TITLE: GCN CIRCULAR NUMBER: 30354 SUBJECT: GRB210702A: MeerLICHT multi-colour photometry DATE: 21/07/02 21:33:49 GMT FROM: Andrew Levan at U.of Leicester P.J. Groot (Radboud/UCT/SAAO), S. de Wet (UCT), P.M. Vreeswijk (Radboud), A.J. Levan (Radboud) report on behalf of the MeerLICHT consortium: Following the detection of GRB210702A by Swift and its optical counterpart (Lien et al., GCN30351), the 0.6m MeerLICHT telescope, located at Sutherland, South Africa obtained a series of 60s images in the q,u,q,g,q,r,q,i,q,z,q,u,q,g,q bands, starting at 2021-07-02, 19:23:26.586 UT, 16 minutes after the Swift detection, and 3 minutes after the distribution of the BAT alert. The source identified by Swift UVOT is clearly detected as a new transient at coordinates RA(ICRS) = 168.57839 = 11:14:18.81 (+/-0.06”) DEC(ICRS)= -36.74702 = -36:44:49.27 (+/- 0.04”) MeerLICHT astrometry is calibrated against Gaia DR2. The first source detections are, at: q = 12.815 +/- 0.001 +/- 0.018 (19:23:26 UT) u = 13.585 +/- 0.004 +/- 0.041 (19:25:10 UT) g = 13.394 +/- 0.002 +/- 0.021 (19:28:46 UT) r = 13.193 +/- 0.002 +/- 0.015 (19:32:18 UT) i = 13.096 +/- 0.003 +/- 0.034 (19:35:42 UT) z = 13.100 +/- 0.004 +/- 0.025 (19:39:25 UT) where the first uncertainty on the magnitude is the statistical uncertainty and the second is the uncertainty on the photometric calibration. Our repeated q-band observations show decay consistent with a power law with exponent of approximately -1.2. Further data taking was suspended due to high winds. Reference images of the field show no underlying host galaxy down to the 5-sigma limiting magnitude, at the position of the afterglow, at: u > 19.54 g > 20.44 q > 21.23 r > 20.20 i > 19.72 z > 18.90 MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.