COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1715

                                     Konkoly Observatory
                                     Budapest
                                     1979 December 10


     PHOTOELECTRIC OBSERVATIONS OF RW COMAE BERENICIS


RW Com is a W UMa binary with a very short period, 0.237d. Hence it shows
extreme W-type properties: Ca II emission lines (Struve, 1950), and variable
and strongly asymmetrical light curves (O'Connell, 1951, Milone, 1976). The
star has been observed photoelectrically with the double beam photometer at the
106cm telescope of Hoher List Observatory in 1976. Comparison star has been
BD+27d2145. The B and V light curves are shown in Figs. 1 and 2, the B-V
curve is shown in Fig. 3.

                            [FIGURE 1]

    Fig. 1    B measurements of RW Com relative to BD+27d2145


                            [FIGURE 2]

               Fig. 2    V measurements of RW Com


                            [FIGURE 3]

               Fig. 3    B-V normal points of RW Com

The bluest part of the light curve is the brighter second maximum, indicating
the aspect of highest mean surface temperature. The reddest minimum is the
secondary minimum, which fact seems to be an unusual but common property of the
shortest period contact binaries. The peculiarities in RW Com's light curves
prohibit an analysis of the system's constants, but for a description the
Fourier coefficients of the light curve outside the eclipses (phases
0.16...0.34, 0.66...0.84) shall be given.

l_v=0.7965+0.0284 cos phi -0.1373 cos 2phi
          -0.0587 sin phi -0.0031 sin 2phi
l_b=0.7768+0.0093 cos phi -0.1551 cos 2phi
          -0.0632 sin phi +0.0092 sin 2phi

Though these formulae are impossible for a "rectification", they reveal a
section of constant light between phases 0.98 and 0.02. The eclipses of RW Com
seem to be complete therefore, with the occultation at primary minimum. The
ratio of the "radii" of the components may be of the order of 0.3, that of the
luminosities of the order of 0.2.

Minima times could be determined from the observations as follows:

Min I JD 2442841.3740
Min I    2442842.3215
Min II   2442842.4370

They are close to the ephemeris given in the GCVS, Suppl. 1 of 1971. So a
conclusion of considerable mass loss to the system, as proposed by Milone
(l.c.) is not supported by any obvious period change between 1968 and 1976.
Much more frequent observations of this object are necessary for a solution of
the problems associated with it.

The individual measurements have been sent to the IAU files of unpublished
observations of variable stars. The partly support of this study by DFG grant
Schm 167/12 shall be gratefully acknowledged.


M. HOFFMANN
Observatorium Hoher List
der Universitatssternwarte Bonn,
5568 Daun, F.R.G.

References:

O'Connell, D.J.K., 1951, Riverview Publ. 2, 85
Milone, E.F., 1976, Bull. American Astron. Soc. 8, 521 [BIBCODE 1976BAAS....8..521M ]
Struve, O., 1950, Astrophys. J. 111, 658 [BIBCODE 1950ApJ...111Q.658S ]


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