TITLE:   GCN CIRCULAR
NUMBER:  42505
SUBJECT: GRB 251028B: CALET Gamma-Ray Burst Monitor detection
DATE:    25/10/28 16:08:21 GMT
FROM:    Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>

Y. Akaike (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, 
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 251028B (Fermi GBM Final Localization Correction: Fermi GBM team,
GCN Circ. 42502) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 
07:48:06.24 UTC on 28 October 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1445672396/index.html).
The burst signal was seen by all CGBM detectors. 

The burst light curve shows a multi-peaked structure that starts
at T-0.5 sec, peaks at T+9.9 sec, and ends at T+11.5 sec.
The T90 and T50 durations measured by the SGM data are 11.3 +/- 0.4 sec
and 8.5 +/- 0.3 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1445672396/

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