TITLE: GCN CIRCULAR NUMBER: 42751 SUBJECT: EP251118a: NOT candidate optical counterpart DATE: 25/11/19 05:20:57 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), L. Cotter (UCD), J. An, Z.P. Zhu, D. Xu (NAOC), P. G. Jonker (Radboud), L. Fuglsang (NOT), report on behalf of a larger collaboration: We observed the field of the transient event EP251118a (Jiang et al., GCN 42749) detected by the Einstein Probe Wide-field X-ray Telescope (EP WXT), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (5x200 s) bands, starting on 2025-11-19 at 03:55:38 UT (11.22 hr after the EP/WXT trigger). In our first r-band exposure, within the WXT uncertainty region, we detect a source significantly brighter than in the archival images from the Legacy Survey. This object has coordinates: RA(J2000): 08:12:39.4 Dec(J2000): +10:56:18.88 with an uncertainty of 0.5" in both RA and Dec. In the NOT image, we measure an AB magnitude of r = 20.52+/-0.04, calibrated against the Pan-STARRS catalog and not corrected for Galactic extinction. At this location, a source can be marginally seen in the deeper Legacy Source images, with an AB magnitude of r = 24.18 +/- 0.26. The source seen in the NOT images is a candidate optical afterglow of EP251118a, and the archival counterpart in the Legacy Survey is its candidate host galaxy. Further multi-wavelength observations are encouraged to confirm the nature of this object. View this GCN Circular online at https://gcn.nasa.gov/circulars/42751. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...