MAXI/GSC observation of the bright outburst from Be/X-ray binary pulsar EXO 2030+375

ATel #15228; M. Nakajima (Nihon U.), T. Mihara (RIKEN), M. Serino (AGU), S. Nawa (Chuo U.) H. Negoro, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Tamagawa, J. Li, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, K. Komachi, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga, J. Kohara (Chuo U.), M. Shidatsu, M. Iwasaki (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka, M. Kurihara (JAXA), Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu, K. Inaba (Kyoto U.), H. Tsunemi (Osaka U.), M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC)
on 18 Feb 2022; 11:35 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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We report on another large outburst from Be/X-ray binary pulsar EXO 2030+375. The MAXI/GSC nova-alert system (Negoro et al. 2016) triggered on an X-ray activity from EXO 2030+375 on 12 February, 2022. The trigger date was at the peak orbital phase of the normal outburst of this source. However, the source flux continued increasing after the trigger, and the day-averaged 5-12 keV flux on 17 February reached 0.243 ± 0.013 photons/s/cm² (258 ± 13 mCrab). The current flux is comparable to the half of the peak flux of the previous giant outburst in 2021 (ATel#14809, #14911, #14931, #15006), and the flux is still increasing. Such a large outburst was observed from this source after the 2006 giant outburst (e.g. Wilson et al. 2008). The current activity might be tracing the previous one after the 2006 giant outburst. Or it might be the onset of another giant outburst.

The latest X-ray light-curve can be checked at the following pages;
MAXI ( http://maxi.riken.jp/pubdata/v7lrkn/J2032+376/index.html ),
Swift/BAT ( https://swift.gsfc.nasa.gov/results/transients/EXO2030p375/ ),
Fermi/GBM ( https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/exo2030.html ), and
the BeXRB monitor page ( http://integral.esac.esa.int/bexrbmonitor/Plots/sim_plot_EXO2030+375.html ).