GCN Circular 14248
Subject
GRB 130216A: possible radio counterpart is steady field source
Date
2013-02-21T20:15:01Z (11 years ago)
From
Alexander van der Horst at U of Amsterdam <A.J.vanderHorst@uva.nl>
A.J. van der Horst (U. of Amsterdam), R.D.E. Saunders (MRAO),
K.J.B. Grainge (U. of Manchester), R.P. Fender, T.D. Staley
(U. of Southampton), A. Rowlinson, R.A.M.J. Wijers (U. of Amsterdam)
report on behalf of a large collaboration:
"We have observed the Swift/BAT error circle of GRB 130216A (GCN 14229)
at multiple epochs with the AMI Large Array and the Westerbork Synthesis
Radio Telescope, at 15 and 4.8 GHz respectively. The radio source we
reported in GCN 14234 was clearly detected at all epochs at this
position: RA, Dec (J2000) = 04:31:34, +14:39:36 (+/- 2 arcsec).
Our flux density measurements are given in the table below.
Epoch Delta T Freq. Flux density
============== ======== ======= ============
Feb 16.94-16.98 0.03 days 15 GHz 0.78 +/- 0.08 mJy
Feb 18.55-19.01 1.86 days 15 GHz 0.80 +/- 0.04 mJy
Feb 19.51-19.59 2.62 days 4.8 GHz 1.11 +/- 0.09 mJy
Feb 19.86-19.99 3.00 days 4.8 GHz 1.15 +/- 0.06 mJy
Feb 20.50-20.64 3.64 days 4.8 GHz 0.92 +/- 0.07 mJy
Feb 20.91-20.99 4.02 days 4.8 GHz 1.09 +/- 0.08 mJy
The source is constant in flux between our observing epochs and also
within the 11-hour AMI observation. The spectral index between 4.8
and 15 GHz is -0.3. There is no significant polarization detected
in the combined Westerbork data, with a 3-sigma upper limit of 15%.
From these observations we conclude that this source is not the
counterpart of GRB 130216A, but possibly a radio galaxy or AGN.
Based on the combined 9C and 10C Surveys of Radio Sources
(see, e.g., Davies et al. 2011, MNRAS, 415, 2708), we estimate that
the probability for a source as bright or brighter than the one we
detect to occur by chance inside the Swift/BAT error circle is 2%.
We would like to thank the AMI and WSRT staff for scheduling and
obtaining these observations."