TITLE: GCN CIRCULAR NUMBER: 24738 SUBJECT: GRB 190531B: CALET Gamma-Ray Burst Monitor detection DATE: 19/06/04 08:09:40 GMT FROM: Valentin Pal'shin at AGU Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa, S. Torii (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 190531B (Fermi-LAT detection: Axelsson et al.,GCN Circ. 24701; Fermi-GBM observations: Veres and Meegan, GCN Circ. 24705; Insight-HXMT/HE detection: Yi et al., GCN Circ. 24713; Konus-Wind observation: Svinkin et al., GCN Circ. 24730) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 20:10:20.034 UTC on 31 May 2019. The burst signal was seen by all CGBM detectors. No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). The burst light curve shows a multi-peaked emission episode which starts at T-9.7 sec, peaks at 14.5 sec and ends at T+74.5 sec. The T90 and T50 durations measured by the SGM data are 36.8 +- 20.0 sec and 13.5 +- 0.9 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1243368627/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.