Gamma-ray burst observations with the CALET Gamma-ray Burst Monitor

The CALET Gamma-ray Burst Monitor (CGBM) is a secondary scientific instrument of the CALET. The CGBM has been monitoring X-ray and gamma-ray sky since October 2015. The main observational target of the CGBM is a gamma-ray burst (GRB). The CGBM can observe GRB light curves and spectra in the energy range from 7 keV to 20 MeV thanks to two kinds of scintillation detectors which are the Hard X-ray Monitor (HXM) and the Soft Gamma-ray Moni- tor (SGM). As of the end of June 2019, CGBM has detected 161 GRBs since October 2015. The durations of GRBs detected by the CGBM were measured by the SGM in the 40 ∼ 1000 keV energy band. As a result, 19 out of 161 GRBs were short bursts which are a primary candidate of the electromagnetic counterparts of gravitational wave source. We performed spectral analysis for bright 4 short GRBs out of 19. We found spectral parameters of the 4 GRBs were consistent with an expectation by the synchrotron shock model. Although observed fluxes of the 4 GRB in the 30 ∼ 1000 keV range were more than ∼ 10 times as large as GRB 170817A, Epeak of GRB 180703B was similar to that of GRB 170817A.