MAXI/GSC detection of a new X-ray outburst from RX J1709.5-2639(=XTE J1709-267)

ATel #5319; H. Negoro (Nihon U.), N. Kawai (Tokyo Tech), Y. Nakagawa (JAXA) T. Mihara, M. Sugizaki, M. Serino, M. Morii, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka, (RIKEN), S. Ueno, T. Tomida, S. Nakahira, M. Kimura, M. Ishikawa (JAXA), 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, M. Shidatsu, T. Kawamuro (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, K. Yoshidome, H. Yamada, Y. Ogawa (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 24 Aug 2013; 02:06 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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At 17:24:07 on August 20th, 2013 (UT), the MAXI nova alert system triggered on an X-ray enhancement from the position consistent with that of the recurrent neutron star soft X-ray transient RX J1709.5-2639 (=XTE J1709-267 or 1RXS J170930.2-263927).

Examining the earlier X-ray images of the field, we found that the source already showed a sign of enhancement on August 15-16th suggesting the beginning of the outburst, though the source was located near the edge of the detectors. The source region had been unobservable since August 17th until just before the trigger.

The one-day averaged 2-4 keV and 4-10 keV X-ray count rates on August 21th (MJD 56525) were 0.074+/-0.005 c/s/cm2 (~42 mCrab) and 0.054+/-0.004 c/s/cm2 (~45 mCrab), respectively.

RX J1709.5-2639 exhibited outbursts at intervals of 2-3 years (see ATel #255, #1302), e.g., recent outbursts occurred in July 2010 (ATel #2729) and in June-August 2012 (ATel #4304, Degenaar et al. ApJ 767, L31, 2013). It is to be noted that only one year has passed since the previous outburst even though the previous one was relatively large with a 4-10 keV peak flux of ~170 mCrab, almost twice as bright as the earlier ones.

Trigger information and recent MAXI light curves can be seen at:
http://www.maxi.riken.jp/alert/novae/6524621118/6524621118.htm
http://maxi.riken.jp/top/index.php?cid=000000000001&jname=J1709-266

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