COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2582

                                        Konkoly Observatory
                                        Budapest
                                        12 September 1984

                                        HU ISSN 0374 - 0676


          PHOTOMETRY OF THE ECLIPSING STAR W CRUCIS

In I.B.V.S. Number 2524, Plavec (1984) made an appeal to southern observers
for photoelectric observations of the puzzling eclipsing star W Crucis. In
particular an update of the ephemeris of the time of primary minimum is
necessary to plan future ultraviolet spectrum observations during or near
totality.
At Auckland Observatory we have been making three colour UBV observations
since 1984 March 8 following a suggestion from E. Budding of the Carter
Observatory Wellington who has been corresponding with Plavec. We have
successfully covered one primary and one secondary minimum for which times
and details are presented below.
The equipment used was the Mark I photometer on the Edith Winstone-Blackwell
50cm Cassegrain telescope, described previously (Walker and Marino, 1978).
Light and colour curves during the secondary minimum show considerable
complexity, with asymmetry suggesting a multiple eclipsing object, for example,
a star plus a circumstellar shell, accretion disk and/or obscuring clouds.
Ingress was well advanced when observations started, but we were able to
determine a mid-eclipse time for the V data of J.D. 2445795.45 +- 0.40d. If a
circular orbit is assumed the ephemeris quoted by Plavec yields an O-C =+1.34
days.
Primary eclipse is more regular in V and B and does not appear to total in V.
The U observations, however, show similar complexity and asymmetry to that found
at secondary minimum. From the observations to this date we have determined a
V mid-eclipse time of J.D. 2445894.08 +- 0.13d. This yields an O-C = + 0.70d.
The data are summarised in Figure 1 as light and colour curves plotted against
phase using the ephemeris from Plavec (1984).
Observations are continuing and will be presented elsewhere in greater detail
when the present observing season ends.


                              [FIGURE 1]

 Figure 1. Three colour observations of W Crucis covering the
 interval JD 2445767 to JD 2445915. Phases are computed from
                     E = JD 2440731.6 + 198.53d


                  BRIAN F. MARINO, W.S.G, WALKER and G. HERDMAN
                 Auckland Observatory of the Auckland Astronomical
                                  Society Inc.

References :

Plavec, M.J., 1984, I.B.V.S. Number 2524.
Walker, W.S.G., and Marino, B.F., 1978 Publ No 6 (C78), V.S. Sect., Roy, Ast.
   Soc. N.Z.