TITLE: GCN CIRCULAR NUMBER: 40365 SUBJECT: SVOM/sb25050601: EP-FXT observations DATE: 25/05/06 15:18:15 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

M.H. Zhang, W. Chen (NAO, CAS), H. L. Peng (NNU), H.W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation on SVOM/sb25050601 at 2025-05-06T04:26:39 (UTC), about 2 hours after the SVOM/ECLAIRs trigger (Wang et al., GCN #40358). Considering the improved ECLAIRs position (Maggi et al., GCN #40364), an uncatalogued X-ray source (EPF_J143707.6+285246) is detected within the ECLAIRs error circle, and is potentially associated with SVOM/sb25050601.

Preliminary analysis of this source was automatically conducted, with the following results: RA (J2000): 219.2802 Dec (J2000): 28.8812 Flux: 2.32 x 10^-11 erg/cm^2/s (observed, 0.5-10 keV) Flux_error: 3.4 x 10^-12 erg/cm^2/s (1 sigma) Note: The upper limit given by ROSAT is 2.86x 10^-13 erg/cm^2/s (0.2-2 keV)

The position uncertainties of the above sources are about 10 arcsec in radius (90% C.L. statistical and systematic).

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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