TITLE: GCN CIRCULAR NUMBER: 27330 SUBJECT: LIGO/Virgo S200302c: No notable candidates in GOTO imaging DATE: 20/03/07 00:13:26 GMT FROM: Kendall Ackley at Monash University Y.-L. Mong (1); K. Ackley (1); D. K. Galloway (1); D. Steeghs (2); V. Dhillon (3); P. O'Brien (4); G. Ramsay (5); D. Pollacco (2); E. Thrane (1); S. Poshyachinda (6); R. Kotak (7); L. Nuttall (8); E. Pall\'e (9); K. Ulaczyk (2); J. Lyman (2); R. Cutter (2); A. Levan (2); T. Marsh (2); R. West (2); E. Stanway (2); B. Gompertz (2); K. Wiersema (2); T. Killestein (2); A. Casey (1); M. Brown (1); B. Muller (1); M. Dyer (3); J. Mullaney (3); E. Daw (3); S. Littlefair (3); J. Maund (3); L. Makrygianni (3); U. Burhanudin (3); R. Starling (4); R. Eyles (4); S. Tooke (4); S. Aukkaravittayapun (6); U. Sawangwit (6); S. Awiphan (6); D. Mkrtichian (6); P. Irawati (6); S. Mattila (7); T. Heikkil\"a (7); E. Rol (1) We report on optical observations with the Gravitational-wave Optical Transient Observer prototype in response to S200302c (GCN #27278). Targeted observations started shortly after the preliminary event notification was received. These spanned 102 unique tile pointings containing 30.8% of the source location probability (based on the initial BAYESTAR skymap) and were acquired between 20:15 UT Mar 02 2020 and 20:35 UT Mar 04 2020 (starting 18.3 hours after the event trigger time 01:58 UT Mar 02 2020). No new transients that could be credibly associated with S200302c were detected. Each pointing spans 4.9x3.7 square degrees and consisted of 3x60s exposures in our L-band filter (400-700nm passband similar to g+r) with a median 5-sigma photometric depth equivalent to g=19.1 for an individual pointing. Limits are based on a photometric calibration against PS1 sources. Most pointings were observed multiple times, typically 2-3 times. 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 classifier and cross-matched against a variety of catalogs, including the MPC and PS1. Human candidate vetting was performed following data acquisition and automated classifier cuts. 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, the University of Turku and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org/)