TITLE: GCN CIRCULAR NUMBER: 10778 SUBJECT: GRB 100518A: BOOTES-3 optical observations DATE: 10/05/19 08:44:42 GMT FROM: Antonio Deugarte at IAA-CSIC A. de Ugarte Postigo (INAF-OAB), A.J. Castro-Tirado, J. Gorosabel, M. Jelinek (IAA-CSIC), P. Kubanek (IPL UV, IAA-CSIC), R. Cunniffe, S. Guziy (IAA-CSIC), P. Yock (Auckland Univ.), W.H. Allen (Vintage Lane Obs.), I. Bond (Massey Univ.), G. Christie (Stardome Obs.) report on behalf of a larger collaboration: "We have observed the field of the INTEGRAL GRB 100518A (Mereghetti et al., GCN 10772) using the 0.6m Yock-Allen robotic telescope (BOOTES-3) located in Blenheim, New Zealand. Preliminary analysis of a combined 40x60s unfiltered exposure taken (mid-epoch) on 18th May 2010, 14:01 UT (2.47 hours after the burst, when acceptable weather allowed to perform the observations) does not show any source at the position of the optical afterglow candidate (Cano et al., GCN 10776) down to a 3-sigma limiting magnitude of R ~ 20.7 using USNO-B1.0 as photometric reference."