[vsnet-alert 8499] Re: V4641 Sgr: very active on late June 28

[Makoto Uemura]

Re: V4641 Sgr: very active on late June 28

>     Most recent observations by Peter Nelson and Chris Stockdale indicate
> that V4641 Sgr became violently variable later on June 28.  Large variations
> with full amplitudes of 0.8-0.9 mag were recurring.  More detailed analysis
> in combination with other data will be presented by Uemura-san.

As reported by Kato-san, the object was again active on June 28 
(vsnet-campaign-xray 327).

Just now, we have received newest data from K. Nakajima on June 29.5-.7.
While the weather condition seems to have been bad, the data shows that  
the object was relatively calm, ~0.1mag above the quiescent level.

Since June 26, the object has, in most times, kept magnitudes slightly 
above the quiescent level, and apparently shown ellipsoidal modulations.  
Only one exception was June 28.  
Such behavior is remniscent of post-outburst active phases observed 
in 2002 and 2004 outbursts.  In 2004, in particular, 
"the object was recorded 0.05-0.4 mag brighter than the quiescent 
level until it finally returned to the quiescence on JD 2453209. 
The post-outburst active phase, hence, continued for 17 d after 
the main outburst." (from Uemura et al., 2005, IBVS 5626).

Based on past observations, we need to monitor V4641 Sgr at least 
more two weeks.  No one can predict when the next flaring state 
(like June 28) will come.

Regards,
Makoto Uemura
Hiroshima University