TITLE:   GCN CIRCULAR
NUMBER:  23252
SUBJECT: GRB 180914B: GOTO optical detection
DATE:    18/09/17 22:22:19 GMT
FROM:    Danny Steeghs at U.of Warwick/GOTO  <D.T.H.Steeghs@warwick.ac.uk>

G.Ramsay (Armagh O.), K.Ulaczyk, D.Steeghs, J.Lyman (U. Warwick),
M.Dyer (U. Sheffield),  B.Gompertz, A.Levan, R.Cutter (U. Warwick)
K. Ackley, D.Galloway, E.Rol (Monash U.), V.Dhillon (U. Sheffield),
P.O'Brien, R.Starling (U. Leicester), S.Poshyachinda (NARIT),
D.Pollacco (U. Warwick), E.Thrane (Monash U.), E.Palle (IAC)

report on behalf of the GOTO collaboration:

The Gravitational-wave Optical Transient Observer observed the field
of the long GRB 180914B (Ursi et al. GCN Circ. 23226, Bissaldi et al. GCN
Circ. 23232) from Roque de los Muchachos Observatory.

In a combined L-band image (400-700nm passband), with a total exposure
time of 600s at a mid-time 2018-09-16 21:57:04 UT, 2.149 days since
burst, we detect the optical counterpart (Zheng et al. GCN
Circ. 23237; Troja GCN Circ. 23238; de Ugarte Postigo et al. GCN
Circ. 23239; Mazaeva et al. GCN Circ. 23244; Lipunov et al. GCN
Circ. 23245) with a preliminary magnitude of g=20.9 +/- 0.2 based on a
comparison to Panstarrs g-band calibrators.


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/)