TITLE: GCN CIRCULAR NUMBER: 42505 SUBJECT: GRB 251028B: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/28 16:08:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp> Y. Akaike (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 251028B (Fermi GBM Final Localization Correction: Fermi GBM team, GCN Circ. 42502) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 07:48:06.24 UTC on 28 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1445672396/index.html). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure that starts at T-0.5 sec, peaks at T+9.9 sec, and ends at T+11.5 sec. The T90 and T50 durations measured by the SGM data are 11.3 +/- 0.4 sec and 8.5 +/- 0.3 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1445672396/ 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/42505. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...