TITLE: GCN CIRCULAR NUMBER: 39663 SUBJECT: GRB 250308A: CALET Gamma-Ray Burst Monitor detection DATE: 25/03/11 09:19:04 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University kawakubo@phys.aoyama.ac.jp

Y. Kawakubo, A. Yoshida, T. Sakamoto, S. Sugita (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), 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 short GRB 250308A (SVOM/GRM observation: the SVOM team, GCN Circ. 39632, 39636; IPN triangulation: Kozyrev et al., GCN Circ. 39653) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:06:30.72 UTC on 8 March 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1425492335/index.html). The burst signal was seen by SGM and HXM2.

The burst light curve shows a single pulse that starts at T-0.1 sec, peaks at T+0.1 sec, and ends at T+0.3 sec. The T90 and T50 durations measured by the SGM data are 0.4 +/- 0.2 sec and 0.2 +/- 0.1 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1425492335/

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

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