[vsnet-chat 3534] R Cen

["Peter F Williams" <pfwilliams@onaustralia.com.au>]

Hi Stan and John,

The recent discussion on R Cen (vsnet-chat 3520, 3523 3530) prompted me to
'eyeball' my observations of this interesting star.  In recent years I have
mainly observed it with binoculars and I have a reasonable record of its
maxima since 1973.

These observations seem to cover almost all maxima during these 28 years. 
Unfortunately, my own data does not provide much information about the
minimum phase of the light curve.

Interestingly, the AAVSO Bulletin 63 for 2000 indicates R Cen to be at
maximum MI in January 2000, followed by minimum mI in May and coming again
to maximum MII this September.  This sequence seems to differ from that in
the VSS RASNZ Publications No2 (1974) which has MI followed by mII, then
MII and finally mI (mI being the primary deep minimum).

During May this year R Cen faded to near magnitude 8.6, suggesting this is
actually mII (shallow minimum, not primary minimum mI).  The previous
minimum (mI) occurred around Nov/Dec 1999 when R Cen was unfavourably
placed for me, but my observations suggest it did not fade much blow
magnitude 9 (can someone confirm this?), indicating the reduced amplitude
suggested by John.  The same also appears the case for several cycles prior
to this.

My data on the maxima of R Cen is summarised here:

YEARS		MAGNITUDE	PERIOD
		MI	MII

1973-79		6.14	6.47	549 days
1980-89		6.23	6.67	526 days
1990-99		6.41	6.97	521 days

Apart from squeezing nearly 30 year's data into just 3 lines and making me
feel just a little old, both maxima appear to have gradually become fainter
during this interval and with a greater difference between their peak
brightness.  There is also the clear decrease in period as mentioned by
both Stan and John.

I currently estimate R Cen near magnitude 8.0 and at this rate would not
expect it to attain much brighter than magnitude 7 during the coming MII
maximum due in September.  This is in line with the MII magnitudes given
above.

The data bases of the VSS RASNZ and the AAVSO would, of course, be much
more complete than my own observations used here.  It would seem R Cen may
be worthy of more detailed investigation.

Hope this is of interest.

Regards

Peter Williams
Heathcote NSW

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