TITLE: GCN CIRCULAR NUMBER: 14330 SUBJECT: report: GRB 130315A: Zadko observatory - Gingin optical observations DATE: 13/03/26 14:26:44 GMT FROM: Husne Dereli at ARTEMIS/OCA/TAROT/ZADKO GRB 130315A: Zadko observatory - Gingin optical observations ------------------------------**------------------------------**---------- H. Dereli (UNS-CNRS-OCA), A. Klotz (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D. Coward (UWA), B. Gendre (IRAP-CNRS-OMP), M. Boer, K. Siellez, O. Bardho (UNS-CNRS-OCA), A. Williams (PO-UWA), R. Martin (PO-UWA) report: We imaged the field of GRB 130315A detected by SWIFT (trigger 551126) with the Zadko robotic telescope (D=100cm) located at the observatory - Gingin, Australia. The observations started 1.22h after the GRB trigger. The elevation of the field increased from 65 degrees above horizon and weather conditions were good. We co-added a series of unfiltered exposures and we substracted images taken with the same telescope 4h to 8h later to eliminate contaminations by foreground stars. We did not detect any optical transient at the position provided by Schmidl et al. (GCNC 14325): t0+1.22h to t0+1.54h : Rlim = 20.4 This limiting magnitude and the detection of Schmidl et al. (GCNC 14325) implies a decay with alpha < 0.67. As Schmidl et al. (GCNC 14325) announced alpha > 0.75 after 12h we suspect a late rising of a faint afterglow or a break of the decay. Magnitudes were estimated with the nearby NOMAD1 stars and are not corrected for galactic dust extinction.