COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2566

                                        Konkoly Observatory
                                        Budapest
                                        30 July 1984

                                        HU ISSN 0374-0676


   PERIOD AND LIGHT-CURVE OF THE CLOSE ECLIPSING BINARY FZ ORIONIS

 FZ Orionis (alpha 1950 = 5h38m45s, delta 1950 = 2d 35.0') was discovered by
Hoffmeister (1934). The General Catalogue of Variable Stars (Kukarkin et al.,
1969) gives the following information: type EW?, photographic magnitude range
10.0 to 11.0, period 1.597 day (?), spectral type G0. The W UMa-type light-curve
was suspected by Soloviev (1945). The period of 1.597 day is given by Kippenhahn
(1953) (type Beta Lyrae).
 Analysing 1229 visual estimates of FZ Ori made by GEOS, Figer (1983) has
shown that it is a W UMa-type eclipsing binary (EW) with a period about 0.4
day. Figer's work leads to the ephemeris:

       Min I = Hel. J.D. 2444024.4583 + 0.3999866 E
                            +-28             +-18


                             [FIGURE 1]

          Figure 1   V and B-V light-curve of FZ Ori


  In order to check this result and to obtain BV light curves (Johnson and
Morgan system), FZ Ori was measured with a photoelectric photometer attached
to the 1m telescope at Pic du Midi Observatory (France). FZ Ori was observed
during 4 nights from 1983 December 4 to 7. These measurements alone confirm
the period given by Figer (1983) and the EW nature of FZ Ori (typical V light
curve and constant B-V: Figure 1). The photoelectric measurements also confirm
the discrimination between primary minimum and secondary minimum as made by
Figer (1983). Table I gives dates and O-C's for the 3 individual photoelectric
minima obtained from 1983 December 4 to 7. The O-C values are referred to
Figer's ephemeris.

                       Table I

                  UT          HJD           O-C        type of minimum
1983 Dec 5        2h14    2445673.598     -0.005 d           I
1983 Dec 6        2h14        674.598     -0.005 d          II
1983 Dec 7       21h25        676.398     -0.005 d           I

  Since the star was observed during 4 successive nights only, no precise
ephemeris can be computed from the photoelectric measurements alone. Lumping
the 44 GEOS' visual minima (weight 1) and the 3 photoelectric minima
(weight 3), one obtains the following ephemeris (95% level of confidence for
the error bands):

         Min I = Hel. J.D. 2444024.4580 + 0.3999860 E
                                   +-25        +-12

  Figure 1 shows the V and B-V light curve of FZ Ori using the latter
ephemeris, V magnitudes range from 10.61 to 11.02 (Min. I) and 10.95 (Min II).
The mean B-V is equal to 0.51. These values are consistent with an EW type.
Although no correction for interstellar extinction was made, this B-V value
is in good agreement with Eggen's period-colour relation for contact binaries
(1961, 1967).


                   J.F. LE BORGNE *, A. FIGER #, M. DUMONT #
                  *Observatoire du Pic du Midi et de Toulouse
                   14 Avenue Edouard Belin
                   F-31400 TOULOUSE

                                    #  GEOS
                                    12 Rue Bezout 
                                    F-75014 Paris 

References:
Eggen, O.J., 1961, R.Obs.Bull., 31, 101 [BIBCODE 1961RGOB...31..101E ]
Eggen, O.J., 1967, Mem.R.Astr.Soc., 70, 111 [BIBCODE 1967MmRAS..70..111E ]
Figer, A., 1983, GEOS Circular on Eclipsing Binaries no 8
Hoffmeister, C., 1934, Astron.Nachr.. 253, 195 [BIBCODE 1934AN....253..195H ]
Kippenhahn, R., 1953, Astron.Nachr. 281, 153 [BIBCODE 1953AN....281..153K ]
Kukarkin, B.V. et al., 1969, General Catalogue of Variable Stars, Third Edition
  Moscow 
Soloviev, A., 1945, Astr.Tsirk. (Kazan), 41, 8