[vsnet-chat 2098] Re: [vsnet-alert 3203] VW Hyi in outburst ... again

[Lew Cook <lcoo@yahoo.com>]

--- Berto Monard <LAGMonar@csir.co.za> wrote:
> VW Hyi has evolved into another outburst.
> For the past ten years (and probably longer back)
> the outburst cycle
> period of VW Hyi has been around 24 days, recently
> it has gotten
> closer to 14 days. Something new?
--------

In 1988 I did a short paper on VW Hyi outburst
frequencies for 1953 to 1980. The star goes through
long intervals where the outbursts are on one
frequency for times up to several hundred days and
will then abruptly change. The outburst frequencies
ranged from 18.6 days to 44.4 days figured on the
average time between outbursts during each of the
supercycles (intervals between superoutbursts).
Overall, the outburst frequency was every 27.02 days.
Supercycle average was 178.44 days, and this varied
(167 days for supercycles with 4 outbursts to 185 days
with supercycles with 7,8 or 9 outbursts) but not in
relation to the variation of the outburst frequencies.

I've looked at several dwarf novae in this manner.
These stars all seem to show this type of behavior
where they will speed up and slow down. In SS Aur and
AH Her, when the outbursts speeded up, the number of
wide outbursts decreased, but the Supermaxima of VW
Hyi did not show that behavior. (In SS Aur the wide
outbursts disappeared for years in one case).

Regards,
Lew

Reference:

Pub. Var. Star. Sec., RASNZ, No. 14, p.44, 1988

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