[vsnet-alert 8464] Re: V4641 Sgr active !!
Makoto Uemura
uemuram at hiroshima-u.ac.jp
Fri Jun 24 20:15:27 JST 2005
Re: V4641 Sgr active !!
According to the ASAS3 system, no sign of the outburst can be
seen before 23.21 June. Recent observations posted to VSNET are:
SGRV4641 050502.805 148C Myy
SGRV4641 050504.762 142C Myy
SGRV4641 050507.73442 13.78V Mhh
SGRV4641 050512.653 142C Myy
SGRV4641 050531.71027 13.84V Mhh
SGRV4641 050604.702 <138 Mdy
SGRV4641 050605.710 <138 Mdy
SGRV4641 050609.587 144C Myy
The object showed a very bright (8.9mag) outburst which lasted
only for one day in September 1999. Relativistic jets were associated
with this outburst.
After 1999, optical outbursts were recorded in May 2002, August 2003,
and July 2004. All of them showed similar characteristics, and
different from that observed in 1999. X-ray luminosities during these
three outbursts are much smaller than that in 1999. So, these outbursts
are rather lower energetic events. Interestingly, the object frequently
showed rapid variations during the outbursts in 2002--2004.
Such optical rapid variations imply that the optical emission originated
from a vicinity of a black hole or jets. Now, you may be able to see
a black hole with your eyes.
Studies of V4641 Sgr have been very difficult because the object
changed their states very rapidly; outbursts lasted only for one week,
and even during outbursts, characteristics of variations dramatically
changed day by day. So, dense time-series observations with short
exposure times are needed.
Regards,
Makoto Uemura
Hiroshima University
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