TITLE: GCN CIRCULAR NUMBER: 41159 SUBJECT: GRB 250725A: BOOTES-7 early optical detection DATE: 25/07/25 10:03:36 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es> I. Perez-Garcia, E. Fernandez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. of Malaga), L. Hernandez-Garcia (Univ. of Valparaiso), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), B.-B. Zhang (Nanjing Univ.), and A. Maury (Space Obs., San Pedro de Atacama), on behalf of a larger collaboration, report: Following the detection of GRB 250725A by Swift, the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) automatically responded to this high-energy event starting on July 25, 01:52:17 UT (i.e. 41 sec after detection). Series of images in clear filter were gathered and we detect an optical source consistent with the one reported by Buckley et al. (GCN 41151) and Li et al. (GCN 41158). Using GaiaDR3 Gmag as a reference, we measure an initial magnitude of 15.5 +/- 0.1 in the first 10 sec exposure image. In subsequent stacked images of 1 sec images we do not detect any source up to mag 15.7, mid exposure time on July 25, 01:53:27. Further analysis of the additional images is ongoing. We would like to thank the staff at San Pedro de Atacama Space Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/41159. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...