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GCN Circular 32289

Subject
GRB 220627A: MeerLICHT candidate optical afterglow
Date
2022-06-28T22:59:47Z (2 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), D.B. Malesani (Radboud and
DAWN/NBI), A.J. Levan (Radboud) and D. Pieterse (Radboud) report on behalf
of the MeerLICHT consortium:

Following the Fermi/LAT detection and localisation of GRB 220627A (Di Lalla
et al., GCN 32283), also proposed to be a lensed or ultra-long GRB
candidate by Fermi/GBM (Roberts et al., GCN 32288), the 0.6 m wide-field
MeerLICHT optical telescope obtained 2x300s observations in the q-band of
two fields encompassing the LAT error box starting at 17:12:15 UT on 2022
June 28, approximately 1.17 days after the GBM trigger. We note that these
two fields were not observed during observations of the Fermi/GBM error box
from the previous night (Groot et al., GCN 32281). We also note that the
two transient candidates from those observations are not consistent with
the Fermi/LAT errorbox, therefore we exclude their association with GRB
220627A.

Within the error box of the uncatalogued X-ray Source 3 discovered by
Swift/XRT through ToO observations (Evans, GCN 32284), we detect a new
transient candidate at the following coordinates:

RA (J2000) = 13:25:28.49 (201.36872d)
Dec (J2000) = -32:25:33.31 (-32.42592d)

calibrated against Gaia DR2, with a positional uncertainty of 0.1" in each
coordinate. The same object is detected in a further 2x300s observations ~1
hour later. The source is detected with an AB magnitude of

q = 21.25 +/- 0.09

in the first exposure. We detect no source at the transient location in an
archival image of the same field down to a 3-sigma limiting magnitude of q
> 21.71. We suggest this may be the afterglow of GRB 220627A. Further
follow-up is encouraged.

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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