S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan and
P.M. Vreeswijk (Radboud) report on behalf of the MeerLICHT consortium:
"Following the detection of GRB210610B by Swift and its optical
counterpart (Page et al., GCN 30170), the 0.6m MeerLICHT telescope,
located at Sutherland, South Africa began observations of the field at
2021-06-10, 21:00:54 UT (1h9m after burst) with a repeating
sequence of optical filters: q,u,q,g,q,r,q,i,q,z, at 60s integration
time each. The q-band wavelength limits are 440-720nm.
First detections are:
q_AB = 17.25 +/- 0.01 +/- 0.02 at 21:00:54 UT
u_AB = 17.48 +/- 0.05 +/- 0.05 at 21:02:18 UT
g_AB = 17.39 +/- 0.02 +/- 0.03 at 21:05:27 UT
i_AB = 17.12 +/- 0.03 +/- 0.01 at 21:11:25 UT
z_AB = 17.10 +/- 0.07 +/- 0.02 at 21:14:26 UT
r_AB = 17.37 +/- 0.02 +/- 0.02 at 21:23:29 UT
where the first uncertainty on the magnitude is the statistical
uncertainty and the second is the uncertainty on the photometric
calibration. No correction for Galactic extinction has been made.
Inspection of DECaLS/DR3 data (Dey et al., 2019, AJ 157, 168) shows an
underlying blue galaxy, centered on RA,Dec (J2000) = 243.91823,
+14.39901, with magnitude g=22.97, r=22.87 and z=22.57.
Further monitoring is continuing.
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."