TITLE: GCN CIRCULAR NUMBER: 12011 SUBJECT: GRB 110503A: TAROT Calern observatory optical observations DATE: 11/05/06 16:56:18 GMT FROM: Alain Klotz at CESR-CNRS Klotz A. (CESR-OMP), Gendre B. (ASDC), Boer M. (OHP-OAMP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 110503A detected by SWIFT (trigger 451901) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 1.9h after the GRB trigger (trigger occured during daytime). The elevation of the field decreased from 69 degrees above horizon and weather conditions were good. We detect the candidate couterpart mentioned by Stamatikos et al. 2011 (GCNC 11991) on co-added series of exposures. We used the reference star USNO B1.0 1421-0227752 (08:51:10.01 +52:11:04.75 J2000) described by Kann et al. 2011 (GCNC 11996) assuming R=16.819 (Updike et al. GCN 12001). start stop R 1.96h - 2.65h 18.42 +/- 0.15 2.71h - 3.99h 19.11 +/- 0.10 4.04h - 5.33h 19.51 +/- 0.12 5.38h - 7.43h 19.93 +/- 0.15 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. From 1.96h to 7.43h, the decay slope is alpha = 1.1.