[vsnet-alert 8466] V4641 Sgr very active / large flare

[B Monard]

In response to the reported brightening of V4641 Sgr, timeseries photometry
were dedicated to it at CBA Pretoria.

Observations, covering the time period JD 2453546.36 to 3546.66, showed
strong oscillations superimposed on a gradual brightening from unfiltered
magnitude 13.3 to 11.8.
At UT 20050624.9236 (JD 3453546.4236) a giant flare/flash (sudden
brightening over about 1 magnitude) was observed, lasting for less than one
exposure. In view of the selected timeresolution (exposures of 28 sec) it is
probable that the flash was shorter in duration and larger in magnitude.

Follow up observations at all timezones are strongly encouraged. With ASAS
1600-48 having faded to below magnitude 15.5, this might be a good
substitution target for Southern CBA observers, while keeping some guard on
the latter CV for eventual echo brightenings.


Berto Monard
Bronberg Observatory / CBA Pretoria