TITLE:   GCN CIRCULAR
NUMBER:  22792
SUBJECT: GRB 180618A: LT prompt observations
DATE:    18/06/18 08:18:45 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), 
A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large 
collaboration report:

The 2-m Liverpool Telescope automatically began observing Swift GRB 
180618A (LaPorte et al. GCN 22790) on June 18, 00:46:30 UT (197 s since 
the GRB trigger time) with the RINGO3 polarimeter and the IO:O camera in 
the SDSS-R filter. The optical counterpart identified by Swift-UVOT is 
clearly detected with r'=19.36 +- 0.05 mag in a 6x10s exposure at a mid 
time of 36.3 minutes post GRB, as calibrated against nearby SDSS objects.