TITLE: GCN CIRCULAR NUMBER: 38896 SUBJECT: GRB 250107C: CALET Gamma-Ray Burst Monitor detection DATE: 25/01/10 16:51:07 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University kawakubo@phys.aoyama.ac.jp

A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (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 long GRB 250107C (SVOM/GRM observation: SVOM/GRM team, GCN Circ. 38870; IPN triangulation: Svinkin et al., GCN Circ. 38879; Konus-Wind detection: Frederiks et al., GCN Circ. 38895) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 18:52:15.99 UTC on 7 January 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1420311052/index.html). The burst signal was seen by only the SGM detector. Because of a problem with the ground alert processing script, the GCN notice was not distributed automatically for this event.

The burst light curve shows a double-peaked structure that starts at T-0.2 sec, peaks at T+0.7 sec, and ends at T+3.0 sec. The T90 and T50 durations measured by the SGM data are 2.6 +/- 0.2 sec and 1.6 +/- 0.1 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1420311052/

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

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