COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1960

                                    Konkoly Observatory
                                    Budapest
                                    1981 May 4

                                    HU ISSN 0374-0676



      RW Dor, LIGHT CURVE AND STUDY OF THE PERIOD


  The variability of RW Dor (HV 2435, Bph = 10.8) was announced
in Harv. Ann. 60, 100, 1908. Hertzsprung (B.A.N., II, 77, 1925)
determined the first photographic elements and found a light curve
of W UMa type; he quotes the spectral type K5 as given in Harv.
Bull. 754, 1921, suggesting the star to have dwarf characteristics
and a sensible proper motion. Schilt (B.A.N., III, 88, 1925)
published an improved photographic light curve, he obtained a
difference in depth of minima of 0.11 mag and estimated preliminary 
geometrical elements. Further, Hertzsprung (B.A.N., IV,
146, 1928) published photographic minima and a period P=
0.14273194d + 0.00000006d. These elements are given in the GCVS
(Kukarkin et al. 1969) and in the Finding List I.B.S. (Wood et
al. Philadelphia, 1980). Jones (M.N.R.A.S., 85, 1924-5) measured
the proper motion of RW Dor and Dworak (I.B.V.S., 846, 1973)
computed the photometric parallax including the system among the
the eclipsing binaries within 100 ps from the sun. These data
confirmed Hertzsprung's 1925 suggestion.
  We included RW Dor in our programme of UBV photoelectric 
observations at the Bosque Alegre Station of Cordoba Observatory.
From about 500 observations obtained in 1979-1980 we derived eight
times of minimum light for each pass-band of the UBV system. The
colour-average of these minima are listed in Table I (mean errors
are in parenthesis) together with the photographic minima 
published by Hertzsprung (1928).
  A linear least squares ephemeris for Hertzsprung values gives,

  (1) PM = JD Hel 2418240.3154 + 0.28546389d x E',
                      +-0.0015 +-0.00000010d m.e.

while for our photoelectric data we obtain

     (2) PM = JD Hel 2444514.97510 + 0.28546261d x E "
                         +-0.00020 + 0^d.00000053 m.e.

  The above light elements show that the period has not changed
within the errors since 1920's. Therefore all minima (Table I)
have been included in the analysis for a linear ephemeris, giving

     (3) PM = JD Hel 2430938.60171 + 0.285463812d x E
                         +-0.00078 + 0.000000016d m.e.


                                Table I
                                Minima of RW Dor
Min   Colour   J.D. Hel               E         (O-C)  (O-C)'    (O-C)" Remarks
               (2400000+)                                                  
 II   Pg       11298.835         -68799.5       0.0008  0.002              1
 II   Pg       14168.883         -58745.5      -0.0044 -0.004              1
 II   Pg       15621.901         -53655.5       0.0028  0.003              1
 II   Pg       16013.836         -52282.5      -0.0040 -0.004              1
 II   Pg       16489.714         -50615.5       0.0058  0.006              1
  I   Pg       17075.903         -48562        -0.0051 -0.005              1
  I   Pg       23784.600         -25061         0.0069  0.005              1
  I   Pg       24172.537         -23702        -0.0014 -0.004              1
 II   BV       44313.5813(10)     46853.5       0.0008           0.00007   2
 II   BV       44464.8764(10)     47383.5       0.0002          -0.00002   2
  I   UBV      44581.7728(8)      47793        -0.0009          -0.00055   2
  I   UBV      44608.6063(5)      47887        -0.0010          -0.00059   2
 II   UBV      44608.7488(6)     -47887.5      -0.0012          -0.00073   2
 II   UBV      44609.6063(8)      47890.5      -0.0001           0.00029   2
  I   UBV      44609.7493(5)      47891         0.0002           0.00062   2
 II   UBV      44610.7487(9)      47894.5       0.0005           0.00092   2



Remarks: 1/ Hertzsprung (1928), 2/ Present observations.


  The cycles E and residuals (O-C) of these elements are listed
in columns 4 and 5 of Table I, while (O-C)' and (O-C)" from (1)
and (2) are in columns 6 and 7. Note that the cycles E' and E"
are not given in Table I and that their zeros are different.
  The differential light curves corresponding to the nights of
January, 3, 4, 5 and 6, 1981, are displayed in Figure 1. They        
are relative to an uncatalogued star (Delta alpha=28.8s E, Delta 
delta=6'30" N)

                       [FIGURE 1]

of about the same colours. It is seen that the light curve of
RW Dor is similar to a W UMa star as previously classified,
however, primary minima are deeper than secondary minima by
delta DeltaV ~= 0.22, delta DeltaB ~= 0.23, delta DeltaU ~= 0.22, indicating a 
considerable difference of temperatures of the components, also the colours
at primary minimum are redder than the combined light at maxima
by about 0.1 mag.





                           F. MARTON *
                           A. GRIECO
                     Observatorio Astronomico
                     Laprida 854 - 5000 Cordoba
                     Argentina
                     * Fellow of C.O.N.I.C.E.T.