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MAXI/GSC detection of a gradual increase in the X-ray flux of Eta Carinae and possible historically brightest X-ray flares on June 15 and 17, 2014

ATel #6289; H. Negoro, K. Fukushima (Nihon U.), T. Mihara, T. Takagi (RIKEN), Y. Tsuboi (Chuo. U.), S. Nakahira (JAXA), N. Kawai (Tokyo Tech), M. Sugizaki, M. Serino, M. Morii, J. Sugimoto, A. Yoshikawa, M. Matsuoka (RIKEN), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), M. Nakajima, T. Onodera, K. Suzuki, M. Fujita, T. Namba, F. Honda (Nihon U.), T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), A. Kawagoe (Chuo U.), M. Yamauchi, Y. Morooka (Miyazaki U.), K. Yamaoka (Nagoya U.), report on behalf of the MAXI team:
on 4 Jul 2014; 07:11 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Binary, Star

Referred to by ATel #: 6298

MAXI/GSC has detected a gradual increase in the X-ray flux of Eta Carinae, and the 2-10 keV flux reaches approximately 0.07 photons/s/cm2 (~20 mCrab) in the end of June, 2014. The flux increase is thought to result from 2024 days periodicity of the system (e.g., Moffat & Corcoran 2009).

MAXI/GSC further detected bright flares on June 15 (MJD 56823.387-56823.518) and June 17 (56825.384-56825.579), 2014. From MAXI/GSC On-demand analysis, we found that the 2-10 keV flux of the flare on June 15, averaged over 3 scan transits, was 0.14 +/- 0.03 photons/s/cm2 (~ 39 +/- 9 mCrab), and the flux of the flare on June 17, averaged over 4 scan transits, was 0.15 +/- 0.03 photons/s/cm2 (~ 41 +/- 8 mCrab).

The peak flux time is close to the day, ~ June 22 (MJD 56830), expected from the 2024 days periodicity and the previous largest flare on December 6, 2008. The peak fluxes are more than twice larger than those in previous RXTE observations (~ 15 mCrab, Moffat & Corcoran 2009), and detailed analysis results will be reported elsewhere.

The source activity is expected to continue till the middle of July, and the MAXI public archive of Eta Car can be found at the following URL:

MAXI public archive : Eta Carinae