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GCN Circular 25099

Subject
LIGO/Virgo S190718y: Upper limits from CALET observations
Date
2019-07-19T04:01:41Z (5 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
V. Pal'shin, A. Yoshida, T. Sakamoto, S. Sugita (AGU), 
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka, S. Ozawa, S. Torii (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:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger 
time of S190718y T0 = 2019-07-18 14:35:12.068 UT (The LIGO
Scientific Collaboration and Virgo Collaboration, GCN Circ. 25087).

No CGBM on-board trigger occurred around the event time.  Based
on the LIGO-Virgo localization sky map, the summed LIGO probabilities 
inside the CGBM HXM (7-3000 keV) and SGM (40 keV - 28 MeV) fields 
of view are 9 % and 17 %, respectively (and 22 % credible region of the 
initial localization map was above the horizon).  The HXM and SGM fields
of view were centered at RA = 203.3 deg, Dec = -18.0 deg and 
RA = 195.8 deg, Dec = -11.1 deg at T0, respectively.

Based on the analysis of the light curve data with 0.125 sec
time resolution from T0-60 sec to T0+60 sec, we found no
significant excess (signal-to-noise ratio >= 7) around the trigger
time in either the HXM or the SGM data.

The CALET Calorimeter (CAL) was operating in the low energy
trigger mode at the trigger time of S190718y. Using the CAL data,
we have searched for gamma-ray events in the 1-10 GeV
band from -60 sec to +60 sec from the GW trigger time and
found no candidates.
The 90% upper limit of CAL is 1.7x10^-6 erg/cm^2/s (1-10 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA = 195.8 deg, DEC = -11.1 deg at T0.
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