TITLE: GCN CIRCULAR NUMBER: 39081 SUBJECT: GRB 250128B: NOT optical upper limit DATE: 25/01/29 12:03:24 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University d.malesani@astro.ru.nl
K. E. Heintz (DAWN/NBI), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. de Ugarte Postigo (CNRS, OCA and LAM), Benjamin N. Hauptmann (NOT, DTU Space), Arthur M. Kadela (NOT, NBI), report on behalf of a larger collaboration:
We observed the field of the short Fermi and Swift GRB 250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Three exposures by 300 s each were secured in the r band, with a mean epoch 2025 Jan 29.2095 UT (12.65 hr after the trigger). The sequence was interrupted in order to observe GRB 250129A (Izzo et al., GCN 39073).
No source is detected within or close to the UVOT-enhanced XRT position (Evans et al., GCN 39069), down to a 3-sigma limiting AB magnitude r > 23.45, calibrated against nearby stars from the Pan-STARRS catalog.
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