[vsnet-grb-info 24481] GRB 191221B: ATCA detection of the radio afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26580
SUBJECT: GRB 191221B: ATCA detection of the radio afterglow
DATE:    19/12/25 16:43:35 GMT
FROM:    Tanmoy Laskar at U of Bath  <tanmoylaskar at gmail.com>

T. Laskar (University of Bath), S. Bhandari (CSIRO), K. D.
Alexander (Northwestern), E. Berger (Harvard), R. Chornock (Ohio U.), D.
Coppejans (Northwestern), M. Drout (U. Toronto), H. van Eerten (University
of Bath), Wen-fai Fong (Northwestern), C. Guidorzi (U. Ferrara), G.
Hosseinzadeh (Harvard), R. Margutti (Northwestern), C. G. Mundell
(University of Bath), and P. Schady (University of Bath) report:

"We observed GRB 191221B (Laha et al., GCN 26534) with the Australia
Telescope Compact Array (ATCA) at multiple frequencies and multiple epochs
beginning on 2019 December 22 14:17 UT (0.73 days after the burst). We
detect a varying radio counterpart at 5.5, 9.0, 16.7, and 21.2 GHz at a
position consistent with the X-ray position (Beardmore et al., GCN 26540)
and optical position (Lipunov et al., GCN 26537). We identify this source
as the radio afterglow of GRB 191221B.

Further analysis and observations are on-going.

We thank the CSIRO staff for approving these observations."