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MAXI/GSC detection of a possible superburst from IGR J17062-6143/Swift J1706.6-6146

ATel #8241; H. Negoro (Nihon U.), M. Serino (RIKEN), R. Sasaki (Chuo U.), T. Sakamoto (AGU), S. Nakahira, S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), A. Yoshida, 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)
on 3 Nov 2015; 15:52 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Neutron Star, Transient

Referred to by ATel #: 8253

At 10:29:46 UT on 2015 November 3, the MAXI/GSC nova alert system triggered a bright X-ray burst from the position consistent with that of the low-mass X-ray binary IGR J17062-6143/Swift J1706.6-6146 (Churazov et al. A&A 467, 529, 2007). The 4-10 keV X-ray flux averaged over the scan transit assuming a constant flux was 2834 +- 116 mCrab (4-10keV, 1 sigma error).

No interstellar absorption is necessary for a blackbody fit to a GSC spectrum above 2 keV obtained in the scan transit at 10:29. The blackbody model fit to the spectrum in the 2-10 keV band gives the blackbody temperature of 1.44 +- 0.05 keV and the source radius of 17.2 +- 6.3 km if we assume the source distance to be 5 kpc, though the reduced Chi-squared is relatively large, 1.43 for 56 dof.

There was no significant excess flux in the previous transit at 08:57 UT with an upper limit of 20 mCrab. In the following scan transits at 12:03 and 13:35, the 4-10 keV fluxes were 179 +- 32 mCrab and 9 +- 14 mCrab, respectively.

On 2012 June 25, IGR J17062-6143 showed a similar, energetic and long X-ray burst lasting at least ~1100 sec (Barthelmy et al. GCN 13386; Degenaar et al. ATel #4219, ApJ 767, L37, 2013). This time, no burst like profile could be seen during the scan transit at 10:29, suggesting that the burst started before the scan transit, and lasted more than 11000 sec.

A Swift/XRT followup observation was requested, and approved.

MAXI data products for IGR J17062-6143/Swift J1706.6-6146