[vsnet-alert 8490] Recent V4641 Sgr activity

[Taichi Kato]

Recent V4641 Sgr activity

   As many have noted, the object seems to have a 2-day period in its
activity phase.  Please remember that there was a 2.5-day apparent
periodicity preceding the 1999 super-Eddington outburst.

   cf. Kato et al. (1999) IBVS 4777

   The nature of the object was unknown at the time of the 1999 event
(particularly before the giant outburst), and little is known about the
short-term variation and nothing about spectra during the 1999 pre-event
phase.  If the current activity eventually leads to the 1999-like event,
everyone would regret about the current lack of spectroscopic and
continuous multiwavelength observation, including interferometric radio
observation.

   If the object would brighten above ca. mag 10, this possibility might
come true...  Gamma-ray/X-ray satellite may need to be switched off to
prevent a damage as in the 1999 case...