[vsnet-alert 7341] V4641 Sgr: strong oscillation!!

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

V4641 Sgr: strong oscillation!!

    V4641 Sgr is not in a monotonic fading, but still very active!
As already reported by B. Monard in [vsnet-alert 7339], by 
M. Linnolt in [vsnet-alert 7340], and by A. Pearce in 
[vsnet-obs 39944], the object has been showing short-term modulations.  

    Furthermore, the combined data set shows that the object is now 
oscillating between 11.5 - 13 mag with a time-scale of 1 day.  
After the first maximum observed by R. Stubbings on May 19, the 
object once faded.  Then, B. Monard's observations detected a 
rising phase to the second maximum on May 21.

    Our CCD observations at Kyoto last night shows a fading from 
the second maximum.  It was 12.68mag (average) at that time.  
The short-term modulations seem to be less prominent during our 
observations.  A. Pearces observations on May 22 shows that the 
object again brightened, indicating the third maximum.  He reports 
that short-term modulations again appear.

    Durations of each oscillation is short, no longer than 1 day. 
Multi-longitude observations are essential to study the correlation 
between short-term modulations and larger-scale oscillations.

Regards,
Makoto Uemura

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