TITLE: GCN CIRCULAR NUMBER: 44729 SUBJECT: EP260527a / GRB 260527A: NOT optical observations DATE: 26/05/28 23:47:22 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk> G. Corcoran (UCD), J. An (NAOC), A. van Hoof (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), Dimple (Birmingham), R. A. J. Eyles-Ferris (Leicester), B. P. Gompertz (Birmingham), P. G. Jonker (Radboud), A. J. Levan (Radboud and Warwick), J. A. Quirola-Vasquez (Radboud), A. M. Kadela (NOT and NBI), report on behalf of a larger collaboration: We observed the optical afterglow (Aguilar-Ruiz et al., GCN 44719; Li et al. GCN 44720; Busman et al., GCN 44728) of EP260527a (Yang et al., GCN 44718), likely associated with GRB 260527A (Svinkin et al., GCN 44722; Yu et al., GCN 44724; Kawakubo et al., GCN 44726), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. Observations were secured in both the i (25x120 s) and z (16x120 s) bands. At mean epochs of 2026 May 28.911 and 28.946 UT (39.59 and 40.44 hr after the Konus/Wind trigger time, respectively), we measure for the counterpart the following magnitudes: i = 23.17 +- 0.15 z = 23.25 +- 0.31 These magnitudes are calibrated against the Pan-STARRS catalog and are not corrected for Galactic extinction. We note the presence of a faint, underlying object cataloged in the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey (Aihara et al., doi:10.1093/pasj/psab122) at r = 25.72 +/- 0.17, i = 25.44 +/- 0.18 and z = 25.32 +/- 0.29 (all AB). Due to the lack of sufficient high S/N multiband detections, there is no reliable reported photometric redshift for this object. View this GCN Circular online at https://gcn.nasa.gov/circulars/44729. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...