TITLE:   GCN CIRCULAR
NUMBER:  45587
SUBJECT: GRB 260915A: EP-FXT follow-up observation
DATE:    26/09/15 14:28:31 GMT
FROM:    EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

R.Shi, Y. F. Liang, J. Y. Liu (PMO, CAS), Y. Q. Zhao (PRIC, USTC), F. F. Song (YNAO, CAS), C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation of GRB 260915A, detected by SVOM/ECLAIRs and SVOM/GRM (sb26091501; Liang et al., GCN 45570), which was also observed in optical (Yin et al., GCN 45573; Wu et al., GCN 45575; Li et al., GCN 45581; Ducoin et al., GCN 45580; Zhu et al., GCN 45577; Perez-Garcia et al., GCN 45578). The observation started at 2026-09-15 02:51:49 (UTC), about 1.66 hours after the SVOM/ECLAIRs trigger, with an exposure time of 5195 s.

On-ground analysis of the EP-FXT data found two uncataloged X-ray sources within the SVOM/ECLAIRs error region (Liang et al., GCN 45570). Both show no clear decay. The preliminary results for the X-ray sources are as follows:

Source 1: EPF_J003237.9+081455
R.A., Decl. (J2000) = 8.1577, 8.2486 deg
Localization error radius = 10 arcsec
0.5-10 keV flux = 7.80e-12 erg/cm^ 2/s
Flux error = 4.12e-13 erg/cm^2/s (1 sigma)
Separation = 1.72 arcmin

Source 2: EPF_J003224.9+081259
R.A., Decl. (J2000) = 8.1037, 8.2161 deg
Localization error radius = 10 arcsec
0.5-10 keV flux = 5.43e-13 erg/cm^ 2/s
Flux error = 1.37e-13 erg/cm^2/s (1 sigma)
Separation = 2.20 arcmin

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).