XRISM/Xtend Transient Search (XTS) detected an X-ray flare possibly from 2MASS J05333511-6854544

ATel #17761; J. Kurashima, K. Mori (U. of Miyazaki), Y. Kanemaru, 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.), T. Narita (RIKEN), 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. Terashima (Ehime U.), Y. Tsuboi (Chuo U.), H. Uchida (Kyoto U.), A. Yoshimoto (NWU), M. Yoshimoto (Ehime U.), Y. Terada (Saitama U., JAXA)
on 23 Apr 2026; 13:59 UT
Credential Certification: Tomokage Yoneyama (tyoneyama263@g.chuo-u.ac.jp)

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XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J0534-6855, on 2026-04-17 TT. The source position is determined to be (R.A., Dec.) = (83.396, -68.915) with a systematic error of ∼ 40 arcsec. One of the plausible counterparts is a 2MASS J05333511-6854544 at 127 pc, also catalogued as Gaia DR3 4111834567779557376, which is located ∼ 1.4 arcsec apart from the position of XRISM J0534-6855. All statistical uncertainties in this report are provided at a 90% confidence level unless stated otherwise.

The flare started at 2026-04-17 01:05 TT and reached its peak on 2026-04-17 at around 01:10 TT. The flare exponentially decayed in (2.5 +1.0/-0.5) × 10³ sec. The peak flux is calculated as 3 × 10^-11 erg s^-1 cm^-2. A systematic error of roughly 20% should be added to the statistical error. The corresponding luminosity is 5 × D_127pc² × 10³¹ erg s^-1.

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.