TITLE: GCN CIRCULAR NUMBER: 22438 SUBJECT: GRB 180221B CALET Gamma-Ray Burst Monitor detection DATE: 18/02/23 10:45:37 GMT FROM: Takanori Sakamoto at AGU S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo, M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The long GRB 180221B (Konus-Wind trigger time on 12:30:00.79) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 12:29:59.616 UTC on 21 February 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure which starts at T0, peaks at T0+16 sec and ends at T0+78 sec. The T90 and the T50 durations measured by the SGM data are 66.6 +- 6.8 sec and 21.1 +- 6.3 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1203251126/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.