MAXI/GSC detection of renewed activity of the black hole X-ray binary GS 1354-64

ATel #17563; H. Negoro (Nihon U.), K. Fujiwara (Kyoto U.), M. Nakajima, K. Takagi, H. Nishio (Nihon U.), T. Mihara, 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, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, 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.), and S. Yamada (Tohoku U)
on 26 Dec 2025; 16:54 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Tweet

The MAXI/GSC nova alert system triggered on a bright X-ray transient source at 22:00 UT on December 25, 2025. Assuming that the source flux was constant over eight transit from 09:37 on December 25 to 20:23 on December 26, we obtain the source position at
(R.A., Dec) = (210.541 deg, -64.488 deg) = (14 02 09, -64 29 16) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.32 deg and 0.25 deg, respectively. The roll angle of the long axis from the north direction is 127.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scans was 33 +- 6 mCrab (4.0-10.0keV, 1 sigma error). The X-ray flux tends to increase during the above period.

The source position is consistent with that of the black hole X-ray binary GS 1354-64 (Kitamoto et al. 1990, ApJ, 361, 590). GS 1354-64 showed outbursts in February 1987 (by Ginga, Makino IAUC 4342 ), November 1997 (RXTE, Remillard et al. IAUC 6772 ; Revnivtsev et al. 2000, ApJ, 530, 955), and June 2015 (Swift/BAT and MAXI, Miller et al. ATel #7612). These suggest that the source exhibits outbursts at intervals of 8-10 years, though an outburst around 2006 has not been reported yet. GS 1354-64 is also known as one of the most distant black hole X-ray binaries in our galaxy (Casares et al., 2009, ApJS, 181, 238). The outburst in 1997 is the largest one in total energy radiated during an outburst in known-distance galactic black hole X-ray novae (Tetarenko et al., 2016, ApJS, 222, A15). Follow-up observations are encouraged.

MAXI data of GS 1354-64