B. Gompertz (1); K. Wiersema (1); D. K. Galloway (2); R. Starling (3);
J. Lyman (1); K. Ackley (2); Y.-L. Mong (2); D. Steeghs (1); V.Dhillon
(4); P. O'Brien (3); G. Ramsay (5); D. Pollacco (1); E. Thrane (2); S.
Poshyachinda (6); R. Kotak (7); L. Nuttall (8); E. Pall\'e (9); K.
Ulaczyk (1); R. Cutter (1); A. Levan (1); T. Marsh (1); R. West (1); E.
Stanway (1); T. Killestein (1); A. Casey (2); M. Brown (2); B. Muller
(2); M. Dyer (4); J. Mullaney (4); E. Daw (4); S. Littlefair (4); J.
Maund (4); L. Makrygianni (4); U. Burhanudin (4); R. Eyles (3); S. Tooke
(3); S. Aukkaravittayapun (6); U. Sawangwit (6); S. Awiphan (6); D.
Mkrtichian (6); P. Irawati (6); S. Mattila (7); T. Heikkil\"a (7); E.
((1) Warwick University, (2) Monash University, (3) University of
Leicester, (4) University of Sheffield, (5) Armagh Observatory &
Planetarium, (6) National Astronomical Research Institute of Thailand,
(7) University of Turku, (8) University of Portsmouth, (9) Instituto de
Astrofisica de Canarias)
report on behalf of the GOTO collaboration:
We carried out observations with the Gravitational-wave Optical
Transient Observer (GOTO) in response to GRB 200723A (Fermi GBM; GCN 28155).
We made a series of 4x90 s exposures using our wide L-band filter
(400-700 nm) covering the Fermi GBM error box (GCN 28155), with midtime
22:42:55 UT on 23 July 2020.
Using a difference imaging analysis with recent survey observations of
the same pointings as reference, we detect an uncatalogued source in a
tiled observation taken at 21:25 UT (4.8 hours after trigger) with a
magnitude of L = 18.5 �� 0.05 mag based on PS1 catalogue calibrators
located at (J2000):
This source is coincident with a galaxy in the 2MASS redshift survey
(Huchra et al, 2012) at a redshift of z = 0.0557. Given the large Fermi
GBM uncertainty region, the probability that this source is an unrelated
transient is large. We have registered it with the TNS with the ID
AT2020qer. A previous GOTO observation taken on July 17 23:28:49 UT
places a limiting magnitude of L > 19.2 (5 sigma) on this source 6 days
prior to the Fermi GBM trigger.
GOTO is operated at the La Palma observing facilities of the University
of Warwick on behalf of a consortium including the University of
Warwick, Monash University, Armagh Observatory, the University of
Leicester, the University of Sheffield, the National Astronomical
Research Institute of Thailand (NARIT) and the Instituto de Astrofisica
de Canarias (IAC) (https://goto-observatory.org