MAXI/GSC detection of renewed activity of the Be/X-ray binary pulsar 4U 0115+63

ATel #15967; M. Nakajima (Nihon U.), T. Mihara (RIKEN), H. Negoro, K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, J. Kohara, S. Urabe, S. Nawa, N. Nemoto (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, T. Kurihara (JAXA), Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba, Y. Nakatani (Kyoto U.), M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) , W. Iwakiri (Chiba U.)
on 30 Mar 2023; 09:56 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

Tweet

The MAXI/GSC nova alert system triggered an X-ray transient source on 2023 March 28 (MJD 60031). Assuming that the source flux was constant over the transits, we obtain the source position at (R.A., Dec) = (19.377 deg, 63.541 deg) = (01 17 30, +63 32 27) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.37 deg and 0.27 deg, respectively. The roll angle of the long axis from the north direction is 105.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The obtained position coincides with that of the Be/X-ray binary pulsar 4U 0115+63. The onset date of this outburst corresponds to the orbital phase of ~0.1, which is derived from the following orbital parameters, T_peri=55601.751(MJD), P_orb=24.31689 d (Sugizaki et al. 2017, PASJ, 69, 100). The source flux in 4-10 keV continues brightening with the increase rate of ∼20 mCrab/day, and reached 0.080 ± 0.008 photons/s/cm² (64 ± 6 mCrab) on 2023 March 29 (MJD 60032). These features of this outburst onset are comparable to that of the previous giant outbursts observed in 2017 (ATel#10608), 2015 (ATel#8179,#8231), and 2011 (ATel#3677,#3745). Thus, the current brightening is expected to develop into a giant outburst. Multi-wavelength observations are encouraged to monitor this source.

The latest X-ray light-curve can be checked at the following pages;
MAXI ( http://maxi.riken.jp/pubdata/v7lrkn/J0118+637/index.html ),
Swift/BAT ( https://swift.gsfc.nasa.gov/results/transients/weak/4U0115p634/ ),
Fermi/GBM ( https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/4u0115.html ), and
the BeXRB monitor page ( http://integral.esac.esa.int/bexrbmonitor/Plots/sim_plot_4U0115+63.html ).