TITLE: GCN CIRCULAR NUMBER: 39093 SUBJECT: GRB 250128B: VLA radio upper limit DATE: 25/01/30 06:35:37 GMT FROM: Eleonora Troja nora.gsfc@gmail.com

Roberto Ricci (U Rome), Muskan Yadav (U Rome), Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome) and Eleonora Troja (U Rome) report:

We observed the field of the short GRB 250128B discovered by Fermi/GBM (Fermi GMB team, GCN 39057) and Swift/BAT (Evans et al. GCN 39058) with the Very Large Array at the centre frequency of 6 GHz (C band) with a bandwidth 4 GHz. The observations started on 2025-01-29 at 12:48 UT and lasted for 47 mins, resulting in a mid elapsed time of 20.8 hours after trigger. The primary calibrator was 3C286 and the phase calibrator J1546+0026.

Within the enhanced Swift/XRT position (Evans et al., GCN 39069) no counterpart is found down to a 3-sigma upper limit of 15 microJy. Additional follow-up is planned.

We thank the VLA staff for promptly observing the target.

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