The object has recently been bright. The brightness of the object in V band reached about 14 mag. The V-J color became bluer when the object was in bright state.
The figure shows V-band light curve obtained by KANATA/TRISPEC for the recent 2.5 years. The horizontal axis denotes the orbital phase calculated with a orbital period of 2.81728 days (Orosz et al. 2001). In 2007(red) and 2009(blue), the V magnitudes of V4641 Sgr were almost on the ellipsoidal modulations of its quiescent level. In 2008 (green), we observed some weak brightening events only in 2008 Oct (ATel #1797). We'll continue monitoring of this object for the research of flaring events of the black hole X-ray binaries.