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GCN Circular 31196

Subject
GRB 211130A: MeerLICHT identification of possible afterglow candidate
Date
2021-12-10T09:16:11Z (2 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan (Radboud),
P.M. Vreeswijk (Radboud), report on behalf of the MeerLICHT consortium:

We observed the field of the Fermi/GBM long GRB candidate GRB 211130A
(Fermi GBM Team, GCN 31151) with the 0.6m wide-field MeerLICHT
optical telescope located at Sutherland, South Africa, starting at
2021-11-30,
18:31:26 UT, approximately 3 hours 15 minutes after the GRB trigger.
With a field of view of 2.7 square degrees, 72 MeerLICHT pointings were
required to cover the GBM sky map to a probability level of 90%. We
observed 67 out of the 72 fields three times on the first night of
observations.
The remaining 5 fields were observed once. All observations were conducted
in the q-band (g+r) with a 60s exposure time. The average 5-sigma full-frame
limiting magnitude was q = 20.79 across the observations.

Following the IPN triangulation of GRB 211130A (Kozyrev et al., GCN 31161),
a refined search for transient candidates in our data reveals a single
promising
afterglow candidate at coordinates:

RA (J2000) = 01:24:52.46 (21.2186d)
Dec (J2000) = -27:41:57.48 (-27.6993d)

calibrated against Gaia DR2. The candidate is, however, located just North
of
the IPN triangulation region, an angular distance of 8.7' from the centre
of the
IPN region and still consistent with the Konus-Wind/GBM triangulation
region.
The candidate was detected at three epochs and appears to show fading
behaviour, with 5-sigma AB magnitudes at time post-trigger of:

q = 19.83 +/- 0.07 at 3.74 hours
q = 20.05 +/- 0.10 at 5.57 hours
q = 20.66 +/- 0.20 at 7.05 hours.

No underlying source is visible in PanSTARRS and Legacy Survey DR9 images
at this position.

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.
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