TITLE: GCN CIRCULAR NUMBER: 39076 SUBJECT: GRB 250128B: OHP/T193 optical upper limit DATE: 25/01/29 09:08:55 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), F. Schussler (CEA Paris-Saclay), M. Dennefeld (IAP), J. Palmerio (CEA/Irfu) report on behalf of a larger collaboration: We observed the field of the GRB250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058; Izzo et al., GCN 39059; Lipunow et al., GCN 39061; Ulaczyk et al., GCN 39062; Muers et al., GCN 39063; Osborne et al., GCN 39064; Lipunov et al., GCN 39067; Evans et al., GCN 39069) with the T193cm telescope at the Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained a total of 2490sec (1x30s + 1x300s + 3x720s) in the i-band using the red MISTRAL setting from 20250129_043822UT to 20250129_050703UT (mid-time ~12.5h after the trigger). In the stacked image, we do not detect any new source at the XRT source position (Evans et al., GCN 39069) down to the following 3-sigma limit: i > 20.6 The photometric calibration was performed using nearby stars from the PanSTARRS catalog. We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean Balcaen, and the Sophie observer Alice Radcliffe View this GCN Circular online at https://gcn.nasa.gov/circulars/39076. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...