TITLE: GCN CIRCULAR NUMBER: 40420 SUBJECT: GRB 250510A: follow-up observation with EP-FXT DATE: 25/05/10 15:12:36 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn

A. Li, B. B. Zhang (BNU), Q. C. Liu (THU), Z. X. Ling (NAOC, CAS) on behalf of the Einstein Probe (EP) team:

Following the possible detection of the GRB 250510A (Cheng et al., GCN 40415) and its multi-wavelength follow-up observations (Antier et al., GCN 40417), we performed an observation with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe mission.

The observations began at 2025-05-10T07:54:01 (UTC), about 3.3 hours after the SVOM-ECLAIRs detection. The exposure time is 4035 seconds. Preliminary analysis shows there are three source was detected in this epoch within the ECLAIRs error circle: ------------------------------------------------------------------------------------------------------ | Source Name | RA | DEC | Flux(erg/s/cm2) | Flux_err | ------------------------------------------------------------------------------------------------------ |EPF_J185647.0+182414| 284.1957 | 18.4041 | 9.91e-14 | 3.41e-14 | ------------------------------------------------------------------------------------------------------ |EPF_J185624.3+182129| 284.1012 | 18.3581 | 1.07e-13 | 2.59e-14 | ------------------------------------------------------------------------------------------------------ |EPF_J185624.8+181937| 284.1033 | 18.3269 | 1.35e-13 | 2.92e-14 | ------------------------------------------------------------------------------------------------------

EP-FXT will continue monitoring the source. More follow-up observations are encouraged.

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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