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MAXI/GSC detection of a bright X-ray flare from Mkn 421

ATEL # 2368; N. Isobe (Kyoto U.), S. Nakahira (AGU), M. Sugizaki, T. Mihara, M. Kohama, Y.E. Nakagawa, T.Yamamoto (RIKEN), M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Suzuki, M. Ishikawa (JAXA), N.Kawai, M. Morii, K. Sugimori (Tokyo Tech), A. Yoshida, K.Yamaoka (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, M. Nakajima, S. Miyoshi, H. Ozawa, R. Ishiwata (Nihon U.), Y. Ueda, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.) report on behalf of the MAXI team:
on 5 Jan 2010; 9:40 UT
Password Certification: Hiroshi Tomida (

Subjects: X-ray, AGN

A bright X-ray flare from the BL Lac object Mkn 421 was detected by MAXI/GSC. Its 1.5-10 keV X-ray flux started to rise from about 20 mCrab on 2009 December 27 (MJ D 55192), and reached a maximum of 116 +- 10 mCrab (1-sigma statistical uncertainty) at 2010 January 01 (MJD 55197.4). The peak flux of this flare is comparable to those in the recent strong outbursts observed in 2006 June (Donnarumma, et al. 2009, ApJ, 691, L13), 2008 March (Krimm et al, ATEL #1449), and 2009 October-November (Krimm et al. ATEL #2292, D'Ammando et al., ATEL #2295). Multiwavelength observations of this source are encouraged.

The MAXI lightcurve of the source is updated daily at the following URL: .

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R. E. Rutledge , Editor
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