TITLE: GCN CIRCULAR NUMBER: 40298 SUBJECT: GRB 250424A: CALET Gamma-Ray Burst Monitor detection DATE: 25/05/01 03:19:12 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University kawakubo@phys.aoyama.ac.jp

GRB 250424A: CALET Gamma-Ray Burst Monitor detection

S. Nakahira (JAXA), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), 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 250424A (Swift detection: Cenko et al., GCN Circ. 40224; Swift-BAT refined analysis: Markwardt et al., GCN Circ. 40255; AstroSat CZTI detection: Harsha et al., GCN Circ. 40231; Konus-Wind detection: Ridnaia et al., GCN Circ. 40243; EIRSAT-1 GMOD Detection: McKenna et al., GCN Circ. 40249; SVOM/GRM observation: Jin-Peng et al., GCN Circ. 40252) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 06:52:04.323 UTC on 24 April 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1429512582/index.html). The burst signal was seen by all CGBM detectors.

The burst light curve shows a single pulse that starts at T+2.5 sec, peaks at T+8.4 sec, and ends at T+27.5 sec. The T90 and T50 durations measured by the SGM data are 13.5 +/- 0.8 sec and 4.6 +/- 0.2 sec (40-1000 keV), respectively.

The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1429512582/

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

View this GCN Circular online at https://gcn.nasa.gov/circulars/40298. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...