TITLE:   GCN CIRCULAR
NUMBER:  19345
SUBJECT: GRB 160422A: CALET Gamma-Ray Burst Monitor detection
DATE:    16/04/26 01:27:37 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, 
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), 
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), 
W. Ishizaki (ICRR), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena) 
and the CALET collaboration:

The long-duration GRB 160422A (Burns et al., GCN circ. 19331; Yassine et al., 
GCN circ. 19329; INTEGRAL-ACS #7450) triggered the CALET Gamma-Ray Burst Monitor (CGBM) 
at 11:59:08.28 on 22 April 2016.  The burst signal was only seen by the SGM instrument.  
This fact is consistent that the GRB location of the Fermi-LAT (Yassine et al., 
GCN circ. 19329) was outside the field of view of the CALET CALorimeter (CAL) instrument, 
which has the capability to observe gamma-rays above 1 GeV, at the trigger time.  
The boresight angle of the SGM to the Fermi-LAT position was ~105 deg.  

The light curve of the SGM shows at least two episodes.  The first episode starts at 
T0-7 sec, peaks at T0-6 sec and ends at T0-4 sec.  The second episode shows the emission 
starting at T0, peaking at T0+1 sec and ending at T0+4 sec.  The T90 duration measured by 
the SGM data is 8.7 +- 0.3 sec (100-1000 keV). 

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