{
  "subject": "EP260329b: GOTO detection of optical counterpart",
  "circularId": 44169,
  "submitter": "d.s.oneill@bham.ac.uk",
  "body": "D. O'Neill, R. Starling, A. Kumar, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Gompertz, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration\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 the  EP/WXT alert EP260329b (Song et al; GCN 44142).\n\nWe detect the counterpart candidate previously reported (Li et al., GCN 44139; Eyles-Ferris et al., GCN 44144; Magnani et al., GCN 44146; Aryan et al., GCN 44147; Lipunov et al., GCN 44150) with an L-band magnitude of 18.73 ± 0.09 AB mag (+0.74h) at 2026-03-29 11:20:38 UT. We find no evidence of the source prior to the GRB trigger time in previous GOTO observations taken at 2026-03-28 11:41:26 (-22.91h) down to a 3-sigma depth of L>20.10 AB mag.\n\nGOTO (https://goto-observatory.org) is a network of telescopes that is\nprincipally funded by the STFC and operated at the Roque de los Muchachos\nObservatory on La Palma, Spain, and Siding Spring Observatory in NSW,\nAustralia, on behalf of a consortium including the University of Warwick,\nMonash University, Armagh Observatory & Planetarium, the University of\nLeicester, the University of Sheffield, the National Astronomical Research\nInstitute of Thailand (NARIT), the University of Turku, the University of\nPortsmouth, the University of Manchester, the  University of Birmingham\nand the Instituto de Astrofisica de Canarias (IAC).\n",
  "submittedHow": "web",
  "bibcode": "2026GCN.44169....1O",
  "format": "text/plain",
  "createdOn": 1774978784294,
  "eventId": "EP260329b"
}