XRISM/Xtend Transient Search (XTS) detected an X-ray flare from XRISM J1046-5939

ATel #17364; M. Mizumoto (UTEF), T. Hakamata (UOsaka), K. Fukushima, Y. Kanemaru, S. Ogawa, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), H. Kuramoto (UOsaka), J. Kurashima (U. of Miyazaki), Y. Maeda (JAXA), H. Matsumoto (UOsaka), T. Matsushima (U. of Miyazaki), A. Miyamoto (UOsaka), K. Mori (U. of Miyazaki), Y. Motogami (Saitama U.), N. Nagashima (Chuo U.), T. Narita (Kyoto U.), M. Nobukawa (NUE), H. Noda (Tohoku U.), Y. Sakamoto (Tohoku U.), M. Shidatsu (Ehime U.), H. Sugai (Chuo U.), H. Takahashi (Hiroshima U.), T. Takagi (Ehime U.), S. Takatuska (UOsaka), R. Takemoto (U. of Miyazaki), Y. Terada (Saitama U.), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), M. Yoshimoto (Ehime U.)
on 29 Aug 2025; 15:52 UT
Credential Certification: Megumi Shidatsu (shidatsu.megumi.wr@ehime-u.ac.jp)

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XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1046-5939 on 2025-08-27 TT. The source position is determined to be (R.A., Dec.) = (161.535,-59.651), with a systematic error of ∼ 40 arcsec. A plausible counterpart is 2MASS J10460982-5938267 (YSO), which is located ∼ 38.5 arcsec apart from the position of XRISM J1046-5939, or 2MASS J10460999-5939103 (Long-Period Variable Candidate), which is located ∼ 13.6 arcsec apart. The nearest X-ray source is 4XMM J104611.0-593905 and CXOGSG J104607.3-593905, which is located ∼ 14arcsec apart. All statistical uncertainties in this report are provided as a 90% confidence level unless stated otherwise.

The flare started at 2025-08-27 at ∼ 09:45 TT. The flare reached its peak on 2025-08-27 at ∼ 10:55 TT. The flare exponentially decayed in ∼5000 sec. The peak flux is calculated as 1 × 10^-12 erg s^-1 cm^-2 (0.4 – 10.0 keV). A systematic error of roughly 20% should be added to the statistical error.

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 with the corresponding counterparts in the same field of view.