MAXI/GSC detects X-ray brightening of Cir X-1

ATel #2608; M. Nakajima (Nihon U.), M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), T. Mihara, Y. E. Nakagawa, M. Sugizaki, M. Suzuki, T. Yamamoto, T. Sootome (RIKEN), N. Kawai, M. Morii, K. Sugimori (Tokyo Tech), A. Yoshida, K. Yamaoka, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa, T. Matsumura, K. Yamazaki (Chuo U.) report on behalf of the MAXI team
on 10 May 2010; 16:37 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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MAXI/GSC has detected X-ray brightening of a LMXB, Cir X-1 since 2010 May 7 (UT). Since 2008 Apr 20, the source flux in 2--10 keV monitored by XTE/ASM and MAXI/GSC had been at a low level, about 10 mCrab on average and at most 70 mCrab. The X-ray flux from this source suddenly increased to 180 +- 20 mCrab on 2010 May 7 ( MJD = 55323.4 ) then reached at 320 +- 30 mCrab on May 8. This may suggest that Cir X-1 entered an active state. Multiwavelength observations are strongly encouraged. The latest light curve and the image of this source are available at the following URL: http://maxi.riken.jp/sourcelist.html.

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