GRB 210104A: CALET Gamma-Ray Burst Monitor detection

The long bright GRB 210104A (Swift detection: Troja et al., GCN Circ. 29233, Palmer et al., GCN Circ. 29251; Fermi GBM detection: Malacaria et al., GCN Circ. 29246; Konus-Wind detection: Frederiks et al., GCN Circ. 29258; https://gcn.gsfc.nasa.gov/other/210104A.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 11:26:56.318 UTC on 4 January 2021 (http://cgbm.calet.jp/cgbm_trigger/flight/1293794541/). The burst signal was seen by all CGBM detectors. The burst light curve shows multiple partially overlapped pulses which start at T+2.5 sec and end at T+36.5 sec. The T90 and T50 durations measured by the SGM data are 31.2 +- 2.0 sec and 11.6 +- 9.4 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1293794541/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.