TITLE:   GCN CIRCULAR
NUMBER:  22653
SUBJECT: GRB 180416B: CALET Gamma-Ray Burst Monitor detection
DATE:    18/04/18 12:47:28 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

Y. Kawakubo, A. Yoshida, T. Sakamoto, V. Pal'shin, A. Tezuka, S. Matsukawa,
H. Onozawa (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-duration GRB 180416B (Fermi-GBM trigger #545609416; Konus-Wind trigger
time on 22:10:10.60 UT) triggered the CALET Gamma-ray Burst Monitor (CGBM) at
22:10:09.279 UTC on 16 April 2018. The burst signal was seen by all CGBM detectors.

The burst light curve shows a single pulse which starts at T+1.6 sec, peaks at
T+3.1 sec and ends at ~T+14 sec, followed by a weak tail seen up to ~T+62 sec.
The T90 and the T50 durations measured by the SGM data are 51.6 +- 12.7 sec
and 17.4 +- 8.4 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1207951766/

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