TITLE:   GCN CIRCULAR
NUMBER:  23163
SUBJECT: GRB 180821A: LCO Siding Springs observations
DATE:    18/08/22 06:59:47 GMT
FROM:    Cristiano Guidorzi at Ferrara U,Italy  <guidorzi@fe.infn.it>

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

We automatically observed Swift GRB 180821A (Tohuvavohu et al. GCN 
23158) with the LCO 2-m unit at Siding Springs on August 21, from 16:54 
to 17:07 UT (corresponding to 14 to 27 minutes from the GRB trigger 
time) with the SDSS i' filter. Within the enhanced Swift-XRT error 
circle (Evans et al. GCN 23162) we do not detect any source down to 
i'>21.0 mag from a 10x60s exposure at a mid time of 0.33 hours post GRB, 
as calibrated against nearby USNOB1 objects.