[vsnet-grb-info 21018] GRB 180809B: CALET Gamma-Ray Burst Monitor detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23116
SUBJECT: GRB 180809B: CALET Gamma-Ray Burst Monitor detection
DATE:    18/08/10 12:21:10 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, V. Pal'shin,
S. Sugita, Y. Kawakubo, A. Tezuka, S. Matsukawa, H. Onozawa,
T. Ito, H. Morita, Y. Sone (AGU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR),
S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The long, bright GRB 180809B (Swift-BAT trigger #852553: Moss et al.,
GCN Circ. 23105) triggered the CALET Gamma-ray Burst Monitor (CGBM)
at 20:28:41.478 UTC on 9 August 2018 while exiting the radiation belts.
The burst signal was seen by all CGBM detectors.

The burst light curve shows the main multi-peaked emission episode which
starts at T-5 sec, peaks at T+41.4 sec, and ends at T+79.9 sec, followed by
a weaker pulse which starts at T+210.0 sec and ends at T+254.6 sec.
The T90 and the T50 durations measured by the SGM data are
227.6 +- 5.4 sec and 28.3 +- 5.7 sec (40-1000 keV), respectively.
Since the CGBM HV was set to its nominal value at T-21 sec for
the HXM1 and HXM2 detectors and at T-5 sec for the SGM detector,
CGBM was blind to a possible earlier emission.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1217881726/

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