MAXI/GSC observation of an X-ray brightening from the symbiotic X-ray binary 4U 1954+319
ATel #17422; M. Nakajima (Nihon U.), T. Mihara (RIKEN), H. Negoro (Nihon U.), K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U)
on 26 Sep 2025; 13:24 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
Referred to by ATel #: 17464
MAXI/GSC has observed an X-ray brightening from the symbiotic X-ray binary 4U 1954+319 since 2025-08-25 (MJD 60912). The 1-day averaged flux in the 4â10 keV band began increasing at a rate of ~3 mCrab/day and reached 99 +/- 6 mCrab on 2025-09-22 (MJD 60940). This flux is comparable to the highest level recorded by MAXI/GSC in 2010 (ATel #2702). The current flare shows a longer brightening phase than the major flare in 2010, which rose to its peak within ~20 days. There is a possibility that the source may develop into the brightest flare ever observed. We encourage follow-up observations.
The latest light curve and the image of this source are available at the following URL:
http://maxi.riken.jp/pubdata/v7.7l/J1955+320/index.html
