TITLE: GCN CIRCULAR NUMBER: 40572 SUBJECT: EP J1350.0-8622: EP-FXT follow-up observation DATE: 25/05/29 13:35:43 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

D. H. Zhao, M. J. Liu (NAO, CAS), Y. Wang (PMO, CAS),W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team:

After the EP-WXT detection of the X-ray transient candidate EP J1350.0-8622 (Liu et al., GCN 40548, I. Perez-Garcia et al., GCN 40549), a follow-up observation was performed by EP-FXT at 2025-05-26T23:17:23 (UTC), about 24 hours after the detection, with an exposure time of 1.85 ks. An X-ray source is detected at R.A., Dec. = 207.5779, -86.3934 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% confidence level, including both statistical and systematic errors), which is likely associated with the 1eRASS J135031.1-862323. The unabsorbed 0.5-10 keV flux is estimated to be 1.9 (+1.2, -0.9) x 10^-13 erg/cm^2/s, derived using an absorbed power law model with the hydrogen column density fixed to the Galactic value of 8.2 x 10^20 cm^-2 and the photon index fixed at 2.0, due to the limited photon statistics. All uncertainties quoted above are at the 90% confidence level.

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).

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