TITLE:   GCN CIRCULAR
NUMBER:  43860
SUBJECT: GRB 260226A: CALET Gamma-Ray Burst Monitor detection
DATE:    26/02/27 08:55:16 GMT
FROM:    Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>

K. Kobayashi (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, 
Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, 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 260226A (Fermi GBM Final Real-time Localization: Fermi
GBM team, GCN Circ. 43840; BALROG localization: Preis et al., GCN Circ
43843; Fermi-LAT detection: Depalo et al., GCN Circ 43844; AstroSat CZTI
detection: Harsha et al., GCN Circ 43846; Fermi-LAT refined analysis: Depalo
et al., GCN Circ 43850; Fermi GBM observation: Bissaldi et al., GCN Circ 43851;
NuSTAR detection: Waratkar et al., GCN Circ 43854; Glowbug gamma-ray detection:
Woolf et al., GCN Circ 43855) triggered the CALET Gamma-ray Burst Monitor (CGBM)
at 10:38:04.46 UTC on 26 February 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1456137494/index.html).
The burst signal was seen by all CGBM detectors.  

The burst light curve shows a multi-peaked structure that starts
at T-3.9 sec, peaks at T+11.1 sec, and ends at T+37.0 sec.
The T90 and T50 durations measured by the SGM data are 16.0 +/- 0.3 sec
and 8.2 +/- 0.1 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1456137494/

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