[vsnet-grb-info 28065] GRB210610A: MeerLICHT multi-colour photometry

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30168
SUBJECT: GRB210610A: MeerLICHT multi-colour photometry
DATE:    21/06/10 18:56:04 GMT
FROM:    Paul Vreeswijk at Radboud U/Nijmegen  <p.vreeswijk at astro.ru.nl>

S. de Wet (UCT), P.M. Vreeswijk (Radboud), P.J. Groot
(Radboud/UCT/SAAO), A. Levan (Radboud) report on behalf of the
MeerLICHT consortium:

Following the detection of GRB210610A by Swift and its optical
counterpart (Page et al., GCN 30160), reported at a redshift of z=3.54
by Zhu et al. (GCN 30163), the 0.6m MeerLICHT telescope, located at
Sutherland, South Africa began observations of the field at
2021-06-10, 16:48:47 UT 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 = 19.60 +/- 0.08 +/- 0.02 at 16:48:47 UT
r_AB = 19.09 +/- 0.10 +/- 0.01 at 16:56:12 UT
i_AB = 18.74 +/- 0.12 +/- 0.02 at 16:59:10 UT
z_AB = 18.37 +/- 0.19 +/- 0.02 at 17:02:09 UT, 
where the first uncertainty on the magnitude is the statistical
uncertainty and the second is the uncertainty on the photometric
calibration.

In g-band the afterglow is detected only once, at 17:08:11 UT, at
g_AB = 20.18 +/- 0.18 +/- 0.03, close to the limiting magnitude of the
frame. 

The source is not detected in the u-band, starting at 16:50:11 UT, at
a 5-sigma limiting magnitude of u_AB > 18.76.

Further fading of the source is observed during the ongoing sequence. 

MeerLICHT is built and run by a consortium consisting of Radboud
University, the University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam.