MAXI/GSC detection of an onset of X-ray brightening from Be/X-ray binary pulsar GX 304-1
ATel #7441; M. Nakajima (Nihon U.), T. Mihara (RIKEN), Y. Ono (Tokyo Tech), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), H. Negoro, T. Namba, M. Fujita, F. Honda, K. Tanaka, T. Masumitsu (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM)
on 24 Apr 2015; 11:51 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
On 2015 April 24.20 (MJD 57136.20), the MAXI/GSC Nova alert system detected an X-ray brightening at a position consistent with the Be/X-ray binary pulsar GX 304-1. The data of 6 hour bin showed that the source flux in 2-20 keV band started to increase moderately from April 23.00 (MJD 57135.00), and reached 46 +- 11 mCrab on MJD 57136.13. The Swift/BAT transient monitor also detected the current X-ray brightening. The 15-50 keV flux reached 30 +- 6 mCrab on MJD 57135. According to the updated orbital parameters ( Porb = 132.189 d, T0 = MJD 55425.02 ; Sugizaki et al. 2015), the orbital phase of the onset of X-ray brightening is ~0.94, which is consistent with the previous outburst ones observed in 2014 December. The present observational information indicates that the current brightening is classified as a normal outburst.
The latest light curve and the image are available at the following URL:
http://maxi.riken.jp/top/index.php?cid=1&jname=J1301-616