COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2037
 
      ROTHNEY ASTROPHYSICAL OBSERVATORY PUBLICATION
                    SERIES B, No. 6

                                  Konkoly Observatory
                                  Budapest
                                  1981 November 5

                                  HU ISSN 0374-0676



                R PHOTOMETRY OF RW Com





   The 0.24 day W Ursae Majoris system RW Com has been the subject
of intensive UBV photoelectric monitoring (Milone et al. (1980)) as
well as JHKL photometry (Milone and Clark (1981)). Due to the sizeable
wavelength gap between V and J it was decided to obtain a light curve
in R.


   The system was studied by T.J. Davidge and J.D. Himer during 3
nights in June 1980 with the 0.40 meter reflector at the Rothney
Astrophysical Observatory. The detector used was a dry ice cooled
FW 118 photomultiplier,run at - 1900 volts. The comparison star used
was that designated as "b" in Tsesevich's (1953) study of the system.
Each variable star observation was bracketed by a comparison star
observation. Sky measurements were made directly after each star
measurement. 
   The light curve is shown in Figure 1. Phases were calculated using
the ephemeris given by Milone et al. (1980). Of particular importance
in the light curve shown here is the size of the "O'Connell Effect"
(O'Connell (1951), Milone (1969)). The O'Connell Effect is defined
to be the difference in magnitudes between the two maxima. It is
positive if the maximum following primary minimum is brighter than that
following secondary minimum. For this system it would appear that the
size of the O'Connell Effect increases  with wavelength. In the published
UBV light curves spanning 8 years, the O'Connell Effects in U, B, and
V remain fairly constant at about -0.09, -0.09, and -0.06 magnitudes
respectively (Davidge (1981)). In JHKL light curves the O'Connell Effect
appears not to be less than -0.02 magnitudes and not to exceed 0.00
magnitudes (Milone and Clark (1981)). Therefore it might be expected that the
O'Connell Effect in R should lie somewhere between the values quoted for
V and the infrared. Although there is considerable scatter in the maximum
following primary minimum in Figure 1, it can be seen that the O'Connell

                           [FIGURE 1]

             Figure 1:  R light curve of RW Com.


Effect appears to be comparable to, or even less than, -0.06 magnitudes.
This is not what would be expected from the above arguments.
   Clearly, more intensive photoelectric monitoring of this system
is necessary in R and I to confirm this finding and to uncover the
complete wavelength dependence of the O'Connell Effect in this system.



                        T.J. DAVIDGE
                        J.D. HIMER
                        E.F. MILONE
                        Rothney Astrophysical Observatory
                        Physics Department
                        University of Calgary
                        Calgary, Alberta, Canada
                        T2N 1N4





References:



Davidge, T.J., (1981), M.Sc. Thesis, University of Calgary, 36.
Milone, E.F., (1969), in "Non-Periodic Phenomena in Variable Stars"
   L. Detre ed., Academic Press: Budapest, 457. [BIBCODE 1969CoKon..65..457M ]
						[CoKon No. 65]
Milone, E.F., Chia, T.T., Castle, K.G., Robb, R.M., (1980), Ap. J.
   Supp. 43, 339. [BIBCODE 1980ApJS...43..339M ]
Milone, E. F., Clark, T. A., (1981), in preparation.
O'Connell, D.J.K., (1951), Riverview Pub. 2, 85.
Tsesevich, V.P., (1953), Odessa Izvestia 4, 218.