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X-ray re-brightening of Cir X-1 confirmed by MAXI/GSC

ATEL # 2674; N. Isobe (Kyoto U.), H. Ozawa, H. Negoro (Nihon U.), N. Kawai (Tokyo Tech), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), T. Mihara, Y.E. Nakagawa, M. Sugizaki, M. Suzuki, T. Yamamoto, T. Sootome, M. Matsuoka (RIKEN), M. Morii, K. Sugimori, R. Usui (Tokyo Tech),@ A. Yoshida, K. Yamaoka, S. Nakahira (AGU),@H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima, F. Suwa (Nihon U.), Y. Ueda, 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 14 Jun 2010; 16:26 UT
Password Certification: Hitoshi Negoro (

Subjects: X-ray, Binaries, Neutron Stars, Transients

On 2010-06-13 23:23:06.00, the automatic nova alert system of MAXI/GSC detected a significant increase of the X-ray flux from Cir X-1. The average flux over on 2010 June 13 reached to 95+-9 mCrab (4-10 keV). The nova alert was delivered to the subscribers (currently after human inspection). We find with the ground analysis that the current rebrightening of Cir X-1 starting on 2010 June 12 with a daily average flux of about 64 mCrab (4-10 keV), consistent with the suggestion based on a Swift observation (ATel #2671). After the outburst starting on 2010 May 7 (ATel #2608), the X-ray flux (4-10 keV) from Cir X-1 had decreased to less than 10 mCrab on 2010 June 3, comparable to the pre-outburst level, until June 11. We note that the current rebrightening occurred at almost two complete binary cycles from the start of the previous brightening on May 7, which was accompanied by series of X-ray bursts detected by RXTE and Swift (ATels #2643, #2650, #2651, #2653, Linares et al. arXiv:1006.1379), and also by MAXI (MAXI News: Multiwavelength observations are encouraged. Subscription to the MAXI nova alerts can be made at the MAXI web site at For galactic sources, please subscribe to the mailing list named "X-ray-star". The MAXI/GSC light curve of Cir X-1 is updated daily at the following URL.

MAXI Home Page

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R. E. Rutledge , Editor
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