TITLE: GCN CIRCULAR NUMBER: 41085 SUBJECT: GRB 250713A: EP-FXT counterpart detection DATE: 25/07/14 03:06:19 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

Y. F. Liang (PMO, CAS), M. H. Zhang (NAO, CAS), C. Y. Dai (NJU), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 250713A (SVOM/sb25071320) at 2025-07-13T18:52:11 (UTC), about 2 hours after the SVOM/ECLAIRs trigger, with an exposure time of 4919s. Five uncatalogued sources are detected within the ECLAIRs error circle, among which Source 2 is spatially consistent with the candidate counterpart detected by SVOM/MXT (Maggi et al. GCN #41078). Preliminary analysis on these source are automatically conducted, and the details are listed as follows.

Source 1: EPF_J222746.7+384738 RA (J2000): 336.9445 Dec (J2000): 38.7939 Flux: 2.68 x 10^-13 erg/s/cm^2 (observed, 0.5-10 kev) Flux_err: 4.65 x 10^-14 erg/s/cm^2 (1 sigma)

Source 2: EPF_J222734.0+384613 RA (J2000): 336.8919 Dec (J2000): 38.7702 Flux: 1.05 x 10^-13 erg/s/cm^2 (observed, 0.5-10 kev) Flux_err: 4.09 x 10^-14 erg/s/cm^2 (1 sigma) Note: This source is spatially consistent with the candidate counterpart detected by SVOM/MXT.

Source 3: EPF_J222734.3+384800 RA (J2000): 336.8931 Dec (J2000): 38.8000 Flux: 1.39 x 10^-13 erg/s/cm^2 (observed, 0.5-10 kev) Flux_err: 3.05 x 10^-14 erg/s/cm^2 (1 sigma)

Source 4: EPF_J222729.6+384709 RA (J2000): 336.8733 Dec (J2000): 38.7859 Flux: 9.13 x 10^-13 erg/s/cm^2 (observed, 0.5-10 kev) Flux_err: 2.37 x 10^-13 erg/s/cm^2 (1 sigma)

Source 5: EPF_J222815.4+384825 RA (J2000): 337.0641 Dec (J2000): 38.8070 Flux: 8.94 x 10^-14 erg/s/cm^2 (observed, 0.5-10 kev) Flux_err: 3.54 x 10^-14 erg/s/cm^2 (1 sigma)

The Source 1, 2, and 3 were detected by both FXT-A and FXT-B, while Source 4 and 5 were detected only by FXT-B. The positional uncertainty of the 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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