GCN 44177: GRB 260401A: CALET Gamma-Ray Burst Monitor detection

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

The long GRB 260401A (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 44174; BALROG localization: Preis et al., GCN Circ 44175; 
MAXI/GSC detection: Usuki et al., GCN Circ 44176) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 10:53:31.52 UTC on 1 April 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1459075956/index.html).
The burst signal was seen by all CGBM detectors.  

The burst light curve shows a single pulse that starts
at T+1.4 sec, peaks at T+2.2 sec, and ends at T+6.3 sec.
The T90 and T50 durations measured by the SGM data are 4.4 +/- 0.6 sec
and 2.0 +/- 0.3 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1459075956

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