TITLE: GCN CIRCULAR NUMBER: 11257 SUBJECT: EVLA detection of radio afterglow of GRB100901A DATE: 10/09/07 21:09:26 GMT FROM: Poonam Chandra at Royal Mil. College Canada Poonam Chandra (RMC) and Dale A. Frail (NRAO) report on behalf of a larger collaboration: "We observed GRB 100901A (Immler et al. GCN 11159) with the Expanded Very Large Array (EVLA) on September 06.47 UT at a C band wide receiver (receiver frequency range 4-8 GHz). We detect the radio afterglow of the GRB at the Swift-XRT position (Osborne et al. GCN 11167) at 4.5 and 7.9 GHz frequencies. The flux densities at 4.5 and 7.9 GHz bands are 331+/-30 uJy and 440+/-27 uJy, respectively. The EVLA is still undergoing active commissioning and we caution that these results should be considered preliminary. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."