TITLE: GCN CIRCULAR NUMBER: 35765 SUBJECT: GRB 240218A: MeerLICHT upper limits DATE: 24/02/20 20:32:37 GMT FROM: Simon de Wet at University of Cape Town <simdewet@gmail.com> S. de Wet (UCT), P.M. Vreeswijk (Radboud) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium: The 0.6m wide-field MeerLICHT optical telescope located in Sutherland, South Africa, obtained a repeating series of 60s exposures in the q,u,g,r,i,z filters following the detection of GRB 240218A by Swift (Page et al., GCN 35742). Our observations began 96 seconds after the Swift trigger and continued for approximately 1 hour following the filter sequence quqgqrqiqz. We do not detect an optical source at a position consistent with the high-redshift counterpart detected by REM and the VLT (D'Avanzo et al., GCN 35747; Malesani, GCN 35749; Saccardi et al., GCN 35756) in any individual exposure. Our earliest 3-sigma AB limiting magnitudes in each filter are: u > 19.29 at 3.6 minutes post-trigger g > 20.58 at 6.5 minutes post-trigger q > 21.10 at 2.1 minutes post-trigger r > 20.29 at 9.4 minutes post-trigger i > 19.81 at 13.4 minutes post-trigger z > 18.87 at 15.3 minutes post-trigger. We additionally co-added all of the images in each filter and obtain the following 3-sigma AB limiting magnitudes at an average time of 36 minutes post-trigger: u > 20.33 g > 21.61 q > 22.67 r > 21.21 i > 20.54 z > 19.54. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/35765. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...