GCN Circular 37788
Subject
GRB 240916A: radio detection with the VLA
Date
2024-10-15T12:26:12Z (9 days 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 00:43:57 UT on 2024 Sept 18 (T_mid = 2.00 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 240916A
(Fermi GBM team, GCN 37518; Pawar et al., GCN 37519;
Dafcikova et al. 37543) at a central frequency of 6, 10
and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J1543-0757 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is clearly detected at a position:
RA: 15:43:39.205 +- 0.001
Dec: -07:45:53.30 +- 0.02
consistent with the optical (GOTO collaboration, GCN 37522;
Jiang et al., GCN 37526; Jiang et al., GCN 37540) and
X-ray (Beardmore et al., GCN 37531) transient.
The surface brightness peak is 35 uJy/beam, 44 uJy/b and
135 uJy/beam at 6, 10 and 15 GHz, respectively.
The r.m.s. noise level of the image is 8 uJy/beam at all
frequencies.
The synthesized beams are 1.25x0.72 arcsec (PA: 42deg)
at 6 GHz, 1.10x0.52 arcsec (PA: 37deg) at 10 GHz
and 0.56x0.33 arcsec (PA: 26deg) at 15 GHz.
No source is detected with a 3sigma confidence at the
aforementioned position in previous radio surveys (FIRST, NVSS,
VLASS, RACS), with r.m.s. noise levels (1sigma) above
100 uJy/b.
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.