TITLE: GCN CIRCULAR NUMBER: 44573 SUBJECT: GRB 260511B: OHP/T193 spectroscopic observations DATE: 26/05/12 09:05:55 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU), E. Le Floc'h (CEA-Saclay) report on behalf of a larger collaboration and on behalf of the transient team of the OHP 2026 special call: We observed the optical counterpart (Wu et al., GCN 44547 ; Sasada et al., GCN 44549 ; Jiang et al., GCN 44551 ; Wu et al., GCN 44552 ; Li et al., GCN 44557 ; Vijaykumar et al., GCN 44561 ; de Ugarte Postigo et al., GCN 44565 ; Lee et al., GCN 44567; Li et al., GCN 44568; Wang et al., GCN 44571; Belkin et al., GCN 44572) of GRB 260511B (FERMI team, GCN 44542 ; Godet et al., GCN 44543; Roberts et al., GCN 44554; Waratkar et al., GCN 44556; Arya et al., GCN 44560) in spectroscopic mode using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained a total of 145 min of exposures (10min + 15min + 4 x 30min) with the MISTRAL spectroscopic blue setting from 4200 to 8000 AA, starting at 2026-05-11 22:04:34 UT under modest weather conditions. The host environment at z=2.006 detected by the GTC and reported by de Ugarte Postigo et al. (GCN 44565) and Wang et al. (GCN 44571) is visible in our data, in particular with the 2344 AA and 2600 AA (rest-frame) FeII lines observed at a consistent redshift of z=2.007 +/- 0.001. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen. View this GCN Circular online at https://gcn.nasa.gov/circulars/44573. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...