COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2986

                                                         Konkoly Observatory
                                                         Budapest
                                                         18 February 1987

                                                         HU ISSN 0374 - 0676


         PHOTOELECTRIC LIGHT CURVES OF V523 CASSIOPEIAE

The very short period eclipsing binary system V523 Cas was
discovered by Weber (1957). V523 Cas and CC Com have the shortest
orbital periods, 0d.234 and 0d.221, respectively, of any of the known
eclipsing systems. Subsequent photoelectric light curves have been
published by Lavrov and Zhukov (1976), Bradstreet (1981) and Hoffman
(1981). Zhukov (1985) studied all available light curves and reported
both long term and short term cyclic variations.
   The present observations of V523 Cas were made on three nights
during October, 1986. The 24 inch f/13.5 reflector at Lowell
Observatory was used with standard Johnson B, V filters and a
thermoelectrically cooled EMI 6256 photomultiplier tube. The comparison
and check stars were BD 49d0160 and BD 49d0151, respectively.
Approximately 460 observations were obtained at each effective
wavelength.
   Six epochs of minimum light were determined, using the Hertzsprung
technique (1928), from observations made during three primary and three
secondary eclipses. These are given in Table I.


                   Table I

 JD Hel.
2446700+    Minimum    Cycles     (O-C)

6.66816        I       -9.0       0.0002
7.71907       II       -4.5      -0.0005
7.83668        I       -4.0       0.0003
7.95309       II       -3.5      -0.0002
8.65443       II       -0.5       0.0001
8.77141        I        0.0       0.0002

   The ephemeris given by Lavrov and Zhukov was based on both
photoelectric and photographic observations. Since Bradstreet retains
their initial epoch in his improved ephemeris, a new ephemeris based on
photoelectric observations only is needed.
   However, a least squares fit to all available photoelectric minima
(which cover a span of about 23,500 cycles) leads to large O-C's. This
result is apparently due to a change in the period of the system since
Lavrov's and Zhukov's observations. This matter will be discussed at
length in a forthcoming paper. Due to these considerations, an improved
ephemeris has been calculated based on the photoelectric minima
determined subsequent to Lavrov's and Zhukov's observations. The minima
listed in Table I along with the eighteen other photoelectric minima of
Bradstreet (1981) and Hoffman (1981) were introduced with equal weights
into a least squares solution to obtain the following improved
ephemeris:

   JD Hel Min. I = 2446708.7712 + 0d.23369145
                            +-2           +-2 (p.e.)

   This ephemeris was used in calculating the O-C's in Table I, and in
determining the phases in Figure 1.

                         [FIGURE 1]

   Fig. 1 - Light curve of V523 Cas defined by the individual observations.

   The B and V light curves of V523 Cas defined by the individual
observations are shown in Figure 1 as delta m versus phase. The analysis of
the observations is underway.


                      RONALD G. SAMEC
                    BEVERLY B. BOOKMYER

                 Dept. of Physics & Astronomy
                 Clemson University
                 Clemson, SC 29634-1911, USA



References:

Bradstreet, David H. 1981, Astron. Journal 86 (1), 98. [BIBCODE 1981AJ.....86...98B ]
Hertzsprung, E. 1928, Bull. Astron. Inst. Neth. 4, 179. [BIBCODE 1928BAN.....4..178H ]
Hoffman, M. 1981, Inf. Bull. Var. Stars No. 1976.
Lavrov, M. I. and Zhukov, G. V. 1976, Trudy Kazan. Gorod. Astron. Obs.
   Nos. 42-43, 46. [BIBCODE 1978TrKaz..42...46L ]
Weber, R. 1957, Bull. Soc. Astron. Fr. 71, 36.
Zhukov, G. V. 1985, Sov. Astron. Lett. 11 (1), 42. [BIBCODE 1985SvAL...11...42Z ]