S. Sugita, A. Yoshida, T. Sakamoto, V. Pal'shin (AGU), Y. Kawakubo (LSU),
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 soft GRB 181227A (Fermi GBM detection: Bissaldi & Veres,
GCN Circ. 23569; IPN Triangulation: Hurley et al., GCN Circ. 23577;
Konus-Wind observation: Svinkin et al., GCN Circ. 23589)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 06:17:09.332 UTC
on 27 December 2018.
Because of a problem in one of the ground alert processing scripts,
the GCN notice was not distributed automatically for this event.
Since the burst incident direction was at ~110 deg relative
to the detector's axes, the signal is barely seen in the HXM detectors,
and it was heavily attenuated in the SGM detector.
The burst light curve shows a single emission episode which starts
at T-9.0 sec and ends at T+7.1 sec.
The T90 and the T50 durations measured by the SGM data are
13.9 +- 2.4 sec and 5.9 +- 2.3 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.