MAXI/GSC detection of a bright X-ray flare from FK Aqr

ATel #6120; S. Nakahira (JAXA), A. Kawagoe, Y. Tsuboi (Chuo U.), H. Negoro ,M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki, M. Fujita, T. Namba, F. Honda (Nihon U.), T. Mihara, M. Sugizaki, M. Morii, M. Serino, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), N. Kawai, 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.), M. Yamauchi, Y. Morooka (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 5 May 2014; 17:56 UT
Credential Certification: Satoshi NAKAHIRA (nakahira@crab.riken.jp)

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On 2014-05-05 11:35:08 (UT) UT (=MJD 56782.48273), the MAXI/GSC transient alert system triggered ( trigger ID= 6782395557) on enhanced X-ray emission at (R.A., Dec) = (339.761 deg, -20.383 deg).
We obtained a refined position of the source at,
(R.A., Dec) = (339.714 deg, -20.523 deg) = (22 38 51, -20 31 22) (J2000)
with a statistical error of 0.18 degree radius with an additional systematic uncertainty of 0.1 degree (90% containment radius).
This position is consistent with a dMe star, FK Aqr.

The 2-20 keV flux averaged over the triangular transit was about 175±25 mCrab, corresponding to a luminosity of 3 ×10³¹ ergs s^-1 for an assumed distance of 8.6 pc. The flux decayed to an upper limit of ~20 mCrab at the next scan performed 92 minutes later. This flare from FK Aqr is the 2nd detection with MAXI/GSC, and is the largest among the two flares.