[vsnet-chat 2548] Best or Worst Stars?

["William S G Walker" <astroman@voyager.co.nz>]

Greetings, All,

I've been giving thought to this topic but the mention of eta Carinae
brings up the memory of a star which could qualify for both lists.

In the early 1970s Brian Marino and I did photometry on one of eta's
comparisons as it was clearly variable. This is now QZ Carinae. The period
was so close to 6 days that every night we could forecast the readings to a
few percent. The period has now been refined to 5.9981 days which means
that eclipses - there are two in each 6 day cycle - take about 9 years to
repeat at the same longitude. In any one season they can only be observed
from one longitude band.

The star itself is intriguing. We measure the main eclipsing pair, a couple
of O9III stars, but there is a companion pair, two  O9.5I stars, with an SB
period of 20.73 days. All the stars will be ellipsoidal one presumes, which
adds to the complexity of the light curves. One could spend a lifetime on
this star (Brian and I gave up after 20 years) and still not get a
definitive light curve of either system. With this bunch of components it's
also one of the brightest intrinsically variable stars in the Galaxy. 

Oddly enough, it's followed immediately in the HD catalogue by another 6
day binary. So the eta Carinae region has more than its share of
interesting stars. 

Regards,
Stan

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