TITLE:   GCN CIRCULAR
NUMBER:  20916
SUBJECT: LIGO/Virgo G277583: CALET Observations
DATE:    17/03/18 22:39:29 GMT
FROM:    Takanori Sakamoto at Aoyama Gakuin U  <tsakamoto@phys.aoyama.ac.jp>

K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, Y. Kawakubo,
M. Moriyama, Y. Yamada (AGU), 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), S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time
of G277583 (GCN Circ. 20860).  No CGBM on-board trigger occurred at the time
of the event.  Based on the LIGO localization sky map (cWB_plus_LIB.fits),
the part of the southern arc of the high probability area was in the field-of-view of
CGBM.  The summed LIGO probabilities inside the HXM and the SGM field of view
are 19% and 41%.

Based on the analysis of the light curve data with 0.125 sec time resolution
from -60 sec to 60 sec from the trigger time, we found no significant excess
around the trigger time in either the HXM (7-3000 keV) or the SGM (40 keV -28 MeV)
data.

The CALET Calorimeter (CAL) was operating in high energy trigger mode at the
trigger time of G277583.  However, no LIGO high probability region was included
in the CAL's field of view at the time of the trigger.