K.Ulaczyk, D.Steeghs (U. Warwick), G.Ramsay (Armagh O.), M.Dyer
(U. Sheffield), B.Gompertz, J.Lyman, A.Levan, R.Cutter (U. Warwick)
K. Ackley, D.Galloway, E.Rol (Monash U.), V.Dhillon (U. Sheffield),
P.O'Brien, N.Tanvir (U. Leicester), S.Poshyachinda (NARIT),
D.Pollacco (U. Warwick), E.Thrane (Monash U.)
report on behalf of the GOTO collaboration:
In response to GRB 180706A (GCN 22909, 22910, 22916, 22917, 22919,
22921), the Gravitational-wave Optical Transient Observer (GOTO)
observed the field near the XRT position as reported by Osborne
et al. (GCN 22916).
Observations started at 2018-07-06T21:26:42 UT (13 hours after the
burst) and ended at 2018-07-06T23:49:54 and consisted of a set of
12x120s exposures in our wide L filter(400-700nm). We did not detect
a significant source corresponding to the reported optical counterpart.
A stacked image was used to derive a 5-sigma upper limit of V>21.6,
after astrometric and photometric (APASS V) calibrations.
This is consistent with the photometric evolution between the early
optical detections (GCN 22910, 22922) and the TSHAO magnitude reported
in Volnova et al. (GCN 22923).
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)