TITLE:   GCN CIRCULAR
NUMBER:  11309
SUBJECT: GRB 100925A / MAXI J1659-152: WSRT Radio and Polarization Detection
DATE:    10/09/27 01:15:56 GMT
FROM:    Alexander van der Horst at NASA/MSFC  <Alexander.J.VanDerHorst@nasa.gov>

  A.J. van der Horst (NASA/MSFC/ORAU), J. Granot (U of Hertfordshire),
Z. Paragi (JIVE), C. Kouveliotou (NASA/MSFC), R.A.M.J. Wijers (U of
Amsterdam) and E. Ramirez-Ruiz (UC Santa Cruz) report:

"We observed the position of the hard X-ray transient GRB 100925A /
MAXI J1659-152 (GCN 11296, ATel #2873, GCN 11307) with the Westerbork
Synthesis Radio Telescope at 4.8 GHz, at September 26 14.27 to 19.75 UT,
i.e. 1.37 days after the Swift/BAT trigger (GCN 11296) and 1.60 days
after the start of the source brightening in MAXI/GSC (ATel #2873).
We detect a radio source at the Swift/UVOT position of the transient
(GCN 11298), with a flux density of 4.92 +/- 0.04 mJy. The source is
linearly polarized at a level of 23 +/- 2 %, but there is no circular
polarization detected, with a 3-sigma upper limit of 2 %.

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