TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1613 SUBJECT: GRB 021004 - VLA Radio Observations DATE: 02/10/10 06:31:25 GMT FROM: Edo Berger at Caltech E. Berger, D. A. Frail, and S. R. Kulkarni report on behalf of a larger collaboration: "We observed the radio afterglow of GRB 021004 (Frail & Berger GCN 1574; Berger, Kulkarni, & Frail GCN 1612) with the VLA at 1.43, 4.86, and 8.46 GHz on October 10.17 UT. We measure the following flux densities: F(1.43)=48+/-53 microJy, F(4.86)=359+/-38 microJy, and F(8.46)=598+/-33 microJy. The resulting spectral slope is beta~1 (F_nu~nu^beta), in excellent agreement with the unusual value of beta=0.9 between 8.5 and 86 GHz measured by Berger, Kulkarni, & Frail (GCN 1612). This again indicates that the spectrum is not due to a transition from optically-thick (nu^2) to optically-thin (nu^1/3) emission, and it further highlights the unusual nature of this radio afterglow." This message may be cited.