TITLE:   GCN CIRCULAR
NUMBER:  34560
SUBJECT: GRB 230818B: CALET Gamma-Ray Burst Monitor detection
DATE:    23/08/26 04:35:14 GMT
FROM:    Yuta Kawakubo at Louisiana State University <kawakubo1@lsu.edu>

Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, 
S. Sugita (AGU), Y. Kawakubo (LSU),K. Yamaoka (Nagoya U),
S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, 
K. Kobayashi (Waseda U), T. Tamura (Kanagawa U), 
N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long GRB 230818B (AstroSat CZTI detection: 
Navaneeth et al., GCN Circ. 34524; VZLUSAT-2 detection: 
Dafcikova et al., GCN Circ. 34525; Konus/Wind detection at 
2023-08-18 10:12:54.913 UT) triggered the CALET Gamma-ray 
Burst Monitor (CGBM) at 10:12:54.02 UTC on 18 August 2023
(http://cgbm.calet.jp/cgbm_trigger/flight/1376388662/).
The burst signal was seen by all CGBM detectors.
Because of a problem in one of the ground alert processing script,
the GCN notice was not distributed automatically for this event.

The burst light curve shows a multi-peaked structure that starts
at T-0.6 sec, peaks at T+0.6 sec, and ends at T+32.0 sec.
The T90 and T50 durations measured by the SGM data are 27.6 +/- 1.2 sec
and 13.3 +/- 0.6 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1376388662/index.html

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