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

ATel #10608; M. Nakajima (Nihon U.), T. Mihara, M. Sugizaki (RIKEN), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), M. Serino, S. Nakahira, W. Iwakiri, M. Shidatsu, M. Matsuoka (RIKEN), N. Kawai, S. Sugita, T. Yoshii, Y. Tachibana, S. Harita, Y. Muraki, K. Morita (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU), H. Tsunemi, T. Yoneyama (Osaka U.), H. Negoro, T. Kawase, A. Sakamaki (Nihon U.), Y. Ueda, T. Hori, A. Tanimoto, S. Oda (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki, H. Kawai (Chuo U.), M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.)
on 1 Aug 2017; 04:02 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar

On 2017 July 27 (MJD 57961), the MAXI/GSC nova-alert system (Negoro et al. 2016) detected an X-ray flux increase from Be/X-ray binary pulsar 4U 0115+63. Subsequent monitoring observations have revealed that the 4-10 keV flux is still increasing steadily. It reached 0.141 +- 0.013 photons/s/cm2 (123 +- 11 mCrab) on 2017 July 30 (MJD 57964). The current brightening started at the orbital phase of ~0.90 (Raichur et al. 2010; Porb=24.3174 d, T0=53243.038(MJD)). Its orbital-phase profile agrees well with that of the previous giant outburst in 2011 June (http://maxi.riken.jp/plot/4U0115p63_2017.gif ; Atel#3408, #3430, #3434). Therefore, the current outburst is expected to develop into the giant like those in 2011 June (Atel#3430) and 2015 September (Atel#8179). Multi-wavelength observations are strongly encouraged to monitor this source.

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).