TITLE: GCN CIRCULAR NUMBER: 43610 SUBJECT: GRB 260131A/B: OHP/T193 optical observations DATE: 26/02/03 14:29:32 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> C. Adami (LAM/Pytheas/AMU), S. Basa (UAR Pytheas), N. Globus (UNAM), A. Watson (UNAM), B. Schneider (LAM), E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRAL GRB collaboration: We carried out observations of GRB 260131A/B (Fermi GBM Team, GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et al., GCN 43590; Luo et al., GCN 43591; Jiang et al., GCN 43600; Li et al., GCN 43605) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 7 exposures for a total of 14 min in the r-band at a midtime of 2026-02-01 19:48UT, corresponding to T-T0 = 37.15 hours. The afterglow reported by Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Shi et al., GCN 43601; Sanchez-Ramirez et al., GCN 43604; Jayaraman et al., GCN 43606; Zhu et al., GCN 43607 ; Zheng et al., GCN 43609 is well detected in r’ with a preliminary magnitude of : r’ = 19.09 +/- 0.08 The photometric calibration was performed using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and Stephane Favard, and the SOPHIE observer Xavier Delfosse. View this GCN Circular online at https://gcn.nasa.gov/circulars/43610. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...