MAXI/GSC detection of a new outburst from NGC 6440

ATel #15033; H. Negoro (Nihon U.), M. Ishikawa (JAXA), M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, K. Komachi, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Tominaga, T. Nagatsuka, T. Kurihara (JAXA), Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu, K. Inaba (Kyoto U.), H. Tsunemi (Osaka U.), M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), and M. Sugizaki (NAOC)
on 14 Nov 2021; 11:33 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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At 13:31 on November 13, 2021, the MAXI/GSC nova-alert system triggered on a faint X-ray transient at (R.A., Dec.) = (267.423 deg, -20.467 deg), which is at about 0.22 arc-degree from the center of the globular cluster NGC 6440. Due to a data processing problem, we can not obtain a precise source position. A typical uncertainty of the trigger position is about 0.37 arc-degree (1-sigma, Negoro et al. 2016, PASJ, 68, S1). MAXI/GSC data show that the outburst started on November 10 (MJD 59528), and the 4-10 keV flux increased to about 30 mCrab on November 12.

At least 24 X-ray sources are present in NGC 6440 (Pooley et al. 2002, ApJ, 573, 184). After MAXI began the observation in August 2009, the accreting millisecond pulsar, AMP, SAX J1748.9-2021 (CX1) exhibited two bright (~250-300 mCrab) outbursts in December 2009 (Suzuki et al., ATel #2360) and February 2015 (Kuulkers et al., ATel #7098), and a faint one in October 2017 (Negoro et al. ATel #10821). Another transient AMP NGC X-2 (a.k.a. CXOGlb J174852.7-202124) was also discovered in July 2009 (Heinke et al. ATel #2139; Altamirano et al. 2010, ApJ 712, L58; Heinke et al. 2010, ApJ 714, 894), and showed frequent outbursts, e.g., in March 2010 (Altamirano et al., ATel #2500) and June 2010 (Patruno et al., ATel #2672). SAX J1748.9-2021 sometimes showed X-ray bursts, but no X-ray burst has been detected from this transient source, yet. The nature of this transient is unknown, and we tentatively name the source MAXI J1749-204.

Followup observations are encouraged.

Trigger Information about a new outburst from NGC 6440