GRB 150101B/Swift J123205.1-105602: continued WSRT radio and VLT optical observations
ATel #6955; A. J. van der Horst (George Washington Univ.), A. J. Levan (Univ. of Warwick), K. Wiersema, N. R. Tanvir (Univ. of Leicester), J. Hjorth (DARK/NBI)
on 19 Jan 2015; 17:12 UT
Credential Certification: Alexander van der Horst (ajvanderhorst@gwu.edu)
Subjects: Radio, Optical, AGN, Gamma-Ray Burst, Transient
We reobserved the field of GRB 150101B/Swift J123205.1-105602 at 4.9 GHz with the Westerbork Synthesis Radio Telescope (WSRT) at January 9 00.25 to 09.00 UT, and January 17 23.75 to January 18 08.50 UT, i.e. 7.37 - 7.73 and 16.35 - 16.71 days after the burst (ATel #6871), respectively.
The two radio sources within the BAT error circle (ATel #6871) that were detected in the first WSRT observation (ATel #6883) do not display significant variability. The flux density of the brightest source is 7.21 +/- 0.07, 7.56 +/- 0.07, and 7.40 +/- 0.07, in the three epochs, which is consistent with a steady source when a 5% calibration uncertainty is taken into account. The second source has a flux density of 0.99 +/- 0.18, 0.77 +/- 0.19, and 0.78 +/- 0.18 mJy, in the three epochs, again consistent with a steady source.
In addition, we obtained IR observations with VLT/HAWK-I on January 16, deeper than the ones reported in ATel #6873. There is still no evidence for any source at the location of the second, fainter radio source to a preliminary limiting magnitude of H(AB)>23.5.
We would like to thank the WSRT staff for scheduling and obtaining these observations.
