TITLE:   GCN CIRCULAR
NUMBER:  22892
SUBJECT: GRB 180703A: LCO Sutherland possible optical candidate
DATE:    18/07/04 13:26:02 GMT
FROM:    Renato Martone at Universita' di Ferrara  <mrtrnt@unife.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:

One of the LCO 1-m units at Sutherland Observatory (South Africa) began observing Fermi-LAT GRB 180703A (Racusin et al. GCN 22883) on July 04, 02:34 UT (5.5 hours after the GRB trigger time) with the SDSS i' filter. On the border of the Swift-XRT error circle of source S1 (Gibson et al. GCN 22891) we marginally detect an object at the following position:

RA(J2000)=  00:25:52.35
DEC(J2000)= -67:10:43.4

with an error radius of ~1" and a magnitude of i'=20.6 +- 0.3 at a mid time of 5.65 hours post GRB, as calibrated against nearby USNOB-UCAC4 stars.