TITLE: GCN CIRCULAR NUMBER: 25255 SUBJECT: IceCube 190730A: No counterpart candidates or blazar activity in GOTO observations DATE: 19/08/02 12:19:28 GMT FROM: Danny Steeghs at U.of Warwick/GOTO D.Steeghs(1), Y-L.Mong(2), G.Ramsay(5), L.Makrygianni(3), M.Kennedy(8), D.Galloway(2), K.Ulaczyk(1), J.Lyman(1), K.Ackley(2), A.Obradovic(2), M.Dyer(3), V.Dhillon(3), P.O'Brien(4), D.Pollacco(1), E.Thrane(2), S.Poshyachinda(6), E.Palle(7), K.Wiersema(1), R.Cutter(1), T. Marsh(1), R.West(1), B.Gompertz(1), E.Stanway(1), A.Casey(2), M.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3), E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4), S.Tooke(4), U.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6), S.Aukkaravittayapun(6), P.Irawati(6), R.Breton(8), D.Mata-Sanchez(8), T.Heikkila(9), R.Kotak(9), L.Nuttall (10) (1) Warwick University; (2) Monash University; (3) Univ. of Sheffield; (4) University of Leicester; (5) Armagh Observatory & Planetarium; (6) National Astronomical Research Institute of Thailand; (7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester; (9) University of Turku; (10) University of Portsmouth report on behalf of the GOTO collaboration: We carried out observations with the Gravitational-wave Optical Transient Observer (GOTO), in response to the 190730A IceCube neutrino event (GCN #25225, #25241). We obtained a series of 3x60s exposures using our wide L-band filter (400-700 nm) with four pointings covering the directional constraint reported in GCN #25225. Two sky passes have been completed so far, starting on 2019 July 31 21:16 UT and 2019 Aug 1 21:15 UT. Our mean 5-sigma detection limit was g=20.2 mag based on PS1 catalogue calibrators. Images are processed immediately after acquisition using the GOTOphoto pipeline. Difference imaging was performed on the median of each triplet of exposures using recent survey observations of the same pointings. Source candidates were initially filtered using a trained classifier and cross-matched against a variety of catalogs, including the MPC and PS1. Human candidate vetting was performed on those candidates identified by the classifier. The region was also visually inspected for any notable detections in case our classifier mis-scored a detection. No viable optical counterpart candidates were identified. We investigated the long-term behaviour of the FSRQ source PKS 1502+106 that was noted to be consistent with the directional constraints. Our sky survey coverage of this sources shows no notable signs of activity in recent months, including our recent epochs following the neutrino event. These findings are consistent with the ZTF coverage noted in Stein et al. 2019, ATEL 12974. Additional visits are planned, both scheduled and as part of the sky survey, to monitor any changes. ===== GOTO is operated at the La Palma observing facilities of the University of Warwick on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Portsmouth and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org)