GCN Circular 3521
D. Bersier, A. Fruchter, J. Rhoads, (STScI), A. Levan (U. of Leicester), N. Tanvir (Hertsfordshire) report on behalf of a larger collaboration: We have observed the field of GRB 050509b (Hurkett et al, GCN 3379) with the Gemini Multi-Object Spectrograph on the Gemini-North telescope. We obtained imaging data (Sloan filters) on May 13, May 17 and May 28. PSF-matched image subtraction of the May 13 and May 17 data from the May 28 image reveals no variable sources down to 26.5 on May 14 and 26.4 on May 17 (3-sigma limits). At the redshift of the cluster this would imply that any unextincted SN would be more than 4 magnitude fainter than SN 1998bw. Furthermore, our detection limit on May 28 is ~27.4. At that epoch, a supernova like SN 1998bw would be 6 mag brighter than this. There is no such bright source in the XRT error circle.