GCN 43982: GRB 260307A: CALET Gamma-Ray Burst Monitor detection

2026-03-13T10:45:12.905Z | rev 0 | event: GRB 260307A
Y. Shimizu (Kanagawa U), 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), 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 260307A (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 43939; Glowbug gamma-ray detection: Cheung et al., GCN Circ. 43950;
GECAM-B observation: Zao et al., GCN Circ. 43961) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 11:27:56.49 UTC on 7 March 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1456918069/index.html).
The burst signal was seen by all CGBM detectors. 

The burst light curve shows a multi-peaked structure that starts
at T+2.8 sec, peaks at T+5.2 sec, and ends at T+8.0 sec.
The T90 and T50 durations measured by the SGM data are 4.6 +/- 0.5 sec
and 2.0 +/- 0.2 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1456918069/

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