TITLE: GCN CIRCULAR NUMBER: 5768 SUBJECT: GRB 061028: z band imaging DATE: 06/10/28 18:51:37 GMT FROM: Josh Bloom at UC Berkeley GRB 061028: z-band imaging J. S. Bloom (UC Berkeley), D. Charbonneau, M. J. Holman, E. E. Falco (Harvard/CfA), H-. W. Chen (U Chicago) report on behalf of a larger collaboration: "We observed the field of GRB 061028 (Sakamoto et al. GCN 5762) using the z-band filter of Keplercam mounted on the Mt. Hopkins 48-inch telescope. In a stacked series of 5 minute exposures from 06:20 - 07:21 Oct 28, 2006 UTC (from about 4 - 5 hours after the GRB trigger), we find no detected source consistent with the revised XRT position (Cusumano et al. GCN 5767). We do note the presence of a marginally detected faint red source (S1) to the north of the error circle that is not in the DSS2 F or N plates at position 06:28:54.6, 46:18:01 (J2000). Photometric calibration is in progress but, for reference, S1 is about 2.1 mag fainter in z-band than the object at 06:28:54.1, +46:18:15. Our 3 sigma limiting magnitude is roughly 0.2 mag fainter than S1." An image of the field (XRT 90% confidence region circled) is located at: http://lyra.berkeley.edu/~jbloom/grb061028_zcompare_bloom.ps.gz This message may be cited.