TITLE: GCN CIRCULAR NUMBER: 5871 SUBJECT: GRB 061121: ATCA & WSRT Radio Observations DATE: 06/11/27 15:58:28 GMT FROM: Alexander van der Horst at U of Amsterdam A.J. van der Horst, R.A.M.J. Wijers (University of Amsterdam) and E. Rol (University of Leicester) report on behalf of a larger collaboration: "We observed the position of the GRB 061121 afterglow (GCN 5823) at 2.3 GHz with the Westerbork Synthesis Radio Telescope, and at 4.8 and 8.6 GHz with the Australia Telescope Compact Array. We do not detect a radio counterpart of the optical afterglow (GCN 5824). Our results are given in the table below. We note that the three-sigma flux limit at 8.6 GHz at ~5.2 days after the burst is significantly lower than the VLA detection at ~0.8 days after the burst (GCN 5843). Epoch Delta T Frequency 3-sigma rms noise Formal flux =============== ======== ========= ================= ============== Nov 26.76-26.92 5.2 days 8.6 GHz 246 uJy/beam 10 +/- 82 uJy Nov 26.76-26.92 5.2 days 4.8 GHz 210 uJy/beam 13 +/- 70 uJy Nov 27.01-27.30 5.5 days 2.3 GHz 144 uJy/beam -50 +/- 48 uJy We would like to thank the WSRT staff for obtaining these observations in between VLBI observation runs. Also we would like to thank the staff of the Australia Telescope National Facility, in particular Philip Edwards, for obtaining these Target of Opportunity observations."