MAXI/GSC detection of the outburst from binary X-ray pulsar 4U 1901+03

ATel #12498; M. Nakajima, H. Negoro (Nihon U.), T. Mihara (RIKEN), M. Serino (AGU), A. Sakamaki, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, T. Hashimoto, A. Yoshida (AGU), N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita, M. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, T. Midooka (JAXA), Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.), Y. Kawakubo (LSU)
on 12 Feb 2019; 12:16 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 the X-ray brightening from the binary pulsar 4U 1901+03 on 2019-02-08 (MJD 58522). This is the fourth X-ray outburst from this source in 40 years, after the ones in 1970-71 (Forman et al. 1976), in 2003 (Galloway et al. 2005) and in 2011 (Sootome et al. 2011, Atel#3829). The day-averaged 5-12 keV flux reached 0.109 +- 0.016 ph/s/cm² (118 +- 17 mCrab) on 2019-02-09 (MJD 58523). Due to the source region was in the out of the MAXI FOV till 2019-02-07 (MJD 58521) from 2019-01-12 (MJD 58495), MAXI/GSC did not observe the outburst onset. The preliminary analysis reveals that the source flux increase still continues with the rate of ~20 mCrab per day. Comparing with the previous outbursts, the flux increase rate and the orbital phase (P_orb=22.5827d, T₀=52682.244(MJD); Galloway et al. 2005) of the current one nicely matches with that of the 2003 outburst profile. Therefore, the maximum flux (~300 mCrab in the 5-12 keV energy band) is expected at the orbital phase of 0.3, i.e., in about 13 days. The current brightening is also reported by the Swift/BAT observation (Kennea et al. 2019, GCN 23882). Multi-wavelength observations are encouraged to monitor this source activities.

The latest X-ray light-curve can be followed at the following pages:
MAXI (http://maxi.riken.jp/pubdata/v3/J1903+031/index.html),
Swift/BAT (https://swift.gsfc.nasa.gov/results/transients/weak/4U1901p03/), and
Fermi/GBM (https://gammaray.msfc.nasa.gov/gbm/science/pulsars/lightcurves/4u1901.html).