[vsnet-alert 16820] Fwd: ATel #5803 (X-ray outburst of the black hole system, V4641 Sgr)

[Makoto Uemura]

According to the MAXI team, the blackhole X-ray transient, V4641 Sgr 
is now active in X-ray. Follow-up optical observations are encouraged.

http://www.astronomerstelegram.org/?read=5803

Regards,
Makoto Uemura
Hiroshima University
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MAXI/GSC detection of a renewed X-ray activity of the black hole candidate V4641 Sgr

ATel #5803; Y. Tachibana (Tokyo Tech), T. Takagi, M. Serino, M. Morii (RIKEN), S. Nakahira (JAXA), H. Negoro (Nihon U.), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, J. Sugimoto, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, R. Usui, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, M. Sasaki (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 24 Jan 2014; 09:35 UT
Credential Certification: Mikio Morii (morii at hp.phys.titech.ac.jp)

Subjects: X-ray, Black Hole

  

We report on an enhancement of soft X-ray flux from the black hole candidate V4641 Sgr detected with MAXI/GSC. The MAXI/GSC nova alert system triggered the event at 11:42 on 2014 January 11 (UT) (MJD 56668) and at 02:24 on January 23 (MJD 56680) (for the latter trigger event, see http://maxi.riken.jp/pipermail/x-ray-star/2014-January/000254.html ) The 2-4 and 4-10 keV X-ray flux is 32 +- 4 and 22 +- 4mCrab on MJD56673.0-56674.0, respectively The result indicates that the source is now entering into a new outburst. Recent outbursts are reported in, e.g. ATel#2785. The long-term 2-10 keV light curve of MAXI/GSC shows at least two outbursts with peak fluxes of about 5 mCrab around MJD 55420 and MJD 56090, and the interval is 670 days. Since the position of the source could not be observed from MJD 56638 to MJD 56666, the onset of the current outburst is not clear. The interval from the onset of previous outburst may be around 570 days. The latest light curves and Image of this s
 ource are available at the following URL: http://maxi.riken.jp/top/index.php?cid=1&jname=J1819-254. Multi-wavelength observations are encouraged.

The latest light curves and Image of this source