MAXI/GSC detection of a new X-ray outburst from XTE J1859+083/MAXI J1859+082
ATel #7034; H. Negoro, K. Suzuki, T. Namba (Nihon U.), S. Nakahira (JAXA), Y. Tachibana (Tokyo Tech), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Morii, M. Serino, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), M. Nakajima, K. Fukushima, T. Onodera, M. Fujita, F. Honda (Nihon U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, A. Kawagoe (Chuo U.), M. Yamauchi, Y. Morooka, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 8 Feb 2015; 07:47 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
Subjects: X-ray, Black Hole, Neutron Star, Transient, Pulsar
At 00:42 on 2015 February 8, the MAXI/GSC nova alert system triggered an X-ray increase at the position
(R.A., Dec) = (284.854 deg, 8.208 deg) = (18 59 25, +08 12 29) (J2000)
with a 90% confidence error radius of 0.6 deg.
The source was observed with the GSC A0 detector, of which the high-voltage of the gas counter has been decreased, and the source position was calibrated by using nearby bright sources, GRS 1915+105 and Ser X-1.
Weak, but not significant enhancement was often recognized on GSC images since February 2, suggesting the outburst is ongoing. A quick-look analysis shows the daily averaged fluxes on February 6 and 7 are approximately 20 mCrab.
The source position is consistent with that of XTE J1859+083, which lies 5.8 min from the GSC position. XTE J1859+083 was discovered in RXTE PCA observations on 1999 August 8, and found to be a 9.8 pulsar (Marshall et al. 1999). Later, a more precise position was obtained using archival data of BeppoSAX WFC observations (Corbet et al. 2009). The source has been in a quiescent state since 1999 (e.g., Romano et al. ATel #1287). We also name the source in outburst MAXI J1859+082 because of the positional uncertainty.
Followup observations are strongly encouraged.
