MAXI/GSC detection of an X-ray brightening from V 0332+53

ATel #9447; M. Nakajima, H. Negoro (Nihon U.), Y. Sugawara (JAXA), W. Iwakiri, T. Mihara (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa (JAXA), Y. E. Nakagawa (JAMSTEC), 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, S. Harita, Y. Muraki (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R. Shomura (Osaka U.), 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 2 Sep 2016; 11:42 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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On 2016 September 2 (MJD 57633), the MAXI/GSC nova-alert system (Negoro et al. 2016) detected an X-ray brightening from a Be/X-ray binary pulsar, V 0332+53. Preceded this trigger information, GSC had detected a weak flux enhancement from this source on August 28 (MJD 57628). The 4-10 keV flux of 6 hour binned data reached 0.119 +- 0.042 ph/s/cm² (96 +- 34 mCrab) on 2016 September 1.62 (MJD 57632.62). The trigger date corresponds to the orbital phase of ~0.86 which is derived from the following orbital parameters, T₀=53330.584 (MJD) and P_orb=36.50 d (Raichur et al. 2010). Swift/BAT also detected the current X-ray flux increase. The 15-50 keV flux is 0.0154 +- 0.0020 ct/cm²/sec (70 +- 9 mCrab) on September 1 (MJD 57632). Before the current brightening, BAT observed two X-ray outbursts synchronized with the binary orbital period. Each outburst started from the orbital phase of ~0.8, and they exhibited the moderate flux increase rate of ~0.003 ct/cm²/sec/day. The average peak flux of the previous outbursts is ~0.007 cts/cm²/sec (30 mCrab). The onset phases and the peak fluxes of the previous outbursts indicate that those events are the normal outbursts. Comparing with the previous events, the current outburst shows a flux increase rate of ~0.007 ct/cm²/sec/day which is twice as large as that of the previous ones. Whereas the current rate is half of that of the last giant outburst observed on 2015 June (Atel#7682,#7685,#7822). Therefore, at this moment, it is not clear whether the present activity is a giant outburst or not.

The latest source flux can be checked at the following pages;
MAXI(http://maxi.riken.jp/top/index.php?cid=1&jname=J0334+531),
Swift/BAT(http://swift.gsfc.nasa.gov/results/transients/V0332p53/),
Fermi/GBM(http://gammaray.msfc.nasa.gov/gbm/science/pulsars/lightcurves/v0332.html), and
the BeXRB monitor page(http://integral.esac.esa.int/bexrbmonitor/webpage_oneplot.php).