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GCN Circular 30458

Subject
Recent activity of SGR 1935+2154 as observed by CGBM
Date
2021-07-13T09:59:01Z (3 years ago)
From
Valentin Pal'shin at AGU <val@phys.aoyama.ac.jp>
S. Nakahira (RIKEN),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), Y. Asaoka (ICRR),
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:

During the recent reactivation of SGR 1935+2154 reported by
INTEGRAL (GCN 30395), GECAM (GCNs 30400, 30415, 30430, 30437, 30449),
Fermi-GBM (GCN 30407), and Konus-Wind (GCNs 30409, 30418, 30450)
the CALET Gamma-ray Burst Monitor (CGBM) has triggered on two bright
short soft bursts from this SGR (alerted trigger 1309652996:
http://cgbm.calet.jp/cgbm_trigger/flight/1309652996/
and trigger 1309983742, which was not alerted).
Additional two weaker short soft bursts observed in the waiting mode
(125-ms time resolution, 8 energy channels) with high S/N were also likely
originated from SGR 1935+2154 (these bursts have not been reported by other
instruments so far).

The following table summarizes the bursts:

        Time, UTC           Mode     Other reported detections
--------------------------------------------------------------
2021-07-07 00:33:31.593   Trig      GECAM,Fermi GBM,Konus-Wind
2021-07-10 20:26:04.635   Trig*     Konus-Wind,Fermi GBM
2021-07-11 14:42:55       BG                -
2021-07-12 16:58:51       BG                -
--------------------------------------------------------------
*- Because of a problem in one of the ground alert processing script,
    the GCN notice was not distributed automatically for this trigger.

At the listed times, SGR 1935+2154 was in the FOVs of the CGBM detectors.

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