TITLE: GCN CIRCULAR NUMBER: 39289 SUBJECT: GRB 250205A / EP250205A: radio detection with the VLA DATE: 25/02/11 16:51:06 GMT FROM: Stefano Giarratana at INAF-OAB s.giarratana@ira.inaf.it
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 08:59:34 UT on 2025 Feb 7 (T_mid = 1.51 days post-burst) the Karl G. Jansky VLA observed the field of GRB 250205A / EP250205A (Saccardi et al., GCN 39154; Mukherjee et al., GCN 39171) in three bands, with central frequencies of 6, 10 and 15 GHz.
The standard 3C286 was used as bandpass and flux density calibrator, while J0741+3112 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source is detected at a position (J2000):
RA: 07:34:02.649 +- 0.003 Dec: 32:22:18.84 +- 0.05
consistent with the X-ray (Kennea et al., GCN39161; Liu et al., GCN 39165) and optical (Gompertz et al., GCN 39156; Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160; Watson et al., GCN 39162; Busmann et al., GCN 39169) 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] ================================================================ 1.51 6 27 7 0.49x0.32 66 1.51 10 44 8 0.32x0.19 65 1.51 15 40 7 0.19x0.13 66 ================================================================
No source is detected with a >3sigma confidence at the aforementioned position in previous radio surveys (NVSS, FIRST, VLASS), 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.
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