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MAXI/GSC detects a renewed activity from binary X-ray pulsar GX304-1

ATEL # 3075; M. Nakajima (Nihon-U), T. Yamamoto, T. Mihara, M. Sugizaki, M. Serino, Y.E. Nakagawa, T. Sootome, M. Matsuoka (RIKEN), N. Kawai, M. Morii, K. Sugimori, R. Usui (Tokyo Tech), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M.Ishikawa (JAXA), A. Yoshida, K. Yamaoka, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, H. Ozawa, F. Suwa (Nihon U.), M. Shidatsu, Y. Ueda, N. Isobe, S. Eguchi, K.Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa, T. Matsumura, K. Yamazaki (Chuo U.) on behalf of the MAXI team
on 9 Dec 2010; 23:46 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Motoki Nakajima (

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

The MAXI/GSC auto transient-alert system has detected a new activity from a binary X-ray pulsar, GX 304-1 on 2010-12-08. The current source activity is the fourth event since the MAXI/GSC observation started on 2009 August. The source flux started to increase on 2010-12-05 (MJD 55535.5) and reached 20 mCrab (2-20 keV) on 2010-12-08 (MJD 55538.5). Comparing with the previous outburst (Atel#2779), the current flux increase is about 1-week earlier than that of the previous one within the orbital cycle of 132.5-day period. Thus, the current activity may be a precursor, or an onset of an anomalous giant outburst that occurs out of regular recurrent phase. In case of A0535+26 (Atel#2970), precursor events are seen in large outbursts (Atel#2970). Among the previous three outbursts from GX 304-1, only the last one, which developed into the giant outburst, had a precursor. Applying this relation, the incoming outburst is supposed to become giant. The latest light curve and folded light curve are available at the following URL:@ and also in the news page URL:

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