GCN Circular 45434
Subject
GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
Event
Date
2026-08-24T06:29:10Z (7 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
C. Plasse (HKU), Z.M. Wang (BNU) and H. Goto (RIKEN, CEA) report on behalf of the SVOM and Einstein Probe teams:
We performed two additional observations at the location of the SVOM/ECLAIRs GRB 260818A (Yin et al., GCN 45391) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observations started on 2026-08-18 at 18:10:40 UT (0.76 days after the trigger) and on 2026-08-20 at 18:05:05 UTC (2.75 days after the trigger), both with a total exposure time of ~6000 s.
The source EPF_J232025.8-320549, detected by EP/FXT about 1.67 hr after the SVOM trigger, reported in GCN 45400, fades by a factor 2 in the second observation, from a flux of (13.1 +/- 2.6) x 10^-14 erg/s/cm^-2 down to a flux of (6.7 +/- 1.9) x 10^-14 erg/s/cm^-2 (0.3-10 keV; 1-sigma uncertainty). At this source position of RA, Dec: 350.1064 -32.0978 (with an error radius of 10 arcsec ), 5.9 arcmin from ECLAIRs position, no X-ray source is detected in the third observation.
The fading behaviour of this X-ray source confirms it as the afterglow of GRB 260818A.
We encourage further multi-wavelength follow-up of this source.
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).