TITLE: GCN CIRCULAR NUMBER: 22425 SUBJECT: GRB 180218A CALET Gamma-Ray Burst Monitor detection DATE: 18/02/20 06:02:34 GMT FROM: Takanori Sakamoto at AGU W. Ishizaki (ICRR), 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), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The bright GRB 180218A (Svinkin et al., GCN circ. 22423; Poolakkil et al., GCN circ. 22424) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 15:14:05.326 UTC on 18 February 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a single multi-peaked pulse which starts at T+0.5 sec, peaks at T+4.6 sec and ends at T+8.5 sec. The T90 and the T50 durations measured by the SGM data are 4.75 +- 1.27 sec and 1.88 +- 0.13 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1203001776/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.