however were observed delayed
by more than 20 minutes (compared to the expected times of minima), 
which implies that the period has increased between our
observations in 1979 and 1980. It is suggested that this change
of sign of (dP/dT)/P is caused by a variation in the mass loss
from the binary system. In fact SV Cen has been proved recently
to be a mass loosing star by Drechsel et al. (1980a).







    H.DRECHSEL, H.-D.RADECKE, J.RAHE, G.RUPPRECHT, B.WOLF

          Dr.-Remeis-Sternwarte Bamberg,
          Sternwartstr. 7., D-8600 Bamberg






References:
Drechsel, H., Rahe, J., Wolfschmidt, G., Kondo, Y., Mc Cluskey,
      G.E.: 1977, in "The Interaction of Variable Stars
      with their Environment", Proc. IAU-Coll.No.42 (eds.
      R. Kippenhahn, J.Rahe, W. Strohmeier), Bamberg
Drechsel, H., Rahe, J., Wolf, B.: 1980a, Proceedings of Second
       IUE Conference, Tubingen, ESA SP-157, 213 [BIBCODE 1980ESASP.157..213D ]
Drechsel, H., Radecke, H.-D., Rahe, J., Rupprecht, G., Wargau,
      W., Wolf, B.: 1980b, Proc.IAU-Coll. No.59,Trieste
      (in preparation)
Kwee, K.K., van Woerden, H.: 1956, B.A.N. 12, 327 [BIBCODE 1956BAN....12..327K ]