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GCN Circular 21706

Subject
LIGO/Virgo G298936: CALET Observations
Date
2017-08-26T00:08:19Z (7 years ago)
From
Takanori Sakamoto at Aoyama Gakuin U <tsakamoto@phys.aoyama.ac.jp>
Y. Asaoka (Waseda U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama,
Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), I. Takahashi (IPMU), 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 G298936 (The LIGO Scientific Collaboration and Virgo Collaboration,
GCN Circ. 21656).  No CGBM on-board trigger occurred at the time
of the event.  Based on the LIGO-Virgo localization sky map (bayestar-HLV.fits.gz),
the part of the northern 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 57% and 66%.

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 G298936.  Similar to CGBM, the northern arc of the high probability area of the
LIGO-Virgo localization map was in the field of view of CAL.  Using CAL data, we have
searched for gamma-ray events in the 10-100 GeV band from -60 sec to +60 sec from
the GW trigger time and found no candidates.  The 90% upper limit of CAL is
2e-5 erg/cm2/s (10-100 GeV) when the summed LIGO-Virgo probabilities reaches at 20%.
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