TITLE:   GCN CIRCULAR
NUMBER:  22366
SUBJECT: GRB 180120A CALET Gamma-Ray Burst Monitor detection
DATE:    18/01/23 08:44:54 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo,
M. Moriyama, Y. Yamada, A. Tezuka, S. Matsukawa (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
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-duration GRB 180120A (Fermi-GBM trigger #538117098;
Konus-Wind trigger time on 04:58:18.23) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 04:58:09.54 on 20 January 2018.
The burst signal was seen by the all CGBM instruments.

The light curve shows two bright overlapping pulses.  The first pulse starts
at T-2 sec, peaks at T+6 sec and ends at T+20 sec.  There is a possible
additional pulse around T+15 sec.  The second pulse starts at T+15 sec,
peaks at T+25 sec and ends at T+40 sec.  The T90 and the T50 durations
measured by the SGM data are 24.9 +- 4.1 sec and 16.3 +- 0.4 sec
(40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1200459271/

The CALET data used in this analysis are provided by the Waseda CALET Operation
Center located at the Waseda University.