TITLE:   GCN CIRCULAR
NUMBER:  22888
SUBJECT: GRB 180703B: CALET Gamma-Ray Burst Monitor detection
DATE:    18/07/04 09:24:53 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

I. Takahashi (IPMU), A. Yoshida, T. Sakamoto, 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),
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 Fermi-LAT GRB 180703B (Racusin et al. GCN Circ. 22884) triggered
the CALET Gamma-ray Burst Monitor (CGBM) at 22:46:51.183 UTC on 3 July 2018.
The burst signal was seen by all CGBM detectors.

The burst light curve shows two short pulses which start at T+0.1 sec,
peaks at T+1.4 sec and ends at T+2.1 sec.  The T90 and the T50 durations
measured by the SGM data are 1.4 +- 0.2 sec and 0.4 +- 0.1 sec (40-1000 keV),
respectively.

Despite its very high brightness the burst spectrum is soft with almost
no emission seen in the CGBM data above ~500 keV. So, this is a very bright,
short, and soft GRB.
The follow-up observations of this interesting event is highly encouraged.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1214693124/

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