TITLE:   GCN CIRCULAR
NUMBER:  40519
SUBJECT: GRB 250520A: CALET Gamma-Ray Burst Monitor detection
DATE:    25/05/22 02:30:45 GMT
FROM:    Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>

Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), S. Torii, Y. Akaike, 
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 short GRB 250520A (Swift Detection: Eyles-Ferris et al., GCN Circ. 40491;
SVOM/GRM observation: Wang et al., GCN Circ. 40495; AstroSat CZTI detection:
Tembhurnikar et al., GCN Circ. 40497; Konus-Wind detection: Frederiks et al.,
GCN Circ. 40512) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 
02:42:16.72 UTC on 20 May 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1431743946/index.html).
The burst signal was seen by all CGBM detectors. 

The burst light curve shows a single pulse that starts
at T+0.06 sec, peaks at T+0.19 sec, and ends at T+0.31 sec.
The T90 and T50 durations measured by the SGM data are 0.21 +/- 0.04 sec
and 0.09 +/- 0.01 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1431743946/

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