TITLE: GCN CIRCULAR NUMBER: 44990 SUBJECT: EP260618a: LCO optical counterpart confirmation DATE: 26/06/19 08:41:05 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), J. A. Quirola-Vasquez (Radboud), J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), J. Chacon (PUC), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260618a (Yang et al., GCN 44978), possibly the afterglow of GRB 260618A (Fermi GBM team, GCN 44973), using an LCO 1m telescope located at the Teide Observatory (Spain) equipped with the SINISTRO instrument. We obtained 6x300 s exposures in the SDSS-r filter starting on 2026-06-18 at 21:56:12 UT (13.56 hr after the trigger). The object reported by Becerra et al. (GCN 44988) is detected in the stack of our images, with a magnitude of r = 21.93 +/- 0.16 (AB), calibrated against the Pan-STARRS catalogue and not corrected for Galactic extinction. We note that our magnitude indicates little or no fading compared to the COLIBRÍ observation, which was carried out about 6.5 hr later (Becerra et al., GCN 44988). Further follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44990. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...