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MAXI/GSC detection of a new outburst from the black hole candidate XTE J1856+053

ATel #13511; H. Negoro, M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi, R. Takagi (Nihon U.), T. Mihara, C. Guo, Y. Zhou, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Oeda, K. Shiraishi (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team:
on 21 Feb 2020; 05:50 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Black Hole, Transient

Referred to by ATel #: 16131

The MAXI/GSC nova alert system triggered on a faint X-ray transient source at 08:45 UT on 2020 February 14 in 4-day time-bin. This time, 2-4 keV GSC data give a more accurate source position than 4-10 keV data. Then using 2-4 keV data and assuming that the source flux was constant over 19 scan transits from 12:36 on February 13 and 9:32 on February 15, we obtain the source position at

(R.A., Dec) = (284.308 deg, 5.290 deg) = (18 57 13, +05 17 24) (J2000)

with a statistical 90% C.L. elliptical error region with long and short radii of 0.41 deg and 0.33 deg, respectively. The roll angle of the long axis from the north direction is 158.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The position is consistent with that of the black hole candidate XTE J1856+053 (Marshall et al. 1996, IAUC # 6504 ). The 2-4 keV X-ray flux during the above scan period is stable at approximately 10-20 mCrab.

The last successive outbursts from this source were detected in 2015 March (ATel #7233, #7278, #7338), and 2015 May (ATel #7579, #7591). Such successive outbursts were also recognized in 1996 and 2007 (e.g., ATel #1024). Followup observations are encouraged to confirm that this transient source is identical to XTE J1856+053, and obtain a recurrence interval of outbursts. Tentatively, we also name the source MAXI J1857+052.

Trigger information of XTE J1856+053