MAXI/GSC observation of an outburst onset of a Be/X-ray binary pulsar GS 1843+00
ATel #17706; M. Nakajima, H. Negoro (Nihon U.), T. Mihara (RIKEN), M. Sugizaki (Kanazawa U.), K. Takagi, H. Nishio (Nihon U.), T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, D. Iijima, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U)
on 3 Mar 2026; 13:25 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
Referred to by ATel #: 17722
GS 1843+00 (Ginga 1843+009) is a Be/X-ray binary hosting a 29.5-s X-ray pulsar (Israel et al. 2001). This source was discovered by Ginga in 1988 (Makino 1988, IAUc. 4583), and several X-ray outbursts have since been observed by Ginga, RXTE, Swift, INTEGRAL and MAXI. Following the major outburst in 2009 March (ATel #1959, #1973, #1977) and two subsequent minor outbursts in 2009 November and 2010 March, no significant X-ray activity has been reported for the past 16 years.
On 2026 February 27 (MJD 61098), MAXI/GSC detected a weak X-ray enhancement from a position consistent with that of GS 1843+00. The latest MAXI/GSC public data (https://maxi.riken.jp/v7l3h/J1845+008/index.html) show that the current brightening began on 2026 February 19 (MJD 61090) and the daily averaged 2-20 keV flux reached 0.099 ± 0.016 photons s-1 cm-2 (28 ± 4 mCrab) on March 1 (MJD 61100). After 16 years of quiescence, we confirm that GS 1843+00 has resumed X-ray activity.
The average flux increase rate over the past 5 days is 0.012 photons s-1 cm-2 day-1 (3 mCrab day-1). The current brightening behavior resembles that of the previous event observed in 1997 February by RXTE/ASM. If the present outburst follows the evolution of the previous brightening, it is expected to peak around 2026 March 16 (MJD 61115). Follow-up observations are encouraged to clarify the nature of this source.
