TITLE:   GCN CIRCULAR
NUMBER:  22607
SUBJECT: GRB 180404C CALET Gamma-Ray Burst Monitor detection
DATE:    18/04/06 01:23:16 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, V. Pal'shin,
Y. Kawakubo, A. Tezuka, S. Matsukawa (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,
and the CALET collaboration:

The long-duration, hard-spectrum, bright GRB 180404C triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 21:42:08.587 UTC on 4 April 2018.
The burst signal was seen by all CGBM detectors.  This GRB is also clearly
seen by the publicly available INTEGRAL SPI-ACS light curve.

The burst light curve shows a single pulse which starts at T+1.7 sec, peaks at
T+5.5 sec and ends at T+34.1 sec.  The T90 and the T50 durations measured
by the SGM data are 25.4 +- 3.1 sec and 9.5 +- 1.4 sec (40-1000 keV), respectively.
CGBM HV was turned off at ~T+65 sec due to entering the radiation belts, so
no CGBM data are available from that time until ~T+1000 sec.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1206913306/

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