GCN Circular 30479
Subject
GRB 210702A: ALMA detection of mm-band rebrightening
Event
Date
2021-07-22T22:50:41Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (U. of Bath) reports on behalf of a larger collaboration:
"Following the initial detection of the mm counterpart of GRB 210702A (Lien
et al., GCN 30351) with the Atacama Large Millimeter/Submillimeter Array
(ALMA) on 2021 July 03, 26 h after the burst (Laskar & Perley, GCN 30423),
we have been monitoring this source with ALMA at 97.5 GHz. The mm-band
counterpart was observed to fade to a flux density of ~ 0.3 mJy in
observations taken on 2021 July 11 at a mid-time of 8.3 days after the
burst.
We observed GRB 210702A with ALMA again beginning on 2021 July 20 21:02
UTC. Preliminary analysis reveals a strong (~ 50 sigma) detection at 97.5
GHz with a flux density of ~ 0.8 mJy at a mid-time of 18.1 days after the
burst, implying a significant rebrightening of the mm-band afterglow,
contemporaneous to the radio rebrightening observed at 34, 21.2, and 16.7
GHz with ATCA (Laskar & Bhandari, GCN 30477). Further observations are
planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."