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MAXI/GSC detected an increasing soft X-ray component of Swift J1753.5-0127

ATel #2341; H. Negoro (Nihon U.), K. Yamaoka (AGU), M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Suzuki, M. Ishikawa (JAXA), T. Mihara, M. Kohama, Y. E. Nakagawa, M. Sugizaki, T. Yamamoto (RIKEN), N. Kawai, M. Morii, K. Sugimori (Tokyo Tech), A. Yoshida, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima, S. Miyoshi, H. Ozawa, R. Ishiwata (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.) report on behalf of the MAXI team
on 9 Dec 2009; 17:24 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Binary, Black Hole, Transient, Variables

Referred to by ATel #: 4056, 7196

MAXI/GSC detected an increasing soft X-ray component of the black hole candidate Swift J1753.5-0127. The possible state transition started around 2009-11-25.5 (UT), and the soft X-ray count rate in the 1.5-4 keV band increased by a factor of 2 (about 50 mCrab before the transition, reaching about 100 mCrab around 2009-11-28), while the hard X-ray count rate at 4-20 keV stayed in a similar level as those before. Swift/BAT data also show that harder X-ray counts decreased gradually from the rise time date of the present soft increase trend. (link: http://heasarc.gsfc.nasa.gov/docs/swift/results/transients/SWIFTJ1753.5-0127 ). This anti-correlation between the soft (1.5-4 keV) and hard (15-50 keV) bands is suggestive to the soft state transition of this source for the first time. MAXI in the commission phase will continues to monitor this source. Follow-up observations with multi-wavelength are encouraged.