MAXI/GSC detection of an ongoing X-ray outburst from SAX J1747.0-2853 or a new X-ray transient MAXI J1746-290

ATel #12576; H. Negoro, W. Maruyama, M. Nakajima, A. Sakamaki, M. Aoki, K. Kobayashi (Nihon U.), T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, T. Hashimoto, A. Yoshida (AGU), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita, M. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, T. Midooka (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori, Y. Kurihara (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.), and Y. Kawakubo (LSU)
on 14 Mar 2019; 10:28 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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We report an ongoing X-ray outburst from the direction of the galactic center. The outburst started from 2019 February 11, MJD 58525, and the 2-20 keV X-ray flux peaked at about 160 mCrab on February 16. The current flux is still roughly 80 mCrab.

The source flux is enough to determine the position accurately. Due to a problem of our source localization program, we could not determine the source position systematically. Instead, assuming the source flux is dominant over nearby source fluxes, we obtain the peak-flux (source) position in a smoothed image obtained on February 12-16 at
(R.A., Dec) = (266.625 deg, -29.033 deg) = (17 46 30, -29 02) (J2000).
The uncertainty should be less than 0.4 arcdeg.

It is difficult to identify the source because the source direction, (l, b) = (0.0 deg, -0.2 deg), is close to the direction of the galactic center. A recurrent outburst source SAX J1747.0-2853 is 0.19 arcdeg apart from the above position, but the Swift BAT light curve do not show any significant variation (https://swift.gsfc.nasa.gov/results/transients/weak/SAXJ1747.0-2853/). This, however, does not exclude the possibility that the source in outburst is SAX J1747.0-285. Because in the previous outburst in 2013 April, SAX J1747.0-2853 was not clearly detected with BAT (ATel #5041, also see #3172). We also note that the outburst in 2013 was relatively soft and short compared with the ongoing outburst.

The BAT light curve of the persistent X-ray source 1E 1743.1-2843 lying 0.3 arcdeg showed weak enhancement starting from around 2019 January 29, MJD 58512 (https://swift.gsfc.nasa.gov/results/transients/weak/1E1743.1-2843/). The X-ray flux in the galactic region obtained with the GSC also tended to increase gradually from January 27 to February 10, MJD 58510-58524 (http://maxi.riken.jp/pubdata/v3.rkn/J1745-290/). However, the source position determined by using GSC data on January 26-28 is (R.A., Dec) =(266.209 deg, -29.306 deg), which is 0.45 arcdeg apart from the above position and more consistent with those of KS 1741-293 and 1E 1740.7-2942.

Since there is no strong reason to identify the source as a known catalogued source, we tentatively name the source MAXI J1746-290. XRT followup observations will be requested.

MAXI Galactic Center Region