[vsnet-grb-info 470] GRB 021004 - VLA Radio Observations

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

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  <ejb@astro.caltech.edu>

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."

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