[vsnet-grb-info 20971] GRB 180728B: GOTO optical search over IPN region

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23069
SUBJECT: GRB 180728B: GOTO optical search over IPN region
DATE:    18/07/31 21:56:14 GMT
FROM:    Danny Steeghs at U.of Warwick/GOTO  <D.T.H.Steeghs at warwick.ac.uk>

D.Steeghs, J.Lyman (U. Warwick), G.Ramsay (Armagh O.), M.Dyer
(U. Sheffield), K.Ulaczyk, 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.)

report on behalf of the GOTO collaboration:

In response to the short-duration GRB 180728B (GCN 23056, 23057, 23060),
the Gravitational-wave Optical Transient Observer (GOTO) observed the
IPN triangulation region as reported in Svinkin et al. (GCN 23056).

Observations were spread over four telescope array pointings,
beginning 2018-07-29T21:24 UT (24.25 hours after the burst) and employ
sets of 3x120s exposures in our wide L filter(400-700nm). These fields
were repeated on 2018-07-30 to permit difference imaging analysis.
Conditions were affected by dust, typically achieved a 5 sigma limiting
magnitude of V=19.8-20.1 on 2018-07-29 and V=20.4-20.6 on 2018-07-30.

We made use of the GLADE galaxy catalog to pay particular attention to
possible source candidates near galaxies within 200 Mpc. We find no
significant sources that could be credibly associated with the GRB.

Furthermore, we see no evidence for a source at the position reported
in Lipunov et al. (GCN 23065), noting that our observations started
4.7 hours later than the MASTER observations and thus the source
may have faded below our detection limit by then.


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/