GCN Circular 17309
Subject
GRB 150101B/Swift J123205.1-105602: continued WSRT radio and VLT optical observations
Event
Date
2015-01-19T17:06:48Z (11 years ago)
From
Alexander van der Horst at George Washington U <ajvanderhorst@gwu.edu>
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."