TITLE: GCN CIRCULAR NUMBER: 30744 SUBJECT: GRB 210822A: CALET Gamma-Ray Burst Monitor detection DATE: 21/08/30 07:06:23 GMT FROM: Valentin Pal'shin at AGU val@phys.aoyama.ac.jp
K. Kobayashi (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (ICRR), S. Torii, Y. Akaike (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 210822A (Swift detection: Page et al., GCN Circ. 30677, Lien et al., GCN Circ. 30689; GECAM detection: Wang et al., GCN Circ. 30678, 30696; Fermi-LAT detection: Ohno et al., GCN Circ. 30687; AstroSat CZTI detection: Prasad et al., GCN Circ. 30693; Konus-Wind detection: Frederiks et al., GCN Circ. 30694; GRBAlpha detection: Ohno et al., GCN Circ. 30697; https://gcn.gsfc.nasa.gov/other/210822A.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:18:18.162 UTC on 22 August 2021. 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 which starts at T-0.2 sec, peaks at T+0.1 sec and ends at T+11.0 sec. The T90 and T50 durations measured by the SGM data are 10.1 +- 0.5 sec and 5.8 +- 0.4 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1313658800/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.