MAXI/GSC detection of an outburst from a transient binary X-ray pulsar 4U 1901+03

ATel #3829; T. Sootome (RIKEN), M. Nakajima (Nihon U.), T. Mihara, M. Sugizaki, M. Serino, S. Nakahira, T. Yamamoto, M. Matsuoka (RIKEN), H. Negoro, F. Suwa (Nihon U.), S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), N. Kawai, M. Morii, K. Sugimori, R. Usui, T. Toizumi (Tokyo Tech), A. Yoshida, K. Yamaoka (AGU), H. Tsunemi, M. Kimura, H. Kitayama (Osaka U.), Y. Ueda, K. Hiroi, M. Shidatsu (Kyoto U.), Y. Tsuboi, T. Matsumura, K. Yamazaki (Chuo U.), M. Yamauchi, Y. Nishimura, T. Hanayama (Miyazaki U.) report on behalf of the MAXI team
on 26 Dec 2011; 21:45 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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We report on the detection of a new outburst from a transient X-ray binary pulsar 4U 1901+03 with MAXI/GSC. On 2011 December 20 (MJD 55915), the MAXI nova-search system triggered on a small flux enhancement from the position consistent with 4U 1901+03. The source flux in 4-10 keV band was 13 +/- 4 mCrab on MJD 55915, and slowly increased to 23 +/- 4 mCrab on MJD 55920. The flux increase is also seen in the Swift/BAT light curve. The activities from this source is rare. This is the third X-ray outburst from this source in 40 years, after the ones in 1970-71 (Forman et al.\ 1976) and in 2003 (Galloway et al.\ 2005). The latest source flux can be checked at the following page; http://maxi.riken.jp/top/index.php?cid=1&jname=J1903+031