TITLE: GCN CIRCULAR NUMBER: 44574 SUBJECT: GRB 260511B: LCO optical observations DATE: 26/05/12 09:48:43 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> A. Saccardi (CEA/Irfu), C. Wu (NAOC), J. X. Cao (GXU), L. Zhang (IHEP), D. Kong (GXU), report on behalf of the SVOM mission team: We observed the field of the SVOM/ECLAIRs GRB 260511B (Godet et al., GCN 44543), also detected by Fermi/GBM (Fermi GBM team, GCN 44542; Roberts et al., GCN 44554), NuSTAR (Waratkar et al., GCN 44556), and AstroSat (Arya et al., GCN 44560), with the LCO 1m telescope at Cerro Tololo Observatory equipped with the Sinistro instrument. Our observation started on 2026-05-12 at 00:14:08 UT (about 13.23 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters. 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; Adami et al., GCN 44573) is clearly detected in our images. We measure the following magnitudes calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: r = 19.68 +/- 0.02 AB (mid-time 13.29 hr after the trigger); z = 19.71 +/- 0.09 AB (mid-time 18.14 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/44574. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...