[vsnet-chat 84] Re: EG Cnc - first one?

[Fraser Farrell <fraserf@dove.net.au>]

G'day Stan (and vsnet readers),

On 1997-02-10 astroman@voyager.co.nz said:
   >Fraser Farrell wrote:
   >> WX Hyi's frequency of outburst was about 2 or 3 times per month a
   >>few  years ago, and outbursts were typically less than 2 days long.
   >>Even its  superoutbursts lasted no more than a week.  Now it is
   >>going off more  frequently, and for longer maxima. Taichi Kato
   >>seems to be right in  suggesting WX Hyi is trying to join "The ER
   >UMa Club".

   >I saw your note about WX Hydri. Rather than it being more active
   >lately it seems to have reverted to the earlier behaviour patterns.
   >We looked at this star from Auckland years ago - I think about the
   >mid-1970s - looking for an orbital period using pep. At that time
   >it seemed to be bright almost more often than it was faint and
   >weekly outbursts weren't unusual.

Eric Harries-Harris confirms that...

   >Not too long ago (in the last couple of years) it was suggested
   >that WX Hydri had stopped having outbursts. I'm unsure whether this
   >was normal or super, or even when the supposed cessation occurred.
   >Was this ever true?

You may be thinking of WX _Ceti_.  Our (incomplete) records of WX Hyi
show outbursts almost every month since 1990.  The VSS RASNZ Circulars
show at least two outbursts every month for the last several years; but
outbursts were shorter in the late 1980's - early 1990's.

   >In the normal outbursts we measured there was no pause at maximum -
   >decline began immediately as with several other southern UGSU stars
   >- although this may be difficult to pick visually. The supermaxima
   >had good superhumps at the start but they soon became rather messy.

WX Hyi does seem to stay at max for about a day in normal outbursts now.
We didn't detect any superhumps (visually) in the last supermax; but the
weather wasn't good for most of us.

Your note and the Circulars suggest we may be seeing a long-term
periodic variation (~20 years??) in the behaviour of WX Hyi. If so, it
may revert to lesser activity in about ten years or so.

I speculate that EG Cnc may represent an extreme example - decades of
inactivity, then months (years??) of vigorous activity, then inactivity
again.  Perhaps this should be part of the definition of ER UMa stars?
I await discussion from our professional readers!

cheers,

Fraser Farrell
Variable Stars Group
Astronomical Society of South Australia

WWW: http://vsnet.gist.net.au/assa/   email: fraserf@dove.net.au
traditional:  GPO Box 199, Adelaide, SA 5001, Australia

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