TITLE: GCN CIRCULAR NUMBER: 29548 SUBJECT: GRB 210222B: GOTO confirmation of afterglow detection DATE: 21/02/23 00:25:43 GMT FROM: Travis Mong at Monash University Y-L Mong (1); K. Wiersema (2); K. Tse (1); K. Ackley (1); D. K. Galloway (1); M. Dyer (3); J. Lyman (2); K. Ulaczyk (2); D. Steeghs (2); V. Dhillon (3); P. O'Brien (4); G. Ramsay (5); S. Poshyachinda (6); R. Kotak (7); L. Nuttall (8); D. Pollacco (2); R. Breton (9) ((1) Monash University, (2) Warwick University, (3) University of Sheffield, (4) University of Leicester, (5) Armagh Observatory & Planetarium, (6) National Astronomical Research Institute of Thailand, (7) University of Turku, (8) University of Portsmouth, (9) University of Manchester) report on behalf of the GOTO collaboration: We carried out observations with the Gravitational-wave Optical Transient Observer (GOTO) on La Palma in response to GRB 210222B (Gropp et al; GCN 29545). We made a series of 4x90 s exposures using our wide L-band filter (400-700 nm) covering the Swift XRT error box, beginning around 54 s after the trigger, with midtime of the first observation 22:42:05.21 UT on 22 February 2021. We detect an uncatalogued source located at (J2000): RA 10:18:25.42 Dec +53:24:55.89 confirming the OT reported by MASTER (Lupinov et al.; GCN 29544), BOOTES-1 (Malesani et al.; GCN 29546) and LCO (Strausbaugh et al.; GCN 29547). We find an equivalent magnitude of g = (16.58 +/- 0.03) mag based on calibration against PanSTARRS DR1 photometry in ATLAS_REFCAT2 (Tonry et al. 2018). Observations are continuing. 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), Turku University, Portsmouth University, Manchester University and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org)