TITLE: GCN CIRCULAR NUMBER: 38569 SUBJECT: GRB 241209D: CALET Gamma-Ray Burst Monitor detection DATE: 24/12/14 09:21:25 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 241209D (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ 38488; Swift detection of a burst: Parsotan et al., GCN Circ 38489; Fermi GBM Observation: Malacaria et al., GCN Circ 38507; AstroSat CZTI detection: Tembhurnikar et al., GCN Circ 38518; Konus-Wind detection: Ridnaia et al., GCN Circ 38526) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 10:59:46.760 UTC on 9 December 2024 (https://cgbm.calet.jp/cgbm_trigger/flight/1417777157/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 single pulse that starts at T-4.0 sec, peaks at T+0.6 sec, and ends at T+6.7 sec. The T90 and T50 durations measured by the SGM data are 9.2 +/- 0.7 sec and 4.6 +/- 0.4 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1417777157/

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

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