TITLE: GCN CIRCULAR NUMBER: 23259 SUBJECT: GRB 180923A: CALET Gamma-Ray Burst Monitor detection DATE: 18/09/24 00:10:40 GMT FROM: Valentin Pal'shin at AGU A. V. Penacchioni, A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (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), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The MAXI GRB 180923A (Maruyama et al., GCN Circ. 23257) was detected in ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data near the MAXI/GSC trigger time at T0=04:08:25 UT on 23 September 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure which starts at T-18 sec and ends at T+107 sec. The T90 and the T50 durations measured by the SGM data are 122 +- 15 sec and 95 +- 58 sec (40-1000 keV), respectively. The significant emission is seen only below ~100 keV. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1221710834/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.