TITLE: GCN CIRCULAR NUMBER: 41512 SUBJECT: GRB 250823A: Liverpool Telescope optical detection DATE: 25/08/23 22:19:16 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk> B. P. Gompertz (U. Birmingham) and Dimple (U. Birmingham) report on behalf of a larger collaboration: We conducted follow-up observations of GRB 250823A (Fermi GBM Team, GCN Circ. 41510, Siegel et al., GCN Circ. 41511) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:26:55 UT on 2025-08-23, 1.28 hr after the Swift trigger, and consisted of 5 x 120 s exposures in each of the SDSS g, r, i, and z filters. We detect a new optical source with an AB magnitude of r = 21.25 +/- 0.09 (mid-time t0+1.45 hr) at a position of RA(J2000) 19:49:54.7, Dec -24:59:44.9 (0.2” uncertainty). The source is not present in archival Pan-STARRs imaging and is spatially consistent with the localisation by Swift/XRT (Siegel et al., GCN Circ. 41511). We therefore conclude it is the optical counterpart of GRB 250823A. Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41512. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...