TITLE:   GCN CIRCULAR
NUMBER:  43663
SUBJECT: GRB 260208B: EP-FXT observation
DATE:    26/02/09 11:06:20 GMT
FROM:    EP Team at NAOC/CAS <ep_ta@bao.ac.cn>

S. Q. Jiang, H. N. Yang, Y. L. Wang, Y. Liu (NAO, CAS), Z. H. Yang, Q. C. Zhao (IHEP, CAS) on behalf of the Einstein Probe (EP) team:

EP-FXT performed a follow-up observation on GRB 260208B detected by Fermi/GBM (The Fermi GBM team, GCN 43638; Preis & Greiner, GCN 43639; Sonawane et al., GCN 43649), Fermi/LAT (Longo et al., GCN 43647) and SVOM/GRM (Luo et al., GCN 43650) at 2026-02-09T06:37:35 (UTC), about 20.748 hours after the Fermi/GBM trigger.

Two uncatalogued X-ray sources are detected around the Fermi/LAT error circle.
Preliminary informations are listed as follows: 

Source 1: EPF_J063834.1-135348 
RA (J2000): 99.6419
Dec (J2000): -13.8965
Flux: 1.12 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)

Source 2: EPF_J063827.9-134635 
RA (J2000): 99.6162
Dec (J2000): -13.7764
Flux: 0.96 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
The position is consistent with the source 1 detected by Swift-XRT (Evans et al., GCN 43651) and the optical candidate detected by SVOM/VT (Li et al., GCN 43659).

The position uncertainties of the above sources are about 20 arcsec in radius (90% C.L. statistical and systematic). The current result is based on the FXT on-board alert and will be updated when the telemetry data are received..

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).