TITLE: GCN CIRCULAR NUMBER: 44966 SUBJECT: GRB 260616B: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/17 15:25:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp> Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260616B at 07:05:24.65 UTC on 16 June 2026 (trigger #1465628601; https://cgbm.calet.jp/cgbm_trigger/flight/1465628601/index.html). A CGBM Notice was distributed in near real time. This event was also reported by Fermi GBM (Preis et al., GCN #44951; Malacaria et al., GCN #44953). The burst signal was seen by HXM2 and SGM. The burst light curve shows a double-peaked structure starting at T-7.7 s, peaking at T+2.6 s, and ending at T+4.1 s. The T90 and T50 durations measured with the SGM data are 11.2 +/- 0.3 s and 8.1 +/- 0.2 s in the 40-1000 keV band, respectively. Einstein Probe/WXT detected an X-ray transient, EP 260616a (Li et al., GCN #44956), about 9 s before the CGBM trigger. The position of EP 260616a was marginally above the Earth horizon as seen from CALET/ISS at the trigger time, at an incident angle of 110 degrees. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465628601/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44966. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...