GCN Circular 41512
Subject
GRB 250823A: Liverpool Telescope optical detection
Event
Date
2025-08-23T22:19:16Z (a day ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
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.