COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 2990

                                                        Konkoly Observatory
                                                        Budapest
                                                        25 February 1987

                                                        HU ISSN 0374 - 0676


            PHOTOELECTRIC LIGHT CURVES OF VZ PISCIUM

The very short period eclipsing binary system VZ Psc was confirmed,
photoelectrically, as a W Ursae Majoris-type system by Moorehead (Wolff
et al. 1965). Subsequent photoelectric observations, made by Eggen
(1967), Poretti (1984, 1985), Davidge and Milone (1984) and Fry and
Milone (1985), have resulted in three published photoelectric minima and
an initial period determination of 0.261 days. Bradstreet (1985) has
obtained two well covered one-color photoelectric light curves.
However, these have high probable errors of a single observation of
+-0.018m and +-0.022m. He applied the Wilson-Devinney code to his most
recent light curve but no unique solution was determined. Hrivnak and
Milone (1985) have conducted a recent spectroscopic study and stated
that VZ Psc has a mass ratio near unity. The shallow depths of minima
(about 0.3) and the apparent variability of the amplitude and shape of
the light curve have hampered work on the system.
   The present observations were made on October 10 and 11, 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 star was BD +04d5010. The check
star is the 11m.5 star eastward and adjacent to the comparison star shown
on the chart by Giclas et al. (1959). Approximately 320 were obtained at
each effective wavelength.
   Four epochs of minimum light were determined from observations made
during two primary and two secondary eclipses. The bisection of chords
technique was used. These are given in Table I.

 JD Hel
2446700+   Minimum    Cycles     (O-C)

 9.6894      II        -4.5     -0.0008
 9.8228       I        -4.0      0.0018
10.7344      II        -0.5     -0.0009
10.8658       I         0.0     -0.0001



                          [FIGURE 1]

   Fig. 1 - Light curve of VZ Psc defined by the individual observations.


   These four minima along with thirteen other photoelectric minima by
Eggen (1967), Bradstreet (1985), and Poretti (1984, 1985) were
introduced with equal weights into a least squares solution to obtain
the following improved ephemeris:

   JD Hel Min. I = 2446710.8659 + 0d.26125897
                            +-4           +-4  (p.e.)

   This ephemeris was used in calculating the O-C's in Table I and the
phases of the present observations.
   The B and V light curves of VZ Psc 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, D. H. 1985, Ap. J. Supp. Series 58(3), 413. [BIBCODE 1985ApJS...58..413B ]
Davidge, T. J. and Milone, E. F. 1984, I.B.V.S. No. 2639.
Eggen, 0. J. 1967, Ap. J. 150, L111. [BIBCODE 1967ApJ...150L.111E ]
Fry, D. J. and Milone, E. P. 1985, Pub. Astron. Soc. Pac. 97, 88. (Abstract)
Giclas, H. L., Slaughter, C. D. and Burnham, R. 1959, Lowell Obs. Bull. No 102. [BIBCODE 1959LowOB...4..136G ]
Hrivnak, B. J. and Milone, E. F. 1985, B.A.A.S. 17(2), 584. (Abstract) [BIBCODE 1985BAAS...17..584H ]
Poretti, E. 1984, I.B.V.S. No. 2487.
Poretti, E. 1985, I.B.V.S. No. 2671.
Wolff, S. C., Wallerstein, G. and Sandage, A. R. 1965, Pub. Astron. Soc.
    Pac. 77, 370. [BIBCODE 1965PASP...77..370W ]