TITLE: GCN CIRCULAR NUMBER: 39084 SUBJECT: GRB 250128B: VLT/HAWKI near-infrared observations DATE: 25/01/29 14:09:47 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata yyang@roma2.infn.it

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

We observed the field of GRB 250128B (Evans et al., GCN 39058, Myers et al., GCN 39063) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations began 0.68 days after the trigger and were carried out in the J filter at an average seeing of 1.3".

Based on a preliminary analysis, we do not detect any new source within the XRT afterglow position (Evans et al., GCN 39069) down to J > 24 AB mag (3 sigma), calibrated using nearby stars in the 2MASS catalogue. A low-significance (~2 sigma) source is identified at RA, Dec (J2000) = 15:25:42.11, -0.32:21.21. Further observations to determine the significance and possible variability of this source are planned.

We thank the staff at the VLT, for the rapid execution of these observations.

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