TITLE:   GCN CIRCULAR
NUMBER:  17286
SUBJECT: GRB 150101B/Swift J123205.1-105602: WSRT radio observation
DATE:    15/01/07 20:25:51 GMT
FROM:    Alexander van der Horst at U of Amsterdam  <A.J.vanderHorst@uva.nl>

A.J. van der Horst (Univ. of Amsterdam), K. Wiersema (Univ. of Leicester),
A.J. Levan (Univ. of Warwick), J. Hjorth (DARK/NBI), N.R. Tanvir (Univ.
of Leicester) report on behalf of a large collaboration:

"We observed the position of GRB 150101B/Swift J123205.1-105602 at 4.9 GHz
with the Westerbork Synthesis Radio Telescope at January 7 00.30 to 09.15
UT, i.e. 5.38 - 5.74 days after the burst (GCN 17267).
We detect two radio sources within the BAT error circle (GCN 17267), with
flux densities of 7.21 +/- 0.07 and 0.99 +/- 0.18 mJy. The brightest
source coincides with the XRT position (GCN 17268), the position of the
galaxy 2MASX J12320498-1056010 (GCN 17271), and the NRAO VLA Sky Survey
source at 1.4 GHz (GCN 17285). The spectral index from 1.4 to 4.9 GHz of
this source is -0.3, consistent with the radio emission emanating from
an AGN (GCN 17285).
The second source is located at
RA (J2000) = 12:32:08.2
Dec (J2000) = -10:56:14
with an uncertainty of 5", which is large because of its low declination.
There is no counterpart of this source in a stacked XRT image, no optical
counterpart in our VLT observation (GCN 17281), and also not at 1.4 GHz
in the NRAO VLA Sky Survey.

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