COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                          NUMBER 79

                                        Konkoly Observatory
                                        Budapest
                                        18 January 1965



              ON THE VARIABLE STAR SVS 1284 IN M67


     The note by four authors (1) attracted anew our attention to the
variable stars in M67 (2, 3). The stars SVS 1283 and SVS 1284
have been again investigated on 50 plates obtained with the 16-inch
astrograph of the Sternberg Astronomical State Institute (JD 2434059.37
-2437699.33). 54 exposures of M67 were made on two days (JD
2437377.25-2437378.43) on 4 plates. It has permitted to derive the
elements of variable SVS 1284:

Min I hel = 2437378.322 + 0d.3604364. E
Max I = 13m.82; Max II = 13m.80; Min I = 14m.24; Min II = 14m.23 pg.


     The mean light curve is shown in fig. 1. Each point is equivalent
to 5 observations. Thus, the classification of the star SVS 1284 
belonging to the W UMa type, according to (1), is confirmed.

      An attempt was made to compute a model of the system of this
double star. If the modulus of M67 is m-M=9m.38 (4) and the physical
properties of the components are identical, then we have m_max=14m.57
pg, m_max=13m.97 pv for the magnitudes of each component, and T_e=
6000deg, IPg-IPv=+0m.60, BC=0m.05 for the stars of spectral class
G0 (5). Using the formula M_bol=96.57-10 log T_e-5 log R (6), the following
radii of the components were obtained: R_{1,2}=0.773. 10^6 km=1.112 R_{solar}.
Hence if the mass is proportional to R^3, then M_{1,2) =1.374M_{solar}. 
According to Kepler's law we can compute now the radius of the relative
circular orbits: a_0=2.078. 10^6 km, or R_{1,2}=0.377 a_0.

     The dimensions of the components are probable such that they
fill or nearly fill the innermost contact surfaces of Roche's model (7).
The radius of the star perpendicular to the plane of the orbit should be
in this case equal to y_{1,2}=0.374 a_0.

     The intensity of the light in the minimum I is 0.679 of the total
intensity of the components. This corresponds to the inclination
i_0 ~ 64deg between the plane of orbit and the visual plane (the tidal
form of the components were taken into account graphically).

     It is interesting that the period is constant over the interval of
about 3640d or ~ 1000P. It can be considered as the evidence of
rather high stability of this close binary system.

     The amplitude of the light variation of the second variable star
in M67, SVS 1283, is so small, that its investigation seems to be
practically impossible by photographic methods.

                        [FIGURE 1]

REFERENCES

1. Y. N. Efremov, P. N. Kholopov, B. V. Kukarkin, A. S. Sharov, 
   IBVS, No 75, 1964
2. N. E. Kurockin, Astr. Circ. USSR, No 212, 1960. [BIBCODE 1960ATsir.212....9K ]
3. N. E. Kurockin, Astr. Circ. USSR, No 220, 1961. [BIBCODE 1961ATsir.220...16K ]
4. O. J. Eggen, A. R. Sandage, ApJ 140, 130, 1964. [BIBCODE 1964ApJ...140..130E ]
5. H. L. Vanderlinden, Medd Univ Gent, No 10, 1955.
6. C. W. Allen, Astrophysical Quantities 1955.
7. M. Plavec, P. Kratochvil, BAC 15, 165, 1964. [BIBCODE 1964BAICz..15..165P ]

Sternberg State Astronomical Institute
Moscow, 5 January 1965.

                           N. E. KUROCKIN