TITLE: GCN CIRCULAR NUMBER: 20803 SUBJECT: GRB 170228B CALET Gamma-Ray Burst Monitor detection DATE: 17/03/03 06:13:49 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 170228B (Fermi GBM trigger #509999585; Xiao et al, GCN Circ. 20792) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:32:58.03 on 28 February 2017. The burst signal was seen by the HXM2 and SGM instrument. The light curve of the SGM shows two peaks. The first peak starts at T0, peaks at T+5 sec and ends at T+18 sec. The second peak starts at T+20 sec, peaks at T+25 sec and ends at T+35 sec. The T90 duration measured by the SGM data is 32.2 +- 1.2 sec (40-1000 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1172341676/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.