GCN Circular 45459
Subject
GRB 260818B: Further EP-FXT observation
Event
Date
2026-08-28T17:30:16Z (3 days ago)
From
Yu-Han Yang at University of Rome Tor Vergata <yyang@roma2.infn.it>
Via
Web form
Yu-Han Yang, Eleonora Troja (U Rome), Jun Yang (ZZU), Qinyu Wu (NAO, CAS) report:
We re-observed the field of the short GRB 260818B (SVOM/ECLAIRs; Cordier et al., GCN 45398) with EP-FXT through a ToO request. The observation started on 2026-08-27 at 16:48:47 UT (9.5 d post-trigger), with a total exposure of ~6 ks.
Compared with the previous EP-FXT observation (Wu et al., GCN 45407), the X-ray source EPF_J025955.0+072535, located close to the radio source S10 (Schroeder et al., GCN 45418; Ricci et al. GCN 45452) and the candidate optical counterpart (Ducoin et al., GCN 45450; Yadav et al., GCN 45458), shows no significant variability.
No fading X-ray source is found within the 90% confidence region of the ECLAIRs localization (Cordier et al., GCN 45398). Expanding the search region to 5-sigma level, we identify a fading X-ray source EPF_J025906.7+072552 at R.A. = 44.7791 deg, Dec. = 7.4315 deg (J2000), with a localization uncertainty of 10 arcsec (radius, 90% C.L., statistical and systematic). The source lies 9.7 arcmin away from the center of the ECLAIRs localization.
We thank the EP team for scheduling and executing the ToO observation.