TITLE: GCN CIRCULAR NUMBER: 19865 SUBJECT: GRB 160821A: CALET Gamma-Ray Burst Monitor detection DATE: 16/08/26 01:59:26 GMT FROM: Takanori Sakamoto at AGU P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), 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), and the CALET collaboration: The long-duration GRB 160821A (Siegel et al., GCN Circ. 19830; McEnery et al., GCN Circ. 19831; Stanbro et al., GCN Circ. 19835; INTEGRAL-SPI/ACS trigger #7537) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 20:36:21.91 on 21 August 2016. The burst signal was seen by all CGBM instruments. Note that the CGBM trigger time is 111 sec after the trigger time of Swift/BAT. This is because the CGBM triggered at the bright main peak of the burst (Markwardt et al. GCN Circ. 19840). The light curve of the SGM shows a bright peak with several overlapping pulses. The emission starts from T sec, peaks at T+24 sec and ends at T+80 sec. There is a hint of the emission in the SGM light curve around the trigger time of Swift/BAT. The T90 duration measured by the SGM data is 35.1 +- 0.8 sec (40-1000 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1155846835/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.