[vsnet-j 2178] V4641 Sgr: remarkable flaring state!!

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

V4641 Sgr: remarkable flaring state!!

Dear Colleagues,

    We have just received time-series photometry on July 7 (UT) by
Roland Santallo.  Although the observation was slightly affect by the
clouds, V4641 Sgr shows *dramatic* repeated flare-like brightenings
by 0.5 mag.  The typical e-folding decay time of the flares was only
a few minutes.  The rise usually took 30 s to 2 min.  A 0.3 mag fading
within 40 s(!) was also observed in one of these flares.  Such a dramatic
activity reminds us of the repeated flaring state of the microquasar
GRS 1915+105 observed in X-rays.  We hope we will be able to
report on the analysis of the Kyoto data just following Santallo's
observation.  Such dramatic variation of any variable star was totally
unprecedented and unexpected.  Please keep as close as eye as possible
on this monster black hole binary!

Regards,
Taichi Kato
VSNET Collaboration team

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