{
  "body": "D. B. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF/OAC and DARK/NBI), A. Martin-Carrillo (UCD), B. P. Gompertz (Birmingham), A de Ugarte Postigo (LAM), A. Henderson de la Fuente (NOT) report on behalf of a larger collaboration:\n\nWe observed the optical counterpart (Gompertz & Dimple, GCN 41512; Fernandez-Garcia et al., GCN 41513; Strausbaugh & Cucchiara, GCN 41514) of the Swift and Fermi GRB 250823A (Siegel et al., GCN 41511; Smith et al., GCN 41517) using the Nordic Optical Telescope (NOT) located in La Palma (Canary Islands, Spain). Observations were carried out in the r and z filters.\n\nCalibrated against nearby Pan-STARRS pointlike objects, we report the following magnitudes:\n\n| Filter | Mean epoch (UT) | Time since trigger (hr) | Exp time (s) | Magnitude (AB) |\n| ------ | --------------- | ----------------------- | ------------ | -------------- |\n| r      | 2025 Aug 24.022 | 4.36                    | 3x300        | 21.89 +- 0.05  |\n| z      | 2025 Aug 24.036 | 4.69                    | 5x250        | 21.15 +- 0.12  |\n\nThese values are not corrected for Galactic extinction.\n",
  "submitter": "Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>",
  "bibcode": "2025GCN.41520....1M",
  "createdOn": 1756025665061,
  "submittedHow": "web",
  "subject": "GRB 250823A: NOT optical observations",
  "format": "text/markdown",
  "circularId": 41520,
  "eventId": "GRB 250823A"
}