MAXI/GSC detection of X-ray outburst from Be/X-ray binary pulsar 4U 0115+63

ATel #9291; M. Nakajima (Nihon U.), W. Iwakiri (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa, Y. Sugawara (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, N. Isobe, S. Sugita, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R. Shomura (Osaka U.), H. Negoro, K. Tanaka, T. Masumitsu, T. Kawase (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.)
on 1 Aug 2016; 03:07 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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On 2016 July 30 (MJD 57599), the MAXI/GSC nova alert system (Negoro et al. 2016) detected the X-ray brightening from the position consistent with the Be/X-ray binary pulsar 4U 0115+63. Before this firm detection, the system had already found a weak X-ray flux enhancement from the same position on July 25 (MJD 57594) which corresponds to the orbital phase of ~0.95 (P_orb=24.3174 d, T₀=53243.038(MJD); Raichur et al. 2010). The precursor event lasted for 2 days with the peak flux of ~15 mCrab in 2-20 keV band. Swift/BAT also observed both the precursor event and the current brightening. The current brightening started on July 28 (MJD 57597; ~0.05 orbital phase), and the latest fluxes on July 30 reached to 0.169 +/- 0.044 counts/s/cm² (47 +/- 12 mCrab) in 2-20 keV band and 0.00496 +/- 0.0011 counts/s/cm² (23 +/- 5 mCrab) in 15-50 keV band. The orbital phase of the outburst onset and the moderate flux increase indicate that the present event is the normal outburst.

The latest source flux can be checked at the following pages;
MAXI(http://maxi.riken.jp/top/index.php?cid=1&jname=J0118+637),
Swift/BAT(http://swift.gsfc.nasa.gov/results/transients/weak/4U0115p634/),
Fermi/GBM(http://gammaray.msfc.nasa.gov/gbm/science/pulsars/lightcurves/4u0115.html),
and the BeXRB monitor page (http://integral.esac.esa.int/bexrbmonitor/webpage_oneplot.php).