[vsnet-alert 18913] V4641 Sgr active (ATEL)

[Taichi Kato]

V4641 Sgr active (ATEL)

   As everyone? knows, this object showed violent optical
variation during the active phase in 2002 and others.

===

ATEL #7858							     ATEL #7858

Title:	MAXI/GSC detection of renewed activity of the black hole candidate
		V4641 Sgr
Author:	T. Yoshii (Tokyo Tech), H. Negoro, (Nihon U.), S. Ueno, H.
		Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
		T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi,
		M. Matsuoka (RIKEN), N. Kawai, Y. Tachibana (Tokyo Tech), A. Yoshida,
		T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani
		(Osaka U.), M. Nakajima, T. Masumitsu, K. Tanaka (Nihon U.), Y. Ueda,
		T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.),
		M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii
		(ISM) report on behalf of the MAXI team:
Queries:	negoro at phys.cst.nihon-u.ac.jp
Posted:	30 Jul 2015; 15:04 UT
Subjects:X-ray, Binary, Black Hole, Transient

We report on an enhancement of X-ray flux from the black hole candidate
V4641 Sgr detected with MAXI/GSC. The MAXI/GSC nova alert system triggered
the event at 19:16 on 2015 July 29 (UT) (MJD 57232) (for the trigger event,
see http://maxi.riken.jp/pipermail/x-ray-star/2015-July/000387.html). MAXI
daily light curves of this source show that this new outburst has started
around 2015 July 20, and the 2-4 keV and 4-10 keV fluxes have gradually
increased, reaching 17.3 +/- 8.8 and 26.9 +/- 8.2 mCrab on MJD57232.0-57233.0,
respectively.

The long-term 2-10 keV light curve of MAXI/GSC shows at least three outbursts
with peak fluxes of beyond about 5 mCrab around MJD 55420 (ATel #2785,
#2832, #2892) ,MJD 56090 and MJD 56660 (ATel #5803, #5836), and the interval
is about 600 days.

The latest light curves and image of this source are available at the following
URL: http://maxi.riken.jp/top/index.php?cid=1&jname=J1819-254. Multi-wavelength
observations are encouraged.