XRISM/Xtend Transient Search (XTS) detected an X-ray flare possibly from an M-type star Gaia DR3 1706200845241330432
ATel #17470; Haruki Kuramoto (UOsaka), Yoshitomo Maeda (ISAS), K. Fukushima, Y. Kanemaru, S. Ogawa, Y. Uchida, T. Yoneyama (JAXA), M. Audard (U. de Geneve), E. Behar (Technion), T. Hakamata (UOsaka), S. Inoue (Kyoto U.), Y. Ishihara (Chuo U.), C. Kang (Ehime U.), T. Kiyomoto (Saitama U.), T. Kohmura (TUS), J. Kurashima (U. of Miyazaki), H. Matsumoto (UOsaka), T. Matsushima (U. of Miyazaki), A. Miyamoto (UOsaka), M. Mizumoto (UTEF), 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., JAXA), Y. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), M. Yoshimoto (Ehime U.), I. Zhuravleva (U. of Chicago)
on 3 Nov 2025; 00:30 UT
Credential Certification: Tomokage Yoneyama (tyoneyama263@g.chuo-u.ac.jp)
Subjects: X-ray, Star, Transient
XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1703+7849 on 2025-11-01 TT. The source position is determined to be (R.A., Dec.) = (255.836, +78.820), with a systematic error of ∼ 40 arcsec. The plausible counterpart is Gaia DR3 1706200845241330432, likely an M-type star, located ∼ 1 arcsec apart from the position of XRISM J1703+7849. A previously cataloged X-ray source, 4XMM J170321.0+784912, is located ∼ 1 arcsec from both XRISM J1703+7849 and Gaia DR3 1706200845241330432.
The flare reached its peak on 2025-11-01 at ∼ 10:37. The flare exponentially decayed in 7 × 103 sec. The peak flux is calculated as ∼ 3 × 10-12 erg s-1 cm-2 (0.4 – 10.0 keV). The corresponding luminosity is 8 × 1031 erg s-1, assuming a distance to XRISM J1703+7849 of 150 pc, based on Gaia DR3 1706200845241330432.
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.
