XRISM/Xtend Transient Search (XTS) detected an X-ray flare possibly from 2SXPS J232525.2+583935

ATel #17819; T. Narita (RIKEN), H. Uchida (Kyoto U.), Y. Kanemaru, A. Miyamoto, Y. Omiya, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), K. Fukushima (TUS), T. Hakamata (UOsaka), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), H. Kuramoto (UOsaka), Y. Maeda (JAXA), H. Matsumoto (UOsaka), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), Y. Motogami (Saitama U.), M. Nobukawa (NUE), H. Noda (Tohoku U.), S. Ogawa (TUS), Y. Sakamoto (Tohoku U.), M. Shidatsu (Ehime U.), H. Takahashi (Hiroshima U.), T. Takagi (Ehime U.), S. Takatsuka (UOsaka), F. Takisawa (Ehime U.), Y. Terada (Saitama U., JAXA), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), A. Yoshimoto (NWU), M. Yoshimoto (Ehime U.), P. P. Plucinsky (CfA)
on 28 May 2026; 11:23 UT
Credential Certification: Hiroyuki Uchida (uchida@cr.scphys.kyoto-u.ac.jp)

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XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J2325+5840 on 2026-5-26 TT. The source position is determined to be (R.A., Dec.) = (351.357, 58.660), with a systematic error of ∼ 40 arcsec. The plausible counterparts are X-ray sources 2SXPS J232525.2+583935 located ∼ 3 arcsec apart from the position of XRISM J2325+5840, respectively. All statistical uncertainties in this report are provided as a 90% confidence level unless stated otherwise.

The flare started at 2026-05-26 at ∼ 19:29 TT. The flare reached its peak on 2026-05-26 at ∼ 19:29. The flare exponentially decayed in ∼ 3 × 10⁴ sec. The peak flux is calculated as 3.1 × 10^-13 erg s^-1 cm^-2 (0.4 – 10.0 keV). A systematic error of roughly 20% should be added to the statistical error. The corresponding luminosity is 1.5 × 10³¹ erg s^-1 by assuming the distance to XRISM J2325+5840 of 200 pc.

We derived the above systematic error for the flux by comparing our derived values for the sources detected with XTS in several observations with those for the corresponding X-ray counterparts. We estimated the systematic error for the source position from the separations between the detected sources and their corresponding counterparts in the same field of view.