TITLE: GCN CIRCULAR NUMBER: 41455 SUBJECT: GRB 250818B: 10 GHz VLA detection DATE: 25/08/20 18:16:07 GMT FROM: Roberto Ricci at INAF-IRA ricci@ira.inaf.it

R. Ricci, M. Yadav, E. Troja (U Rome) on behalf of a larger collaboration:

We observed the short-duration GRB 250818B discovered by SVOM (GCN 41405) with Very Large Array in X-band at the centre frequency of 10 GHz with a bandwidth of 4 GHz on Aug 20th 2025, 2.3 days after the burst.

After reducing the data in latest CASA version (v6.6.1) with standard procedures a detection was found at a position compatible with GOTO (GCN 41406) and NOT (GCN 41426) optical transient. We estimate a flux density of approximately 120 microJy.

We thank the VLA staff for promptly executing the observations.

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