TITLE: GCN CIRCULAR NUMBER: 11081 SUBJECT: GRB 100805A: Swift/UVOT Observations of a Possible Late-Time Brightening DATE: 10/08/11 19:48:49 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/USRA/GSFC) and E. A. Hoversten (PSU) report on the behalf of the Swift UVOT team: Swift/UVOT observations of the optical afterglow of GRB 100805A (Hoversten, et al., 2010, GCN Circ, 11047) suggest that the afterglow may have brightened in the UVOT white band between approximately 1 day and 6 days after the BAT trigger. This may indicate the presence of a supernova component in the light curve. Our analysis is complicated by the presence of several bright stars near the optical afterglow. Further observations are needed to confirm that this possible brightening is real. Follow-up observations of this source are strongly encouraged.