TITLE:   GCN CIRCULAR
NUMBER:  40385
SUBJECT: GRB 250507A: follow-up observation with EP-FXT
DATE:    25/05/07 15:44:09 GMT
FROM:    EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

M. H. Zhang, H. Sun (NAO, CAS), Y. J. Zhang (THU), W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation of GRB 250507A at 2025-05-07T07:33:50 (UTC), about 1 hour after the SVOM/ECLAIRs trigger (Wang et al., GCN # 40374). 
An uncatalogued X-ray source (EPF_J121215.7−233519) was detected within the ECLAIRs error circle, and is potentially associated with GRB 250507A.

Preliminary analysis of this source was automatically conducted, with the following results:
RA (J2000): 183.0647 deg
Dec (J2000): -23.5883 deg
Flux: 4.91 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
Flux_error: 1.54 x 10^-13 erg/cm^2/s (1 sigma)

The position uncertainty of the above source is about 10 arcsec in radius (90% C.L. statistical and systematic). 

We note that this source is spacially consistent with the one reported by SVOM/MXT (Maggi et al., GCN # 40381). The flux measured by EP-FXT shows a rapid decline of more than two orders of magnitude compared to the MXT measurements over a timescale of approximately 50 minutes, consistent with the rapid decay reported previously.


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).