TITLE:   GCN CIRCULAR
NUMBER:  33582
SUBJECT: GRB 230405B: MeerLICHT upper limits
DATE:    23/04/06 19:05:47 GMT
FROM:    Simon de Wet at UCT  <dwtsim002@myuct.ac.za>

S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), P.M. Vreeswijk (Radboud),
D. Pieterse (Radboud) and D.B. Malesani (Radboud and DAWN/NBI) report on
behalf of the MeerLICHT consortium:

Following the detection of GRB 230405B by Swift/BAT along with its X-ray
counterpart (Page et al., GCN 33571), the 0.6 m wide-field MeerLICHT
optical telescope located at Sutherland, South Africa, obtained a repeated
series of 60-s exposures in the q,u,g,r,i,z bands following the sequence
quqgqrqiqz. Observations began 6.38 hours after the Swift trigger at 2023
April 6 02:20:05 UT and continued for a further 1.82 hours.

Our individual 60-s exposures show no new optical source consistent with
the enhanced XRT position (Beardmore et al., GCN 33574) when compared to
archival DECam images of this field. We therefore co-added the images in
each filter in order to obtain deeper limits. We report the following
3-sigma AB magnitude limits at the XRT position at ~7.2 hours post-trigger:

u > 20.5
g > 21.3
q > 22.6
r > 21.2
i > 21.1
z > 20.1

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.