GRB 170428A CALET Gamma-Ray Burst Monitor detection

The short-duration GRB 170428A (Beardmore et al., GCN Circ. 21042; Tsvetkova et al., GCN Circ. 21045) was detected the CALET Gamma-ray Burst Monitor (CGBM) by the ground process pipeline at 09:13:42.36 on 28 April 2017 at 5.1 sigma which is below the trigger threshold of the on-board trigger. The burst signal was seen only by the SGM instrument. Because there was no on-board trigger, no event data were stored for this event. The continuous light curve data recorded in 0.125 s time resolution are not fine enough to investigate the temporal structure and the duration of this event. The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1177405621/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.