TITLE:   GCN CIRCULAR
NUMBER:  40575
SUBJECT: GRB 250527D: CALET Gamma-Ray Burst Monitor detection
DATE:    25/05/30 03:02:08 GMT
FROM:    Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>

Y. Akaike (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
K. Kobayashi (Waseda U), 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 250527D (Swift/BAT-GUANO localization skymap: DeLaunay et al.,
GCN Circ. 40573) triggered the CALET Gamma-ray Burst Monitor (CGBM)
at 23:38:44.85 UTC on 27 May 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1432424119).
The burst signal was seen by all CGBM detectors.  

The burst light curve shows a multi-peaked structure that starts
at T+2.1 sec, peaks at T+5.1 sec, and ends at T+5.6 sec.
The T90 and T50 durations measured by the SGM data are 3.1 +/- 0.2 sec
and 1.7 +/- 0.2 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1432424119

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