TITLE: GCN CIRCULAR NUMBER: 39926 SUBJECT: GRB 250329B: GWAC-F50A optical upper limit DATE: 25/03/29 13:31:32 GMT FROM: Liping Xin at NAOC, SVOM <xlp@nao.cas.cn> L. P. Xin(NAOC), Y. G. Yang(HNU), X. H. Han, C. WU, Y. L. Qiu, J. Wang, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang, H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y. Wei(NAOC), X. G. Wang, E. W. Liang(GXU) report on behalf of the SVOM/F50A team: We began to observe GRB 250328A (Xie et al., GCN 39925) with 50cm telescope (GWAC-F50A) at Xinglong station, China, at 2025-03-29T12:27:17.58 (UT), about 7.0 min after the burst. With the first observations with exposure time of 4*100 sec, no any uncatalogued source was detected in our stacked image down to a 3 sigma limit magnitude of 18.5 mag in R band, at the mid time of 10.3 min after the burst, comparing to several nearby USNO B1.0 stars. Further observations are ongoing. We acknowledge the excellent support from observation assistant Yangtong Zheng and Winlong Dong. View this GCN Circular online at https://gcn.nasa.gov/circulars/39926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...