COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2623

                                 Konkoly Observatory
                                 Budapest
                                 9 November 1984

                                 HU ISSN 0374 - 0676




             PRIMARY MINIMUM OF W CRUCIS




In response to the request by Plavec (1984) for observations of
W Crucis during the primary eclipse predicted for JD 2445893, 
photoelectric photometry was carried out on the 1.0m and 0.5m telescopes at
the Sutherland observing station of S.A.A.O by J. Spencer Jones,
F. Marang end J.D. Laing. The nearby Star HD 106015 was used as a
comparison star and was assumed to have the following magnitude and
colours: V = 8.990, B-V = 0.110, U-B = 0.237, (V-R)_c = 0.094 and
(V-I)_c = 0.200 where the last. two colours are on the Cousins' System
(Cousins, 1980). The results are listed in Table I below. Errors
are estimated to be +- 0.005 for all quantities.


                    Table I

                Photometry of W Cru

HJD
2445800+      V       B-V     U-B     (V-R)c   (V-I)c
      85.297  8.860   1.146   0.710   0.633    1.180
      86.260  8.899   1.140   0.683   0.627    1.168
      87.252  8.945   1.152   0.702   0.635    1.178
      88.258  8.968   1.152   0.665   0.631    1.166
      89.244  8.978   1.143   0.615   0.632    1.169
      90.248  8.992   1.117   0.575   0.624    1.163
      91.248  8.997   1.125   0.582   0.621    1.159
      92.255  8.995   1.118   0.570   0.612    1.137
      93.241  8.992   1.106   0.525   0.617    1.139
      97.273  8.988   1.112   0.609   0.614    1.129
     100.267  8.914   1.112   0.532   0.595    1.108
     104.272  8.778   1.125   0.633   0.619    1.142
     122.238  8.254   1.024   0.645   0.557    1.100
     123.235  8.258   1.042   0.621   0.585    1.130
     125.230  8.263   1.029   0.630   0.589    1.116
     126.235  8.255   1.054   0.626   0.586    1.128

                        [FIGURE 1]

       Figure 1: Light and colour curves for W Cru

The results are shown graphically in Figure 1. for the period 2445885
to 2445904.
From our data, it appears that the primary eclipse is total in V,
totality lasting at least three, and possibly as long as six days.
The simple expedient of reflecting the points of the V light curve
about a vertical axis of symmetry leads to our estimate of the time
of mid-eclipse of 2445893.7 +-0.1d which yields an O-C = +0.32d with
respect to the ephemeris given by Plavec (1984).


All colours become progressively bluer up to the time of mind eclipse,
with (U-B) changing the most.


Apart from our discovery that primary minimum is total, our results
appear to agree well with those of Marino, Walker and Herdman (1984).


                    J.W. MENZIES and J. SPENCER JONES
                    South African Astronomical Observatory




References:

Cousins, A.W.J, 1980. Mon. Not. Astr. Soc. S. Africa, 39, 22. [BIBCODE 1980MNSSA..39...22C ]
Marino, B.F., Walker, W.S.G. and Herdman, G., 1994. I.B.V.S. Number 2582.
Plavec, M.J., 1984. I.B.V.S., Number 2524.