TITLE: GCN CIRCULAR NUMBER: 40975 SUBJECT: EP250704a/GRB 250704B: GSP observations of the optical counterpart DATE: 25/07/05 12:56:03 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992@gmail.com> W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report: Following the detection of the fast X-ray transient EP250704a/GRB 250704B (Li et al., GCN 40491, 40956; Wang et al., GCN 40940; Frederiks et al., GCN 40972), we initiated observations of the fast X-ray transient location starting on July 05 at 4:16 UT (~20 hours after the EP/WXT trigger) in the g, r and i bands. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at the Cerro Tololo Inter-American Observatory in Chile. The optical counterpart, detected by COLIBRÍ (Schneider et al., GCN 40942), VLT/FORS2 (Malesani et al., GCN 40945), BOOTES-5 (Pérez-García et al., GCN 40957), Pan-STARRS (Gillanders et al., GCN 40958), SVOM/VT (Xin et al., GCN 40960), GROWTH-India (Mohan et al., GCN 40962), SAO RAS (Moskvitin et al., GCN 40963), JinShan (Liu et al., GCN 40965), VLT/X-shooter (An et al., GCN 40966), VLT/HAWK-I (Yang et al., GCN 40970), and NOT (Ricci et al., GCN 40970), is clearly detected in all LCO exposures, with preliminary magnitudes of g ≈ 20.2, r ≈ 20.1, and i ≈ 20.0 (AB mag). These observations were taken as part of the Global Supernova Project. View this GCN Circular online at https://gcn.nasa.gov/circulars/40975. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...