GCN Circular 31063
Subject
MeerLICHT follow-up of GRB 211106A
Date
2021-11-09T10:31:00Z (3 years ago)
From
Simon de Wet at UCT <dwtsim002@myuct.ac.za>
S. de Wet (UCT), P.M. Vreeswijk (Radboud), A.J. Levan (Radboud),
P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT
consortium and the Stargate collaboration:
We observed the field of the Swift/BAT-GUANO short GRB candidate
GRB211106A (Tohuvavohu et al., GCN 31049) with the 0.6m wide-field
MeerLICHT optical telescope located at Sutherland, South Africa,
taking 10x60s exposures in the q-band starting at 2021-11-06,
18:37:17 UT, approximately 14 hours after the GRB trigger.
We co-added the images to reach a full-frame 5-sigma AB limiting
magnitude of q = 21.90. An archival reference image with limiting
magnitude of q = 20.54 was used to perform image subtraction
through our transient detection pipeline. The MeerLICHT field-of-view
fully covers the BAT-GUANO error box and includes all the X-ray
sources found through Swift-XRT follow-up observations
(D'Elia et al., GCN 31051).
Our transient pipeline finds 1 candidate in the BAT-GUANO error
box, at the same position as the XRT source coincident with a known
X-ray source. The coordinates of the transient coincide with a star
with brightness G = 17.49 in the Gaia EDR3 catalogue, spatially
very close to galaxy LEDA 432583. We believe the transient detection
is due to the star showing variable behaviour rather than a transient
in the galaxy, owing to an increase in brightness of the star from
q = 17.73 mag in the reference image to q = 17.47 in the new image.
We detect no source in our images at the position of the known X-ray
source 1RXS J225507.9-531312.
No other promising transient candidates are found in the error boxes
of the 9 XRT sources nor the BAT-GUANO error box, down to a transient
limiting magnitude of 20.34.
There is one other potential transient candidate in our FOV, but it
is 15.6��� away from the centre of the BAT-GUANO error box, so unlikely
to be associated with GRB 211106A. The coordinates are
RA, Dec (J2000) = 22:54:17.88, -52:58:35.22. The Legacy Survey DR9
images show a spiral galaxy at this position, which could be showing
variable behaviour or may be due to a transient near the galaxies' core.
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.