GCN Circular 33840

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.