TITLE: GCN CIRCULAR NUMBER: 6517 SUBJECT: GRB070612B: P60 Observations DATE: 07/06/12 08:56:35 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko, A. Rau (Caltech) and D. B. Fox (Penn State) report on behalf of a larger collaboration: We have imaged the field of GRB070612B (Grupe et al., GCN 6511) with the automated Palomar 60-inch telescope. Images were taken in the Kron R and Sloan i' and z' filters beginning approximately 12 minutes after the burst. We find no sources inside the XRT error circle (Grupe and Evans, GCN 6514). Photometric calibration for the limits below was performed using USNO B-1 mangitudes converted to the SDSS photometric sytem using empirical relations from Jordi, Grebel & Ammon (A&A 460, 339, 2006): t_b (min.) Filter Mag. Limit ----------------------------------------------------------------------- 21.2 i' > 21.0 22.7 z' > 20.5 We marginally detect a source just outside of the XRT error circle in our i' coaddition. The source, with i' magnitude ~ 22.0, is located at coordinates (J2000.0): RA: 17:26:54.936 Dec: -08:45:08.35 This source is not present in either our R- our z'-band imaging of this field. Because of the faintness, we cannot assess the variability of this source at the present time.