TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3863 SUBJECT: GRB050820a: PROMPT RcIc Observations DATE: 05/08/23 21:22:02 GMT FROM: Chelsea Louise MacLeod at UNC-Chapel Hill/PROMPT C. MacLeod, M. Nysewander report on behalf of the UNC team of the FUN GRB Collaboration: We have observed the position of the GRB 050820a afterglow reported by Fox et al. (GCN 3829). We detect the afterglow in RcIc: Mean Time Integration Filter Magnitude Telescope Since GRB Time 2.2 hr 39 x 40 sec Ic 17.40 +/- .08 PROMPT-3 2.2 hr 22 x 30 sec Rc 17.64 +/- .09 PROMPT-5 21.5 hr 136 x 40 sec Ic 18.42 +/- .11 PROMPT-3 21.7 hr 179 x 30 sec Rc 20.06 +/- .31 PROMPT-5 Rc and Ic calibrations were made relative to 7 calibration stars posted by Henden (GCN 3845). PROMPT is still being built and commissioned.