TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3850 SUBJECT: GRB 050822: ROTSE-III Prompt Optical Limits DATE: 05/08/22 04:43:28 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich) reports on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 050822 (Swift trigger 151486), producing images beginning 5.8 s after the GCN notice time. An automated response took the first image at 03:50:00.8 UT, 31.7 s after the start of the burst, and during the gamma-ray emission (GCN 3849). These observations were affected by proximity to the full moon as well as early twilight. We took 10 5-sec, and 70 20-sec eposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma BAT error circle or at the XRT position, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 15.0-16.2; we set the following specific limits. start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd? -------------------------------------------------------------------- 03:50:00.8 3:50:05.8 5 15.1 31.7 N 03:50:00.8 3:51:24.8 84 16.6 31.7 Y 03:51:25.5 3:56:12.0 286 17.5 412.6 Y