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

ATel #9149; M. Nakajima (Nihon U.), M. Sugizaki (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa, Y. Sugawara (JAXA), T. Mihara, M. Serino, W. Iwakiri, 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 14 Jun 2016; 03:35 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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An X-ray brightening from the transient Be/X-ray binary pulsar 4U 0115+63 has been detected by the MAXI/GSC nova alert system (Negoro et al. 2016) on 2016 June 12 (MJD 57551). The last X-ray activity of this source was reported on 2015 October (Atel#8179), and that event developed into giant outburst as predicted. Although the current sky coverage for 4U0115+63 is by the gas-leaking camera, we have tentatively estimated the 2-20 keV flux to be 0.15 +- 0.02 counts/s/cm² (42 +- 6 mCrab) on 2016 June 11 (MJD 57550) with the preliminary caldb (calibration database) of GSC. The other all sky monitors, Swift/BAT and Fermi/GBM, also detected the current brightening. According to the Swift/BAT data, the onset of the current outburst corresponds to the orbital phase of ~0.87 (P_orb=24.3174 d, T₀=53243.038(MJD); Raichur et al. 2010). The preliminary MAXI/GSC data also indicates that the onset phase is ~0.87 (MJD 57544). The 15-50 keV flux has displayed a steady increase, and reached 0.0101 +- 0.0014 counts/s/cm² (46 +- 6 mCrab) on June 12 (MJD 57551). Comparing with the previous results of the normal outbursts observed from this source so far, it is turned out that the parameters of the present outburst (onset phase and flux increase rate) are comparable to the previous ones. Thus the present event can be considered as 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).