{
  "eventId": "GRB 260604C",
  "createdOn": 1780652863217,
  "subject": "GRB 260604C: GOTO detections of the optical afterglow",
  "submitter": "Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>",
  "body": "B. P. Gompertz,  S. Moran, D. O’Neill, A. Kumar, G. Ramsay, R. Starling, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein and M. Pursiainen, on behalf of the GOTO collaboration:\n\n\nWe report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 260604C, discovered by Fermi/GBM and SVOM (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823).\n\n\nObservations were taken in the GOTO-L filter (400 - 700nm) with 4x90s exposures. Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835) was detected in three epochs:\n\n\n| mid-time(UT) | t-t0(hr) | ABmag |\n\n| 2026-06-04 23:46:15 | 3.46 | 18.45 ± 0.04 |\n\n| 2026-06-05 00:54:05 | 4.59 | 18.70 ± 0.08 |\n\n| 2026-06-05 02:00:28 | 5.70 | 19.06 ± 0.12 |\n\n\nMagnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.\n\n\nGOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC).\n\n",
  "submittedHow": "email",
  "circularId": 44837
}