XRISM/Xtend Transient Search (XTS) detected an X-ray flare from TWA 11

XRISM/Xtend Transient Search (XTS) detected an X-ray flare from an X-ray source XRISM J1236-3952 on 2025-06-22 TT. The source position is determined to be (R.A., Dec.) = (189.005, -39.874), with a systematic error of ? 40 arcsec. A plausible counterpart is a Young Stellar Object Candidate TWA 11 (HD 109573). TWA 11 is located ? 13 arcsec apart from the position of XRISM J1236-3952 All statistical uncertainties in this report are provided as a 90% confidence level unless stated otherwise. The flare started at 2025-06-22 at ? 04:16 TT. The flare reached its peak on 2025-06-22 at ? 05:09. The flare exponentially decayed in 4 × 103 sec. This source also showed fluctuations in flux within a range of ? 10 times during the observation conducted the day before. The peak flux is calculated as 1 × 10-11 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 8 × D70pc × 1030 erg s-1 by assuming the distance to XRISM J1236-3952 of D67pc. 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.