[vsnet-alert 1275] Re: SW UMa

[Taichi Kato <tkato>]

Dear Rudolf and VSNET colleagues,

(reply to vsnet-chat 672,
http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-chat/msg00672.html)

> This should be very interesting to confirm results of OUDA and Brno
> observations from last year - increasing period during superoutburst and
> QSO's. And of course more covered first stages of superoutburst - we had
> just one night last year.

   Yes, the current presumable superoutburst would provide an excellent
opportunity to reconfirm the peculiarities in SW UMa and related objects.
As mentioned by R. Novak, SW UMa is unique in at least two points.  The
one is the positive period derivative (Pdot) of fully grown superhumps.
Very few dwarf novae are known, and only very recently become known, to show
similar behavior (V1028 Cyg, AL Com, HV Vir are good examples; I will continue
on some related issues in vsnet-chat).  The postive Pdot during the 1996
April superoutburst of SW UMa was unmistakable, but it is not still known
whether this object _always_ shows positive Pdot.  It's quite exciting to
know on the current occasion.

   The second peculiarity is the occasional presence of super-QPOs
(not QSOs.. ;-).  Super-QPOs were observed during the 1992 superoutburst
of SW UMa (Kato et al. 1992, PASJ 44, L215).  Super-QPOs consisted of a queer
recurring pattern of dip-like features amounting ~0.2 mag(!) every 6 minutes.
My speculation is that super-QPOs are only present during the developmental
stage of superhumps, and there may by some physical relation between these
gigantic QPOs and superhumps.  Observers are strongly urged to observe this
object with the highest achievable time resolution to record the profile
of possible super-QPOs.

   Some more information may be obtained from the URL

http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/swuma.html

   The present superoutburst of SW UMa is just in progress, as reports
tell.  We should surely have a good chance!  Please keep us informed
of the progress using vsnet-alert, vsnet-obs and vsnet-chat.

> I hope that dr. Kato will send article about SW UMa to vsnet soon - to
> inform you about results of our work.

   I hope Nogami-san, the first author of this paper, could!

Regards,
Taichi Kato

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