MAXI/GSC detection of renewed activity from Be/X-ray binary pulsar V 0332+53 (X0331+53)

ATel #9596; M. Nakajima, H. Negoro (Nihon U.), T. Mihara (RIKEN), A. Tanimoto (Kyoto U.), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. Sugawara (JAXA), Y. E. Nakagawa (JAMSTEC), M. Sugizaki, 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, 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 (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.)
on 5 Oct 2016; 10:16 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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The MAXI/GSC nova-alert system (Negoro et al. 2016) detected an X-ray brightening from the Be/X-ray binary pulsar V 0332+53 (X0331+53) on 2016 October 1 (MJD 57662). Following the previous report (Atel#9447) on September 2, the source again exhibited the X-ray outburst. According to the orbital parameters (Porb=33.850 d, T0=57157.88(MJD); Doroshenko et al. 2016), it is turned out that the trigger date corresponds to the orbital phase of 0.89. Besides, the time interval between the present event and the last one is consistent with the orbital period. Thus, the current brightening is likely a normal outburst. This is the 4th detection of the consecutive X-ray outbursts which started from 2016 June. This series of the outbursts have been monitored by MAXI/GSC and Swift/BAT.

A remarkable point of the consecutive outbursts is that a precursor have been detected three times in a row by both MAXI/GSC and Swift/BAT. Each precursor lasted for less than a day, and took place at the orbital phase of ~0.90. The peak fluxes of the precursors are ~20 mCrab in 4-10 keV band and ~50 mCrab in 15-50 keV. Such a short duration precursor have been observed from another Be/X-ray binary pulsar, A 0535+26 (Caballero et al. 2008; Postonov et al. 2008). As far as we know, there are no reports about the detection of the consecutive precursors from this source. We encourage multi wave-length observations to investigate this peculiar phenomenon.

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).