GCN Circular 43128
Subject
GRB 251202A: radio detection with the VLA
Event
Date
2025-12-15T16:38:56Z (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),
L. Nava (INAF-OAB)
At 12:00:00 UT on 2025 December 5 (T_mid = 3.45 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 251202A /
EP251202A (Fermi GBM team, GCN 42933, 42957; Einstein Probe team,
GCN 42937, GCN 42946; AstroSat CZTI collaboration, GCN 42967;
Insight-HXMT team, GCN 42970; SVOM team, GCN 42997) in three
bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density
calibrator, while J0818+4222 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is detected at a position (J2000):
RA: 08:08:27.466 +- 0.001
Dec: +40:36:44.70 +- 0.01
consistent with the X-ray (Einstein Probe team, GCN 42937;
Swift-XRT team, GCN 42943) and optical (GOTO collaboration,
GCN 42947; Quirola-Vasquez, GCN 42948; Swift/UVOT team,
GCN 42956; KAIT GRB team, GCN 42964; SVOM/VT team, GCN 42966;
Bochenek et al., GCN 42977; Contreras et al., GCN 42999)
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]
================================================================
3.45 6 111 10 1.08x1.02 57
3.45 10 169 7 0.71x0.60 59
3.45 15 310 8 0.45x0.42 34
================================================================
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 130 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.