Johannesburg Centre, Astronomical Society of Southern Africa


Variable of the Month:
UW Cen re-revisited.

This interesting variable featured in both the 1998 May and 1998 July issues of Canopus.

It is necessary to add an important footnote to the UW Cen story. Members will recall that in 1997 June, the American amateur Tom Cragg visited the Johannesburg Centre following an AAVSO meeting in Sion, Switzerland. Back in 1990, Tom reported a brightening of UW Cen at a time when nobody else saw the star. Some of us were skeptical and Tom's observation was discounted as "one of those things".

A number of months later, UW Cen brightened to about magnitude 9.5, stayed bright for some years and then faded again. This brings us to the description in the 1998 May Canopus, where I said that it was at minimum and invisible. Lo and behold, the VSNet, an active Japanese organisation, announced last month that UW Cen had brightened to mag 12.6 during November, fading to invisibility within a few weeks. I missed seeing it due to bad weather and visit to Australia but should have seen it on at least one night. Berto Monard of Pretoria did in fact observe it during its outburst and remarked that something funny is going on.

So Tom's 1990 observation was probably a good one and it all goes to show that we cannot have too many amateurs watching a given star. I sometimes get the impression that amateurs tend not to observe, thinking: "What's the use, the regulars are all watching it".

Nothing can be further from the truth so go out there, observe UW Cen and help the astrophysicists to unravel its mystery.

Danie Overbeek.


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