MAXI/GSC detection of an X-ray outburst from Be/X-ray binary pulsar GX 304-1
ATel #5205; M. Nakajima (Nihon U.), Y. E. Nakagawa, S. Nakahira (JAXA), T. Mihara, M. Sugizaki, M. Morii, M. Serino, T. Yamamoto, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa (JAXA), N. Kawai, R. Usui, K. Ishikawa, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Nakano (AGU), H. Tsunemi, M. Sasaki (Osaka U.), H. Negoro, M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro (Kyoto U.), Y. Tsuboi, M. Higa (Chuo U.), M. Yamauchi, K. Yoshidome, Y. Ogawa, H. Yamada (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
on 11 Jul 2013; 09:13 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
On 2013 July 09 (MJD 56482), the MAXI Nova alert system detected an X-ray flux increase from a Be/X-ray binary pulsar GX 304-1. The daily-averaged X-ray flux in 4-10 keV band reached 33 +- 19 mCrab on MJD 56481, and 57 +- 7 mCrab on MJD 56482. From the orbital parameters ( Porb = 132.20 d; T0 = MJD 55554.75 ), the orbital phase when the flux increase was detected is ~0.02. Before the current brightening, the source exhibited anomalous activities; a weak flux enhancement at ~0.7 orbital phase on MJD 56441 and a multi-peaked weak outburst at the previous periastron passage (MJD 56349). According to the previous researches (Nakajima et al. 2012; Caballero et al. 2013), the multi-peaked or the double peaked outburst often follows a giant outburst. In addition, the giant outburst is explained by an interaction between the neutron star orbit and the warped Be-disc (Okazaki et al. 2013). Thus, this situation is suitable to study the relation between the giant outburst and the Be-disc profile. We encourage optical observations to monitor the V/R profiles of emission lines.
The folded MAXI/GSC X-ray light curves by the orbital period is displayed at
http://maxi.riken.jp/news/en/?p=1042
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
