TITLE:   GCN CIRCULAR
NUMBER:  18619
SUBJECT: GRB 151118A: Early optical limit from pt5m, La Palma
DATE:    15/11/18 17:56:51 GMT
FROM:    Liam K Hardy at U of Shffield  <liam.hardy@sheffield.ac.u>

L. K. Hardy (Sheffield), V. S. Dhillon (Sheffield, IAC),
S. P. Littlefair (Sheffield), T. Butterley (Durham) and
R. W. Wilson (Durham) report:

Our automated robotic telescope 'pt5m' (Hardy et al. 2015, MNRAS 454,
4316) on La Palma observed the field of
GRB 151118A (Amaral-Rogers et al., GCN 18611) starting
at 03:16:27 UT on Nov 18, 10 min after the GRB detection.

Observations comprised of 46 x 60-second exposures in
the R-band. We detect no new source within the XRT error box (Evans et
al., GCN 18614). The 3-sigma limiting magnitude of
a combined image is R = 22.1 mag. The mean time of the
combined exposure is 03:42 UT (36 mins after the burst).
We obtained photometry using the nearest comparison star,
USNOB1.0:1559-0079286, R=15.6.