MAXI observation of an X-ray brightening from a black hole binary MAXI J1543-564 or a Be/X-ray binary XTE J1543-568
ATel #17552; C. Kang (Ehime U.), M. Nakajima, H. Negoro (Nihon U.), T. Mihara (RIKEN), K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U)
on 19 Dec 2025; 15:18 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient, Pulsar
The MAXI/GSC nova alert system triggered a bright X-ray transient source on December 19, 2025. Assuming that the source flux was constant over the two scan transits, we derived the source position at (R.A., Dec) = (236.034 deg, -56.510 deg) = (15 44 08, -56 30 35) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.22 deg and 0.21 deg, respectively. The roll angle of long axis from the north direction is 139.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 91 ± 28 mCrab (4.0-10.0keV, 1 sigma error).
Since the derived position is ~0.15 deg from MAXI J1543-564 (100 mCrab transient in 2011, ATel#3330) and ~0.20 deg from XTE J1543-568 (50 mCrab transient in 2000, in't Zand et al. 2001; smaller outburst in 2012, ATel#4008), we cannot distinguish which source was active considering the positional accuracy of MAXI/GSC. In addition, the possibility of a new transient source cannot be excluded, we therefore tentatively designate this transient as MAXI J1544-565. We encourage follow-up observations.
