TITLE: GCN CIRCULAR NUMBER: 31332 SUBJECT: GRB 211225B: CALET Gamma-Ray Burst Monitor detection DATE: 21/12/29 07:10:45 GMT FROM: Valentin Pal'shin at AGU N. Cannady (GSFC/UMBC), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), 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 211225B (Swift detection and refined analysis: Page et al., GCN Circ. 31305, Laha et al., GCN Circ. 31312; https://gcn.gsfc.nasa.gov/other/211225B.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 13:13:05.685 UTC on 25 December 2021 while exiting the radiation belts. The burst signal was seen by all CGBM detectors. Because of a problem in one of the ground alert processing script, the GCN notice was not distributed automatically for this event. The burst light curve shows a single pulse which starts at T-2.2 sec, peaks at T+3.6 sec and ends at T+42.0 sec. The extended tail is seen in the low energy channels as long as a hint of the preceding emission (which is clearly seen in the Swift-BAT light curve: Laha et al. GCN Circ. 31312). The T90 and T50 durations measured by the SGM data are 32.7 +- 8.1 sec and 14.6 +- 1.9 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1324473176/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.