COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3150



                                     Konkoly Observatory
                                     Budapest
                                     22 February 1988

                                     HU ISSN 0374-0676


              SV Cen - UBV LIGHT CURVE 1974-79

  The light curve of the eclipsing variable SV Cen (HD 102552) is presented
here with details of minima and maxima. Comparison star HD 102503 was used for
all observations and differential magnitudes in the sense Variable - Comparison
are presented here graphically and numerically in the file No. 177 of the IAU
Archives of Unpublished Photoelectric Observations of Variable Stars, The 
observations were done with standard UBV photometers at Perth Observatory and
Siding Spring Observatory.


                              [FIGURE 1]

 Fig. 1. Light curve of SV Cen in the UBV photometric system during
 the period 1974-79 (Perth and Siding Spring). Ordinates:
 Differential magnitude Var-Com in B, for V shift +.2 and for U shift -.2.
 Abscissae: Phase.


                              [FIGURE 2]

 Fig. 2. Differential magnitudes in B for phase close to primary
 minimum in detail. The digits represent the last digit of the
 year of observation between 1974-79, their center coordinates
 B(mag) and phase. For comparison, the 1970 observations of
 Irwin, Landolt (1972), and 1972 of Landolt (1973) are added.


                              [FIGURE 3]

 Fig. 3. The same as in Fig. 2 but for secondary minimum.

                              [FIGURE 4]

 Fig. 4. As for Fig. 2 for the higher maximum with expanded magnitude
 scale.

                              [FIGURE 5]

 Fig. 5. As for Fig. 2 for the lower maximum with expanded magnitude
 scale.


  Some observations have already been published by the author (Kviz 1976a)
but the majority of observations is available in the files mentioned above.
As the period of SV Cen varies very fast and in a rather complex way (Kviz
1976b, 1979, 1980; Herczeg, Drechsel 1985; Irwin, Landolt 1979) the calculation
of the phase was based on interpolated values of epochs and periods. The main
aim of these observations was the study of the variability of the period and
of changes in the depth of minima. Some results concerning this topic have
already been published (Kviz 1976b, 1982, 1983).

   Figure 1 shows the light curve in V,B, and U differential magnitudes.
Figures 2 and 3 show details of the primary and secondary minima respectively,
distinguishing the observed points for individual years of observation. Primary
minimum shows larger fluctuations from year to year than the secondary. To be
sure that the variation in the depth of minima (discussed in previous papers:
Kviz 1976b, 1982, 1983) is not caused by the variation of the zero point of the
whole light curve, the observation at both maxima was carefully carried on and
the details are presented in the Figures 4 and 5. As can be seen there are no
variations of the brightness at maxima (note the changed vertical scale for
maxima in comparison with minima, Figs. 2 and 3).
  The fluctuation in the depth of minima is thus real and observers are reminded
to pay sufficient attention not only to the time of the minimum but also
to the depth by measuring carefully the magnitude of the minima. Observations
on Siding Spring finished in 1979 because of discontinued support by the 
Australian Research Grant Commission. More observation of this star have been done
by the author in the Geneva photometric system: they are being reduced and the
results will be published in due time.


                      Z. KVIZ

                      School of Physics
                      University of New South Wales
                      P.O. Box 1 
                      KENSINGTON, N.S.W. 2033
                      AUSTRALIA





References:
Herczeg, T.J., Drechsel, H. 1985, Astrophys, Space Sci. 114, 1. [BIBCODE 1985Ap&SS.114....1H ] 
Irwin, J.B., Landolt, A.U. 1972, PASP 84, 686. [BIBCODE 1972PASP...84..686I ]
Irwin, J.B., Landolt, A.U. 1979, Coll. No. 46, Hamilton, N.Z. p. 465. [BIBCODE 1979ctvs.conf..465I ]
Kviz, Z, 1976a, IBVS No. 1162.
Kviz, Z. 1976b, Proc. Astron. Soc. Australia, 3, 45. [BIBCODE 1976PASAu...3...45K ]
Kviz, Z. 1979, New Zealand Journ. Sci., 22, 469. [BIBCODE 1979NZJS...22..469K ]
Kviz, Z. 1980, IBVS, No. 1864.
Kviz, Z. 1982, Proc. Astron. Soc. Australia, 4, 405. [BIBCODE 1982PASAu...4..405K ]
Kviz, Z. 1983, Trans. IAU XVIII B. p. 290.
Landolt, A.U. 1973, PASP, 85, 117. [BIBCODE 1973PASP...85..117L ]


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