COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2868

                                        Konkoly Observatory
                                        Budapest
                                        20 February 1986

                                        HU ISSN 0374 - 0676



           THE ECLIPSING BINARY V651 CASSIOPEIAE


   The binary V651 Cassiopeiae (also known as BV 326, CSV 8883 and
NSV 14717) was discovered by Strohmeier and Knigge (1960), although they
published only a finding chart. Using 193 Hartha Sky-patrol-plates,
Berthold (1982) derived ephemerides of JD2,437,016.435+0.4900267d E for the
interval from JD2,436,637 - 2,439,029 and JD2,443,015.413+0.4900322d E
for the interval from JD2,439,052 - 2,443,016. He claimed that an
abrupt period change in October 1965 had been detected. He also
classified the star as a W UMa variable and gave photographic magnitudes
of 10.5 - 11.0. The variable received its current name recently
(Kholopov et al. 1985).

   The binary was put on the program of spectroscopic orbital
determinations of short-period eclipsing binaries. Since July 1985,
forty-one spectrograms have been obtained with the 1.8-m telescope of
the Dominion Astrophysical Observatory (DAO) at a dispersion of
15 A/mm. Twenty-three of them were secured with the intensified
Reticon detector and measured by the program VCROSS (Hill 1982); while
the rest were obtained with the shectograph and measured by the software
package RETICENT (Pritchet, Mochnacki and Yang 1982).
   The velocities obtained do not agree with the period of 0.49d. A
new period of 0.9969d, a little longer than double the old one, has been
derived. The new ephemeris is:

          Min. HJD = 2,446,430.3159 + 0.996864d E
                                 22         41


Preliminary orbital solutions were tried with circular orbits assumed
and the systemic velocity of -30 km/s fixed. This value was estimated
from the spectrogram taken at HJD2,446,442.6299, which looked
single-lined. Radial-velocity curves are shown in Figure 1. These
curves must be very preliminary since only one node is covered.
However, the minimum mass of the system can be estimated to be
1.61 (0.83 + 0.78) Msun. The mass ratio then is close to unity (0.94),
which is significantly different from those of the W UMa group.


                            [FIGURE 1]

 Figure 1. Incomplete radial-velocity curves of V651 Cas. Dots denote
           absorption-line velocities and open circles CaII H and K
           emission-line velocities.



    Absorption features in the spectrum are quite sharp and not
distorted. This also indicates that the binary is probably not a member
of the W UMa group, whose spectral features are usually severely
broadened, diffused and distorted. Both components clearly show H and K
lines in emission, the velocities of which (also shown in Figure 1)
agree well with the absorption line velocities arising from the same
component. In the MK system, the components of the binary can be
assigned to G5V (more luminous component) and G8-K0 with some
uncertainty. In addition, the line-strength ratio was measured to be
about two.
    These properties suggest that the binary may be a member of the
RS CVn group (Hall 1976). If it is, the period of about one day (if
correct) is very important because it fills the period gap between the
long and short-period RS CVn groups:
   Further observations will be continued in future observing seasons
at DAO. Both photoelectric and spectroscopic observations at other
longitudes would be useful.
   I am grateful to Dr. A.H. Batten for his help in the analysis. I
would also like to thank Drs. D. Crampton, G. Hill, C.L. Morbey, and
C.J. Pritchet for placing their reduction programs at my disposal.




                  WENXIAN LU*

Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics,
5071 W. Saanich Road, Victoria, B.C., Canada V8X 4M6


* On leave of absence from Shanghai Observatory, Academia Sinica,
Shanghai, People's Republic of China

References:

Berthold, T: 1982, Comm. 27 I.A.U. Inf. Bull. Var. Stars No. 2192.
Hall, D.S. 1976, in Multiple Periodic Variable Stars, I.A.U. Colloq.
   No. 29, W.S. Fitch, ed. (D. Reidel Publishing Company), p. 287. [BIBCODE 1976ASSL...60..287H ]
Hill, G. 1982, Pub. Dominion Astrophys. Obs. 16, 59. [BIBCODE 1982PDAO...16...59H ]
Kholopov, P.N., Samus, N.N., Kazarovets, E.N., and Perova, N.B. 1985,
   Comm. 27 I.A.U. Inf. Bull. Var. Stars No. 2681.
Pritchet, C.J., Mochnacki, S., and Yang, S. 1982, Pub. A.S.P. 94, 733. [BIBCODE 1982PASP...94..733P ]
Strohmeier, W. and Knigge, R. 1960, Veroff. d. Remeis-Sternw. Bamberg,
   Band V(5).