TITLE:   GCN CIRCULAR
NUMBER:  33840
SUBJECT: GRB 230520A: CALET Gamma-Ray Burst Monitor detection
DATE:    23/05/21 06:10:46 GMT
FROM:    Yuta Kawakubo at Louisiana State University <kawakubo1@lsu.edu>

T. Sakamoto, A. Yoshida, S. Sugita (AGU), Y. Kawakubo (LSU), 
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR),
S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, 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 230520A (MAXI/GSC detection: Umeki et al., 
GCN Circ. 33831) was detected in the ground analysis of the CALET 
Gamma-ray Burst Monitor (CGBM) data around 05:03:24 UTC on 20 
May 2023 (referenced to GCN Circ 33831).
The burst signal was seen by all CGBM detectors.

The burst light curve shows a multi-peaked structure that starts
at T-82.9 sec, peaks at T+9.0 sec, and ends at T+34.9 sec.
The T90 and T50 durations measured by the SGM data are 98.1 +/- 4.3 sec
and 67.5 +/- 3.7 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1368594148/

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