GCN 44242: GRB 260407A: CALET Gamma-Ray Burst Monitor detection

M. L. Cherry (LSU), 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), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long GRB 260407A (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 44226; Glowbug gamma-ray detection: Cheung et al., GCN Circ 44237)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:11:06.11 UTC on 7 April 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1459588274/index.html).
The burst signal was seen by all CGBM detectors.  

The burst light curve shows a single pulse that starts
at T-0.5 sec, peaks at T+1.6 sec, and ends at T+27.1 sec.
The T90 and T50 durations measured by the SGM data are 22.6 +/- 5.0 sec
and 7.0 +/- 1.0 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1459588274

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