[vsnet-alert 4658] IY UMa last night observation

[Makoto Uemura <uemura@kusastro.kyoto-u.ac.jp>]

   We obtained 7.3-hour light curve (UT 20.43 - 20.73) including 
one eclipse (others are not available due to clouds) observed at Kyoto 
(vsnet-alert 4655, 4666, 4667) and 5.4-hour light curve (UT 20.79 - 21.01) 
including three eclipses observed at  N. Copenicus Observatory 
(vsnet-alert 4654).

   IY UMa showed rapid decline from 20.43 (14.2 mag) to 
20.55 (14.7 mag) (UT, April 20), and then, the light curve 
becomes rather flat (0.3 mag/day) after 20.55.  
No short time variation was detected.   
The profile of eclipses is characterized with the rapid ingress 
and egress, the 1.2 mag depth, and the rather flat bottom.  

   These observational results are reminiscent of a beginnings of 
superoutburst although the recurence time is very short.  
The tonight observations will determine the nature of this outburst,
so more obsevations are urged.

Regards,
Makoto Uemura, Taichi Kato, Rudolf Novak
on behalf of VSNET collaboration team

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