TITLE: GCN CIRCULAR NUMBER: 44575 SUBJECT: GRB 260511A: SVOM/VT optical observations DATE: 26/05/12 09:53:21 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> H. L. Li, C. Wu, Y. L. Qiu, L. P. Xin, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations of GRB260511A triggered by SVOM/ECLAIRs (sb26051101, Godet et al., GCN 44532). The burst was also detected by Fermi/GBM (Fermi GBM team, GCN 44529; Preis et al., GCN 44531; Preis et al., GCN 44531; Roberts et al., GCN 44548) and NuSTAR (Waratkar et al. GCN 44555). The observation started at 2026-05-11T22:13:58 UTC, about 16.0 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The afterglow (Jiang et al., GCN 44533; Akl et al. GCN 44534; Saccardi et al. GCN 44535; Zheng et al. GCN 44536; Wu et al., GCN 44538, Harper et al., GCN 44545; Brivio et al., GCN 44562) was detected in stack images of both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 18.00 h VT_B 35*70 s 23.43 +/- 0.27 mag 18.00 h VT_R 39*70 s 21.82 +/- 0.13 mag The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/44575. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...