TITLE: GCN CIRCULAR NUMBER: 23117 SUBJECT: GRB 180809A: CALET Gamma-Ray Burst Monitor detection DATE: 18/08/10 12:55:19 GMT FROM: Valentin Pal'shin at AGU S. Ricciarini (U of Florence), 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), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The GRB 180809A (MAXI/GSC detection: Yatabe et al., GCN Circ. 23103; Fermi-GBM trigger #555507497) was detected in ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data near the MAXI trigger time at T0=11:38:25 UT on 9 August 2018. The burst signal was seen by all CGBM detectors. The burst light curve shows a weak pulse which starts at T-15.1 sec and ends at T-4.2 sec. The T90 and the T50 durations measured by the SGM data are 10.0 +- 1.6 sec and 5.0 +- 1.6 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1217849910/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.