TITLE: GCN CIRCULAR NUMBER: 17309 SUBJECT: GRB 150101B/Swift J123205.1-105602: continued WSRT radio and VLT optical observations DATE: 15/01/19 17:06:48 GMT FROM: Alexander van der Horst at George Washington U 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) report on behalf of a large collaboration: "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 (GCN 17267), respectively. The two radio sources within the BAT error circle (GCN 17267) that were detected in the first WSRT observation (GCN 17286) 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 GCN 17281. 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."