GCN 45173: GRB 260618B: EP-FXT follow-up observation upper limit

2026-07-16T11:58:22.390Z | rev 0 | event: GRB 260618B

Y. N. Ma (NAOC), A. Li (BNU), Y. L. Qiu, H. L. Li, L. P. Xin (NAOC), Y. L. Hua (PMO), M. J. Liu (NAOC), X. H. Tang (Tsinghua Univ.), W. D. Zhang (NAOC) on behalf of SVOM and EP missions:

EP-FXT performed a follow-up observation of GRB 260618B detected by Fermi (Fermi GBM team, GCN 44979; Gupta et al., GCN 44983; Veres et al., GCN 45010) and Konus-Wind (Ridnaia et al., GCN 45038). The follow-up observation started at 2026-07-15T10:43:17 (UTC), about 26.7 days after the Fermi trigger, with a total exposure time of around 2.9 ks.

No significant X-ray source was detected at the position of the reported optical candidate (Li et al., GCN 45001; Shi et al., GCN 45014; Li et al., GCN 45151). The upper limit for the 0.5-10 keV band is about 5.0e-14 ergs/cm^2/s (90% C.L.).

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).