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MAXI/GSC observation of an outburst from the Be/X-ray binary pulsar GRO J1008-57

ATel #6465; M. Nakajima (Nihon U.), H. Ohtsuki (AGU), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Morii, M. Serino, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo (AGU), H. Tsunemi, D. Uchida (Osaka U.), H. Negoro, K. Fukushima, T. Onodera, K. Suzuki, T. Namba, M. Fujita, F. Honda (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, A. Kawagoe (Chuo U.), M. Yamauchi, Y. Morooka (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
on 13 Sep 2014; 01:08 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar

Referred to by ATel #: 6630, 6656, 6664, 6819, 6823, 6917, 7490, 8547

The onset of the recurrent outburst of GRO J1008-57 was detected by the MAXI Nova-search system on 2014 September 2. This is the 8-th detection of its normal outburst by the MAXI/GSC since August 2009. The 4-10 keV flux reached 85 ± 6 mCrab on September 4 ( MJD 56904 ), and stays almost in the same flux level till September 11 ( MJD 56911 ). According to the previous GSC observations, no plateau peaks were observed except for the normal outburst (Atel#4319,#4355) preceding the giant one in November 2012 (Atel#4561,#4564,#4573,#4577). The Swift/BAT transient monitor also detected its brightening ( 90 ± 11 mCrab in 15-50 keV on September 4 ). In contrast to the constant 4-10keV fluxes, 15-50 keV data have started to increase on September 8 ( MJD 56908 ) and reached 179 ± 13 mCrab on September 12 ( MJD 56912 ). The hardness ratio of the 15-50 keV to the 4-10 keV flux changed from 0.2 to 0.3. These behavior resembles the onset of the giant outburst occurred in November 2012. Thus, there is a possibility that the current activity of this source would develop into the new giant outburst. We strongly encourage multiwavelength observations.
The latest source flux can be checked at the following page;
http://maxi.riken.jp/top/index.php?cid=1&jname=J1009-582.