GCN Circular 43415
Subject
GRB 251222A: radio detection with the VLA
Event
Date
2026-01-15T15:16:45Z (4 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),
L. Nava (INAF-OAB)
At 03:47:54 UT on 2025 December 24 (T_mid = 1.48 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 251222A /
EP251222B (Fermi GBM team, GCN 43186, 43222; SVOM team,
GCN 43188, GCN 43202; Einstein Probe team, GCN 43201, 43215;
Konus-Wind team, GCN 43214; GECAM team, GCN 43218) in three
bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C48 was used as bandpass and flux density
calibrator, while J0501-0159 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is detected at a position (J2000):
RA: 05:08:46.775 +- 0.001
Dec: -07:12:48.80 +- 0.02
consistent with the X-ray (SVOM team, GCN 43188, 43202; Einstein
Probe team, GCN 43201, 43215; Swift/XRT team, GCN 43213) and optical
(SVOM team, GCN 43189, 43203, 43208; An et al., GCN 43194; Calapai
et al., GCN 43195; Durbak et al., GCN 43197; Gupta et al., GCN 43207;
GOTO collaboration, GCN 43209; Pérez-Fournon et al., GCN 43212;
Gupta et al., GCN 43224; Globus et al., GCN 43225; IKI-GRB-FuN team,
GCN 43226, 43230, 43273; GRANDMA collaboration, GCN 43229, 43237;
Busmann et al., GCN 43233; Lee et al., GCN 43236; Mephisto Team,
GCN 43250) position of the transient.
The preliminary analysis yields the following results:
================================================================
T_mid Freq Peak r.m.s. Beam PA
[days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg]
================================================================
1.48 6 71 7 1.29x0.91 -22
1.48 10 208 8 0.75x0.58 -16
1.48 15 241 8 0.56x0.38 -28
================================================================
No source is detected with a >3sigma confidence level at the
aforementioned position in the VLASS. However, the r.m.s. noise
level of the survey at the GRB location is approximately 150 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 SF181027,
approved in the framework of the Fermi - NRAO joint program agreement.