TITLE: GCN CIRCULAR NUMBER: 45239 SUBJECT: EP260727a: Liverpool Telescope confirmation of optical counterpart DATE: 26/07/28 10:23:11 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBIA and Radboud) and P. T. O’Brien (Leicester) report on behalf of a larger collaboration: We observed the field of the Einstein Probe fast X-ray transient EP260727a (Hu et al., GCN 45235) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150 s and 6x150 s exposures in each of the SDSS r’ and z’ filters starting at 2026-07-28 02:34:17 UT, approximately 5.9 hours after the X-ray detection. We detect the optical counterpart (identified by He et al. (GCN 45234) in the r band) in the z band at an AB magnitude of z = 21.66 +/- 0.17. This is significantly brighter than the historical magnitude for the underlying source of z = 23.46 +/- 0.08 derived from archival HSC imaging. This underlying source was also identified by He et al. in the r band. In the r band, we obtain an upper limit of r > 22.85. As this upper limit is less deep than the detection reported in He et al. (GCN 45234), we cannot assess if the source is fading. Our photometry is calibrated to PanSTARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45239. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...