TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2595 SUBJECT: GRB 040511: ROTSE-III Rapid Optical Upper Limits DATE: 04/05/13 16:23:16 GMT FROM: Don Smith at U michigan D. A. Smith (NSF/U of Michigan) reports on behalf of the ROTSE collaboration: The ROTSE-IIIa telescope (at SSO, Australia) responded rapidly to both the intitial on-board alert and the final ground analysis alert distributed by HETE-2 for GRB 040511 (HETE #3218, Dullighan et al., GCN Circ. #2588). In both cases, the first ROTSE-IIIa exposure began within 3.5 s of the alert time stamp. The final SXC localization was outside the field of view of the first series of ROTSE-IIIa images, so those data are not included in this report. The second series of images began at 15:11:34.57 UTC, ~2.2 h after the burst trigger time. The instrument responded automatically with a pre-programmed sequence of ten 5-s and ten 20-s images, after which it recorded 44 60-s images. The first 60 images were co-added in sets of ten, reaching limiting magnitudes of ~17.2 for the 5-s images and ~17.5 for the others. (ROTSE-III images are unfiltered, but calibrated to USNO A2.0 R-band.) Comparison of these images to the USNO catalogs and the DSS 2nd Generation R-band image reveal no new sources. The detected foreground sources are estimated to cover ~10-15% of the SXC error circle. In short, ROTSE-IIIa provides the following approximate R-band upper limits (the first column is the elapsed time to the middle of the co-added exposure): Time from Exp. Time Upper Limit Burst Trigger (hours) (sec) 2.18 50 17.2 2.24 200 17.5 2.37 600 17.5 2.57 600 17.5 2.76 600 17.6 2.95 600 17.5