[vsnet-alert 7334] IY UMa superoutburst, "triple" humps!

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

IY UMa superoutburst, "triple" humps!

Dear Colleagues,

   We have received three new data sets from Jochen Pietz.  The superhumps
and eclipses followed a generally expected course until May 16 (with
prominent beat phenomenon).  However, the light curve dramatically changed
on May 17, when seemingly "triple" humps appeared.  The light curve is
extremely queer, and does not resemble other SU UMa-type dwarf novae in the
past.

   Slightly similar, but a lesser degree, phenomenon was
observed during certain stages of WZ Sge in 2001
(see http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html ).
We have tentatively identified that two of the "triple" humps come from
ordinary superhumps, and the other one may be emergence of late superhumps,
but owing to the complexity, these identifications need to be verified
by further observations.  It may be possible that a similar phenomenon as
in the great WZ Sge may be taking place in the present IY UMa.  With a higher
inclination and deeper eclipses (than in WZ Sge; IY UMa has a configuration
to eclipse the central part of the accretion disk and the white dwarf),
detailed obvervations of IY UMa during the present superoutburst may
provide an excellent opportunity in revealing the mystery of poorly
understood complexity observed during the rare outburst of WZ Sge.

    IY UMa is truly the "king of SU UMa eclipsers" !!

    Further intensive observations of IY UMa are highly encouraged.

Regards,
Taichi Kato
VSNET Collaboration team

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