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MAXI/GSC observes possible transition to the high-soft state in Cyg X-3

ATEL # 2404; N. Kawai (Tokyo Tech), S. Nakahira, A. Yoshida, K. Yamaoka (AGU), M. Morii, K. Sugimori (Tokyo Tech), M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Suzuki, M. Ishikawa (JAXA), T. Mihara, M. Kohama, M. Sugizaki, Y.E. Nakagawa, T. Yamamoto (RIKEN), H. Negoro, M. Nakajima, R. Ishiwata, S. Miyoshi, H. Ozawa (Nihon U.), H. Tsunemi, M. Kimura (Osaka U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.) report on behalf of the MAXI team
on 26 Jan 2010; 7:06 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Nobuyuki Kawai (

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

MAXI/GSC has observed a sharp increase of the soft (<4 keV) X-ray flux from Cyg X-3 on 2010 January 24 after a slow gradual increase since 2010 January 20. The 1.5-4 keV X-ray flux tripled from January 19 to January 24 while the hard (10-20 keV) X-ray flux stayed almost constant, suggesting that the source is in the transition from the hard spectral state to a soft state. As the gamma-ray and radio flares have been observed after similar state transitions (Tavani et al. 2009 Nature 462, 620, Abdo et al. 2009 Science 326, 1512), multiwavelength follow-up observations are strongly encouraged. The MAXI/GSC light curve and image are updated daily at the following URL:

MAXI Light Curves

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