GCN Circular 45716
GRB 260922A: CALET Gamma-Ray Burst Monitor detection
From: Yuta Kawakubo at Aoyama Gakuin University
Issued: 2026-09-24 05:34 UTC
Type: GRB, Gamma-ray Transient

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

The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260922A
at 10:00:33.96 UTC on 22 September 2026 (trigger #1474106408;
https://cgbm.calet.jp/cgbm_trigger/flight/1474106408/index.html).
A CGBM Notice was distributed in near real time.

This event was also reported by Swift-BAT (Page et al., GCN #45690;
Sakamoto et al., GCN #45703) .

The burst signal was seen by only the SGM detector.
The burst light curve shows a double-peaked structure starting
at T+0.4 s, peaking at T+5.8 s, and ending at T+ 7.5 s.
The T90 and T50 durations measured with the SGM data are 6.2 +/- 0.5 s
and 2.8 +/- 0.4 s in the 40-1000 keV band, respectively.

The ground-processed light curve is available at:
https://cgbm.calet.jp/cgbm_trigger/ground/1474106408/

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

Filter: gamma-ray bursts are posted only if in the top 10% of the past year's — by fluence (total energy received per cm², from Fermi GBM, Konus-Wind, GECAM and similar circulars; now ≥ 3.9×10^-5 erg/cm²) or by the number of GCN Circulars about the burst (now ≥ 14). Thresholds are recalculated monthly.
Relayed automatically from NASA's General Coordinates Network.