TITLE:   GCN CIRCULAR
NUMBER:  11256
SUBJECT: GRB 100901A: Confirmation of WSRT Radio Detection
DATE:    10/09/07 19:33:23 GMT
FROM:    Alexander van der Horst at NASA/MSFC  <Alexander.J.VanDerHorst@nasa.gov>

  A.J. van der Horst (NASA/MSFC/ORAU), K. Wiersema (U of Leicester),
A.P. Kamble, R.A.M.J. Wijers, E. Rol (U of Amsterdam) and
C. Kouveliotou (NASA/MSFC) report on behalf of a large collaboration:

"We observed the position of the GRB 100901A afterglow at 4.9 GHz
with the Westerbork Synthesis Radio Telescope at September 6 20.33 UT
to September 7 08.30 UT, i.e. 5.28 - 5.78 days after the burst (GCN 11159).
We confirm our earlier detection (GCN 11221) and measure a brightening
of the radio counterpart at the position of the X-ray and UV/optical
afterglow (GCN 11195), with a flux density of 193 +/- 30 microJy.

We would like to thank the WSRT staff for scheduling and obtaining these
observations."