MAXI/GSC detection of renewed activity of 4U 2129+47/XB 2129+470

ATel #13332; Y. Kurihara (Miyazaki U.), K. Kobayashi, H. Negoro, M. Nakajima (Nihon U), W. Iwakiri (Chuo U.), T. Mihara (RIKEN), W. Maruyama, M. Aoki, R. Takagi (Nihon U.), C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Oeda, K. Shiraishi (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team:
on 6 Dec 2019; 05:37 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Tweet

The MAXI/GSC nova alert system triggered on a faint X-ray transient source at 21:43 UT on 2019 December 4. Assuming that the source flux was constant over eight scan transits from 20:10 December 4 to 10:06 on December 5, we obtain the source position at

(R.A., Dec) = (322.815 deg, 47.095 deg) = (21 31 15, +47 05 41) (J2000)

with a statistical 90% C.L. elliptical error region with long and short radii of 0.54 deg and 0.50 deg, respectively. The roll angle of the long axis from the north direction is 175.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scans was 14 +- 3 mCrab (4.0-10.0keV, 1 sigma error).

The increase of the 4-10 keV flux was recognized for five days. The current flux is the highest at the region since 2009 September. Quick look analysis shows that the 3-sigma upper limit of the average flux before this activity is about 0.16 mCrab at 2-10 keV. There is no corresponding source in the MAXI 7 year Low-Galactic-latitude catalog (Hori et al. 2018, ApJS, 235, 7). Our upper limit above is consistent with the upper limit of the catalog (~0.5 mCrab at a 6.5-sigma level).

A possible triple system 4U 2129+47/XB 2129+470 (Bozzo et al. 2007, A&A, 476, 301) lies 0.20 arc-degree from the above source position, and well within the error region. 4U 2129+47 showed similar X-ray fluxes in 1970s. Since September 1983, however, the source has been observed in the low flux state (below 1e-12 erg/cm2/s, e.g., Bozzo et al. 2007). Thus, 4U 2129+47 is very likely. 4U 2129+47 is also known as an X-ray burster (e.g., Garcia & Grindlay, 1987, ApJ, 313, L59), but MAXI has not detected any burst from the source, yet. Thus, we tentatively name the source MAXI J2131+470 until confirmation.

Following observations are encouraged.

Trigger information of 4U 2129+47/XB 2129+470