GRB 150101B/Swift J123205.1-105602: WSRT radio observation
ATel #6883; 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)
on 7 Jan 2015; 20:37 UT
Credential Certification: Alexander van der Horst (A.J.vanderHorst@uva.nl)
Subjects: Radio, AGN, Gamma-Ray Burst, Transient
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 (ATel #6871).
We detect two radio sources within the BAT error circle (ATel #6871), 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 (ATel #6881). 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 (ATel #6881).
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 (ATel #6873), 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.
