TITLE: GCN CIRCULAR NUMBER: 44584 SUBJECT: MASS-Cube (GRID 2.0) detection of GRB 260511A DATE: 26/05/12 16:35:13 GMT FROM: GRID Student Team at Tsinghua University <grid@tsinghua.edu.cn> Jiahuan Zhu, Chenyu Wang, Xutao Zheng, Hao Chang, Zirui Yang report on behalf of the MASS-Cube Collaboration: MASS-Cube reports the detection of the long-duration GRB 260511A, which was also observed by Fermi/GBM (GCN #44548, #44548), SVOM (GCN #44532) and GRID. The optical counterpart was detected by TRT (GCN #44533). The event was triggered by MASS-Cube on 2026-05-11 at 06:13:29.2 UTC. The measured burst duration (T90) in the 50-10000 keV range is approximately 9.7 +/- 2.3 seconds. The second peak is not clearly detected by MASS-Cube due to its limited sensitivity. The MASS-Cube light curve of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260511A/MASS_Cube.... MASS-Cube is a pathfinder for a 3D position-sensitive Compton telescope in space, currently considered the next generation of the GRID constellation in the era of multi-messenger astronomy. For more information about MASS-Cube, please refer to the following reference: https://doi.org/10.1007/s10686-024-09920-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/44584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...