TITLE:   GCN CIRCULAR
NUMBER:  31021
SUBJECT: GRB 2121023B: 6 GHz VLA radio upper limit
DATE:    21/10/28 19:26:20 GMT
FROM:    Genevieve Schroeder at Northwestern University  <genevieveschroeder2023@u.northwestern.edu>

G. Schroeder, W. Fong, A. Rouco Escorial, (Northwestern), T. Laskar (Univ.
Radboud), E. Berger (Harvard) report:

"We observed the position of GRB 211023B (Dichiara et al. GCN 30960) with
the Karl G. Jansky Very Large Array (VLA) under program 21B-198 (PI: Fong)
beginning on 2021 October 27.51 UT (3.63 days post-burst) at a mean
frequency of 6 GHz.

Based on preliminary analysis, in 1 hour of observations we do not detect
any radio emission at or near the position of the optical afterglow and
host (Kuin et al. GCN 30975; Pozanenko et al. GCN 30972; Kann et al. GCN
30995; O'Connor et al., GCN 31000; Rastinejad et al., GCN 31002; Pozanenko
et al., GCN 31003) to a 3-sigma limit of 13 microJy. We also do not detect
any source within the XRT position (Beardmore et al. GCN 30966).
Additional, detailed analysis is ongoing.

We thank the VLA staff for quickly approving and executing these
observations."