COMMISSIONS 27 AND 42 OF THE IAU 
             INFORMATION BULLETIN ON VARIABLE STARS 
                          Number 3776 
 
                                         Konkoly Observatory 
                                         Budapest
                                         28 September 1992 

                                         HU ISSN 0374 - 0676 
 
 
        THE SPECTROSCOPIC BINARITY OF MW CYGNI CONFIRMED 
 
 
 The Cepheid variable MW Cyg (P=5.954586d) was found by Szabados 
(1991) to be a new spectroscopic binary Cepheid candidate on the base 
of a considerable difference of gamma-velocities among the 
observations published by Joy (1937), Struve (1945) and Barnes et al. 
(1988). Since July 1991 we have observed the star with the 
photoelectric velocity meter (CORAVEL type; Tokovinin 1987). Our 
first 13 radial velocities for MW Cyg (obtained with the 1-m and 0.6-m 
telescopes in Simeiz and at Mt. Maidanak) have been included in the 
catalog of Cepheid radial velocities (Gorynya et al., 1992). We have 
compared these velocities with those analysed by Szabados and found 
reasonable agreement with the measurements by Barnes et al. (1988); 
the older radial velocities showed great scatter and seemed to us to 
be insufficient to judge on the star's binarity with certainty. 
 
 This summer we gathered 21 new radial velocity measurements of MW Cyg 
with the same equipment at he 1-m telescope of the Simeiz 
International Observatory (Crimea, the Ukraine). The Table contains 
the velocities measured in 1991-1992 with their internal r.m.s. error 
estimates. The Figure shows the radial velocity curve (dots-1991, 
crosses-1992) which definitely confirms the star's spectroscopic 
binarity. We have been able to mention the fact of the binarity 
confirmation in a note added in proof to our catalog (Gorynya et al., 
1992) 


                                [FIGURE 1]

 Figure 1. Radial velocity curve of MW Cyg from our observations.
 Dots-1991, crosses-1992.

 
           Table 1 
Radial velocities of MW Cygni 
 
HJD-2448000     V_r   sigma 
453.506        -6.8    0.5 
495.428        -6.5    0.5 
496.450         1.4    0.7 
448.385       -32.2    0.6 
556.114        -2.2:   1.0 
557.184       -36.4    1.0 
558.156       -32.3    0.6 
559.148       -20.5    0.6 
561.166        -4.1    0.8 
562.144        -5.5    0.8 
563.143       -36.2    0.9 
566.187       -12.2    0.4 
567.135        -1.2    0.9 
795.428       -23.4    0.6 
807.487       -24.1    0.7 
823.405        10.8    0.8 
824.488       -13.6    0.9 
 
825.478       -25.0    0.5 
827.482        -7.7    0.4 
830.498       -16.0    0.7 
831.466       -24.5    0.7 
832.443       -16.9    0.8 
833.434        -7.8    0.5 
834.428        -1.9    0.5 
835.476        12.2    0.5 
846.352        -2.2    0.4 
848.437       -18.5    0.6 
849.407       -24.6    0.5 
850.380       -23.8    0.7 
851.339       -10.5    0.4 
854.313       -17.0    0.7 
856.318       -18.6    0.5 
857.372        -9.5    0.4 
858.373        -3.5    0.6 
 
 We wish to thank Mr. O. Ugolnikov for his assistance during the 
observations. We are grateful to the administrations of the 
observatories for allocating observing time for this program and to 
the staff of the observatories for their help. 
 
 
N. A. GORYNYA 
N. N. SAMUS 
Institute for Astronomy, 
Russian Acad. Sci. 
48, Pyatnitskaya Str., 
Moscow 109017, Russia 
 
T. R. IRSMAMBETOVA 
YU. V. KULAGIN 
A. S. RASTORGOUEV 
M. G. SMEKHOV 
A. A. TOKOVININ 
Sternberg Astronomical Institute 
13, University Avenue, 
Moscow 119899, Russia 
 
 
References: 
 
Barnes, T. G. III., Moffet, T. J., Slovak, M. H., 1988, Astrophys. J. 
  Suppl. 66, 43  [BIBCODE 1988ApJS...66...43B ]
 
Gorynya, N. A., Irsmambetova, T. R., Rastorgouev, A. S., Samus, N. N., 
  1992, Soviet Astronomy Letters, in press  [BIBCODE 1992SvAL...18..316G ]
 
Joy, A. H., 1937, Astrophys. J., 86, 380  [BIBCODE 1937ApJ....86..363J ]
 
Struve, O., 1945, Astrophys. J., 102, 232  [BIBCODE 1945ApJ...102..232S ]
 
Szabados, L., 1991, Commun. Konkoly Obs., No. 96  [BIBCODE 1991CoKon..96..123S ]
						[CoKon No. 96]
 
Tokovinin, A. A., 1987, Soviet Astronomy, 31, 98  [BIBCODE 1987SvA....31...98T ]