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MAXI/GSC observes a rapid spectral softening in XTE J1753-223

ATEL # 2396; H. Negoro, S. Miyoshi, H. Ozawa (Nihon U.), K. Yamaoka, S. Nakahira (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 (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima, 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 23 Jan 2010; 9:32 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Hitoshi Negoro (

Subjects: X-ray, Request for Observations, Binaries, Black Holes, Transients

MAXI/GSC has observed further spectral changes of the black hole candidate XTE J1753-223 (ATel #2258, #2259). After the gradual spectral softening since early January 2010 (ATel #2387), we observed a sharp increase of the soft (<4 keV) X-ray flux and a decline of the hard (>10 keV) X-ray flux on January 22, 2010. On January 22, the MAXI/GSC spectrum clearly shows two spectral components, a disk blackbody component and a power law component (as seen by RXTE, ATel #2391), which implies that the source is now in the soft state. The soft X-ray count rate (1.5-4 keV) increased by more than a factor of two (> 400 mCrab) from January 15 to 22, while the hard X-ray count rate (10-20 keV) decreased to less than half (< 200 mCrab). Further multi-wavelength observations are strongly encouraged. The MAXI/GSC light curve and image are updated daily at the following URL:

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R. E. Rutledge , Editor
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