GCN Circular 38077
Subject
GRB 240821A: further radio observations with the VLA
Date
2024-11-05T09:12:17Z (2 months ago)
From
Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>
Via
email
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB)
At 04:55:36 UT on 2024 Sept 18 (T_mid = 27.5 days post-burst)
and at 05:38:46 UT on 2024 Oct 8 (T_mid = 47.5 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 240821A
(Fermi GBM team, GCN 37219; SVOM team, GCN 37220, 37226)
in three bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C48 was used as bandpass and flux density
calibrator, while J2358-1020 was used as phase calibrator.
From a preliminary analysis, we do not detect the radio counterpart
of GRB 240821A. We derive the following upper limits (UL; 3sigma):
==================================================
T_mid Freq UL r.m.s. Beam PA
[days] [GHz] [uJy] [uJy/b] [arcsec] [deg]
==================================================
27.5 6 21 7 1.07x0.78 -21
27.5 10 22 7 0.82x0.48 -10
27.5 15 27 9 0.57x0.32 -16
47.5 6 21 7 1.26x0.46 71
47.5 10 27 9 0.91x0.28 66
47.5 15 24 8 0.51x0.20 73
==================================================
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF171028,
approved in the framework of the Fermi - NRAO joint program agreement.