MAXI/GSC detection of a new X-ray outburst from XTE J1856+053
ATel #16131; K. Kobayashi, H. Negoro, M. Nakajima, M. Tanaka, Y. Soejima, Y. Kudo (Nihon U.), T. Mihara, T. Kawamuro, S. Yamada, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, S. Urabe, S. Nawa, N. Nemoto (Chuo U.), M. Shidatsu (Ehime U.), I. Takahashi, M. Niwano, S. Sato, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, T. Kurihara (JAXA), Y. Ueda, K. Setoguchi, T. Yoshitake, Y. Nakatani (Kyoto U.), M. Yamauchi, Y. Hagiwara, Y. Umeki, Y. Otsuki (Miyazaki U.), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC), and W. Iwakiri (Chiba U.)
on 13 Jul 2023; 16:26 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)
Subjects: X-ray, Black Hole, Transient
The MAXI/GSC nova alert system triggered on a soft X-ray transient source at 4:37 UT on 2023 July 12. The MAXI/GSC data show the outburst began from July 9, 2023. Assuming that the source flux was constant over 18 transits from 11:32 on July 9 to 11:34 on July 11,
using 2-4 keV data, we obtain the source position at
(R.A., Dec) = (284.205 deg, 5.268 deg) = (18 56 49, +05 16 04) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.65 deg and 0.29 deg, respectively. The roll angle of the long axis from the north direction is 157.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The 2-4 keV flux on July 11 was almost constant at about 30 mCrab. On the other hand, the 4-10 keV flux was less than 10 mCrab (below the detection limit).
The black hole candidate XTE J1856+053 lies in the error region. If this transient source is XTE J1856+053, the soft energy spectrum suggests the source is in a soft state. The last outburst from XTE J1856+053 was observed in 2020 February (ATel #13511). XTE 1856+053 also exhibited (successive) outbursts in 1996 (IAUC # 6504), 2007 February (ATel #1024), and 2015 March and May (ATel #7233, #7579). Followup observations are encouraged.
MAXI/GSC light curve of XTE J1856+053
