GCN Circular 37978
Subject
GRB 240912A: radio detection with the VLA
Date
2024-10-30T17:05:06Z (a day 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 16:50:36 UT on 2024 Oct 8 (T_mid = 26.7 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 240912A
(Fermi GBM team, GCN 37465; Evans et al., GCN 37466; Pawar
et al., GCN 37473; SVOM team, GCN 37484; Konus-Wind team,
GCN 37624) in three bands, with central frequencies of 6,
10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J0815+3635 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is clearly detected at a position:
RA: 08:18:32.389 +- 0.001
Dec: 33:59:56.13 +- 0.02
consistent with the optical (Evans et al., GCN 37466)
and X-ray (Goad et al., GCN 37470) transient.
The preliminary analysis yields the following results:
+-----------+-----------------------+--------------+-----------+-----------+
| Frequency | Peak surf. brightness | r.m.s. noise | Beam size | Beam P.A. |
| (GHz) | (uJy/beam) | (uJy/beam) | arcsec^2 | deg |
+-----------+-----------------------+--------------+-----------+-----------+
| 6 | 171 | 8 | 1.34x0.28 | 60 |
| 10 | 138 | 7 | 0.93x0.17 | 57 |
| 15 | 128 | 7 | 0.54x0.12 | 62 |
+-----------+-----------------------+--------------+-----------+-----------+
No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (FIRST,
VLASS, RACS), all of which have r.m.s. noise levels 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.