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[vsnet-chat 2115] (fwd) Re: VW HYI

 Date: Tue, 13 Jul 1999 14:14:18 +1200 (NZST)
 From: Dr Frank Bateson <varstar@voyager.co.nz>
 Subject: VW HYI

Dear Colleagues,

Re:  VW HYI.        

I refer to your messages.  The last superoutburst was on May 9, 1999, which
was the date I had predicted (Changing Trends No. 70, 5th March 1999).
Normal outbursts followed with the intervals between successive normal
outbursts increasing as usual.  This is the usual pattern for the first four
normal outbursts that follow a super outburst.  When there are more normal
outbursts between consecutive superoutbursts the intervals then become shorter.

VW Hyi has been observed by the VSS, RASNZ, for almost 50 years.  You will
find a detailed Memoir containing a detailed light curve and light curves of
the different types of super outbursts in Bateson, N.Z.J.Sci. 1977 Vol 20
p.73-122. This led to my successful prediction of a superoutburst for
Voyager 2 which enabled the first UV data on VW Hyi to be obtained.  Since
then it has been observed at all wave lengths from x-ray to EUV and there
are well over 50 papers on this star.  Many of the 72 Ph.D students from
many countries referred to me by their supervisors have produced some very
fine and detailed theses on VW Hyi.

I suggestthat you consult the extensive literature noting that if there are
only four normal outbursts between successive superoutbursts the interval
between normal outburst 4 and the following superoutburst is around 35 days
or more.  You should also note that VW Hyi, like other SU UMa variables,
also has short duration flares.  These were originally discovered by me (see
1996. Echevarria, J. et al.  A.J. 467 p. 851-859 for references to my
papers.  These flares can be mistaken for the rise to an outburst.  The mean
supercycle is 179 days but subject to longer or shorter cycles as Vogt's
paper showed.

Hopefully this short note is of interest as it is diffuclt to compress all
the data available into a short message.

Regards,
Frank Bateson

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