MAXI/GSC detection of X-ray enhancement toward the globular cluster Tarzan 1
ATel #5096; H. Negoro (Nihon U), M. Shidatsu (Kyoto U), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano, Y. Kawakubo (AGU), H. Tsunemi, M. Sasaki (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki (Nihon U.), Y. Ueda, T. Kawamuro (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 1 Jun 2013; 13:35 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient
At 23:18 UT on May 24th, 2013, the MAXI/GSC auto-detection system triggered X-ray enhancement at the position consistent with the globular cluster Terzan 1. We have confirmed that the X-ray flux has gradually increased from around May 19th, 2013 (MJD 56431), and still remains stable on timescale of days at the 4-10 keV flux of about 8 mCrab. The central position of the enhanced region in the smoothed 2-20 keV image, obtained from May 19th to May 30th, is (R.A., Dec) = (263.84, -30.48) with a typical uncertainty of 0.3 deg.
XB 1732-304 (a.k.a X 1732-304 and 1RXS J173546.9-302859) in the globular cluster Terzan 1 was known as an active X-ray burster in 1980s (Makishima et al. 1981, ApJ 247, L23), but the source has been long in the quiescent state since the end of the 1990s (Guainazzi et al. 1999, A&A 349, 819). In Terzan 1, another dim X-ray source was detected with Chandra (Wijnands et al. 2002, ApJ 572, 1002). The current X-ray luminosity about 6e35 erg/s assuming the 5.2 kpc distance was similar to those in the active state in the 1980s and 1990s, suggesting renewed activity of XB 1732-304. Since a possibility of a new X-ray transient in/toward Terzan 1 is not excluded, we tentatively name the source MAXI J1735-304.
Followup observations are encouraged to reveal the nature of this new transient.
