MAXI/GSC detection of X-ray brightening of Cir X-1
ATel #4661; M. Kimura (JAXA), M. Nakajima (Nihon U.), M. Serino (RIKEN), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa (JAXA), M. Sugizaki, K. Morihana, T. Yamamoto, J. Sugimoto, T. Takagi, T. Mihara, M. Matsuoka (RIKEN), N. Kawai, M. Morii, R. Usui, K. Ishikawa (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano (AGU), H. Tsunemi, M. Sasaki (Osaka U.), H. Negoro, M. Asada (Nihon U.), Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato, T. Kawamuro (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, Y. Nishimura, T. Hanayama, K. Yoshidome, Y. Ogawa (Miyazaki U.), K. Yamaoka (ISAS) report on behalf of the MAXI team
on 20 Dec 2012; 10:55 UT
Credential Certification: Motoko Suzuki (motoko@crab.riken.jp)
Subjects: X-ray, Binary, Neutron Star
On 2012-12-18T13:58(UT), the MAXI/GSC transient alert system
detected a significant increase of the X-ray flux from Cir X-1.
The flux at the scan transit centered at 13:58 was 67 +- 10 mCrab
(4-10 keV). The flux reached 1339 +- 39 mCrab at the scan transit
at 00:47 on 19 Dec, and then dropped to 123 +- 14 mCrab at 02:20.
Using the ephemeris of the 16.6-d period flares given by Nicolson (ATel #985),
the time of the nearest flaring peak is MJD=56279.980 (= 23:31 on 18 Dec),
which is 76 min before the observed flux peak.
The present maximum flux is the second brightest record of the MAXI observations
and the spectrum is fit by blackbody model with the temperature of
0.78 +- 0.03 keV.
The brightest outburst observed by MAXI peaked at around 12 Jul in 2011
(MJD=55754) with the maximum flux of 2113 +- 126 mCrab (4-10 keV)
and the blackbody temperature of 1.08 +- 0.05 keV.
The MAXI/GSC light curve of Cir X-1 is updated daily at the following URL.
http://maxi.riken.jp/top/index.php?cid=1&jname=J1520-571
