T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita, Y. Kawakubo,
A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), 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),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 181222A (MAXI/GSC detection: Sakamaki et al., GCN Circ. 23547;
Fermi-GBM observation: Vere & Bissaldi, GCN Circ. 23548)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 06:41:33.811 UTC
on 22 December 2018. The burst signal was seen by all CGBM detectors.
Since the burst incident direction was nearly perpendicular to
the HXM detector axes, the signal in these detectors was heavily attenuated.
The burst light curve shows two main emission episodes which start
at T+1.5 sec and end at T+105.8 sec.
The T90 and the T50 durations measured by the SGM data are
98.3 +- 5.3 sec and 44.6 +- 39.7 sec (40-1000 keV), respectively.
The ground processed light curve is available at
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.