COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 679

                                       Konkoly Observatory
                                       Budapest
                                       1972 May 19


        WELCH'S RED VARIABLE STAR IN CRUX 
           AN R CENTAURI LIKE VARIABLE


This star was discovered in September, 1969, by R.G. Welch on photographic
patrol plates exposed by him. In Circular 151 of the RNZAS Variable Star
Section, Bateson published a chart of this star and gave its position as:

AR=12h13.5m, D=-56deg01.9', 1950

Welch advised the Auckland Observatory of his discovery and we have made 100
photo-electric observations during the period 1969 October 11 to 1972
February 9. These will be published shortly in the RNZAS Variable Star
Section Circulars, but copies are available from the authors upon request.
These observations are presented graphically in Figure 1.

All measures were made using the Auckland Observatory 50 cm cassegrain
reflector, and EMI 9502 SA photomultiplier, and standard UBV filters.
Comparison stars used were CPD -55deg4940 and CPD -55deg4926.

                         [FIGURE 1]

 Figure 1  Welch's red variable star in Crux    UBV observations

From the observations made in Auckland we have derived the following elements:
JD 2440827+420.25d E

The light variations range from, at maximum, V=7.2, B-V=+2.5, U-B=+2.0; to
minimum V~10.0, B-V=+3.5, U-B~+3.5.

Following discovery by Welch, Dr Richter of the Sonneberg Observatory has
kindly supplied photographic measures from plates taken in South West Africa in
1937 and 1951. Those in 1951 watch present observations very well but in 1937
the amplitude of the light variations appeared much smaller although there
were some comparison problems arising through the use of several differing
types of film emulsions.

The most notable feature of this star is that its light curve is very similar
to R Cen, in that it exhibits double maxima. The amplitude of the variations
is smaller, but this may be attributable to the greater redness of Welch's star
(+2.5 at maximum as against R Cen +1.9). In all other respects this variable is
very similar to two other stars of this type, R Cen and R Nor. The phase
positions of maxima and minima are very similar and the light variations,
expressed as a percentage of the total light variation are similar, although
the secondary minimum of this Crucis variable is rather shallower than either
of the others.

This star at present has an amplitude in B of about 4 magnitudes and it is
surprising that discovery was so late. We surmise, and this is confirmed by
the 1937 observations, that whilst the period remains reasonably steady the
amplitude may be highly variable. Further observations are continuing.


1972 February, 13

W.S.G. WALKER
BRIAN F. MARINO
Auckland Observatory, of the
Auckland Astronomical Society,
Auckland, New Zealand.