TITLE: GCN CIRCULAR NUMBER: 44821 SUBJECT: GRB 260515A: SVOM/VT optical detection at about 18 days post trigger DATE: 26/06/04 15:44:09 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, 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, A. Saccardi and D. Gotz (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed further ToO observations of GRB260515A triggered by SVOM/ECLAIRs (sb26051504, Brunet et al., GCN 44622, GCN 44666). The burst was also detected by Konus-Wind (Frederiks et al., GCN 44647). The observation started at 2026-06-03T02:02:18 UTC, i.e., 18.28 days post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The counterpart (He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Lipunov et al., GCN 44627; Wu et al., GCN 44628; Dennefeld et al., GCN 44633; Li et al., GCN 44634; Wang et al., GCN 44642; Antier et al., GCN 44643; Pérez-Fournon et al., GCN 44645; Dimple et al. GCN 44646; Moskvitin et al., GCN 44652; Bochenek et al., GCN 44658) with redshift z=0.764 (Malesani et al., GCN 44629) was faintly detected VT_R. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 18.38 d VT_R 108*70 s 23.5 +/- 0.3 mag 18.38 d VT_B 110*70 s >24.0 mag (3 sigma upper limit) 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/44821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...