TITLE: GCN CIRCULAR NUMBER: 41707 SUBJECT: GRB 250902B: CALET Gamma-Ray Burst Monitor detection DATE: 25/09/04 18:04:18 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp> N. Cannady (GSFC/UMBC), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 250902B (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 41660; SVOM/GRM observation: Wang et al., GCN Circ. 41668; AstroSat CZTI detection: Tembhurnikar et al., GCN Circ. 41678) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:45:35.15 UTC on 2 September 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1440873547/index.html). The burst signal was seen by all CGBM detectors. Because of a problem with the ground alert processing script, the GCN notice was not distributed automatically for this event. The burst light curve shows a multi-peaked structure that starts at T-2.4 sec, peaks at T+9.6 sec, and ends at T+17.4 sec. The T90 and T50 durations measured by the SGM data are 17.4 +/- 0.7 sec and 8.8 +/- 0.6 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1440873547/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/41707. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...