MAXI/GSC detection of a new hard X-ray transient source MAXI J1659-152

ATel #2873; H. Negoro (Nihon U.), K. Yamaoka, S. Nakahira (AGU), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), T. Mihara, Y. E. Nakagawa, M. Sugizaki, M. Serino, T. Yamamoto, T. Sootome, M. Matsuoka (RIKEN), N. Kawai, M. Morii, K. Sugimori, R. Usui (Tokyo Tech), A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima, H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), Uzawa, K. Yamazaki, K. Matsumura (Chuo U.), report on behalf of the MAXI team
on 25 Sep 2010; 16:12 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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The MAXI/GSC auto-detection alert system independently detected a new transient source at a position (R.A., Dec) = (+254.79 deg, -15.27 deg) = (16h59m10s, -15d16m05s) (J2000) with a typical systematic uncertainty of 0.2 deg, consistent with GRB 100925A detected by Swift/BAT (Mangano et al. GCN #11296). MAXI/GSC data, however, suggests that the source has brightened since around 2010-09-25 02:30, and almost linearly increased. The 2-10 keV flux was 20+-8 mCrab during a transit around 2010-09-25 05:33 (UT), 19+-8 mCrab (07:04), 30+-9 mCrab (08:36), and 43+-9 mCrab (10:08). The latest (11:39) data show the flux is about 52 mCrab. Note that Swift/BAT triggered the source at 2010-09-25 08:05:05. These data show that the source is not a simple GRB as speculated by Kann (GCN #11299), but a galactic X-ray transient. Further followup observations are strongly encouraged.

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