TITLE: GCN CIRCULAR NUMBER: 44205 SUBJECT: GRB 260330B: SVOM/VT optical candidate DATE: 26/04/03 12:11:54 GMT FROM: Huali Li at at NAOC, SVOM <lhl@nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, J. R. Xu, L. P. Xin, 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. After the initial automatic follow-up (Li et al., GCN 44168), SVOM/VT performed ToO observations of the field of GRB 260330B detected by SVOM/ECLAIRs (sb26033003, Lan et al., GCN 44157), SVOM/GRM (Lan et al., GCN 44157) and Fermi/GBM with sub-threshold detection (Trigg et al., GCN 44159). The observations started at 2026-03-31T07:44:21 UTC, approximately 17.44 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. A catalogued optical candidate within the error box of the EP-FXT source #1 (Guillot et al., GCN 44203) was observed brightening in VT_R within 19 hours post trigger. It overlaps a faint source in the Legacy Survey, with magnitudes g=25.00, r=23.96, z=22.16. The position is at R.A., Dec. = 252.637034, 36.841008 degrees, equivalent to: R.A. (J2000) = +16:50:32.89 Dec. (J2000) = +36:50:27.63 with an uncertainty of 0.5 arcsec. The measurements in AB magnitude are as follows: Mid time | Band | Exposure Time | Brightness 1.00 h VT_R 34*50 sec >22.5 mag (5 sigma upper limit) 4.94 h VT_R 57*100 sec 22.67+/-0.20 mag 19.04 h VT_R 56*70 sec 22.12+/-0.15 mag Our photometry was not corrected for Galactic extinction. Further follow-up observation is scheduled. 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/44205. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...